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Model 2520Pulsed Laser Diode Test System User`s Manual

1. 1 EE Error Event SE Status Event SYS System Error Event 2 Use following queries to read status registers Standard Event ESR Operation Event STAT OPER Measurement Event STAT MEAS Questionable Event STAT QUES Model 2520 User s Manual Status and Error Messages B 7 Eliminating common SCPI errors There are three SCPI errors that occur more often than any others e 113 Undefined header e 410 Query INTERRUPTED e 420 Query UNTERMINATED The following paragraphs discuss the most common causes for these errors and methods for avoiding them 113 Undefined header This error indicates that the command you sent to the instrument did not contain a recog nizable command name The most likely causes for this error are e Missing space between the command and its parameter There must be one or more spaces blanks between the command and its parameter For example SENS2 CURR RANG10e 3 Incorrect no space between command and parameter SENS2 CURR RANG 10e 3 Correct Improper short or long form Check the command list in Section 14 for the correct command name e Blanks spaces within the command name For example SYST ERR Incorrect space between SYST and ERR iSYST ERR Correct 410 Query INTERRUPTED This error occurs when you have sent a valid query to the instrument and then send it another command or query or a Group Execute Trigger GET before it has had a chan
2. symbol Trigger In Event Immediate Trigger Count 1 Timer 0 1s Trigger Out Event Off Unless programmed otherwise the Model 2520 will run in a continuous loop around the trigger model processing one set of readings each time it goes through the loop Operation summary The trigger model is designed to offer versatility for the various source and measure appli cations It allows you to specify input and output triggers for both single reading and sweep operation as follows e When sweeps are disabled the unit will process one set of readings per Trigger In Event and provide one output trigger per reading set If the unit is in the Immediate trigger mode it will process readings continuously e When a sweep is enabled the unit will perform one sweep per Trigger In Event One output trigger will be generated when the sweep is completed e In order to use the RECALL mode the unit must be placed in the INIT CONTIN UOUS OFF mode See Configuring triggering page 8 7 Trigger link Input and output triggers are received and sent via the rear panel TRIGGER LINK connec tor The trigger link has six lines At the factory line 2 is selected for output triggers and line 1 is selected for input triggers These input output line assignments can be changed from the CONFIGURE TRIGGER menu See Configuring triggering page 8 7 The connector pinout is shown in Figure 8 2 Figure 8 2 Rear panel pinout P
3. TIME Timestamp RESet Reset timestamp to zero seconds LOCal Take unit out of remote and cancel local lockout RS 232 REMote Put unit in remote RS 232 RWLock Enable local lockout RS 232 Clearing Error Queue Power up and CLS clears the error queue RST SYSTem PRESet and STATus PRESet have no effect Table 14 9 TRACe command summary Default Command Description parameter SCPI TRACel DATA Access and control sample buffer v DATA Returns raw samples v VALue NRf Returns specified sample after start of pulse POINts lt n gt Sets number of samples to return for 100 v TRAC DATA query 1 to 3000 POINts Queries number of samples to return v 14 14 SCPI Command Reference Model 2520 User s Manual Table 14 10 TRIGger command summary Default Command Description parameter SCPI sINITiate IMMediate Initiate source and measure cycle s v ABORt Reset trigger system Goes to idle state v TRIGger Path to program Trigger Layer v SEQuence 1 Jv LAYer 1 y COUNt lt n gt Specify trigger count 1 to 5000 or INFinite 1 v COUNt Query trigger count INFinite 9 9e37 v SOURce lt name gt Specify control source IMMediate TIMer IMM Jv MANual BUS TLINk NSTest PSTest BSTest SOURce Query control source y TIMer lt n gt Set timer interval in seconds 0 to 99999 99 0 1 y TIMer Query timer interval v TCONfigure Jv ASYNchronous Co
4. Bangalore 560 025 080 212 8027 Fax 080 212 8005 ITALY Viale San Gimignano 38 e 20146 Milano 02 48 39 16 01 Fax 02 48 30 22 74 JAPAN New Pier Takeshiba North Tower 13F 11 1 Kaigan 1 chome Minato ku Tokyo 105 0022 81 3 5733 7555 Fax 81 3 5733 7556 KOREA 2FL URI Building 2 14 Yangjae Dong Seocho Gu Seoul 137 888 82 2 574 7778 Fax 82 2 574 7838 NETHERLANDS Postbus 559 4200 AN Gorinchem 0183 635333 Fax 0183 630821 SWEDEN c o Regus Business Centre Frosundaviks All 15 4tr e 169 70 Solna 08 509 04 600 Fax 08 655 26 10 TAIWAN 13F 3 No 6 Lane 99 Pu Ding Road Hsinchu Taiwan R O C e 886 3 572 9077 Fax 886 3 572 9031 1 03 Model 2520 Pulsed Laser Diode Test System User s Manual 2001 Keithley Instruments Inc All rights reserved Cleveland Ohio U S A Third Printing March 2003 Document Number 2520 900 01 Rev C Manual Print History The print history shown below lists the printing dates of all Revisions and Addenda created for this manual The Revision Level letter increases alphabetically as the manual undergoes subsequent updates Addenda which are released between Revisions contain important change information that the user should incorporate immediately into the manual Addenda are numbered sequentially When a new Revision is created all Addenda associated with the previous Revision of the manual are incorporated into the new Revision of the manual
5. IEEE Addr 25 message is displayed If the RS 232 interface is selected the RS 232 message is displayed After the power up sequence the instrument goes to its normal display state with the out put off blue ON OFF OUTPUT indicator and testhead POWER lights off System identification To obtain the serial number and revision information use the MENU SERIAL selection or the IDN query via remote Fuse replacement A rear panel fuse protects the power line input of the Model 2520 If the line fuse needs to be replaced perform the steps below WARNING Disconnect the line cord and all cables and test leads from the instru ment before changing the line fuse 1 The fuse is located in a holder in the power module adjacent to the AC receptacle Figure 1 2 At the right of the fuse holder is a small tab At this location use a small bladed screwdriver to release the fuse holder Slide the fuse holder out to gain access to the fuse carrier and fuse 3 Remove the carrier with blown fuse and replace the fuse with the correct type listed in Table 1 1 CAUTION For continued protection against fire or instrument damage replace the fuse only with the type and rating listed If the instrument repeat edly blows fuses locate and correct the cause of the problem before replacing the fuse 4 Install the fuse carrier in the fuse holder then insert the fuse holder in the power module Table 1 1 Line fuse Line voltag
6. Select LOW then press ENTER Set the pulse low amplitude to the desired value then press ENTER Press EXIT to return to normal display Press the PW key then set the pulse width to the desired value Press the DELAY key then set the pulse delay as required Press the LASER I key then press EDIT to enter the edit mode While in the edit mode use the RANGE 4A and yw keys to select the desired source range 500mA or 5A Use the EDIT A and w or numeric keys to set the source amplitude to the desired level For the pulse mode this value will be the high pulse level Press the COMPL key then set the voltage compliance limit to the desired value Press ENTER to complete your selection and return to normal display Setting photodiode detector source values The basic procedure for editing photodiode detector source values is outlined below l Press the DETECTOR 1 Vg or DETECTOR Vp key then the EDIT key so the blinking cursor is in the source display field to be edited To simply increment or decrement the displayed source value use the EDIT lt 4 and gt and A and y keys or use the numeric keys to enter the value directly Again the source value will be updated immediately you need not press ENTER to com plete the process Repeat steps and 2 for the other photodiode source 3 12 Basic Operation Model 2520 User s Manual Configuring measurements Follow the general procedures below to set the range and polar
7. Table 11 8 Program and read register programming example Command Description FORM SREG BIN Select binary format to read registers STAT MEAS ENAB 512 Enable BFL buffer full STAT MEAS COND Read Measurement Condition Register STAT MEAS Read Measurement Event Register Queues The Model 2520 uses two queues which are first in first out FIFO registers e Output Queue Used to hold reading and response messages Error Queue Used to hold error and status messages See Appendix B The Model 2520 status model Figure 11 1 shows how the two queues are structured with the other registers Output queue The output queue holds data that pertains to the normal operation of the instrument For example when a query command is sent the response message is placed in the Output Queue When data is placed in the Output Queue the Message Available MAV bit in the Status Byte Register sets A data message is cleared from the Output Queue when it is read The Output Queue is considered cleared when it is empty An empty Output Queue clears the MAY bit in the Status Byte Register A message is read from the Output Queue by addressing the Model 2520 to talk after the appropriate query is sent 11 20 Status Structure Model 2520 User s Manual Error queue The Error Queue holds error and status messages When an error or status event occurs a message that defines the error status is placed in the Error Queue When
8. and the resistance of the laser diode is represented as Rpyy Figure F 1 Model 2520 pulse output circuit model Rout Current source 5A pulse maximum c Compliance voltage 3 10 5V I i V I L Cable inductance Rout Laser diode resistance I I Model 2520 Model 2520 User s Manual Measurement Considerations F 3 Cable inductance Under transient conditions the voltage across the cable inductance is defined as follows di VL Li Where L total cable inductance V voltage across inductance di dt rate of change of current For example the voltage with 100nH of inductance a 5A current pulse and 100ns rise time is 5A 100nH 5V VL 100ns From the above relationship it is obvious that with excessive inductance the voltage across the inductance may cause the current source to go into compliance and effectively become a voltage source with a value equal to the compliance setting 10 5V maximum Under these conditions voltages in the circuit are related as follows di L IR Ve Lit Bour Current while the source is in compliance then rises according the following relationship t Vo L Rpyt l e DUT g From the above discussion it is obvious that the rise time of the current pulse through the laser diode can be affected by the cable and other inductance in the circuit Thus it is important to keep cable lengths as short as possible and use only cables w
9. for a comparison of positive and negative source polarity Select SHAPE then press ENTER Choose DC then press ENTER Press EXIT to return to normal display Press the LASER I key then the EDIT key so the blinking cursor is in the I source display field While in the edit mode use the RANGE 4A and wy keys to select the desired source range 500mA or 5A Use the lowest range possible for best accuracy To simply increment or decrement the displayed source value use the EDIT lt 4 and gt keys to place the blinking cursor on the digit to be changed then increment or decrement the value with the EDIT A and w keys Note that the source value will be updated immediately you need not press ENTER to complete the process but you can press ENTER to exit the edit mode immediately To enter the source value directly simply key in the desired value with the numeric keys while the cursor is blinking Again the source value will be updated immedi ately Press the COMPL key then set the voltage compliance limit to the desired value Press ENTER to complete your selection and return to normal display Model 2520 User s Manual Basic Operation 3 11 Pulse mode eS PSO G0 OY Oe Ga Bo Press CONFIG then LASER I to access the source configuration menu Choose POLARITY then press ENTER Select POSITIVE or NEGATIVE as desired then press ENTER Figure 3 2 Select SHAPE then press ENTER Choose PULSE then press ENTER
10. page 8 2 for details on the follow ing programmable aspects of triggering CONFIGURE TRIGGER menu Press CONFIG and then TRIG to display the menu shown below and in Figure 8 5 Note that bullets indicate the primary items of the menu while dashes and slashes indicate options See Section 1 Rules to navigate menus to check and or change trigger options COUNT Specify the arm count FINITE programmable count or INFINITE never ending count INIT Turns the INIT CONTINUOUS mode ON or OFF For DC non sweep operation this mode is normally set to ON so that readings are processed continu ously For the RECALL mode this mode must be set to OFF OFF will automati cally be selected if the PULSE mode is selected or if a front panel sweep is initiated HALT Use to return the Model 2520 to the idle state HALT does not turn off the output The programmed source levels will still be available at the OUTPUT terminals The following actions will take the Model 2520 out of idle Turn the outputs off and then on again Reselect the arm or trigger event Exit from the menu structure and then re enter it by pressing CONFIG and then TRIG TRIGGER IN Use to select the detection event for the arm layer IMMEDIATE Event detection occurs immediately GPIB Event detection occurs when a bus trigger GET or TRG is received TIMER Initially event detection is satisfied immediately Subsequent event detectio
11. 3 4 Line 4 5 Line 5 6 Line 6 Query OLINe Query output trigger line Description This command is used to select output lines for the Trigger Link For normal operation Trigger Link input and output see ILINe lt NRf gt should not share the same line OUTPut lt name gt STRIGger SEQuence 1 TCONfigure OUTPut lt name gt Enable disable trigger output event Parameters lt name gt TRIGger Trigger on exiting trigger layer NONE Disable trigger layer output trigger Query OUTPut Query output trigger event state Description This command is used to specify whether or not trigger pulses occur on the specified output trigger line of the Trigger Link OLINe With TRIGger selected an output trigger will occur when exiting the trigger layer With NONE selected the trigger layer output trigger is dis abled Specifications 2520 Pulsed Laser Diode Test System LASER DIODE PULSE OR DC CURRENT SOURCE SPECIFICATIONS DRIVE CURRENT OFF CURRENT APPROX RMS NOISE APPROX SOURCE PROGRAMMING ELECTRICAL ACURACY typical PROGRAMMING ELECTRICAL ACURACY RANGE RESOLUTION RESOLUTION rdg mA 1kHz 20MHz RANGE RESOLUTION RESOLUTION rdg mA 0 500 mA 10 pA 8 uA 0 2 0 45 70 pA 0 15 mA 1 pA 7 nA typ 0 2 0 45 0 1 0 ADC 100 pA 80 uA 0 2 4 5 800 pA 0 150 mA 10 uA 70 nA typ 0 2 4 5 0 5 0 A Pulse TEMPERATURE COEFFICIENT 0 18 C amp 28 50 C 0 15 x accuracy SETTING AND PULSE PULSE RISE FALL
12. 3 5 0A maximum pulse mode only 1A maximum in DC mode Settings affected by maximum duty cycle See Section 5 Programming example Table 4 3 summarizes the command sequence for basic laser diode testing Note that most steps correspond to those listed previously in Front panel laser diode testing page 4 3 See Figure 4 1 for basic circuit configuration and Section 2 for detailed connection infor mation These commands set up the Model 2520 as follows e Laser diode voltage measurement range and polarity 10V positive e Detector measurement polarity negative both detectors Detector ranges 10mA detector 1 50mA detector 2 e Laser diode source 0 5A range 0 5A amplitude 5V voltage limit positive polarity e Laser diode source mode pulse delay 200usec width 10usec low I 10mA e Detector 1 bias source 20V amplitude e Detector 2 bias source 10V amplitude e Laser diode math function power e Detector 1 math function MX B B 2 M 0 5 Returned data laser diode power detector 1 MX B math detector 2 current 4 8 Laser Diode Testing Model 2520 User s Manual NOTE See Appendix H for a functional program example Table 4 3 Basic laser diode test command sequence Step Action Commands Comments RST Restore GPIB defaults 1 Configure laser diode measure SENS1 VOLT RANG 10 LD measure range 10V SENS 1 VOLT POL POS LD positive polarity 2 Configure
13. 50 seca ssesdusnasscnsensehon ceded ssbonstvgasesresvaranveadeetes 8 5 Operation SUMMALY 00 0 elects eeeereeeeeeaeeeceeaecneeeaeteeeeaeenees 8 5 Tigger Ink ospici csyes senasnase cdecensnautivetser ea a 8 5 Input trigger requirements 0 eee eee eeeeeeceeeeeeeeeeaeeeees 8 6 Output trigger specifications 00 eee eeeeeeceeeeeeeeeeeeeeeees 8 6 Configuring triggering oe eeeeseceeeeseceeeseeeeeeseeeaeeseeeaeesaees 8 7 CONFIGURE TRIGGER menu eseese 8 7 Remote HIS SHINE scsccsc dace ckseceanssueescesuscvissvesstosurcpacenysoveeasveaseaces 8 9 Trigger model remote Operation 0 0 eee eeeeeeeeeeeeeeeeees 8 9 WANG AN It ALS c0 csccssecainsescasedsuieedecdssboauntgasenseswenacveaseates 8 9 Eyent Cete Ct OM 20s escscee sd ince sendde sei seas iaddetensedpacevaeeesnacbeaiaes 8 11 TAPUL TIS POLS seipsos neiise odanin iaaea 8 11 Delay and pulse phases s esssseseeseeessessesssreerrsrsresrsressesreses 8 12 Delay ph se siioni a e R eta 8 12 P lse phase seoor ne lied OR EES 8 12 Filtering cemere en T E O O voles 8 12 SWEEP POIS cairos rrien E EA i 8 12 COUNT EEE E E E T ST 8 12 Output tH ger siiin eiin eaae a a E OE S 8 13 GPIB defaults snrciers eissir ane E 8 13 Operation SUMMATY s sssssesssesseeseesseesetseessetssesstssresseseresesens 8 13 Remote trigger commands sesssessssessesssrrstrsrsreseeresreserees 8 13 Remote trigger example sssessesessessssesresesrrsresrsresreresresenes 8 14 Digital I O Port Interlocks and Puls
14. B8 B7 B6 B5 B4 B3 B2 B1 Bo Measurement Event Register To Measurement Summary Bit OSB of Status Byte Register Figure 11 3 stat meas enab lt NRF gt stat meas enab SWA RAV M30 M20 M10 INT 615614 e13e1261 B10 B7 B6 B5 B4 B3 B2 B1 BO Measurement Event Enable S1C Laser Source in Compliance M20 MSR 2 Overflow Register OT Over Temperature M10 MSR 1 Overflow SWD Sweep Done INT Hardware Interlock SWA Sweep Aborted amp Logical AND RAV Reading Available OR Logical OR M30 MRS 1 Overflow 11 16 Status Structure Model 2520 User s Manual Questionable event register The used bits of the Questionable Event Register shown in Figure 11 7 are described as follows Bits BO through B7 Not used Bit B8 Calibration Summary Cal Set bit indicates that an invalid calibration constant was detected during the power up sequence This error will clear after successful calibration of the instrument Bits B9 through B13 Not used Bit B14 Command Warning Warn Set bit indicates that a Signal Oriented Measurement Command parameter has been ignored Bit B15 Not used Figure 11 7 Questionable event status TWarn CAL Questionable q B15 B14 B13 B9 B8 B7 BO Register Questionable stat ques Event Register Warn CAL B15 B14 B13
15. DSP interprets the A D samples over the pulse width in order to determine the pulse level value or a DC average which are then sent back to the user Using the TRACe subsystem it is possible to effectively bypass the DSP calculations and directly query single calibrated samples This feature provides basic 14 bit LOMHz digital storage oscilloscope capabilities You can reconstruct a pulse to deter mine pulse parameters such as settling times overshoot and undershoot NOTE None of the TRACe features are available over front panel TRAC DATA And TRAC DATA VAL will return errors unless SOURI MODE is FIXed TRIG ger COUNT is 1 and a reading has been triggered Read sample buffer DATA TRACe DATA Read raw samples from buffer Description This command returns the raw sample data taken during the latest trig gered reading The number of samples is specified by TRAC DATA POINts The sample elements returned are specified by FORM ELEM TRAC see FORMat subsystem page 14 19 VALue lt NRf gt TRACe DATA VALue lt NRf gt Return specific sample Description This command returns the specified sample after the start of the source current pulse If no parameter is specified it returns the sample that immediately followed the one returned for the previous TRAC DATA VAL query If no TRAC DATA VAL query was sent after the last INIT command it returns the first sample after start of pulse The sample elements returned are
16. Dewai Madian Beijing 100029 e 8610 8225 1886 Fax 8610 8225 1892 Tietajantie 2 e 02130 Espoo Phone 09 54 75 08 10 Fax 09 25 10 51 00 3 all e des Garays 91127 Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 Landsberger Strasse 65 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 Unit 2 Commerce Park Brunel Road Theale Berkshire RG7 4AB 0118 929 7500 Fax 0118 929 7519 1 5 Eagles Street Langford Town Bangalore 560 025 080 212 8027 Fax 080 212 8005 Viale San Gimignano 38 20146 Milano 02 48 39 16 01 Fax 02 48 30 22 74 New Pier Takeshiba North Tower 13F 11 1 Kaigan 1 chome Minato ku Tokyo 105 0022 81 3 5733 7555 Fax 81 3 5733 7556 2FL URI Building 2 14 Yangjae Dong Seocho Gu Seoul 137 888 e 82 2 574 7778 Fax 82 2 574 7838 Postbus 559 4200 AN Gorinchem 0183 635333 Fax 0183 630821 c o Regus Business Centre Frosundaviks All 15 4tr e 169 70 Solna 08 509 04 600 Fax 08 655 26 10 13F 3 No 6 Lane 99 Pu Ding Road Hsinchu Taiwan R O C 886 3 572 9077 Fax 886 3 572 9031 Copyright 2003 Keithley Instruments Inc Printed in the U S A 1 03
17. Manual TLink Stest gt On Off tStest M Stest Another Trigger Trigger i 2 Counter 1 Note Sweep performed only if enabled Filter count Filter e Process determines filter process Repeat repeat cycles Z 10usec Bench Default gt Output Trigger Model 2520 User s Manual Triggering 8 3 Idle layer The Model 2520 is in the Idle Layer when it is not operating in the Trigger Layer of the trigger model The Model 2520 can be returned to idle at any time by selecting the HALT menu item of the CONFIGURE TRIGGER menu See Configuring triggering page 8 7 Input triggers The programmable trigger in events for the Trigger Layer are described as follows IMMEDIATE Event detection occurs immediately allowing operation to continue GPIB Event detection occurs when a bus trigger GET or TRG is received TIMER With the Timer selected event detection occurs immediately when the output is turned ON On repeated passes via Another Trigger Yes event detection occurs when the programmed timer interval expires If operation takes the Another Trigger No route the Timer resets allowing event detection to again occur immediately MANUAL Event detection occurs when the TRIG key is pressed TLINK Event detection occurs when an input trigger via the Trigger Link input line is received see Trigger link page 8 5 for more information LSTEST Event detection occurs
18. Reading an event register clears the bits of that register CLS resets all four event registers The commands to read the event registers are listed in Table 11 6 For details on reading registers see Reading registers page 11 6 Table 11 6 Event register commands Command Description Default ESR Read Standard Event Status Register Note STATus OPERation EVENt Read Operation Event Register STATus MEASurement EVENt Read Measurement Event Register STATus QUEStionable EVENt Read Questionable Event Register Note Power up and CLS resets all bits of all event registers to 0 STATus PRESet has no effect 11 18 Status Structure Model 2520 User s Manual Event enable registers As Figure 11 1 shows each status register set has an enable register Each event register bit is logically ANDed amp to a corresponding enable bit of an enable register Therefore when an event bit is set and the corresponding enable bit is set as programmed by the user the output summary of the register will set to 1 which in turn sets the summary bit of the Status Byte Register The commands to program and read the event enable registers are listed in Table 11 7 For details on programming and reading registers see Programming enable registers page 11 5 and Reading registers page 11 6 NOTE The bits of any enable register can be reset to 0 by sending the 0 parameter value with th
19. Remote display programming The display can also be controlled by various SCPI DISPlay subsystem commands Table 1 2 summarizes the basic command to enable or disable the display See DISPlay subsystem in Section 14 for more information on using this and other display commands Table 1 2 Basic display command Command Description DISPplay ENABle lt state gt Enable disable display state ON or OFF Front panel display tests Use the DISPLAY TESTS selection of the main MENU to test various aspects of the front panel Test selections include e KEYS Front panel keys are tested Pressing a key displays a message that iden tifies that key Pressing EXIT twice cancels this test DISPLAY PATTERNS Use this selection to turn on all display pixels and annunciators Subsequent key presses cycle through tests that turn off annunciators and corner pixels of each digit turn on the rows of the top left display digit and turn on all annunciators and pixels of each digit in a sequential manner Press EXIT to cancel this test e CHAR SET This test displays special characters Press EXIT to cancel the test See Menus page 1 17 for more menu information Default settings By using appropriate menu selections you can save and recall various instrument setups define the power on configuration or restore factory defaults as outlined below Saving and restoring user setups You can save and restore up to fiv
20. Set sweep direction UP or DOWN Settings affected by maximum duty cycle See Section 5 If pulse delay and width are not programmed default values of 1 5ms delay and 500ns width will be used and query will return 0 Custom sweep programming example As an example of custom sweep operation assume a five point sweep with the following sweep parameters NOTE See Appendix H for Current sweep mode list custom sweep Sweep current points 0 2A 0 1A 0 4A 0 3A 0 5A Sweep delay points 7ms 4ms 2ms 8ms lms Sweep width points 10uUs 50us 35s 20us 60us a functional program example Model 2520 User s Manual Sweep Operation 7 11 Table 7 5 summarizes the basic remote command sequence for performing the custom sweep described above Table 7 5 Custom sweep programming example Command Description RST FORM ELEM VOLT1 CURR2 CURR3 SOUR1 CURR MODE LIST SOURI LIST CURR 0 2 0 1 0 4 0 3 0 5 SOUR1 LIST DEL 7e 3 4e 3 2e 3 8e 3 le 3 SOURI LIST WIDT 10e 6 50e 6 35e 6 20e 6 60 6 SOUR2 VOLT 5 SOUR3 VOLT 5 OUTP1 ON READ OUTP1 OFF Restore GPIB default conditions Laser diode voltage detector current data Current list sweep mode Set current sweep points Set pulse delay sweep points Set pulse width sweep points Detector 1 bias 5V Detector 2 bias 5V Turn on source outputs Trigger sweep request data Turn off source outputs 8 Tr
21. Some of the commands are global where a single command affects all three channels For example filter commands affect all three channels simultaneously Other commands are unique to a specific measurement channel For example you can program a unique range setting for each channel The commands for this subsystem are summarized in Table 14 5 14 28 SCPI Command Reference Model 2520 User s Manual Select laser diode voltage measurement range UPPer lt n gt SENSe 1 VOLTage DC RANGe UPPer lt n gt IUPIDOWN Select laser diode voltage range Parameters lt n gt 0 to 10 5 Expected reading in volts DEFault 10 MINimum 0 MAXimum 10 5 UP Select next higher measurement range DOWN Select next lower measurement range Query RANGe Query measurement range RANGe DEFault Query RST default range RANGe MINimum Query lowest range returns 0 RANGe MAXimum Query highest range Description This command is used to select the measurement range for the laser diode voltage measurement The range is selected by specifying the expected reading The instrument will then go to the most sensitive reading that will accommodate that reading For example if you expect a reading of approximately 7V then simply let lt n gt 7 in order to select the 10V range You can also use the UP and DOWN parameters to select range Each time UP or DOWN is sent the next higher or lower measurement range is selected When on the maximum ra
22. Table 14 7 STATus command summary Default Command Description parameter SCPI STATus Note 1 Jv MEASurement Control measurement event registers EVENt Read the event register Note 2 v ENABle lt NDN gt Program the enable register Note 3 v or lt NRf gt ENABle Read the enable register Jv CONDition Read the condition register Jv OPERation Control operation status registers v EVENt Read the event register Note 2 v ENABle lt NDN gt Program the enable register Note 3 Jv or lt NRf gt ENABle Read the enable register Jv CONDition Read the condition register v QUEStionable Control questionable status registers v EVENt Read the event register Note 2 v ENABle lt NDN gt Program the enable register Note 3 Jv or lt NRf gt ENABle Read the enable register Jv CONDition Read the condition register v PRESet Return status registers to default states v QUEue Path to access error queue NEXT Read the most recent error message Note 4 v ENABIe lt list gt Specify error and status messages for error queue Note 5 Jv ENABIe Read the enabled messages v DISable lt list gt Specify messages not to be placed in error queue Note 5 DISable Read the disabled messages CLEar Clears all messages from error queue Notes Commands in this subsystem are not affected by RST and SYSTem PREset The effects of cycling power CLS and STATus PRESet are explained by the fo
23. and MEASure commands perform an INITiate and then a FETCh The INITiate command triggers a new source and measure cycle which puts new data in the reading buffer after processing by the DSP FETCh reads that new processed data See Section 13 for more information on READ and MEASure CALCulate1 DATA 2 CALCulate2 DATA CALCulate3 DATA If CALCulatel CALCulate2 or CALCulate3 is enabled SENS1 SENS2 or SENS3 data is fed to the CALC1 laser diode CALC2 detector 1 or CALC2 detector 2 block where the results for the selected math function are calculated The CALC1 DATA CALC2 DATA or CALC3 DATA command will read the results of the math function CALCulate4 DATA If CALC4 is enabled the DSP subtracts individual A D detector 2 readings from A D detector 1 readings and then determines the pulse value or DC average over the pulse width from this new set of delta values TRACe DATA and TRACe DATA VALue All normal readings returned by FETCh READ MEASure and CALCulateX DATA are derived from samples acquired by a 14 bit A D converter that samples at 1OMHz rate An internal DSP section interprets the A D samples over the pulse width in order to deter mine the pulse level value or a DC average which is stored in the reading buffer and then sent back to the computer when requested by these commands With the TRACe subsystem you can bypass DSP calculations and directly query individ ual raw samples allowing you to rec
24. e Baud rate 9600 e Data bits 8 e Parity none Terminator CR e Flow control none RS 232 settings for baud rate Parity and data bits are accessible only from the front panel while RS 232 is enabled An interface is selected and configured from the COMMUNICATIONS SETUP menu accessed with the COMM key For details on the programmable aspects of the interfaces see Primary address page 10 6 and RS 232 interface operation page 10 16 NOTE When changing interface selections the Model 2520 performs a power on reset To check and or change options of the selected interface you must re enter the COMM menu GPIB operation This section contains information about GPIB standards bus connections and primary address selection GPIB standards The GPIB is the IEEE 488 instrumentation data bus with hardware and programming standards originally adopted by the IEEE Institute of Electrical and Electronic Engineers in 1975 The Model 2520 conforms to these standards TEEE 488 1 1987 e JTEEE 488 2 1992 The above standards define a syntax for sending data to and from instruments how an instrument interprets this data what registers should exist to record the state of the instru ment and a group of common commands The Model 2520 also conforms to this standard e SCPI 1996 0 Standard Commands for Programmable Instruments This standard defines a command language protocol It goes one step farther than TEE
25. e cciedeccicecsicsssdevedesveaduslaveseveveocsceseessess 14 16 Enable and read math function result cceeeeeeeeeeeee 14 16 STATO lt b gt celine ele de edhe aah deel 14 16 DATA nereta R 14 17 LATEST Lonironisnnino e a celeste 14 17 DISPlay subsystem oo eee eeeeseeseceseeseeeseceeeeaeceeeeaeseeeeaes 14 17 Control display cceesesseceeseceseeeeeeesseeceeeeeeeceaeeesaeeeaeens 14 17 ENABIE KDS ticescheveteeiettbecserescanaidcasessestenivedouetiedeaas 14 17 ATTRIDUTES hoses opienie aaa 14 18 Read display scscscsscs teesscueccerssstaesisgaienietaidsteasidbiearoeetacteaes 14 18 DATA V verer asr e A a 14 18 Define TEXT messages ssosesesssesseesssresssssresresressreeres 14 18 DATA lt a gt iyi e aaia 14 18 STATE SDS caerra oeeaaeaii eaea RAER OAE 14 19 FORMat subsystem 0 ee eeeeseeseeseeseceseeseeeaeceeeeaeeneeeseeeneeaes 14 19 Data format ccc cecesy ci nea ide tiesto 14 19 DATA lt type gt length oes eeeeeseeeeeeees 14 19 Data Clements oc ccss daceecsescaiessceseesesen ceded ssbesut teas expeaomnatoates 14 22 ELEMents lt item list oo eeeeseeseeeeeeeeseeceneeeneees 14 22 Calculate data elements 0 0 0 0 ceeeesceeseeeeseeeeeeeeneeeseeeeeees 14 23 CAL Culate lt item list oo eeeeeeeesreeeneeeeteeeneees 14 23 TRACe data elements 0 eeeeseeseceeneceseeeeeeeenreeeeeeeneees 14 24 TRACe lt item list sieriem in 14 24 SOURce4 lt name gt oo eeeeeeseceeeseeeseeseeeaeeeeeeaeees 14 25 Ble sOt detec ce 325
26. eee esse eseeeseeseeeseeseeeaeeeeeeaeeeaeeeeeeseeaes 10 10 Command Words 0 0 eeeeeseeseeseesseeseceseeseeeceeaceeaeeeseneeaes 10 10 Commands and command parameters s s s 10 10 Query Commands 00 ee eeeeseeseeeeeeeceeeeseeeseeseeeaeeeeeeeaes 10 12 Case sensitivity iiscecs cessenesecinectes vsstesseuesasnedeevasaseervecoas 10 12 Long form and short form versions s s s 10 12 Short form rules wo ceeecccccccccceseceeeseeeeseesesssssssscnsseeeenees 10 13 11 Program MESSAGES 0 0 cece eeeeseeeeeeeeeeseeseeeaeeseesateeeeeeees 10 13 Single command messages eseeeeseeseeseeeeeeeee 10 13 Multiple command messages n se 10 14 Command path rules eee ee eeeeeeeeeseseeeeeeeeeeaees 10 14 Using common and SCPI commands in the same TNESSASE seco E E vhs idensnscepseeesvicendeestuetes 10 15 Program message terminator PMT eseese 10 15 Command execution rules eeeeeeeeeereeseeaees 10 15 Response MESSAMES 0 0 ee eeeeeeeseeeeeeeeeeeeeseeeseeseeeateateeeeees 10 15 Sending a response message eee eee eeeeseeeeeeeeees 10 15 Multiple response Messages ee eeeeeeeeseeeeeeees 10 15 Response message terminator RMT 0 10 16 Message exchange protocol 0 ee eeeeseeseeseceeeeseeeseeees 10 16 RS 232 interface Operation ee eeeesecseeeseeeeeeeeeeeeseeeeeeees 10 16 Sending and receiving data ole eeeeseeeeeteeeeeenees 10 16 Baud rat sses esiseina re an Eeti E 10 16 Data bits and parity 0 cee eecesscecenecese
27. specification C RANGE LOAD MODE OVERSHOOT TIME PULSE ON TIME 500ns to Sms 100ns programming resolution TYPICAL MAX PULSE OFF TIME 20s to 500ms 10us programming resolution 500mA 10Q Watt Fast 1 0 SSi 80 ns PULSE DUTY CYCLE 21 0 to 99 6 for lt 1 0A AA C D EE ae TE TS 0 to 4 for gt 1 0A 3 VOLTAGE COMPLIANCE 3V to 10V 10mV programming resolution 5 00A 1 5Q 1 Watt Fast 1 0 100 ns 130 ns POLARITY 1 quadrant source polarity reversal available through internal 5 00A 1 5Q 1 Watt Slow 0 1 1 ps 1 3 us relay inversion OUTPUT OFF lt 200mQ short across laser diode measured at Remote Test Head connector LASER DIODE VOLTAGE MEASURE SPECIFICATIONS MINIMUM ACURACY RANGE RESOLUTION rdg volts RMS NOISE typical 5 00 V 0 33 mV 0 3 6 5 mV 60 nV 10 00 V 0 66 mV 0 3 8 mV 120 pV TEMPERATURE COEFFICIENT 0 18 C amp 28 50 C 0 15 x accuracy specification C MAX LEAD RESOLUTION 100Q for rated accuracy INPUT IMPEDANCE 2MQ differential 1MQ from each input to common Input bias current 7 5uA max PHOTODIODE VOLTAGE BIAS SOURCE SPECIFICATIONS each channel RANGE 0 to 20VDC PROGRAMMING RESOLUTION 10mV ACCURACY 1 50mV CURRENT 160mA max with V Bias shorted to I Measure RMS NOISE 1kHz to 5MHz 1mV typical PHOTODIODE CURRENT MEASURE SPECIFICATIONS each channel MINIMUM DC INPUT ACURACY RANGE RESOLUTION IMPEDANCE rdg current RMS N
28. through 222 lt NDN gt Non decimal numeric This parameter is used to send values in the bina ry octal or hexadecimal format The prefix designates the format type BXX X B specifies the binary format Xx X is the binary number using Os and 1s QXX X Q specifies the octal format XX X is the octal number values 0 through 7 HXx x H specifies the hexadecimal format Xx X is the hexadecimal number values 0 through 9 and A through F Examples to send the decimal value 36 in the non decimal formats ESE b100100 Binary format ESE q44 Octal format ESE h24 Hexadecimal format Angle brackets lt gt Angle brackets lt gt are used to denote a parameter type Do not include the brackets in the program message For example OUTPutl lt b gt The lt b gt indicates a Boolean type parameter is required Therefore to enable the selected source you must send the command with the ON or 1 parameter as follows OUTPutl ON OUTPut1 1 10 12 Remote Operations Model 2520 User s Manual Query commands This type of command requests queries the presently programmed status It is identified by the question mark 7 at the end of the fundamental form of the command Most com mands have a query form SOURce1 PULSe DELay Queries the pulse delay Most commands that require a numeric parameter lt n gt can also use the DEFault MINi mum and MAXimum parameters for the query form These quer
29. you can also use the MINimum MAXimum and DEFault parameters to manually select the source range The UP parameter selects the next higher source range while DOWN selects the next lower source range Set amplitudes IMMediate AMPLitude lt n gt SOURce 1 CURRent LEVel MMediate AMPLitude lt n gt Set fixed current source amplitude Parameters lt n gt 0 to 5 0 Set source amplitude amps DEFault OA MINimum OA MAXimum 5 0A Query CURRent Query programmed source amplitude CURRent DEFault Query RST default amplitude CURRent MINimum Query lowest allowable amplitude CURRent MAXimum Query highest allowable amplitude Description This command is used to immediately update the amplitude of a fixed source for both DC and pulse functions with the pulse function the amplitude is the high pulse level This command is not valid if the list or sweep mode is selected NOTE The sourcing MODE command is used to select a fixed source See Select sourcing mode page 14 32 The specified amplitude cannot exceed the selected source range For example if the source is on the 500mA range you will not be able to set the source amplitude to 1A NOTE For the DC function the current cannot be set above 1A LOW lt n gt SOURce 1 CURRent LEVel LOW lt n gt Set current pulse low amplitude Parameters lt n gt 0 to 0 150 Set pulse low amplitude amps DEFault 0A MINimum 0A MAXimum 0 150A Model 2520 User
30. 0 1 Source 100mA TRIG SOUR BUS Select bus trigger input source TRG command TRIG OUTP TRIG Enable output trigger TRIG OLIN 1 Trigger link output line 1 OUTP1 ON Turn on source output INIT Take unit out of idle TRG Trigger reading OUTP1 OFF Turn off source output FETC Request readings 9 Digital I O Port Interlocks and Pulse Sync Output Digital I O Port Discusses the various input output lines on the Digital I O Port as well as the 5V line that can be used to power external logic circuits Interlocks Describes how to use to determine the status of the interlocks Pulse sync output Describes the pulse sync output pulse that can be used to synchronize external equipment to current source pulses 9 2 Digital I O Port Interlocks and Pulse Sync Output Model 2520 User s Manual Digital I O port The Model 2520 has a digital input output port that can be used to control external digital circuitry Port configuration The Digital I O Port is located on the rear panel and is shown in Figure 9 1 Note that a standard male DB 9 connector is used for the Digital I O port Figure 9 1 Digital I O port 1 Digital Output 1 2 Digital Output 2 3 Digital Output 3 4 Digital Output 4 1 5 5 Ground 6 SOT Start of Test Input 0000 o 7 5V 8 Not Connected J D 9 Ground WARNING No INTERNAL OPERATOR SERVICABLE PARTS f ICE BY QUALIFIE
31. 1 DATA LATest 13 3 SENSe2 DATA LATest 13 3 SENSe3 DATA LATest 13 3 FETCh 13 2 MEASure 13 3 READ 13 3 Sink operation 9 3 Software requirements H 2 Source Capacitance F 18 Configuration 3 9 Control outputs on off 14 32 Editing values 3 9 Select function 14 33 Select mode 14 32 Select polarity 14 35 Select range 14 33 Set amplitudes 14 34 14 47 Set pulse times 14 36 Source memory Sweep configuration 7 5 Source operation 9 4 SOURce subsystem 14 32 Source values Setting photodiode detector 3 11 Source measure cycle Abort 14 58 Initiate 14 57 Source measure Concepts 5 1 SPE SPD serial polling 10 8 11 9 Specifications and accessories A 1 Speed Increasing laser diode pulse measurement F 11 Staircase sweeps 5 8 Mode front panel pulse parameters 5 4 Mode remote pulse parameters 5 6 Start of test SOT line 9 3 Status and error messages 1 13 B 1 Status byte and SRQ 11 2 11 7 Commands 11 10 Status register format 14 26 Status register sets 11 2 11 11 Status structure 11 1 STATus subsystem 14 49 Sweep Averaging filter during 6 5 Configure 14 37 Configuring 7 5 Custom 5 8 7 4 Custom sweep commands 7 10 Custom waveform 5 9 Data storage 5 12 Front panel operation 7 5 Linear staircase 7 2 Logarithmic staircase 7 3 Performing 7 6 Points 8 4 8 12 Program examples 14 44 Remote operation 7 8 Staircase 5 8 Staircase commands 7 8 Types 5 8 7 2 Waveforms 5 8 Sweep Operation 7 1 Sweeps Staircas
32. 2 Connect the female end of the supplied power cord to the AC receptacle on the rear panel WARNING The power cord supplied with the Model 2520 contains a separate ground for use with grounded outlets When proper connections are made instrument chassis is connected to power line ground through the ground wire in the power cord Failure to use a grounded outlet may result in personal injury or death due to electric shock 3 Turn on the instrument by pressing the rear panel power switch to the on 1 posi tion Power up sequence On power up the Model 2520 performs self tests on its EPROM and RAM and momen tarily lights all segments and annunciators If a failure is detected the instrument momen tarily displays an error message and the ERR annunciator turns on Error messages are listed in Appendix B NOTE Ifa problem develops while the instrument is under warranty return it to Keithley Instruments Inc for repair If the instrument passes the self tests the firmware revision levels are displayed For example REV A01 A02 A03 where AOI is the main processor ROM revision A02 is the DSP ROM revision A03 is the display board ROM revision 1 12 Getting Started Model 2520 User s Manual The communication interface status is briefly displayed If the IEEE 488 bus is the pres ently selected interface the identification message will include the primary address For example if the primary address is 25 factory default the
33. 2 7 Optimizing laser diode F 2 Pulse sync output 9 9 Remote interlock 2 6 RS 232 10 18 Sense lead F 8 Testhead 2 3 Connectors CURRENT OUTPUT 2 6 DETECTOR 1 9 Digital I O 1 8 GPIB 1 8 Laser diode 1 9 MAINFRAME 1 10 Pulse syne 1 8 RS 232 1 8 Signal 2 5 TESTHEAD 1 8 Triax DETECTOR 2 6 Trigger link 1 8 VOLTAGE SENSE 2 6 Contact information 1 2 Continuous pulse mode I 2 Counter 8 4 8 12 Current pulse output circuit model F 2 Current source Limit lines 5 10 Operating boundaries 5 10 Currents Generated F 18 Offset F 19 Custom sweeps 5 8 7 4 Configure list 14 41 Waveform 5 9 Data elements 14 22 Calculate 14 23 TRACe 14 24 Data flow 5 12 C 1 Data format 14 19 Data lines D 5 Data storage Sweep 5 12 DCL device clear 10 7 Delay Phase 5 3 8 3 8 12 Delay pulse cycle 5 2 8 3 8 12 Delta math function 6 7 Detector current Select measurement range 14 28 Dielectric absorption F 19 Digital I O port 1 8 9 2 Configuration 9 2 Digital output Setting 14 47 Digital output lines 9 2 Configuration 9 3 Controlling 9 4 Display F Basic reading 5 12 Factory default settings 1 15 Control 14 17 Filter 6 4 8 4 8 12 Example 1 13 Averaging 6 4 Format 1 13 Commands 6 6 Front panel tests 1 14 Math function 5 12 Configuration 6 5 Configure and control 14 30 Read 14 18 Control 6 5 Remote programming 1 14 Programming example 6 6 Units 1 13 Remote programming 6 5 DISPlay subsystem 14 17 Fixe
34. 6 4 Filter confi c ration ssssisssres dessinaire 6 5 Filter control ossessi asna 6 5 Remote filter programming ssessesesseesesreresessrerrsrerrsreresresenes 6 5 Filtet command 4 c c c csecvsnescsecesinsesgatieseboeiedaisbeaseteasvases 6 5 Filter programming example sssseeseeeeseeresesrereerrereees 6 6 Measurement math functions seesseseseessereresresesreerrrrerrsreresreseee 6 6 Cond ctance ssrosesssinrcopsi a ensins ie TE ERE 6 7 RESISTANCE fo sccsencssesaisguadstaes argerian eTO A E 6 7 OWED sissies cuiseccsenissessiauastndscnghvouecduiacesanseodeiwesssaix tenveteawen bes 6 7 DE A e A oe cess ycht can A E T 6 7 Delta remote only srespecrscsirsisssrurssisriscersessssscensenrisoiireiie 6 7 Front panel math functions esesseseeseeeeeeeessesrrerssrerrsreresresese 6 8 Math configuration menu sessseseeseeesresrreesrrereseereeresee 6 8 Programming math functions s ssesseeseesseeseseerrsrerrsresese 6 8 Remote math functions 0 eeceeeseceseeseeeseeeeeeeeeeeeaes 6 9 Math function commands sseseseeseeeseeseeeessrerssrerrerese 6 9 Math function programming example ee 6 10 Sweep Operation SWEEP CY PCS i iiccecscrssceecte tacksvsaeeabeeeapaeedeevsdasecdastessedensvodsisvateetsante ees 7 2 Linear staircase sweep sescesceeenecesceeececeseeeeeeeeaeeeeeeeeaeens 7 2 Logarithmic staircase sweep oo eee es eeeeseeeeeeeeeeeeseeneeeaee 7 3 CUSTOM SWEEP oo eeeeecesecsteceseeceaeeeeeeeaeeseeeeaeeeeeseaeeeteee
35. B9 B8 B7 BO To QSB of Status Byte Register Figure 11 3 Questionable stat ques enab lt NRf gt Event Enable stat ques enab Warn CAL B15 B14 B13 B9 B8 B7 BO Register Warn Command Warning Cal Calibration Summary amp Logical AND OR Logical OR Model 2520 User s Manual Status Structure 11 17 Condition registers As Figure 11 1 shows each status register set except the Standard Event Register set has a condition register A condition register is a real time read only register that constantly updates to reflect the present operating conditions of the instrument For example while the Model 2520 is in the idle state bit B10 Idle of the Operation Condition Register will be set When the instrument is taken out of idle bit B10 clears The commands to read the condition registers are listed in Table 11 5 For details on read ing registers see Reading registers page 11 6 Table 11 5 Condition register commands Command Description STATus OPERation CONDition Read Operation Condition Register STATus MEASurement CONDition Read Measurement Condition Register STATus QUEStionable CONDition Read Questionable Condition Register Event registers As Figure 11 1 shows each status register set has an event register When an event occurs the appropriate event register bit sets to 1 The bit remains latched to 1 until the register is reset
36. Bus Overview Model 2520 User s Manual Uniline commands ATN IFC and REN are asserted only by the controller SRQ is asserted by an external device EOI may be asserted either by the controller or other devices depending on the direction of data transfer The following is a description of each command Each command is sent by setting the corresponding bus line true REN Remote Enable REN is sent to set up instruments on the bus for remote opera tion When REN is true devices will be removed from the local mode Depending on device configuration all front panel controls except the LOCAL key if the device is so equipped may be locked out when REN is true Generally REN should be sent before attempting to program instruments over the bus EOI End or Identify EOI is used to positively identify the last byte in a multi byte transfer sequence thus allowing data words of various lengths to be transmitted easily IFC Interface Clear IFC is used to clear the interface and return all devices to the talker and listener idle states ATN Attention The controller sends ATN while transmitting addresses or multiline commands SRQ Service Request SRQ is asserted by a device when it requires service from a controller Universal multiline commands Universal commands are those multiline commands that require no addressing All devices equipped to implement such commands will do so simultaneously when the commands are
37. Configuration D 4 Connections 10 4 Connector 1 8 Defaults 8 13 Front panel operation 10 8 General bus commands 10 6 Operation 10 3 Overview D 1 Standards 10 3 Status indicators 10 9 GPIB 488 1 Protocol G 1 GPIB commands D 7 GPIB description D 2 Ground loops F 20 GTL go to local 10 7 Handshake lines D 5 Hardware requirements H 2 Idle 8 9 Idle layer 8 3 IEEE 488 Bus see GPIB D 1 Connector 10 4 Documentation requirements E 3 Multi unit test system connections 10 4 IFC interface clear 10 7 Indicator lights 1 10 Initiate 8 9 Input triggers 8 3 8 11 Specifications 8 6 Inspection 1 3 Interface function codes D 14 Interlock 1 10 9 5 Connections 2 6 Key 2 7 Operation 9 6 Reading state 9 7 Status 14 27 Status indicator test sequence 9 7 Key interlock 2 7 Keys COMPL 1 6 DETECTOR 1 1 6 DETECTOR 2 1 6 EDIT 1 6 LASER 1 6 LOCAL 10 9 Operation 1 7 RANGE 1 6 Simulate key presses 14 53 Laser diode Configuring measurements 3 12 Configuring source 3 10 Current source 4 4 Current source ranges 3 2 6 3 Front panel test procedure 4 4 Front panel testing 4 3 Impedance matching F 12 Math function 14 15 Measurement function 4 4 Optimizing connections F 2 Polarity 3 6 Remote testing 4 5 Select laser diode voltage measurement range 14 28 Source and measure capabilities 3 2 Source compliance 3 3 Test circuit configuration 4 3 Test commands 4 5 Test connections 2 7 Testing 4 1 Voltage measurement ranges 3 3 Vol
38. FOR CONTINUED PROTECTION AGAINST FIRE HAZARD REPLACE FUSE WITH SAME TYPE AND RATING Model 2520 Instrument Sync Input 10 Remote Operations Differences remote vs local operation Summarizes remote operation enhancements and local to remote and remote to local transitions Selecting an interface Describes how to select between the GPIB and RS 232 interfaces GPIB operation Covers GPIB bus standards bus connections and primary address selection General bus commands Describes general bus commands used for fundamen tal GPIB control Front panel GPIB operation Summarizes GPIB error messages status indica tors and using the LOCAL key Programming syntax Describes the basic programming syntax for both com mon and SCPI commands RS 232 interface operation Outlines use of the RS 232 interface to control the Model 2520 via remote 10 2 Remote Operations Model 2520 User s Manual Differences remote vs local operation Local to remote transition When changing from local to remote operation the following takes place The Model 2520 stops taking readings and is placed into the Idle layer of the Trig ger Model All menus are exited All pending front panel commands are aborted The reading buffer is cleared i e FETCh CALC1 DATA CALC3 DATA CALC3 DATA and CALC4 DATA will not return any data until the Model 2520 takes readings while in remote All other settings remai
39. GPIB defaults as desired then press ENTER to complete the process 1 16 Getting Started Model 2520 User s Manual Table 1 3 Factory default settings Setting BENCH default GPIB default Digital output Level 15 15 Filter State Disabled Disabled Average count 10 10 GPIB address No effect No effect Math function V format Resistance Resistance M factor gain 1 1 B factor slope 0 0 V units X X Ipp units W W State Disabled Disabled Numbers No effect No effect Output Off Off Power on default No effect No effect Polarity Measure V1 Positive Positive Source l1 Vg Positive Positive Range measure VL 10V 10V Ipp 100mA 100mA RS 232 No effect No effect Sources I mode Fixed Fixed I function Pulse Pulse I range 500mA 500mA I amplitude 0A OA I low amplitude 0A 0A I pulse width 10us 10us I pulse delay 0 1ms 0 1ms I compliance 10V 10V Vp amplitude OV OV Model 2520 User s Manual Getting Started Table 1 3 continued Factory default settings Setting BENCH default GPIB default Sweeps I only Type None None Direction Up Up Sweep points 1000 1000 Start OA OA Stop 0A 0A Step OA 0A Center 0A OA Span OA OA Triggering Trigger input Event Immediate Immediate Timer 0 1 0 1 Input line 1 1 Trigger output Event Off Off Output line 2 2 Count 1 1 Init Off Off Remote setups Menus You can also save and recall setups via remote using the fol
40. GROUP RQS REQUEST SERVICE SRQ SERIAL POLL REQUEST STB STATUS BYTE EOI END D 14 IEEE 488 Bus Overview Model 2520 User s Manual Interface function codes The interface function codes which are part of the IEEE 488 standards define an instru ment s ability to support various interface functions and should not be confused with pro gramming commands found elsewhere in this manual The interface function codes for the Model 2520 are listed in Table D 6 The codes define Model 2520 capabilities as follows Table D 6 Model 2520 interface function codes Code Interface function SH1 Source Handshake capability AHI Acceptor Handshake capability T5 Talker basic talker serial poll unaddressed to talk on LAG L4 Listener basic listener unaddressed to listen on TAG SR1 Service Request capability RL1 Remote Local capability PPO No Parallel Poll capability DC1 Device Clear capability DT1 Device Trigger capability CO No Controller capability El Open collector bus drivers TEO No Extended Talker capability LEO No Extended Listener capability SH Source Handshake Function SH1 defines the ability of the instrument to initiate the transfer of message data over the data bus AH Acceptor Handshake Function AH1 defines the ability of the instrument to guarantee proper reception of message data transmitted over the data bus T Talker Function The ability of the instrumen
41. IEEE ADDRESS WITH FRONT PANEL MENU z DIGITAL 1 0 We RS 232 LINE FUSE SLOWBLOW 100 240VAC 50 60Hz 140VA MAX s CAUTION FOR CONTINUED PROTECTION AGAINST FIRE HAZARD REPLACE FUSE WITH SAME TYPE AND RATING TESTHEAD connectors TESTHEAD CONN 1 TESTHEAD CONN 2 Pulse sync connector PULSE SYNC OUT Trigger link connector TRIGGER LINK Digital input output port DIGITAL I O RS 232 connector RS 232 GPIB connector IEEE 488 Power module Contains the AC line receptacle Connects to testhead MAINFRAME CONN1 connector Connects to testhead MAINFRAME CONN2 connector BNC connector provides TTL compatible pulses synchronized with laser diode current source pulses 8 pin micro DIN connector for sending and receiving trigger pulses Use a trigger link cable or adapter such as Models 8501 1 8501 2 8502 8504 Male DB 9 connector for digital output lines output enable line and start of test signal Connector for RS 232 remote operation Use a straight through not null modem DB 9 cable such as a Keithley Model 7009 5 Connector for GPIB remote operation Use a shielded cable Keithley Model 7007 1 or 7007 2 power on off switch and the power line fuse Model 2520 User s Manual Getting Started 1 9 Testhead front and rear panel familiarization Front panel summary The front panel of the Model 2520 testhead is shown in Figure 1 3 Figure 1 3 Testhead fro
42. Model 2520 User s Manual Front panel math functions Math configuration menu Table 6 8 summarizes the math configuration menu Press CONFIG then MATH to access the menu Table 6 8 Math configuration menu Configuration menu item Description CONFIGURE MATH CHANNEL 1 Program V laser diode voltage math function V V Select conductance function I V_ V I Select resistance function V I MX B_UNIT Select MX B function program M B and units PF Select power function V x I CHANNEL2 Program photodiode detector 1 MX B M B and units CHANNEL3 Program photodiode detector 2 MX B M B and units Programming math functions Follow these steps to program math functions Press CONFIG then MATH to access the math configuration menu Select the CHANNEL to be configured then press ENTER For CHANNEL only select the math function When programming the MX B function for all three channels enter the M and B values and the units at the successive prompts and press ENTER after each entry fa Model 2520 User s Manual Range Filter and Math 6 9 Remote math functions Math function commands Table 6 9 summarizes commands to control the measurement math functions by remote See Calculate subsystems page 14 14 for detailed information Table 6 9 Math function commands Command Description CALCulate 1 DATA Request laser diode math reading CALCulate 1 FORMat lt function gt
43. OUTPUT 25 SOUR1 CURR STEP 10e 3 10mA step current PRINT 1 OUTPUT 25 SOUR1 CURR MODE SWE Staircase sweep mode PRINT 1 OUTPUT 25 SOUR1 SWE SPAC LIN Linear sweep PRINT 1 OUTPUT 25 SOUR2 VOLT 5 Detector 1 bias 5V PRINT 1 OUTPUT 25 SOUR3 VOLT 5 Detector 2 bias 5V PRINT 1 OUTPUT 25 OUTP1 ON Turn on outputs CLS PRINT 1 OUTPUT 25 READ Trigger sweep and read data PRINT 1 ENTER 25 Address 2520 to talk LINE INPUT 2 R Input sweep data PRINT Linear staircase sweep data R PRINT 1 OUTPUT 25 OUTP1 OFF Turn off outputs END Model 2520 User s Manual List sweep program Example Programs H 5 The program listing below performs a list custom sweep as covered in Section 7 This program sets up the following operating modes e Source mode list sweep e Source current range 5 00mA Current list points 200mA 100mA 400mA 300mA 500mA e Pulse delay points 7ms 4ms 2ms 8ms Ims e Pulse width points 10us 50us 35us 20us 60us e Detector bias voltages 5V 1 1 2520 primary address 25 OPEN IEEE FOR OUTPUT AS 1 OPEN IEEE FOR INPUT AS 2 PRINT 1 INTERM CRLF PRINT 1 OUTTERM LF PRINT 1 REMOTE 25 PRINT 1 OUTPUT 25 RST PRINT 1 OUTPUT 25 PRINT 1 OUTPUT 25 SOUR1 CURR PRINT 1 OUTPUT 25 SOUR1 LIST PRINT 1 OUTPUT 25 SOUR1 LIST PRIN
44. Operation Event Register shown in Figure 11 5 are described as fol lows Bit BO Calibrating Cal Set bit indicates that the Model 2520 is calibrating Bits B1 through B4 Not used Bit B5 Waiting for Trigger Event Trig Set bit indicates that the Model 2520 is in the trigger layer waiting for a TLINK trigger event to occur Bits B6 through B9 Not used e Bit B10 Idle State Idle Set bit indicates the Model 2520 is in the idle state Bits B11 through B15 Not used Figure 11 5 Operation event status Operation r a 2 alae operands Condition Register Idle Trig Cal B15 B11 B10 B9 B6 B5 B4 B1 BO Idle Trig Cal B15 B11 B10 B9 B6 B5 B4 B1 Bo Operation Stat oper f P Event Register To Operation Summary Bit OSB of Status Byte Register Figure 11 3 Operation Event Enable Register stat oper enab lt NRf gt stat oper enab Idle _ Trig Cal B15 B11 B10 B9 B6 B5 B4 B1 Bo Idle In Idle State Trg Waiting for Trigger Event Cal Calibrating amp Logical AND OR Logical OR 11 14 Status Structure Model 2520 User s Manual Measurement event register The used bits of the Measurement Event Register shown in Figure 11 6 are described as follows Bit BO Not used Bit B1 HW Interlock INT Set bit indicates that the hardware interlock line on the testh
45. Press the DIG OUT key 2 Using the EDIT keys set the digital output parameter to the desired decimal value Table 9 1 For example to set the output lines to L H H H set the digital output parameter value to 7 3 Press EXIT to return to normal display Model 2520 User s Manual Digital I O Port Interlocks and Pulse Sync Output 9 5 Remote digital output control Use the SOURce4 TTL lt NRf gt command to control the digital output line logic levels where lt NRf gt is the decimal value shown in Table 9 1 For example send the following command to set the output lines to L H L H SOUR4 TTL 5 Table 9 1 Digital output line settings Decimal OUT 4 OUT3 OUT2 OUT1 value L L L L 0 L L L H 1 L L H L 2 L L H H 3 L H L L 4 L H L H 5 L H H L 6 L H H H 7 H L L L 8 H L L H 9 H L H L 10 H L H H 11 H H L L 12 H H L H 13 H H H L 14 H H H H 15 L Low Gnd H High gt 3V Interlocks The Model 2520 testhead is equipped with two interlock protection devices The REMOTE INTERLOCK connector is a DB 9 connector intended for such applications as a remote interlock switch while the KEY INTERLOCK connector is intended for connec tions for a security key switch NOTE Both interlocks must be enabled for operation Otherwise the source outputs will not turn on See Section 2 for detailed interlock connection information 9 6 Digital I O Port Interlocks and Pulse Sync Output Mode
46. SEQuence 1 SOURce lt name gt Specify trigger event control source Parameters lt name gt IMMediate Pass operation through immediately TLINk Select Trigger Link trigger as event TIMer Select timer as event MANual Select manual event BUS Select bus trigger as event NSTest Select low SOT pulse as event PSTest Select high SOT pulse as event BSTest Select high or low SOT pulse as event Model 2520 User s Manual Query Description TiMer lt n gt SCPI Command Reference 14 59 SOURce Query programmed control source This command is used to select the event control source With IMMedi ate selected operation immediately continues A specific event can be used to control operation With TLINK selected operation continues when a trigger pulse is received via the Trigger Link With TIMer selected the event occurs at the beginning of the timer interval and every time it times out For example if the timer is pro grammed for a 30 second interval the first pass through the control source occurs immediately Subsequent trigger events will then occur every 30 seconds The interval for the timer is set using the TIMer com mand With MANual selected the event occurs when the TRIG key is pressed With BUS selected the event occurs when a GET or TRG command is sent over the bus With NSTest selected the event occurs when the SOT start of test low pulse is received via the Digital I O port SOT line With PSTest selected th
47. STATus subsystem page 14 49 for more informa tion Model 2520 User s Manual SCPI Command Reference 14 27 OUTPut subsystem This subsystem is used to control the three source outputs and query the state of the inter lock These commands are summarized in Table 14 4 Turn sources on or off STATe lt b gt OUTPut 1 STATe lt b gt Turn all three sources on or off Parameters lt b gt 0 or OFF Turn sources off standby 1 or ON Turn sources on operate Query OUTPut 1 Query state of sources Description This command is used to turn all three source outputs on or off simulta neously Turning the sources off places the Model 2520 in the idle state NOTE The SOURce 1 CLEar command will also turn the sources off Interlock status TRIPped OUTPut 1 INTerlock TRIPped Description This query command is used to determine if the two interlocks have been tripped The tripped condition 1 means that the sources can be turned on interlock line at logic low level A 0 will be returned if the sources cannot be turned on interlock line at logic high level See Section 2 and Section 9 for details on the interlocks SENSe subsystem The SENSe subsystem is used to configure and control the measurement channels of the Model 2520 SENSe 1 controls the laser diode voltage measurement channel SENSe2 controls the detector 1 measurement channel and SENSe3 controls the detector 2 mea surement channel
48. Set laser diode math function MXB 1 CONDuctance 1 POWER 1 or RESistance 1 CALCulate 1 KMATh MBFactor lt B gt Set laser diode MX B offset B value CALCulate 1 KMATh MMFactor lt M gt Set laser diode MX B slope M value CALCulate 1 KMATh MUNits lt units gt Set 1 character MX B units suffix CALCulate 1 STATe lt state gt Enable enable laser diode math ON or OFF CALCulate2 DATA Request detector 1 math reading CALCulate2 KMATh MBFactor lt B gt Set detector 1 MX B offset B CALCulate2 KMATh MMFactor lt M gt Detector 1 MX B slope M CALCulate2 KMATh MUNits lt units gt Set 1 character MX B units suffix CALCulate2 STATe lt state gt Enable enable detector 1 math ON or OFF CALCulate3 DATA Request detector 2 math reading CALCulate3 K MATh MBFactor lt B gt Set detector 2 MX B offset B CALCulate3 K MATh MMFactor lt M gt Detector 2 MX B slope M CALCulate3 KMATh MUNits lt units gt Set 1 character MX B units suffix CALCulate3 STATe lt state gt Enable enable detector 2 math ON or OFF CALCulate4 DATA Request delta detector 1 current detector 2 current CALCulate4 STATe lt state gt Enable disable delta ON or OFF INIT Trigger CALC readings must use before sending CALCn DATA 6 10 Range Filter and Math Model 2520 User s Manual Math function programming example Table 6 10 summarizes command
49. Standard Event 4 202 Settings lost due to rtl EE Standard Event 4 201 Invalid while in local EE Standard Event 4 200 Execution error EE Standard Event 4 B 4 Status and Error Messages Model 2520 User s Manual Table B 1 continued Status and error messages Number Error message Event Status register Bit 178 Expression data not allowed EE Standard Event 5 171 Invalid expression EE Standard Event 5 170 Expression error EE Standard Event 5 168 Block data not allowed EE Standard Event 5 161 Invalid block data EE Standard Event 5 160 Block data error EE Standard Event 5 158 String data not allowed EE Standard Event 5 154 String too long EE Standard Event 5 151 Invalid string data EE Standard Event 5 150 String data error EE Standard Event 5 148 Character data not allowed EE Standard Event 5 144 Character data too long EE Standard Event 5 141 Invalid character data EE Standard Event 5 140 Character data error EE Standard Event 5 128 Numeric data not allowed EE Standard Event 5 124 Too many digits EE Standard Event 5 123 Exponent too large EE Standard Event 5 121 Invalid character in number EE Standard Event 5 120 Numeric data error EE Standard Event 5 114 Header suffix out of range EE Standard Event 5 113 Undefined header EE Standard Event 5 112 Program mnemonic too long EE Standard Event 5 111 Header separator error EE Standard Event 5 110 Command header error EE Standard Event 5 10
50. T sp cton sinsarirri eei peeraa EER 1 3 Options and accessories esseeesseesesesresererstrsreresssrerrsreresrs 1 3 Signal cables and adapters eseeeseeeeeseeeerererrsrerrerese 1 3 Interface cables snini toar 1 4 Rack mount Kits oo ceeeeeceeceseceeeeseseeeeaesneeeaeeeees 1 4 Product OVEFVIEW lt iccs secs csurentensenibecedcssesseecttesnsasotessaesconeosdvesesneses 1 5 Mainframe front and rear panel familiarization 0 0 00 1 6 Front panel summary ec eeceesceseeeseeeseeeeeceneeeeaeeeneeeeaees 1 6 Rear panel summary eee eeeeeeseeeseeeeteeeseeeeseceeeseaeeeseeeeaees 1 7 Testhead front and rear panel familiarization 0 0 0 eee 1 9 Front panel summary 2 00 0 eeceeseeeteeeseeeseeeeaeeeneeeeaeeeseeeeaees 1 9 Rear panel summary 2 0 eeeceeseceseeeeeecesceeeaeeeaeeeeneeeaeeees 1 10 POWE erasoka eraot ereere aaeei Sa eo EE ERa 1 11 TAME VOMAGS scsi ciss aca cecsstcetdes euno ro iea e EE AA e 1 11 Line power connection eeeeeseeeeeeseeeeeeeeeseteeeeeeeeeeeaes 1 11 Powerup SEQUENCE oo ee eeseeseeeeeseeeseeeeeaeeceeaeseeeeaeeeaes 1 11 System identification 20 0 ceeeesecceseeeseeceneesseeceeeeseeesneeeeees 1 12 Fuse replacement 00 eceeeesceeeseceseeeeeeeenceeeneceaeeseaeeeseeeeas 1 12 Display sarpe desinere a N a EE 1 13 Display format fevss isdseezestassecaccassseisesrisdescense anere 1 13 Display example csccisissccassssenssscteaseseusscsasenvenvepesecnines 1 13 Display Units csvcess cke
51. Use the EDIT or w or RANGE A or w keys to increment or decrement the digit e Use the number keys 0 through 9 to key in the value at the selected digit e Use the key to change source value polarity regardless of cursor position Boolean selections such as ON OFF and HIGH LOW are toggled by placing the cursor on the selection and pressing an EDIT A or w or RANGE A or y key e Achange is only executed when ENTER is pressed Entering an invalid parameter generates an error and the entry is ignored However entering an out of range value too small or too large selects the lower or upper limit respectively The EXIT key is used to back out of the menu structure Any change that is not entered is cancelled when EXIT is pressed Main operation menus The main operation menus described in Table 1 5 are accessed by pressing one of these main operation keys e COMM Selects GPIB or RS 232 interface programs interface parameters e SETUP Saves and recalls user and factory configurations e DIG OUT Sets Digital I O port binary output value 1 20 Getting Started Table 1 5 Model 2520 User s Manual COMM SETUP and DIG OUT menus Menu item Description COMM COMMUNICATIONS SETUP2 GPIB ADDRESS GPIB PROTOCOL 488 1 SCPI RS 232 BAUD BITS PARITY TERMINATOR FLOW CTRL SETUP SAVESETUP MENU SAVE RESTORE POWERON BENCH GPIB USER SETUP NUMBER RESET BENCH GPIB DIG OUT DIG
52. VOLTage POLarity lt name gt Set laser diode measurement polarity SENSe2 CURRent POLarity lt name gt Set detector 1 measurement polarity SENSe3 CURRent POLarity lt name gt Set detector 2 measurement polarity Parameters lt name gt POSitive Positive polarity NEGative Negative polarity Query POLarity Query measurement polarity Description These commands are used to select the measurement polarity for laser diode voltage measurements and detector current measurements POSitive selects normal polarity while NEGative selects reversed polar ity See Section 3 Configuring measurements for more information on polarity Query voltage limit TRIPped SENSe 1 VOLTage PROT TRIPped Query if voltage limit reached Query TRIPped Query if voltage limit reached Description This query command is used to determine if the laser diode voltage measurement compliance limit has been reached A returned value of 1 indicates that the voltage limit has been reached see PROTection LEVel lt NRf gt page 14 35 A returned value of 0 indi cates that the limit has not been reached 14 30 SCPI Command Reference Model 2520 User s Manual Query latest readings LATest SENSe 1 DATA LATest Query laser diode voltage reading SENSe2 DATA LATest 2 Query detector 1 current reading SENSe3 DATA LATest 2 Query detector 3 current reading Query DATA LATest Query latest reading Description These queries request the lat
53. Voltage Each Model 2520 photodiode bias source can output DC volt age from 0 to 20V 3 4 Basic Operation Model 2520 User s Manual Photodiode source and measure ranges Table 3 3 summarizes photodiode current measurement ranges resolutions and maxi mum readings Note that each photodiode voltage bias source has a single 20V range See Section 6 for more details on ranging Table 3 3 Photodiode current measurement ranges Current Maximum Maximum range resolution reading 10mA 0 7uA 10 5mA 20mA 1 4uA 21mA 50mA 3 4uA 52 5mA 100mA 6 8uA 105mA Model 2520 User s Manual Basic Operation 3 5 Basic circuit configuration The fundamental circuit configuration for Model 2520 is shown in Figure 3 1 See Figure 2 6 for a more detailed equivalent circuit In addition to the laser diode current source and voltage measurement circuits the unit has two separate photodiode channels each of which includes a feedback ammeter and a 0 20V voltage bias source Figure 3 1 Basic circuit configuration Optional Earth Ground Source Current Measure Voltage Source Voltage Measure Current y Detector 1 4 Detector 2 Source Voltage Measure Current Model 2520 3 6 Basic Operation Model 2520 User s Manual Polarity Polarity for the laser diode current source both detector current measurements and laser diode voltage measurement can be controlled by using
54. a message is placed in the Error Queue the Error Available EAV bit in the Status Byte Register is set An error status message is cleared from the Error Queue when it is read The Error Queue is considered cleared when it is empty An empty Error Queue clears the EAV bit in the Status Byte Register The Error Queue holds up to 10 error status messages The commands to read the Error Queue are listed in Table 11 9 When you read a single message in the Error Queue the oldest message is read and then removed from the queue If the queue becomes full the message 350 Queue Overflow will occupy the last memory location On power up the Error Queue is empty When empty the message 0 No Error is placed in the queue Messages in the Error Queue are preceded by a code number Negative numbers are used for SCPI defined messages and positive numbers are used for Keithley defined messages The messages are listed in Appendix B As shown in Table 11 7 there are com mands to read the entire message code and message or the code only On power up all error messages are enabled and will go into the Error Queue as they occur Status messages are not enabled and will not go into the queue As listed in Table 11 9 there are commands to enable and or disable messages For these commands the lt list gt parameter is used to specify which messages to enable or disable The messages are specified by their codes The following
55. and firmware revision levels of the unit OPC Operation complete command Set the Operation Complete bit in the Standard Event Register after all pending commands have been executed OPC Operation complete query Places an ASCII 1 into the Output Queue when all pending selected device operations have been completed OPT Option query Query Model 2520 for list of installed options RCL lt NRf gt Recall command Returns the Model 2520 to the user saved setup RST Reset command Returns the Model 2520 to the RST default condi tions SAV lt NRf gt Save command Saves the present setup as the user saved setup SRE lt NRf gt Service request enable command _ Programs the Service Request Enable Register SRE Service request enable query Reads the Service Request Enable Register STB Status byte query Reads the Status Byte Register TRG Trigger command Sends a bus trigger to the Model 2520 TST Self test query Performs a checksum test on ROM and returns the result WAI Wait to continue command Wait until all previous commands are executed Status commands are covered in Section 11 Model 2520 User s Manual Common Commands 12 3 Command reference IDN identification query Reads identification code The identification code includes the manufacturer model number serial number and firm ware revision levels and is sent in the following format KEITHLEY INSTRUMENTS INC MODEL 2520 xxx
56. and is enabled when XON XOFF is selected from the RS 232 FLOW CONTROL menu When the input queue of the unit becomes more than 3 4 full the instrument issues an XOFF command The control program should respond to this and stop sending characters until the Model 2520 issues the XON which it will do once its input buffer has dropped below half full The Model 2520 recognizes XON and XOFF sent from the controller An XOFF will cause the instrument to stop outputting characters until it sees an XON Incoming commands are processed after the lt CR gt character is received from the controller 10 18 Remote Operations Model 2520 User s Manual If NONE is the selected flow control there will be no signal handshaking between the controller and the Model 2520 Data will be lost if transmitted before the receiving device is ready RS 232 connections The RS 232 serial port Figure 10 3 is connected to the serial port of a computer using a straight through RS 232 cable terminated with DB 9 connectors such as a Keithley Model 7009 5 Do not use a null modem cable The serial port uses the transmit TXD receive RXD and signal ground GND lines of the RS 232 standard Figure 10 4 shows the rear panel connector for the RS 232 interface and Table 10 2 shows the pinout for the connector If your computer uses a DB 25 connector for the RS 232 interface you will need a cable or adapter with a DB 25 connector on one end and a DB 9 connector on the
57. are not only a safety hazard but will also damage the laser diode under test To enhance impedance matching low impedance cables such as the 15Q coaxial cables supplied with the Model 2520 should be used This cable was designed for fast transient high current response and reduces the mismatch between the laser diode and transmission line Model 2520 User s Manual Measurement Considerations F 13 Model 2520 output circuit model Figure F 11 shows the Model 2520 pulse output circuit model There are several unique features of this pulse circuit The most notable is that the CURRENT OUTPUT HI termi nal provides a path to analog ground while the CURRENT OUTPUT LO terminal sinks the current during the pulse The OUTPUT HI terminal also has a high frequency path to chassis ground While the current flows from the HI to the LO terminal the HI terminal is at ground potential and would be used as the reference ground while connecting an oscil loscope to verify the forward voltage signal across the laser diode under test Figure F 11 Model 2520 output circuit model 10uF Analog Ground Current Output HI Reversing Voltage Clamp 3 10 5V G Y Current Output LO Current Source 0 500mA 0 5A The voltage clamp circuit acts to limit maximum voltage as seen by the output of the pulse circuit Since the clamp circuit is not directly across the laser diode the voltage drop across the transmission line connected between
58. be observed when making test connections to the Model 2520 Testhead preparation Discusses testhead mounting and how to connect the Model 2520 mainframe to the testhead Signal connectors Shows the locations of the signal jacks used for laser diode and photodiode source and measurement and details the terminal configuration of the triax connectors on the testhead Interlock connections Details connections to the remote interlock circuit which is used to inhibit the outputs with external switching Laser diode test connections Provides detailed diagrams for connecting the Model 2520 signal connectors to the laser diode and photodiodes in a laser diode test system 2 2 Connections Model 2520 User s Manual Connection precautions WARNING While the Model 2520 does not incorporate a laser it is designed to operate power laser diode devices Read all safety precautions listed at the beginning of this manual The following safety practices must be used to protect operators and other users of this product from potential exposure to laser radiation Operators must be protected from radiation and electrical hazards at all times The installer must comply with all applicable laws and regulations on laser safety This requirement includes warning signs and opera tor training The interlock is required for safe operation The test fixtures must ensure that the interlock circuit is disabled Source outputs inhib it
59. cir cuit has been optimized to capture the forward voltage drop across the laser diode while minimizing the impact to the laser diode under test Figure F 15 shows the recommended cable connections for pulse sourcing and forward voltage measurement Note that all shields are connected together at the laser diode This scheme provides the minimal impedance mismatch and shortest electrical length for the pulse transmission path Figure F 14 Voltage measurement circuit model Analog to Voltage Digital Sense Converter with Differential Input Voltage Sense LO CLK Figure F 15 Pulse source and forward voltage cable interconnections Current Output HI Current Output LO F 16 Measurement Considerations Model 2520 User s Manual Photodiode current measurement channels Figure F 16 shows the circuit model for the dual photodiode current measurement chan nels Note that the bias circuit provides the bias voltage via the inner shield of the triax cable To minimize measurement error caused by noise and extraneous currents use only low noise triaxial cables See Generated currents page F 18 for more information Figure F 16 Model 2520 photo current measurement channels with dual bias supplies Bias 1 Analog to Convenet _ ne Detector 1 Bias 1 Chassis Ground Analog to IN 2 Digital Detector 2 Converter Bias 2 Model 2520 User s Manual Measurement Considerations F 17 Noise and source impedan
60. eeeeeseeeeeneeeeeeeeeeeeees 10 2 Selecting an interface selasiveerapecnecvesincessesveeiendesseiesensesaasstone coesees 10 2 GPIB Operatio sissaiesssceseissssesesyevecnadeane ianei a E r Aa E EE 10 3 GPIB standard a aicces cis sessctastasceseia ienss et e r a 10 3 GPIB COMMCCHONS 420 55 se ceessesceseisscadessegeseedazenindeuestonsdoasecs 10 4 Primary address 2 cscehsisous cade cesenaus Secess stii e 10 6 General bus commands 0 see eeeeceeeeceeeeseeeeeeeeeeeeaeeeeeeaeeneeeaes 10 6 REN remote enable ccesscessssceeesneeeesneeesseeeesseeeesees 10 7 TFC interface clear ccecssscccssseceesseecesseeessseeeessesessenees 10 7 LLO local lockout cecececcsssececeessssececeeeesssseeeeeeesseees 10 7 GIL go tO OCA ie sescsecis esas detceiteacteveece sienevessesviieressesiaite 10 7 DEL device lear sinnene E 10 7 SDC selective device Clear cccccsccessseeeseseeeesteessseeees 10 8 GET group execute trigger oo eee eeeeeseeeeeeseeeeeenees 10 8 SPE SPD serial polling oo ee eeceeseceneeeneeeeaeeeseeeeees 10 8 Front panel GPIB operation 0 0 0 eee eeeeeeeeseeseeeseeseeeseeeeeeaeees 10 8 Error and status messages cesceeeceeseceseeeseeeeeeeeteeeneeeeee 10 8 GPIB status indicators 0 eee eeeeseeseceeeceeeeeeeeeeseeeeeeaees 10 9 REN aaan E latvinens evtiiete 10 9 E E E E E Perret 10 9 DES TEN E E E E E 10 9 o eO MEE A E 10 9 LOCAL Key scuniocieniniionsiineeinie eee 10 9 Programming SYMtAX oo
61. examples show various forms for using the lt list gt parameter lt list gt 110 Single message 110 222 Range of messages 110 through 222 110 222 220 Range entry and single entry separated by a comma When you enable messages messages not specified in the list are disabled When you dis able messages each listed message is removed from the enabled list NOTE To prevent all messages from entering the Error Queue send the enable com mand along with the null list parameter as follows STATus QUEue ENABle Model 2520 User s Manual Status Structure 11 21 Table 11 9 Error queue commands Command Description Default STATus STATus Subsystem QUEue Read Error Queue Note 1 NEXT Read and clear oldest error status code and message ENABIe lt list gt Specify error and status messages for Error Queue Note 2 ENABle Read the enabled messages DISable lt list gt Specify messages not to be placed in queue Note 2 DISable Read the disabled messages CLEar Clear messages from Error Queue SYSTem SYSTem Subsystem ERRor Read Error Queue Note 1 NEXT Read and clear oldest error status code and message ALL Read and clear all errors status code and message COUNt Read the number of messages in queue CODE Code numbers only NEXT Read and clear oldest error status code only ALL Read and clear all errors status codes only Notes 1 Power up and CLS empti
62. except that they return only the most recent reading for the specified SENSe channel This command is used to trigger and acquire readings The number of readings depends on how the unit is configured If the unit is in the fixed mode this command will trigger and acquire one set of readings How ever if the unit is in the sweep mode this command will trigger the sweep and then acquire all sweep data points When this command is sent the following commands execute in the order they are presented e INITiate e FETCh The INITiate command starts operation by taking the instrument out of idle NOTE READ is illegal when the TRIG SOUR BUS command is in effect See Section 8 Triggering for details After all source and measure operations are completed the Model 2520 goes back into idle at which time the FETCh command is executed The readings are sent to the computer and displayed when the Model 2520 is addressed to talk NOTE The FORM ELEM command controls the reading source See Section 14 FORMat subsystem for details MEASure Description This command performs essentially the same function as the READ command except that it also turns the source outputs on if they were off 14 SCPI Command Reference e Reference tables Summarizes each SCPI command subsystem SCPI subsystems Provides detailed information on all commands in each SCPI subsystem 14 2 SCPI Command Reference
63. expect a root command Since enab is not a root command an error would occur Command path rules Each new program message must begin with the root command unless it is optional e g SENSe 1 If the root is optional simply treat a command word on the next level as the root For fastest operation do not send optional data The colon at the beginning of a program message is optional and need not be used Note that eliminating the first colon will result in fastest operation Example e stat pres stat pres When the path pointer detects a colon it moves down to the next command level An exception is when the path pointer detects a semicolon which is used to sep arate commands within the program message see next rule When the path pointer detects a colon that immediately follows a semicolon it resets to the root level The path pointer can only move down It cannot be moved up a level Executing a command at a higher level requires that you start over at the root command Model 2520 User s Manual Remote Operations 10 15 Using common and SCPI commands in the same message Both common commands and SCPI commands can be used in the same message as long as they are separated by semicolons A common command can be executed at any com mand level and will not affect the path pointer Example stat oper enab lt NRf gt ESE lt NRf gt Program message terminator PMT Each program
64. filter programming Filter command Table 6 6 summarizes filter commands See SENSe subsystem page 14 27 for more details 6 6 Range Filter and Math Model 2520 User s Manual NOTE Filter commands are global Changing the setting using the commands for one measurement function affects filtering for the other two functions Table 6 6 Filter commands Commands Description SENSe 1 AVERage COUNt lt count gt Set average filter count 1 to 100 SENSe 1 AVERage STATe lt state gt Enable disable average filter ON or OFF SENSe2 AVERage COUNt lt count gt Set average filter count 1 to 100 SENSe2 AVERage STATe lt state gt Enable disable average filter ON or OFF SENSe3 AVERage COUNt lt count gt Set average filter count 1 to 100 SENSe3 AVERage STATe lt state gt Enable disable average filter ON or OFF Filter programming example Table 6 7 summarizes the command sequence to program filter aspects as follows e Average filter on e Average filter count 20 Table 6 7 Filter programming example Command Description AVER COUN 20 Set average count to 20 AVER ON Enable average filter Measurement math functions The Model 2520 has built in math functions to calculate the following e Conductance e Resistance e MX B e Power e Delta NOTE Conductance resistance and power are available only for laser diode voltage measurements MX B is available for
65. high the specified output line will be at approximately 5V When set low the output line will be at OV Use the following table to determine the parameter value for the desired decimal digital output pattern Setting bit size Decimal OUT 4 OUT3 OUT2 OUT1 value Le L L L 0 L L L H 1 L L H L 2 L L H H 3 L H L L 4 L H L H 5 L H H L 6 L H H H 7 H L L L 8 H L L H 9 H L H L 10 H L H H 11 H H L L 12 H H L H 13 H H H L 14 H H H H 15 L Low Gnd H High gt 3V BSIZe lt n gt SOURce4 BSIZe lt NRf gt Set Digital I O bit size Parameters lt NRf gt 4 Set 4 bit size 16 Set 16 bit size 2499 DIGIO option Query BSIZe Query Digital I O port bit size Description This command sets the Digital I O bit size to 4 or 16 The 16 bit size is available only with the 2499 DIGIO option connected to the Digital I O port NOTE This command is not affected by RST SYSTem PRESet or RCL Model 2520 User s Manual SCPI Command Reference 14 49 STATus subsystem The STATus subsystem is used to control the status registers of the Model 2520 The com mands in this subsystem are summarized in Table 14 7 NOTE These registers and the overall status structure are fully explained in Section 11 Read event registers EVENt STATus MEASurement EVENt 2 STATus QUEStionable EVENt STATus OPERation EVENt Read Measurement Event Register Read Questionable Event Register Read Operation Event Reg
66. in a location convenient to the test fixture When mounting the testhead be sure to allow sufficient clearance around the heat sink for proper cooling CAUTION _ To prevent damaging heat build up and thus ensure specified perfor mance adhere to the following precautions e Keep the heat sink free of dust dirt and contaminates since its ability to dissipate heat could become impaired e Do not position any devices adjacent to the testhead that force air heated or not into or onto its surfaces or cooling vents This addi tional airflow could compromise accurate performance e Make sure there is adequate airflow around the bottom and sides to ensure proper cooling Adequate airflow enables air tempera tures within approximately one inch of the testhead surfaces to remain within specified limits under all operating conditions Testhead connections CAUTION Turn off the mainframe power before connecting or disconnecting the testhead to the mainframe Figure 2 1 shows connections between the Model 2520 mainframe and the testhead Using the supplied cables make connections as follows e Connect the mainframe TESTHEAD CONN 1 connector to the testhead MAINFRAME CONN 1 connector e Connect the mainframe TESTHEAD CONN 2 connector to the testhead MAINFRAME CONN 2 connector 2 4 Connections Model 2520 User s Manual Figure 2 1 Testhead connections Model 2520 Mainframe WARNING NO INTERNAL OPERATOR SERVICABLE
67. mainframe should be OFF Turn the key in the key interlock to ENABLED At this point the INTERLOCK STATUS indicator should be GREEN and the LASER POWER ON indicator should be OFF on the testhead The OUTPUT ON OFF indicator on the mainframe should be OFF Press the OUTPUT ON OFF switch on the mainframe At this point the INTERLOCK STATUS indicator should be GREEN and the LASER POWER ON indicator should be BLUE on the testhead The OUTPUT ON OFF indicator on the mainframe should be BLUE Turn the key in the key interlock to DISABLED At this point the INTERLOCK STATUS indicator should be BLUE and the LASER POWER ON indicator should be OFF on the testhead The OUTPUT ON OFF indicator on the mainframe should be OFF WARNING Ifat any time the indicators provided on the testhead for INTER LOCK STATUS or LASER POWER ON should fail to light or to properly indicate status immediately contact a Keithley service repre sentative for repair Failure to do so may expose the user to hazards without proper warnings Reading interlock state To read the state of the interlocks send this query via remote OUTP1 INT TRIP The response to this query is either 0 or 1 as follows A returned value of 1 indicates that at least one of the interlocks is tripped circuit open and the outputs cannot be turned on A returned value of 0 indicates neither interlock is tripped circuit closed and the outputs can be turned on 9 8 Digital I O P
68. number of raw voltage and current samples 4 After the pulse the raw samples are processed by a DSP Digital Signal Processor into one set of laser diode voltage and detector current readings 5 Repeat the cycle Figure 5 1 Delay pulse cycle Trigger h Delay Pulse 10MHz A D Conversions Model 2520 User s Manual Source Measure Concepts 5 3 Delay phase The programmable delay specifies the minimum time between two pulses pulse off time in a sweep Note that data processing is part of the delay phase Figure 5 1 The time needed for data processing is directly related to the length of the pulse phase As the pulse width becomes large relative to the pulse delay the actual time between pulses will depend more on the processing time rather than the programmable delay period The delay time for the sweep and fixed mode is defined as follows For the list and sweep modes the actual delay time is the same as the programmed delay period For the fixed mode the total delay is the sum of the programmed delay and the trig ger latency Pulse phase During the pulse phase the unit outputs one current pulse at the specified amplitude with the programmed pulse width Sampling on all three measurement channels laser diode voltage detector and detector 2 current is also performed during this phase In the DC mode the readings are taken during the pulse phase and then averaged Pulse width there fore becomes the aperture
69. oes eeeseesteeeneeeeeeeeees 11 7 Figure 11 4 Standard event Status 0 ee eee esses ceeeeseeseeeseeeeesseeeseesees 11 12 Figure 11 5 Operation event Status oo eee eeseeseeeseeeeeeseeeeeseeseeeaeeees 11 13 Figure 11 6 Measurement event Status oo eee eeeeseeeeeeseeseeeseeeeeeaeeees 11 15 Figure 11 7 Questionable event Status oo eee eseeseeeeeeseenseeseeeeeesetees 11 16 14 SCPI Command Reference Figure 14 1 ASCII data format 2 0 eee osuisi i is 14 20 Figure 14 2 TEEE 754 single precision data format 32 data bits 14 21 C Figure C 1 D Figure D 1 Figure D 2 Figure D 3 F Figure F 1 Figure F 2 Figure F 3 Figure F 4 Figure F 5 Figure F 6 Figure F 7 Figure F 8 Figure F 9 Figure F 10 Figure F 11 Figure F 12 Figure F 13 Figure F 14 Figure F 15 Figure F 16 Figure F 17 Figure F 18 Figure F 19 Data Flow Data flow block diagram 0 ccecceesceeeseceseeeeeeceeeeeeeeeseeeeeees C 2 IEEE 488 Bus Overview TEEE 488 bus configuration ee eeeeseeseeeeeeeeeseeeeeeaeenes D 4 TEEE 488 handshake sequence ee eeeesesceeseeeeeeeeeeeeeaeeees D 6 Command CODES scroscio eee aer riire aE D 11 Measurement Considerations Model 2520 pulse output circuit model s eseseeeeeeeeeeeeereeeeee F 2 Rise time of 4A current pulse oo cee eeseesceeeeeeeseeeeeeeeneeeeeeees F 4 Rise time of 0 45A current pulse cee eeseeeseceseeeeeeeeneeeeeeees F 5 Effects of open loop area ooo eeeeseeseeseeeee
70. points gt Set number of sweep points 2 to 1000 SOURce 1 SWEep DIRection lt direction gt Set sweep direction UP sweep start to stop or DOWN sweep stop to start Maximum DC mode current is 5 00mA Maximum pulse mode current is 5A Model 2520 User s Manual Sweep Operation 7 9 Staircase sweep programming example As an example of linear staircase sweep operation assume the Model 2520 is to be used to test a laser diode For the purposes of this test assume the following basic sweep parameters e Source mode sweep e Start current 1OmA e Stop current 100mA e Step current 10mA Table 7 3 lists the command sequence for laser diode programming example See Section 2 Connections for details on how to connect the laser diode for the test NOTE See Appendix H for a functional program example Table 7 3 Linear staircase sweep programming example Command Description RST Restore GPIB default conditions FORM ELEM Laser diode voltage detector current VOLT 1 CURR2 CURR3 SENS1 VOLT RANG 5 SOURI CURR RANG 0 5 SOURI CURR STAR 10e 3 SOURI CURR STOP 100e 3 SOURI CURR STEP 10e 3 SOURI CURR MODE SWE SOURI SWE SPAC LIN SOUR2 VOLT 5 SOUR3 VOLT 5 OUTP1 ON READ OUTP1 OFF data 5V measure range 500mA source range 10mA start current 100mA stop current 10mA step current Select staircase sweep mode Select linear staircase sweep Detector 1 bias 5V Detector 2 b
71. pulse shape Figure F 10 Optical pulse propagation through differing indices of refraction F 12 Measurement Considerations Model 2520 User s Manual The propagation speed of an electrical current pulse through a conductive material is a function of the material s impedance Any change in propagation speed as a signal passes between different materials or impedances will result in coupling loss and reflections As with the optical realm reflections can result in constructive or destructive interference The resulting signal can exceed the desired level or require considerable settling time and impact system integrity Electrical design engineers have developed techniques to identify and manage impedance mismatches to optimize signal coupling and minimize unwanted reflections This is fundamental in the application of high speed pulses to laser diodes dur ing testing Impedance matching and transmission line effects must be understood and managed to prevent damage or optimize test results Laser diode impedance matching The typical laser diode has a characteristic impedance of 2Q to 6Q This impedance is considerably lower than that of common coaxial cables which typically have characteris tic impedances in the range of 50Q to 75Q Matching a laser diode to the impedance of the coaxial cable would require adding 48Q to 44Q of series resistance However sourcing a 5A pulse across 50Q load would generate a 250V potential Such potentials
72. s Manual SCPI Command Reference 14 35 Query LOW Query programmed low amplitude LOW DEFault Query RST default low amplitude LOW MINimum Query lowest allowable low amplitude LOW MAXimum Query highest allowable low amplitude Description This command is used to set the pulse low amplitude level for all current source pulses For the 500mA source range the low value can be set from 0 to 0 015A For the 5A source range the low value can be set from 0 to 0 150A NOTE This command sets the pulse low amplitude for the pulse source function in the list and sweep modes See Select sourcing mode page 14 32 and Select source function page 14 33 Set voltage limit PROTection LEVel lt NRf gt SOURce 1 VOLTage PROTection LEVel lt NRf gt Set voltage compliance limit Parameters lt NRf gt 3 to 10 5 Set voltage compliance limit Query PROTection Query programmed voltage limit Description This command is used to the set the voltage protection limit which clamps the current source output voltage at the programmed limit See Section 5 Current source operating boundaries for more information Select source polarity POLarity lt name gt SOURce 1 CURRent POLarity lt name gt Set laser diode current source polarity Parameters lt name gt POSitive Positive polarity NEGative Negative polarity Query POLarity Query measurement polarity Description This command is used to select the polarity fo
73. seconds Description This command is used to add one or more values up to 100 to a pulse delay list that already exists The pulse delay values are appended to the end of the list By using multiple appended lists up to 1000 points can be in a list POINts SOURce 1 LIST DELay POINts Query length of pulse delay list Description These commands are used to determine the length of the specified pulse delay list The response message indicates the number of pulse delay values in the list 14 44 SCPI Command Reference Model 2520 User s Manual Sweep and list program examples Linear staircase sweep Linear current sweep from 10mA to 100mA in 10mA increments RST SOURI1 SWE SPAC LIN SOUR1 CURR STAR 10e 3 SOUR1 CURR STOP 100e 3 SOUR1 CURR STEP 10e 3 SOURI1 SWE POIN returns 10 SOUR1 CURR MODE SWE OUTP1 ON INIT List sweep List sweep with 100mA 200mA 300mA 400mA and 500mA current pulses pulse widths of 10us 20uUs 40s 60us and 70us pulse delays of 100ms 150ms 200ms 250ms and 300ms RST SOURLI LIST CURR 100e 3 200e 3 300e 3 400e 3 500e 3 SOURLI LIST WIDT 10e 6 20e 6 40e 6 60e 6 70e 6 SOURLI LIST DEL 100e 3 150e 3 200e 3 250e 3 300e 3 SOUR1 LIST CURR POIN returns 5 SOUR1 LIST WIDT POIN returns 5 SOUR1 LIST DEL POIN returns 5 SOUR1 CURR MODE LIST OUTP1 ON INIT Model 2520 User s Manual SCPI Command Reference 14 45 Logarithmic staircase sweep Logarithmic stair
74. separately to the DUT with the sense leads connected as close to the DUT body as possible Figure F 7 Sense lead connections Current Output HI Connecting Cables Current Output LO A Incorrect sense leads not connected at DUT Current Output HI Voltage Sense HI Connecting Cables Voltage Sense LO Current Output LO B Correct sense leads connected at DUT Model 2520 User s Manual Measurement Considerations F 9 Figure F 8 shows response of a 2A pulse with voltage sense leads 1 4 inch away from the DUT Note the long settling tail corresponding to the DUT resistance 1 66Q and the inductance formed by the leads Figure F 8 Response of 2A pulse with sense leads 1 4 inch away from DUT 2 5 2 0 1 5 Current A 1 0 0 5 0 0 0 0 6 0 8 1 1 2 1 4 1 6 1 8 2 2 2 2 4 Time us F 10 Measurement Considerations Magnetic coupling Model 2520 User s Manual Magnetic coupling between sense and current leads can also affect measurements Figure F 9A shows connections that will result in considerable coupling due to the rela tively long exposed signal lead area Carrying the sense shields as close to the DUT as possible Figure F 9B will reduce magnetic coupling and improve response Twisting the exposed sense leads and even the cables themselves may be necessary to reduce coupling to an acceptable level Figure F 9 Magnetic coupling Current Output HI Voltage Sense HI Couplin
75. stair case sweep pulse waveform aspects These parameters are programmed by sending the appropriate command e Pulse amplitudes determined by parameters programmed with SOUR1 CURR STAR SOUR1 CURR STOP and SOUR1 CURR STEP or SOUR1 SWE POINT for LOG sweep commands e SOUR1 PULS WIDT sets the pulse width e SOUR1 PULS DEL sets the pulse delay time between pulses e SOUR1 CURR LOW This command sets the pulse low level The pulse ampli tude returns to this level during the pulse delay unless the pulse amplitude is below the low level in which case the level is set to OA Model 2520 User s Manual Source Measure Concepts 5 7 Figure 5 6 Remote staircase sweep mode pulse parameters SOUR1 CURR STOP SOUR1 CURR STEP lt SOUR1 CURR LOW ae Start a CURR START OA lt gt lt SOUR1 PULS WIDT SOUR1 PULS DEL Returns to OA because pulse is less than Low Pulse rise and fall times As shown in Figure 5 7 there are two additional pulse characteristics that require discus sion rise time and fall time Characteristics are exaggerated for clarity Note that these characteristics depend on cable connection configuration setting and range load and operating mode See the specifications in Appendix A for details Figure 5 7 Pulse characteristics Current Pulse Exaggerated for Clarity The rise and fall times of the current source pulse can be controlled with the SOURce1
76. the current is flowing out of the triax connector Figure 3 4B the measured current is positive and the polarity setting must be POSITIVE NOTE Detector current measurements are essentially unipolar and the polarity setting must agree with the polarity connections of the photodiode If the polarity is set incorrectly an overflow reading will be displayed Voltage bias polarity The voltage bias outputs are bipolar and there is no separate polarity setting Simply set the voltage bias value to the desired value in the range of 20V This bias voltage value will be output on the inner shield of the detector triax jack relative to the center conductor terminal For example if you set the bias voltage to 10V the inner shield will be at a potential of 10V relative to the center conductor of the triax jack Figure 3 4 Detector current measurement polarity I Current Input Current Input Photodiode Photodiode Voltage Bias Voltage Bias Output Output Detector 1 Detector 1 or Detector 2 or Detector 2 A NEGATIVE polarity connections B POSITIVE polarity connections Note Incorrect polarity setting will result in overflow current reading Model 2520 User s Manual Basic Operation 3 9 Configuring sources Follow the general procedures below to set source and compliance values for the laser diode current source as well as bias voltage values for the two photodiode sources Editing source v
77. the expected current measurement Use the lowest range possible for best accuracy Repeat steps through 3 for DETECTOR 2 Step 3 Configure laser diode current source Set up the laser diode source as follows l at ie aa o gt SA 10 Press CONFIG then LASER I to access the source configuration menu Choose POLARITY then set the polarity to POSITIVE or NEGATIVE as desired Choose SHAPE then select the DC or PULSE mode as desired If you chose PULSE select LOW then set the pulse low amplitude Press EXIT to return to normal display If you chose the PULSE mode in step 3 program the pulse delay and width using the DELAY and PW keys Press the COMPL key then program the voltage compliance limit as desired Press LASER I then press the EDIT key to enter the edit mode Use the RANGE 4A and keys to select the source range 500mA or 5A that will best accommodate the value you want to set Using either the EDIT or numeric entry keys enter the desired current source value Step 4 Configure photodiode detector voltage bias sources Set up the photodiode detector voltage bias sources as follows 1 2 Press DETECTOR 1 Vg to edit the photodiode 1 source Using either the EDIT or numeric entry keys enter the desired source value 0 to 20V Model 2520 User s Manual Laser Diode Testing 4 5 3 Press DETECTOR 2 Vp to select the photodiode 2 source 4 Again using either the EDIT or numeric entry keys
78. the pulse source and the laser diode is not seen by the clamp circuit and cannot be regulated by the clamp As a result care must be taken to minimize the negative effects of the transmission line F 14 Measurement Considerations Model 2520 User s Manual Transmission line model Figure F 12 shows the transmission line scheme that provides the least impedance mis match The laser diode appears as a low impedance path to a current pulse By placing the laser diode in series with the source and termination of the current pulse and by maintain ing uniform impedance in the current path the magnitude of reflections is minimized This method however is not practical The electrical shielding must be compromised to pro vide access to the laser diode as shown in Figure F 13 The compromised shield provides access to the laser diode and upsets the continuity of the impedance of the transmission line To minimize the effects of the discontinuity the shield of the two compromised cable sections must be connected and the length of the inner con ductor must be minimized Figure F 12 Minimal impedance mismatch Current Output HI Current Output LO Figure F 13 Compromised shield provides laser diode access Current Output HI Current Output LO Integrating Sphere Model 2520 User s Manual Measurement Considerations F 15 Forward voltage measurement Figure F 14 shows the model of the Model 2520 voltage measurement channel This
79. this option to enter a discrete number of sweeps to perform with the results stored in the data store buffer The maximum number of finite sweeps that can be performed is determined as follows maximum finite sweep count 1000 Points in sweep INFINITE Select this option to continuously repeat the configured sweep Use the EXIT key to stop the sweep Data is not stored in the buffer Figure 7 4 Sweep configuration menu tree CONFIG INFINITE FINITE 7 6 Sweep Operation Model 2520 User s Manual Performing sweeps Procedures for the various sweep types are covered below NOTE The following procedure assumes that the Model 2520 is already connected to the DUT as explained in Section 2 Performing a linear staircase sweep Step 1 Configure source and measure Configure the Model 2520 source and measure functions as follows 1 Select the current source range by pressing LASER I then EDIT then use the RANGE keys Press LASER V then choose the desired measurement range Use the DETECTOR 1 Vp and DETECTOR 2 Vp keys and EDIT keys to set the photodiode bias voltages to the desired values 4 Set the current measurement ranges by pressing the DETECTOR 1 Ipp DETEC TOR 2 Ipp and RANGE keys See Section 3 Basic circuit configuration for more information Step 2 Configure sweep Configure the sweep as follows Press CONFIG then SWEEP Select TYPE then press ENTER Select STAIR then pres
80. with a parameter value that deter mines the desired state 0 or 1 of each bit in the appropriate register An enable register can be programmed using any of the following data formats for the parameter value binary decimal hexadecimal or octal The bit positions of the register indicate the binary parameter value For example if you wish to sets bits B4 B3 and B1 the binary value would be 11010 where B4 1 B3 1 B1 1 and all other bits are 0 When you use one of the other formats convert the binary number to its decimal hexadecimal or octal equivalent Binary 11010 Decimal 26 Hexadecimal 1A Octal 32 Note that Figure 11 2 includes the decimal weight for each register bit To set bits B4 B3 and B1 the decimal parameter value would be the sum of the decimal weights for those bits 16 8 2 26 Figure 11 2 16 bit status register BitPosiion e7 ee 65 s e 2 siJ so Binary Value on Decimal Weights A Bits 0 through 7 Bit Postion B15 B14 J e13 e12 Jen eo eo ee Binary Value m o Decimal 32768 16384 8192 4096 2048 1024 512 256 Weights 25 219 2 23 2 210 29 28 B Bits 8 through 15 11 6 Status Structure Model 2520 User s Manual The lt NDN gt non decimal numeric parameter type is used to send non decimal values These values require a header B H or Q to identify the data format being sent The letter in the header can be upper or
81. 0 User s Manual aed 1 U0q X 801A 4d LOLG q 90N O7SZ JaPOW Aq pau w jdu Jou joUOD ay21 LOL pue QINBYUOIUN Od A PL2d Add 24ANBYUOD Od P B42d Ddd Oas 99d dnoip dnon puewwop puewwo Asepuosasg ANEW Ld 6 a a a ar OVL v1 0N Dv dnain dnon dnoiy dnoi5 ssouppy ssauppy puewwo gt puewiwos JeL ugs Jesa MUN p ss ppy O Sl SL L L U N vi vl L L W l l L 7 q1 cL cL L L z LL LL oj L Zz Z OL OL 0 L A l 6 6 6 oj x y x H 8 8 g ol M 3 M D Z Z Z L 0 X 4 A d 9 9 9 LI o n N E S S S L 0 p L a v v v Ll o s 2 S 3 0 0 1 q a g c c c 0 0 b e d v L L L ojo d d 0 0 0 ojo wD E moy AE 8 uwnjop G za a oS aS 9 L E E cro D 12 IEEE 488 Bus Overview Model 2520 User s Manual Typical command sequences For the various multiline commands a specific bus sequence must take place to properly send the command In particular the correct listen address must be sent to the instrument before it will respond to addressed commands Table D 3 lists a typical bus sequence for sending the addressed multiline commands In this instance the SDC command is being sent to the instrument UNL is generally sent as part of the sequence to ensure that no other active listeners are present Note that ATN is true for both the listen command and the SDC command byte itself Table D 3 Typical addressed multiline command sequence D
82. 0 or OFF Disable display circuitry 1 or ON Enable display circuitry Query ENABle Query state of display Description This command is used to enable and disable the front panel display cir cuitry When disabled the instrument operates at a higher speed While disabled the display is frozen with the following message FRONT PANEL DISABLED Press LOCAL to resume As reported by the message all front panel controls except LOCAL and OUTPUT OFF are disabled Normal display operation can be resumed by using the ENABle command to enable the display or by putting the Model 2520 into local 14 18 SCPI Command Reference Model 2520 User s Manual ATTRibutes DISPlay WINDow 1 ATTRibutes Query attributes top display DISPlay WINDow2 ATTRibutes Query attributes bottom display Description These query commands are used to determine which characters on the Read display display are blinking and which are not The response message provides that status of each character position for the specified display The pri mary display consists of 20 characters and the secondary display con sists of 32 characters 1 Character is blinking 0 Character is not blinking DATA DISPlay WINDow 1 DATA Read top display DISPlay WINDow2 DATA Read bottom display Description These query commands are used to read what is currently being dis played on the top and bottom displays After sending one of these com mands and addressing the Mo
83. 001 0 5000005 Configuring the 2520 to use Continuous Pulse Mode Front panel Set up pulse mode and triggering 1 Press CONFIG key then TRIG 2 Select INIT then press ENTER 3 Select OFF then press ENTER 4 The 2520 should be at the CONFIGURE TRIGGER MENU Select COUNT then press ENTER 5 Select CONTINUOUS PULSE then press ENTER 6 Press EXIT key to exit CONFIGURE TRIGGER MENU Set the desired Pulse Width 1 Press the PW key 2 Use the EDIT keys lt gt A V to set the desired pulse width Press ENTER when finished Set the desired Pulse Delay in other words Pulse off time 1 Press the DELAY key 2 Use the EDIT keys lt gt A V to set the pulse delay to 000 33ms Press ENTER when finished Set the desired current source value 1 Press the I key 2 Use the EDIT keys lt gt A W to set the desired current value Press ENTER when finished To turn on the continuous pulse mode 1 Press ON OFF OUTPUT key to turn outputs on blue OUTPUT indicator turns on 2 Press the TRIG key The 2520 is now outputting pulses with the first line of the display reading Continuous Pulse To turn off the continuous pulse mode 1 Press EXIT key 2 Press ON OFF OUTPUT key to turn outputs OFF l 4 Continuous Pulse Mode Model 2520 User s Manual Remote configuration over GPIB IEEE 488 Command Comment RST SOUR1 CURR MODE FIX SOUR1 CURR 0 2 SOUR1 PULS DEL 0 00033 SOUR1 PUL
84. 1 10 Status registef SCtS 0 ee eseeescecsececeeseesseeseeeseeseseseeesseeneeesees 11 11 Register bit descriptions 0 0 0 cee eeeeeseeseeeeeeeeeseeseeeaeees 11 11 Standard event register 0 ee eee eseeeeeeseeeeeeeeeaeeee 11 11 Operation event register oo eee eee eeeeeeeeeeeseeeeeeaees 11 13 Measurement event register 0 eee eeeeeeseeereeees 11 14 Questionable event register oo eee eeeeeeeeeseeeereeeneees 11 16 12 13 14 Condition registers 0 eee eeseeseeseeseceeeeseeeseeeeeaeeeseneeaes 11 17 EVent registers lt c csceheecustenesecvineveen estes dieeesestasasvabsouctncoes 11 17 Event enable registers 0 0 eee eeeeseeseeseeeeeeseeseeeaeeseeeaeeees 11 18 Programming example program and read PESISLET SCL oraino ienis Ee E E E E EA 11 19 QUEUES ener e e A kde eal emedens 11 19 O tp t QUCUE srneci eiiiai 11 19 Error QUCUC ani E e e E TE 11 20 Programming example read error queue 11 21 Common Commands Command SUMIMALY viiei einerseits ii R E EE ait 12 2 Command ref renGe siisii tesni isie isire sis tiike Erisan a Eai 12 3 IDN identification query ssseeseeeeseereseeresrerrsreresreeen 12 3 OPC operation complete ssssesesseeeesreseeresrsrrsreresreee 12 3 OPC operation complete Query ceeeeesreeereeeteees 12 3 OPC programming example cele eeeeeeseeeeeeeees 12 4 OPT Option QUeTY eee eseeeercesseeseceneeeeteeeeseeeetenes 12 4 SA
85. 10 5mA 20mA 1 4uA 21mA 50mA 3 4uA 52 5mA 100mA 6 8HA 105mA Model 2520 User s Manual Range Filter and Math 6 3 Maximum readings The full scale input for each measurement range is shown in Table 6 1 and Table 6 2 Input levels that exceed the maximum levels cause the Oflow message to be displayed Setting the measurement range Press the LASER V DETECTOR 1 Ipp or DETECTOR 2 Ipp key then use the RANGE A and F keys to select a range NOTE Use the lowest range possible without causing an overflow to ensure best accu racy and resolution Source ranging As summarized in Table 6 3 the laser diode current source has two ranges To set the range press the LASER I and EDIT keys then use the RANGE A and W keys Table 6 3 Laser diode current source ranges Current Maximum range Resolution output 500mA 104A 500mA 5A 100UA 5 0A Pulse mode only 1A maximum in DC mode Remote range programming Table 6 4 summarizes the commands necessary to control range See SENSe subsystem page 14 27 for more details on these commands Table 6 4 Range commands Commands Description SENSe 1 VOLTage RANGe lt range gt Set laser diode voltage measure range 5 or 10 SENSe2 CURRent RANGe lt range gt Set photodiode 1 current measure range 0 01 0 02 0 05 or 0 1 SENSe3 CURRent RANGe lt range gt Set photodiode 2 current measure range 0 01 0 02 0 05 or 0 1
86. 14 27 Output trigger 8 4 Specifications 8 6 Output triggers 8 13 Parameters Front panel pulse 5 4 Remote pulse 5 6 Photodiode Configuring measurements 3 12 Current measurement ranges 3 4 6 2 Detector measurement functions 4 4 Detector voltage bias source 4 4 Source and measure capabilities 3 3 Photodiode current measurement circuit model F 16 Polarity Considerations 2 8 Detector measurement 3 8 Laser diode 3 6 Select 14 29 Select source polarity 14 35 Voltage bias 3 8 Power math function 6 7 Power module 1 8 Power on Configuration 1 15 Power up 1 11 Sequence 1 11 Primary address 10 6 Product overview 1 5 Programming Examples Set MSS B6 when error occurs 11 10 Programming syntax 10 10 Pulse Characteristics 5 7 Concepts 5 2 Front panel parameters 5 4 Phase 5 3 Remote parameters 5 6 Rise and fall times 5 7 Pulse phase 8 4 8 12 Pulse sync output 9 8 Connections 9 9 Waveform 9 8 Pulse test advantage I 2 Queues 11 2 11 19 Clearing 11 4 Error 11 20 14 52 Output 11 19 Rack mount kits 1 4 Range 6 2 Commands 6 3 Programming example 6 4 Remote programming 6 3 Select source range 14 33 Setting the measurement range 6 3 Source ranging 6 3 Readings Acquiring 13 2 Rear panel Summary mainframe 1 7 Summary testhead 1 10 Registers Bit descriptions 11 11 Clearing 11 4 Condition registers 11 17 Error 14 50 Event enable registers 11 18 Event registers 11 17 Measurement event register 11 14 Operation ev
87. 2520 is configured to perform 10 source and measure operations and send the 10 current measurements to the computer using the binary format Bytes 2 10x 4 1 43 14 22 SCPI Command Reference Model 2520 User s Manual Data elements ELEMents lt item list gt FORMat ELEMents SENSe lt item list gt Specify data elements for data string Parameters lt item list gt CURRent 1 Includes laser diode source value CURRent2 Includes detector 1 current reading CURRent3 Includes detector 2 current reading VOLTage 1 Includes laser diode voltage reading VOLTage2 Includes detector 1source value VOLTage3 Includes detector 2 source value TIME Includes timestamp STATus Includes status information NOTE Each item in the list must be separated by a comma i e VOLT CURR2 TIME Query Description ELEMents Query elements in data string This command is used to specify the elements to be included in the data string in response to the following queries FETCh READ MEASure You can specify from one to all eight elements Each element in the list must be separated by a comma These elements shown in Figure 14 1 are explained as follows NOTE An overflow reading reads as 9 9E37 CURRent 1 This element provides the laser diode current source value CURRent2 This element provides the detector 1 current reading If no current reading is available the NAN not a number value of 9 91e37 is used
88. 3V to 10 5V Settings affected by maximum duty cycle See Section 5 The main operation keys listed in Table 1 6 program these functions e PW Sets laser diode current source I pulse width e DELAY Sets laser diode current source pulse delay e COMPL Sets laser diode current source voltage compliance limit These operating modes are covered in more detail in later sections of this manual Configuration menus There are a number of configuration menus that can be accessed by pressing the CONFIG key followed by the appropriate function or mode key For example you can configure the measurement functions by pressing CONFIG then LASER V DETECTOR 1 Ipp or DETECTOR 2 Ipp Configuration menus which are summarized in Table 1 7 through Table 1 9 are available for the following operating modes e Measure and source functions LASER and DETECTOR keys Table 1 7 e TRIG and FILTER Table 1 8 SWEEP and MATH Table 1 9 These various configuration menus are covered in detail in the pertinent sections of this manual 1 22 Getting Started Table 1 7 Model 2520 User s Manual LASER and DETECTOR configuration menus Configuration menu item Description CONFIG LASER V CHANNEL POLARITY POSITIVE NEGATIVE CONFIG DETECTOR 1 Ipp CHANNEL2 POLARITY POSITIVE NEGATIVE CONFIG DETECTOR 2 Ipp CHANNEL3 POLARITY POSITIVE NEGATIVE CONFIG LASER I CONFIGURE I SOURCE POLARITY POSITIVE NE
89. 4 1 Table 4 2 Table 4 3 6 Table 6 1 Table 6 2 Table 6 3 Table 6 4 Table 6 5 Table 6 6 Table 6 7 Table 6 8 Table 6 9 Table 6 10 7 Table 7 1 Table 7 2 Table 7 3 Table 7 4 Table 7 5 Getting Started Line f se eseri ocitne i naisia a eeleedveves 1 12 Basic display command 0 eee seeeseeseeeeeseeeseeseeeaeeseeeatens 1 14 Factory default settings 0 cee eeeeseseeeeeeseeeseeseeeaeeeeeeatees 1 16 Main MENU cs cescscestecangsczescesasvancsvesecedunssdensee saben ios ensidensttonsens 1 18 COMM SETUP and DIG OUT ments eee 1 20 PW DELAY and COMPL ments ccccccessscceeesssreeeees 1 21 LASER and DETECTOR configuration menus s s s 1 22 TRIG and FILTER configuration menus 1 0 0 0 eee eeeeeeeeee 1 23 SWEEP and MATH configuration menus 1 0 0 0 eee 1 24 Basic Operation Laser diode current source ranges ceeeeeseceseeeeeeneeeeneeeneees 3 2 Laser diode voltage measurement ranges 0 0 0 0 ee eeeeeseeeeeeee 3 3 Photodiode current measurement ranges 0 00 eeeeeseeeeteeeeeees 3 4 Source and measure configuration commands 3 13 Basic source and measure configuration example 3 14 Laser Diode Testing Source and measure configuration MENUS 1 0 0 seers 4 2 Laser diode test commands 00 0 eeeeeeseeeeeeseeeeeeaeeneeeseeeeeeaes 4 6 Basic laser diode test command Sequence ceeeeeeteeereees 4 8 Range Filter and Math Laser diode voltage measu
90. 5 02 Current Current A 3 5 A 2 4 98 1 4 96 0 4 94 0 5 10 15 20 25 Time us Figure 2 Pulse Output Trigger Output Relationship j Trigger 5 S8 4 3 Volts 2 1 0 i Naan Pulse 2 1 00E 06 5 00E 07 0 00E 00 5 00E 07 1 00E 06 1 50E 06 Time Figure 3 HW Rev D 2 26 03 A 4 Specifications Model 2520 User s Manual Accuracy calculations The following information discusses how to calculate accuracy for both measurement and source functions Measurement accuracy Measurement accuracy is calculated as follows Accuracy of reading offset As an example of how to calculate the actual reading limits assume that you are measur ing 5V on the 10V laser diode measurement range You can compute the reading limit range from one year measurement specifications as follows Accuracy of reading offset 0 3 x 5V 8mV 15mV 8mV 23mV Thus the actual reading range is 5V 23mV or from to 4 977V to 5 023V Source accuracy Source accuracy is calculated similarly except that source specifications are used to calcu late source accuracy as follows Accuracy of setting offset As an example of how to calculate the actual source output limits assume that you are sourcing 100mA DC on the 500mA range You can compute the output limits from laser diode current source one year accuracy specifications as follows Accuracy 0 2 of setting 0 45mA offset 0 2 x 100mA 0 45m
91. 520 asd E EA ERN 14 25 BORDer lt name gt 000 aa i a 14 25 Status register format eee ese ceeeeseeeeeeseeeeeeseeeeeenees 14 26 SREGister lt name gt ooo eee eseeeeeeseeeseeseeeseeeeeeeeees 14 26 OUTPUUSUDSYSLEMD siess de casccvs sce svatedocaesscsevsteeesdavtacdesectenees 14 27 Turn sources On OF Off oo eecceeceeeseceseeceeeeeeeeeeeeeaeeeaeens 14 27 ESTATE lt b gt siia o dedek 14 27 Interlock Status sees iseceassccsssscavvecicverscessaieiveseceessisevveresedeess 14 27 REP Ped lt ccsvesease Ses csc etereessszesateasaticsaresterssteseinea ess 14 27 SENSe subsyStein ss sacks hei enn raie 14 27 Select laser diode voltage measurement range 14 28 PUIPPer rn annaa EE N 14 28 Select detector current measurement range cece 14 28 UIP RSE i gt ennn descdoseaxcesten see 14 28 Select polarity riesis inicira E e a E 14 29 POLarity lt name gt ciii iaeiei E E 14 29 Query voltage limit ssessssseseseesessssessrsrssesrrerrersrrsreresresese 14 29 SERUP Pe 25s 2e5 setsins puicescesretaiseze a E S 14 29 Query latest readings oe eee eseeeeereeeseeeeeeeeeeeseeaes 14 30 LAT est ieceres e neni 14 30 Configure and control filter 0 eee eee eeeceeeseeeseeees 14 30 COUN 6 Si E lease cnsehas cdsatousnteisetonpeseastaras 14 30 eS PATS DF nena anaia e 14 31 ADOM SWEEP sess cii tes nteienee diesen cides beet stanbeanssesecie toes 14 31 CABort LEVel lt n gt eesessessessesssrorseres
92. 9 Missing parameter EE Standard Event 5 108 Parameter not allowed EE Standard Event 5 105 GET not allowed EE Standard Event 5 104 Data type error EE Standard Event 5 103 Invalid separator EE Standard Event 5 102 Syntax error EE Standard Event 5 101 Invalid character EE Standard Event 5 100 Command error EE Standard Event 5 000 No error SE Model 2520 User s Manual Status and Error Messages B 5 Table B 1 continued Status and error messages Number Error message Event Status register Bit Measurement events 101 Hardware interlock asserted SE Measurement Event 1 102 Laser diode measurement overflow SE Measurement Event 2 103 Detector 1 measurement overflow SE Measurement Event 3 104 Detector 2 measurement overflow SE Measurement Event 4 106 Reading available SE Measurement Event 6 107 Sweep aborted SE Measurement Event 7 108 Sweep done SE Measurement Event 8 114 Current source in compliance SE Measurement Event 14 Standard events 200 Operation complete SE Standard Event 0 Operation events 300 Device calibrating SE Operation Event 0 305 Waiting in trigger layer SE Operation Event 5 310 Entering idle layer SE Operation Event 10 Questionable events 408 Questionable Calibration SE Questionable Event 8 414 Command Warning SE Questionable Event 14 Calibration errors 500 Date of calibration not set EE Standard Event 3 501 Next date of calibration no
93. A 0 2mA 0 45mA 0 65mA In this case the actual current source output range is 100mA 0 65mA or from 99 35mA to 100 65mA Status and Error Messages B 2 Status and Error Messages Model 2520 User s Manual Introduction This Appendix contains a summary of status and error messages which status register bits are set when messages occur and methods to avoid or eliminate most common SCPI errors Status and error messages Table B 1 summarizes status and error messages which are stored in the Error Queue Each message is preceded by a code number Negative numbers are used for SCPI defined messages and positive numbers are used for Keithley defined messages Note that error and status conditions will also set specific bits in various status registers as sum marized in Table B 1 Section 11 has detailed information on registers and queues Briefly you can use the fol lowing queries to obtain error and status information e SYST ERR reads Error Queue e ESR reads Standard Event Status Register e STAT OPER reads Operation Event Register e STAT MEAS reads Measurement Event Register STAT QUES reads Questionable Event Register NOTE SCPI confirmed messages are described in volume 2 Command Reference of the Standard Commands for Programmable Instruments Refer to the SYS Tem ERRor command Model 2520 User s Manual Status and Error Messages B 3 Table B 1 S
94. AL key is also inoperative For safety reasons the OUTPUT key can be used to turn the output off while in LLO 10 10 Remote Operations Model 2520 User s Manual Programming syntax The information in this section covers syntax for both common commands and SCPI com mands For information not covered here see the IEEE 488 2 and SCPI standards See Section 12 and Section 14 for more details on common and SCPI commands respectively Command words Program messages are made up of one or more command words Commands and command parameters Common commands and SCPI commands may or may not use a parameter The following are some examples SAV lt NRf gt Parameter NRf required RST No parameter used CALCulatel STATe lt b gt Parameter lt b gt required SYSTem PRESet No parameter used NOTE Atleast one space between the command word and the parameter is required Brackets Some command words are enclosed in brackets These brackets are used to denote an optional command word that does not need to be included in the pro gram message For example INITiate MMediate These brackets indicate that MMediate is implied optional and does not have to be used Thus the above command can be sent in one of two ways INITiate or INITiate MMediate Notice that the optional command is used without the brackets When using optional com mand words in your program do not include the brackets Parameter types T
95. B parameters MBFactor lt n gt Set B parameter 9 99999e20 to 9 99999e20 0 MBFactor Query B parameter MMFactor lt n gt Set M parameter 9 99999e20 to 9 99999e20 1 MMFactor Query M parameter MUNits lt string gt Set MX B units 1 character ASCII string W MUNits Query M parameter STATe lt b gt Enable or disable CALC2 math OFF v STATe Query state of math Jv 14 4 SCPI Command Reference Table 14 1 continued CALCulate command summary Model 2520 User s Manual Default Command Description parameter SCPI CALCulate3 Path to configure and control detector 2 math DATA Path to CALC3 data LATest Return only most recent math result DATA Read result of math generated by INIT v KMATh Configure MX B parameters MBFactor lt n gt Set B parameter 9 99999e20 to 9 99999e20 0 MBFactor Query B parameter MMFactor lt n gt Set M parameter 9 99999e20 to 9 99999e20 1 MMFactor Query M parameter MUNits lt string gt Set MX B units 1 character ASCII string Ww MUNits Query M parameter STATe lt b gt Enable or disable CALC3 math OFF Jv STATe Query state of math Jv CALCulate4 Path to control delta detector 1 current detector 2 current DATA Read math result generated by INIT v LATest Return only most recent math result STATe lt b gt Enable or disable CALC4 math OFF Jv STATe Query state
96. CALL key 31 PW key KEY Query last pressed key This command is used to simulate front panel key presses For example to select the laser diode voltage measurement function LASER V1 you can send the following command to simulate pressing the LASER V_ key isyst key 15 The parameter listing above provides the key press code in numeric order The queue for the KEY query command can only hold one key press When KEY is sent over the bus and the Model 2520 is addressed to talk the key press code number for the last key pressed either physi cally or with KEY is sent to the computer The key press code number for the last key pressed either physically or with KEY is sent to the computer Read version of SCPI standard VERSion SYSTem VERSion Description Read SCPI version This query command is used to read the version of the SCPI standard being used by the Model 2520 Example code 1996 0 The above response message indicates the version of the SCPI standard Model 2520 User s Manual RS 232 interface SCPI Command Reference 14 55 NOTE The following commands are intended for use over the RS 232 interface but they can also be used over the GPIB LOCal SYSTem LOCal Description REMote SYSTem REMote Description RWLock SYSTem RWLock Description Reset timestamp RESet SYSTem TIME RESet Description Take Model 2520 out of remote Normally during RS 232 communication
97. CURRent3 This element provides the detector 2 current reading If no current reading is available the NAN not a number value of 9 91e37 is used VOLTage 1 This element provides the laser diode voltage reading If voltage reading is available the NAN not a number value of 9 91e37 is used VOLTage2 This element provides the detector 1 voltage source value Model 2520 User s Manual SCPI Command Reference 14 23 VOLTage3 This element provides the detector 2 voltage source value TIME A timestamp is available to reference each group of readings to a point in time The relative timestamp operates as a timer that starts at zero seconds when the instrument is turned on or when the relative timestamp is reset SYSTem TIME RESet The timestamp for each reading sent over the bus is referenced in seconds to the start time After 99 999 999 seconds the timer resets to zero and starts over The timer value updates for each pass through the Trigger Event Detector see Figure 8 6 Therefore all points in a single sweep will have the same time value STATus A status word is available to provide status information con cerning Model 2520 operation The 16 bit status word is sent in a deci mal form and must be converted by the user to the binary equivalent to determine the state of each bit in the word For example if the status value is 17 the binary equivalent is 0000000000010001 Bits 0 and 4 are set The si
98. Culate result value TIME This element returns the timestamp see CALCulate lt item list gt page 14 23 for description STATus This element returns the 16 bit status word see CALCulate lt item list gt page 14 23 for description TRACe data elements TRACe lt item list gt FORMat ELEMents TRACe lt item list gt Parameters Specify TRACe data string elements lt item list gt VOLTage 1 Includes laser diode voltage CURRent2 Includes detector 1 current reading CURRent3 Includes detector 2 current reading TIME Includes timestamp NOTE Each item in the list must be separated by a comma i e VOLT1 CURR2 TIME Query Description TRACe Query TRACe data string elements This command is used to specify the elements to be included in the data string in response to the TRACe DATA and TRACe DATA VALue queries You can specify from one to all three elements Each element in the list must be separated by a comma These elements are explained as fol lows NOTE An overflow reading reads as 9 9E37 VOLTage 1 This element provides the laser diode voltage measure ment value If no voltage reading is available the NAN not a number value of 9 91e37 is used Model 2520 User s Manual SCPI Command Reference 14 25 CURRent2 This element provides the detector 1 current reading If no current reading is available the NAN not a number value of 9 91e37 is used CURRe
99. D PERSONNEL ONLY m KEITHLEY IEEE 488 MR IN CAT I 4 oTo WIH FRONT PANEL MENU S z BW a DIGITAL 1 0 omme Cap O LINK RS 232 at CONN 1 LINE FUSE Siena P TNE RATING e AE 50 60Hz TESTHEAD c CONN 2 140VA MAX E s CAUTION FOR CONTINUED PROTECTION AGAINST FIRE HAZARD REPLACE FUSE WITH SAME TYPE AND RATING Model 2520 o Digital output lines The port provides four output lines and one input line Each open collector output can be set high 5V or low 0V Each output line can source up to 2mA or sink up to 500mA Model 2520 User s Manual Digital I O Port Interlocks and Pulse Sync Output 9 3 Start of test SOT line The input line SOT is a TTL compatible logic line used by external equipment to start a test With the STEST trigger event selected a low SOT pulse starts the testing process With the TSTEST trigger event selected a high SOT pulse starts the testing process With the TLSTEST trigger event selected a high or low SOT pulse starts the testing process See Section 8 for triggering information NOTE SOT input pulses are referenced to ground pin 9 5V output The Digital I O Port provides a 5V output that can be used to drive external logic cir cuitry Maximum current output for this line is 300mA This line is protected by a self resetting fuse Digital output configuration Figure 9 2 Sink operation There are two basic methods to connect external components to the d
100. D source range PRINT 1 OUTPUT 25 SOUR1 CURR 0 5 500mA LD source current PRINT 1 OUTPUT 25 SOUR1 VOLT PROT 5 5V LD source limit PRINT 1 OUTPUT 25 SOUR1 CURR POL POS Positive LD polarity PRINT 1 OUTPUT 25 SOUR1 FUNC PULS LD source pulse mode PRINT 1 OUTPUT 25 SOUR1 PULS DEL 100e 6 100us pulse delay PRINT 1 OUTPUT 25 SOUR1 PULS WIDT 10e 6 10us pulse width PRINT 1 OUTPUT 25 SOUR1 CURR LOW 10e 3 10mA low pulse level PRINT 1 OUTPUT 25 SOUR2 VOLT 20 20V detector 1 bias voltage PRINT 1 OUTPUT 25 SOUR3 VOLT 10 10V detector 2 bias voltage PRINT 1 OUTPUT 25 CALC1 FORM POWER1 LD power math PRINT 1 OUTPUT 25 CALC2 KMAT MBF 2 Detector 1 MX B B value 2 PRINT 1 OUTPUT 25 CALC2 KMAT MMF 0 5 Detector 1 MX B M value 0 5 PRINT 1 OUTPUT 25 CALC1 STAT ON Enable laser diode math PRINT 1 OUTPUT 25 CALC2 STAT ON Enable detector 1 math PRINT 1 OUTPUT 25 OUTP1 ON Turn on outputs CLS PRINT 1 OUTPUT 25 READ Trigger and read current data PRINT 1 ENTER 25 Address 2520 to talk LINE INPUT 2 R Input detector 2 current reading PRINT Detector 2 current measurement R PRINT 1 OUTPUT 25 CALC1 DATA Read laser diode power data PRINT 1 ENTER 25 Address 2520 to talk LINE INPUT 2 R Input laser diode math reading PRINT Laser d
101. E 488 2 1992 and defines a standard set of commands to control every programmable aspect of an instrument 10 4 Remote Operations Model 2520 User s Manual GPIB connections To connect the Model 2520 to the GPIB bus use a cable equipped with standard IEEE 488 connectors as shown in Figure 10 1 Figure 10 1 IEEE 488 connector To allow many parallel connections to one instrument stack the connectors Two screws are located on each connector to ensure that connections remain secure Figure 10 2 shows a typical connecting scheme for a multi unit test system Figure 10 2 IEEE 488 multi unit test system connections Instrument Instrument Instrument Controller To avoid possible mechanical damage stack no more than three connectors on any one unit Model 2520 User s Manual Remote Operations 10 5 NOTE To minimize interference caused by electromagnetic radiation use only shielded IEEE 488 cables Available shielded cables from Keithley are Models 7007 1 and 7007 2 To connect the Model 2520 to the IEEE 488 bus follow these steps 1 Line up the cable connector with the connector located on the rear panel The con nector is designed so it will fit only one way Figure 10 3 shows the location of the TEEE 488 connector 2 Tighten the screws securely making sure not to overtighten them Figure 10 3 IEEE 488 and RS 232 connector location RS 232 IEEE 488 Connector Connector WARNING no INTERNAL OPA
102. ELVICW E E T F 11 Laser diode impedance matching cece eee eeeeseeeeeeeees F 12 Model 2520 output circuit modelo eee eeeeseeeeeeees F 13 Transmission line model 0 0 ee eeeeeeeeeeeeeeeeeseeeseeseeenees F 14 Forward voltage measurement 0 eee eee esse eeeeereeseeenees F 15 Photodiode current measurement channels eee F 16 Noise and source impedance ee eeeeeeseeeseeseeeeenreeeeeeeeneees F 17 DUD PeSIStannCe siz c5s csheceuschsasiiedossnsssareaacethsee iiis F 17 Source capacitance oo eee eee eeseeeeeeaeeseeeaeeteeeaeeeeeeaeeeaeees F 18 Generated CUITENtS oo eee eeeeseeeeeeeeeeeeaeceeeeaeceesaeteneeaeeneeaes F 18 Offset C TEntS iscissi peisir raraga F 19 Dielectric absorption esssssesssresessessesrsresesrestrsrerrsreresresrnees F 19 Voltage D rdEM asii eara iee Eiaa F 20 General measurement considerations sesessssseseserrserrrrrrrrreee F 20 Ground LOOPS sirsiran F 20 DASH e e E wn ase E F 21 Electrostatic interference seseseeeeseereresrreresrerrrrereereerees F 22 Magnetic fields suosisi F 22 Electromagnetic Interference EMI seese F 23 GPIB 488 1 Protocol Introd ttiom srepet ieena enrii psuasoeseebiteneeven sents G 2 Selecting the 488 1 protocol sesssssesssssssesesreresesresrsrssesreseeresees G 2 Protocol different s 2 55 ceseeccesbsieshes seco stbecsonssvve secede svbesusaseaeaney G 3 Message exchange protocol MEP eee eeeeseeeeeereereees G 3 Using
103. EN line would be set low true 2 Multiline commands General bus commands which are sent over the data lines with the ATN line true low 3 Common commands Commands that are common to all devices on the bus sent with ATN high false 4 SCPI commands Commands that are particular to each device on the bus sent with ATN high false These bus commands and their general purpose are summarized in Table D 1 Table D 1 IEEE 488 bus command summary State of Command type Command ATN line Comments Uniline REN Remote Enable X Set up devices for remote operation EOI End Or Identify X Marks end of transmission IFC Interface Clear X Clears interface ATN Attention Low Defines data bus contents SRQ Service Request X Controlled by external device Multiline LLO Local Lockout Low Locks out local operation Universal DCL Device Clear Low Returns device to default conditions SPE Serial Poll Enable Low Enables serial polling SPD Serial Poll Disable Low Disables serial polling Addressed SDC Selective Device Clear Low Returns unit to default conditions GTL Go To Local Low Returns device to local Unaddressed UNL Unlisten Low Removes all listeners from the bus UNT Untalk Low Removes any talkers from the bus Common High Programs IEEE 488 2 compatible instruments for common operations SCPI High Programs SCPI compatible instru ments for particular operations D 8 IEEE 488
104. Each new Revision includes a revised copy of this print history page Revision A Document Number 2520 900 01 csecssseseeseseessesceeceeseeeeeeeaeeaeeeeaeeeeeeeeeeas June 2001 Revision B Document Number 2520 900 01 ccsessesessesseseseeseeeeeeeseeseeeeseeaeeeeeeeaeeees August 2001 Revision C Document Number 2520 900 01 scessesseseseeteeseseeseeeceeceeseeeeeeeaeeaeeeenees March 2003 All Keithley product names are trademarks or registered trademarks of Keithley Instruments Inc Other brand names are trademarks or registered trademarks of their respective holders KESI Safety Precautions The following safety precautions should be observed before using this product and any associated instrumentation Although some instruments and accessories would normally be used with non hazardous voltages there are situations where hazardous conditions may be present This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury Read and follow all installation operation and maintenance information carefully before us ing the product Refer to the manual for complete product specifications If the product is used in a manner not specified the protection provided by the product may be impaired The types of product users are Responsible body is the individual or group responsible for the use and maintenance of equipment for ensur
105. Erea E Ea 5 8 Staircase SWEEPS sireeni ee eaa Eaa eaa iee e ENEE 5 8 CUSTOM SWEEP visores noire aeae aae iaeiae tes 5 8 Current source operating boundaries sseseseeseereresrereeresreees 5 10 Limit mS isch sets cszevvscsevescccodstesecvaintsisssptnecs tuseoiactsoasdeecaestene 5 10 Loading effects s 0 cssitiecdests bisa auniianinnias abies 5 10 D ta AOW sss 26sicedescass sieves ests tues cuties EE E E R e 5 12 Basic reading display cescessseeseceseecescceeeeeeeeeeneeeaeeees 5 12 Math function display ee ceeeeescceseeceeceeseeceeeeteeeeaeeeees 5 12 SWEEP Cala Storages cesisecsvccveicesecescocasesviaveesecesardeveedsescestais 5 12 Range Filter and Math RINS eean shoes e tot ou sacs sabescadedsedewossdgsWibase docs dvee 6 2 Measurement ranges esceseccesceeseeeeeeeseeeeeaeeeeeeceaeeeneeeeaees 6 2 Laser diode voltage ranges eeceesceesceeeeeeteeeeneeeneees 6 2 Photodiode detector current ranges eeeeeseeeneeeeeees 6 2 Maximum readings eeceeseeececeeeceseeeeseceseeceseeeseeeeaees 6 3 Setting the measurement range ee ee eeeereeeeeeee 6 3 Source ranging ce eeeeeeeeseceeceeseeceeeeeeeceaeeeeeeeeaeeesaeeeaeeeeeeees 6 3 Remote range programming 0 eee eeeeseeeeeeseeeeeeeeeeeeaes 6 3 Range programming example 0 0 eee eeeeeseeeeeeeees 6 4 BMG sorea eere i a rae Stevens sodsoardancvevsesivessonseeeesty 6 4 Averaging filter Overview eessesesseeseseerrsrssreresrsrrsreresresenres
106. GATIVE SHAPE DC PULSE LOW Configure laser diode voltage measurement Select laser diode measurement polarity Select positive measurement polarity Select negative polarity Configure photodiode detector 1 current measure ment Select photodiode detector 1 measurement polarity Select positive measurement polarity Select negative polarity Configure photodiode detector 2 measurement Select photodiode 2 measurement polarity Select positive measurement polarity Select negative polarity Configure laser diode voltage current source Select source polarity Select positive polarity Select negative polarity Select current source output mode DC current output Pulse current output Set pulse low amplitude O 15mA 500mA range 0 to 150mA 5A range Model 2520 User s Manual Getting Started 1 23 Table 1 8 TRIG and FILTER configuration menus Configuration menu item Description CONFIG TRIG Configure triggering CONFIGURE TRIGGER COUNT Specify trigger count FINITE Programmable count INFINITE Never ending count INIT Enable disable INIT continuous ON Turn on continuous OFF Turn off continuous HALT Return unit to idle TRIGGER IN Configure input triggers EVENT Select trigger input detection event IMMEDIATE Immediate event detection GPIB GPIB GET or TRG TIMER After timer interval elapses enter interval MANUAL Front panel TRIG key TLINK Enter trigger link line 1 6 an
107. GR engineering units or SCIENTIFIC nota tion display format for measurement readings NOTES 1 Top level menu choices indicated in bold Indentation identifies each lower submenu level 2 Password is required to unlock calibration See Service Manual Only VIEW DATES is accessible without password 3 Press EXIT key to cancel test Rules to navigate menus Many functions and operations are configured from the front panel menus Use the follow ing rules to navigate through these configuration menus e A menu item is selected by placing the cursor on it and pressing ENTER Cursor position is denoted by the blinking menu item or option The EDIT lt and keys control cursor position A displayed arrow on the bottom line indicates there are one or more additional items or messages to select from Use the appropriate cursor key to display them Model 2520 User s Manual Getting Started 1 19 e A measurement or source range is changed by selecting the function by pressing any one of the LASER or DETECTOR function keys and using the RANGE A or v keys The unit must be in the edit mode to change the laser diode source range Note that when the next higher or lower range is selected the reading increases or decreases by a decade A parameter value is keyed in by placing the cursor on the digit to be changed and using one of the following methods NOTE You can clear a parameter value by pressing the 0000 MENU key
108. ITAL OUTPUT 00000 Select and set up GPIB or RS 232 interface Communications setup menu Select and set up GPIB interface Set primary address 0 30 Default 25 Select protocol see Appendix G Select 488 1 protocol Select SCPI protocol Select and set up RS 232 interface Set baud rate 300 600 1200 2400 2800 9600 19200 38400 57600 Set data bits 7 or 8 Set parity NONE ODD or EVEN Select terminator lt CR gt lt CR LF gt lt LF gt lt LF CR gt Select flow control NONE or XON XOFF Save and recall factory and user setups Setup menu Save user setups 0 4 Restore user setups Set power on configuration Use BENCH defaults as power on Use GPIB defaults as power on User setup 0 4 as power on default Restore factory default configuration Restore bench front panel factory defaults Restore GPIB remote factory defaults Set digital output value 0 15 0 65535 with 2499 DIGIO 16 bit option 1 Main operating keys in bold 2 Changing interface causes reset Model 2520 User s Manual Getting Started 1 21 Table 1 6 PW DELAY and COMPL menus Menu item Description PW Set laser diode current source I pulse width PW 0010 uS Pulse width from 500ns to 5ms DELAY Set laser diode current source pulse delay PD 00 10ms Pulse delay from 20us to 500ms COMPL Set laser diode current source voltage compliance CMPL 10 000 V Compliance limit from
109. KEITHLEY Model 2520 Pulsed Laser Diode Test System User s Manual An Interworld Highway LLC Company A GREAMBR MEASU R BORE ONFIDENCE WARRANTY Keithley Instruments Inc warrants this product to be free from defects in material and workmanship for a period of 1 year from date of shipment Keithley Instruments Inc warrants the following items for 90 days from the date of shipment probes cables rechargeable batteries diskettes and documentation During the warranty period we will at our option either repair or replace any product that proves to be defective To exercise this warranty write or call your local Keithley representative or contact Keithley headquarters in Cleveland Ohio You will be given prompt assistance and return instructions Send the product transportation prepaid to the indicated service facility Repairs will be made and the product returned transportation prepaid Repaired or replaced products are warranted for the balance of the original warranty period or at least 90 days LIMITATION OF WARRANTY This warranty does not apply to defects resulting from product modification without Keithley s express written consent or misuse of any product or part This warranty also does not apply to fuses software non rechargeable batteries damage from battery leakage or problems arising from normal wear or failure to follow instructions THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IM
110. Manual Command Also changes SOURce 1 CURRent STARt SOURce 1 CURRent STOP SOURce 1 CURRent STEP SOURce 1 CURRent POINts SOURce 1 CURRent CENTer SOURce 1 CURRent SPAN SOURce 1 PULSe WIDTh SOURce 1 PULSe DELay SOURce 1 PULSe TRANsition STATe REN GTL SOURce 1 CURRent STEP SOURce 1 CURRent CENTer SOURce 1 CURRent SPAN SOURce 1 CURRent STEP SOURce 1 CURRent CENTer SOURce 1 CURRent SPAN SOURce 1 CURRent POINts SOURce 1 CURRent STEP SOURce 1 CURRent STARt SOURce 1 CURRent STOP SOURce 1 CURRent STEP SOURce 1 CURRent STARt SOURce 1 CURRent STOP SOURce 1 CURRent STEP SOURce 1 PULSe DELay TRACe POINts SOURce 1 PULSe WIDTh SOURce 1 PULSe WIDTh See local and remote transition in Section 10 Differences remote vs local operation Measurement Considerations F 2 Measurement Considerations Model 2520 User s Manual Optimizing laser diode connections There are several key considerations when making connections to the laser diode e Cable length and inductance e Exposed loop area e Correct sense lead connections e Magnetic coupling between sense and current leads Each of these considerations is discussed in detail below Current pulse output circuit model Figure F 1 shows the Model 2520 current pulse output circuit model Components include the current source I and voltage clamp Vc compliance circuit L is the cable inductance
111. Model 2520 User s Manual Reference tables Table 14 1 through Table 14 10 summarize the commands for each SCPI subsystem The following list includes the SCPI subsystem commands and the table number where each command is summarized Summary table Subsystem Function s 14 1 CALCulate VV V I MX B and power math functions 14 2 DISPlay Display format and messages 14 3 FORMat Remote data format 14 4 OUTPut Source outputs on off interlock status 14 5 SENSe Laser diode voltage photodiode current measure ments 14 6 SOURce Laser diode current photodiode source configura tion 14 7 STATus Instrument status 14 8 SYSTem System presets error formats 14 9 TRACe Sample buffer access 14 10 TRIGger Unit triggering control General notes Brackets are used to denote optional character sets These optional characters do not have to be included in the program message Do not use brackets in the program message Angle brackets lt gt are used to indicate parameter type Do not use angle brackets in the program message The Boolean parameter lt b gt is used to enable or disable an instrument operation 1 or ON enables the operation and 0 or OFF disables the operation Upper case characters indicate the short form version for each command word Default Parameter Listed parameters are both the RST and S YSTem PRESet defaults unless noted otherwise Parameter notes are located at t
112. NS3 These raw samples are pro cessed by the DSP section to form processed readings and can be directly accessed with the TRACe commands see below e Reading buffer stores processed readings from the DSP For the fixed mode of operation the number of readings is equal to the trigger count For sweep or list mode operation the reading buffer stores all sweep data with the number of read ings determined both by sweep parameters and the trigger count The FETCh READ and MEASure queries access data from the reading buffer see below Model 2520 User s Manual Data Flow C 3 SENS1 SENS2 and SENS3 INIT The SENS1 block represents the basic laser diode voltage readings The SENS2 and SENS3 blocks represent the basic measured current readings for photodiode detector 1 and photodiode detector 2 respectively If the filter is enabled the readings will be fil tered The SENS blocks also measure time for the timestamp Readings can be taken directly from one of the SENS blocks with one of the DATA queries when the unit is in idle When the INITiate command is sent the programmed number of source and measure operations are performed and the respective data is temporarily stored in a reading buffer For example if 20 source and measure operations were performed then 20 sets of data will be stored in the reading buffer Data from this buffer is then routed to other enabled data flow blocks NOTE Ifthe Model 2520 is in the fixed mo
113. NTERLOCK DB 9 connector for a remote interlock switch KEY INTERLOCK Key interlock switch key must be inserted and rotated to ENABLED position to operate NOTE Both interlocks must be enabled to operate Indicator lights INTERLOCK STATUS Shows interlock status Glows blue when disabled source outputs cannot be turned on Glows green when enabled source outputs can be turned on LASER POWER ON Indicates when source outputs are turned on WARNING Ifat any time the indicators provided on the testhead for INTER LOCK STATUS or LASER POWER ON should fail to light or to properly indicate status immediately contact a Keithley service repre sentative for repair Failure to do so may expose the user to hazards without proper warnings See Interlock status indicator test sequence page 9 7 for instructions on verification of correct operation of the indicators Model 2520 User s Manual Getting Started 1 11 Power up Line voltage The Model 2520 operates from a line voltage in the range of 100V to 240V at a frequency of 50 or 60Hz Line voltage selection is automatic CAUTION Operating the instrument on an incorrect line voltage may cause dam age possibly voiding the warranty Line power connection Perform the following steps to connect the Model 2520 to line power and turn it on 1 Before plugging in the power cord make sure the rear panel power switch located in the power module is in the off 0 position
114. OISE typical 10 00 mA 0 7 pA lt 10Q 0 3 20 pA 90 nA 20 00 mA 1 4 uA lt 6Q 0 3 65 pA 180 nA 50 00 mA 3 4 uA lt 3 0 3 90 pA 420 nA 100 00 mA 6 8 pA lt 2 52 0 3 175 pA 840 nA TEMPERATURE COEFFICIENT 0 18 C amp 28 50 C 0 15 x accuracy specification C INPUT PROTECTION The input is protected against shorting to the associated channel s internal bias supply The input is protected for shorts to external supplies up to 20V for up to 1 second with no damage although calibration may be affected SYSTEM SPEEDS Reading Rates ms 1 Number of Source Points To Memory To GPIB 1 5 3 6 8 10 U8 ZS 18 100 l3 48 120 1000 8 431 1170 GENERAL SPECIFICATIONS DCFLOATING VOLTAGE User may float common ground up to 10VDC from chassis ground COMMON MODE ISOLATION gt 10 Q OVERRANGE 105 of range on all measurements and voltage compliance SOURCE OUTPUT MODES Fixed DC Level Fixed Pulse Level DC Sweep linear log and list Pulse Sweep linear log and list Continuous Pulse continuous low jitter PROGRAMMABILITY IEEE 488 SCPI 1995 0 RS 232 5 user definable power up states plus factory default and RST DIGITAL INTERFACE Safety Interlock External mechanical contact connector and removable key switch Aux Supply 5V 300mA supply Digital I O 2 trigger input 4 TTL Relay Drive outputs 33V 500mA max diode clamped Tlink 6 programmable trigger input outputs Pulse Trig
115. PARTS SERVICE BY QUALIFIED PERSONNEL ONLY m KEITHLEY MADE IN U S A IEEE 488 CHANGE IEEE ADDRESS WITH FRONT PANEL MENU i TRIGGER LINK RS 232 LINE FUSE SLOWBLOW 1 6A 250V 1 D LINE RATING 100 240VAC 50 60Hz 140VA MAX Model 2520 Testhead DISABLED PULL TO BOTH INTERLOCKS MUST BE ENABLED TO OPERATE FEMOVE KEY REMOTE INTERLOCK INTERLOCK DISABLED o e E GREEN ENABLED C RED DISABLED O O INTERLOCK LOEn STATUS POWER ENABLED CONN 2 Cable CONN 1 Cable Model 2520 User s Manual Connections 2 5 Signal connectors Signal connectors Figure 2 2 shows the location of the signal connectors on the front panel of the testhead These connectors are further described below Figure 2 2 Testhead signal connectors Model 2520 Testhead HI_ CURRENT LO A DETECTOR 1 DETECTOR 2 Detector Laser Diode Connectors Connectors 2 6 Connections Model 2520 User s Manual Triax DETECTOR connectors The electrical configuration of each triax DETECTOR connector is shown in Figure 2 3 Connector terminals are designated as follows e Center conductor of the connector and triax cable current input This terminal connects to one terminal of the photodiode being used as a detector Inner ring of the connector and inner cable shield voltage bias source This termi nal connects to the other photodiode terminal Outer rin
116. PIB When using the 488 1 protocol throughput is enhanced up to 10 times for data sent to the Model 2520 command messages and up to 20 times for data returned by the Model 2520 response messages The speed of readings sent over the GPIB is also increased NOTE With the 488 1 protocol selected you will still use SCPI commands to program the Model 2520 Operation differences between the two protocols are discussed in this appendix Selecting the 488 1 protocol Perform the following steps to select the 488 1 protocol Press the COMM key to display the COMMUNICATIONS SETUP menu Place the cursor on GPIB then press ENTER Press ENTER at the ADDRESS prompt to display the GPIB PROTOCOL menu Place the cursor on 488 1 and press ENTER 5 Use the EXIT key to back out of the menu structure Pe oe When switching between the SCPI protocol and 488 1 protocol the instrument does not reset The GPIB protocol setting is saved in EEPROM and the unit will power up with that selected protocol The GPIB protocol cannot be changed over the bus However there is a query command to determine the presently selected protocol When the 488 1 protocol is selected the mes sage exchange protocol MEP disables Therefore if you use the following query to request the state of MEP you will know which protocol is enabled SYSTem MEP STATe If a 1 is returned MEP is enabled and the SCPI protocol is selected A 0 indicates that MEP
117. PLIED INCLUD ING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE THE REMEDIES PROVIDED HEREIN ARE BUYER S SOLE AND EXCLUSIVE REMEDIES NEITHER KEITHLEY INSTRUMENTS INC NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS INC HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES SUCH EXCLUDED DAM AGES SHALL INCLUDE BUT ARE NOT LIMITED TO COSTS OF REMOVAL AND INSTALLATION LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON OR DAMAGE TO PROPERTY KEITHLEY Keithley Instruments Inc 28775 Aurora Road Cleveland Ohio 44139 e 440 248 0400 Fax 440 248 6168 1 888 KEITHLEY 534 8453 e www keithley com Sales Offices BELGIUM Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 CHINA Yuan Chen Xin Building Room 705 e 12 Yumin Road Dewai Madian Beijing 100029 8610 8225 1886 Fax 8610 8225 1892 FINLAND Tiet j ntie 2 e 02130 Espoo Phone 09 54 75 08 10 Fax 09 25 10 51 00 FRANCE 3 all e des Garays 91127 Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 GERMANY Landsberger Strasse 65 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 GREAT BRITAIN Unit 2 Commerce Park Brunel Road Theale Berkshire RG7 4AB e 0118 929 7500 Fax 0118 929 7519 INDIA 1 5 Eagles Street e Langford Town
118. PULSe TRANsition command as covered in SOURce subsystem page 14 32 This command allows you to increase the rise time of the pulse Increasing the rise time will help reduce overshoot and or oscillations that could occur when long cables are used or if poor connections are present in the test setup 5 8 Source Measure Concepts Model 2520 User s Manual Sweep waveforms There are three basic sweep types available linear staircase logarithmic staircase and custom NOTE Staircase sweeps can be programmed both from the front panel and via remote while custom sweeps are available only via remote Staircase sweeps As shown in Figure 5 8 the linear staircase sweep goes from the start level to the stop level in equal linear steps The logarithmic staircase sweep is similar except it is done on a log scale with a specified number of steps per decade For the DC mode the current will remain at a fixed amplitude for the duration of each sweep point For the pulse mode the current will remain at the sweep step amplitude for the programmed pulse width and the time between steps depends on the programmed delay NOTE The duration of each step is the sum of the programmed pulse width and pulse delay times for both DC and pulse sweeps See Section 7 for more details on staircase sweep operation See also the SOUR1 CURR and SOUR1 SWE commands under SOURce subsystem page 14 32 for information on programming staircase sweeps via re
119. Put roe ger ut gt NONE TRIGger PSTest BSTest SOURce1 PULSe DELay Ipsec Filter Process Repeat Note Sweep performed only if enabled Filter count determines filter process SOURce1 PULSe WIDTh repeat cycles 10sec GPIB Default gt Output Trigger Model 2520 User s Manual Triggering 8 11 While operating within the trigger layer most commands will not be executed until the Model 2520 completes all of its programmed source measure operations and returns to the idle state However these commands will be processed while not in the idle state ABORt e SYSTem PRESet e TRG or GET e RST e RCL SDC DCL e IFC NOTE SDC DCL or ABORt place the Model 2520 in the idle state For fastest response use SDC or DCL to return to idle Event detection Once the instrument is taken out of idle operation proceeds through the trigger model to perform the measurement actions In general operation is held up at an event detector waiting for an input trigger until the programmed trigger event occurs Input triggers The programmable trigger in events for the Trigger Layer are described as follows IMMediate Event detection occurs immediately allowing operation to continue BUS Event detection occurs when a bus trigger GET or TRG is received TIMer Event detection occurs immediately on the initial pass through the trigger model Each subsequent detection is satisfied when the progra
120. R POL NEG SENS3 CURR POL NEG SOURI CURR RANG 0 5 SOURI CURR 0 5 SOURI VOLT PROT 5 SOURI CURR POL POS SOURI FUNC PULS SOURI PULS DEL 100e 6 SOURI PULS WIDT 10e 6 SOURI CURR LOW 10e 3 SOUR2 VOLT 20 SOUR3 VOLT 10 Laser diode measure range 10V Laser diode positive measure polarity Detector 1 negative measure polarity Detector 2 negative measure polarity 0 5A laser diode source range Laser diode source output 0 5A 5V laser diode source voltage limit Laser diode source positive polarity Laser diode source pulse mode 100psec pulse delay 10usec pulse width 10mA low current pulse Detector 1 bias source level 20V Detector 2 bias source level 10V Laser Diode Testing Source and measure configuration menus Briefly summarizes the menus for configuring the laser diode source as well as all three measurement functions Front panel laser diode testing Provides a detailed procedure for performing laser diode tests from the front panel Remote laser diode testing Summarizes remote commands for testing laser diodes via remote and also gives a programming example 4 2 Laser Diode Testing Model 2520 User s Manual Source and measure configuration menus Table 4 1 summarizes the measurement and source configuration menus used in this sec tion See Section 3 for configuration procedures WARNING Itis the responsibility of the customer to operate instruments in a sa
121. RATOR SERVICABLE PARTS SERVICE BY QUALIFIED PEXSONNEL ONLY keme EEE 488 MADE IN CAT I i oe PULSE Nee Witt FRO PANEL MENU C SYNC A DIGYAL 1 0 OUT OCR TRIGGER LINK RS 232 TESTHEAD CONN 1 LINE FUSE SLOWBLOW 1 6A 250V qm Ae tae 100 240VAC 50 60Hz TESTHEAD h CONN 2 140VA MAX s CAUTION FOR CONTINUED PROTECTION AGAINST FIRE HAZARD REPLACE FUSE WITH SAME TYPE AND RATING Model 2520 3 Connect any additional connectors from other instruments as required for your application 4 Make sure the other end of the cable is properly connected to the controller Most controllers are equipped with an IEEE 488 style connector but a few may require a different type of connecting cable See your controller s instruction manual for information about properly connecting to the IEEE 488 bus NOTE You can only have 15 devices connected to an IEEE 488 bus including the con troller The maximum cable length is either 20 meters or two meters multiplied by the number of devices whichever is less Not observing these limits may cause erratic bus operation 10 6 Remote Operations Primary address Model 2520 User s Manual The Model 2520 ships from the factory with a GPIB primary address of 25 When the unit powers up it momentarily displays the primary address You can set the address to a value from 0 to 30 but do not assign the same address to another device or to a controller that is on the
122. S WIDT 0 000001 Reset 2520 Set source mode to FIXed not sweep Set current pulse amplitude to 200mA Set pulse delay time between pulses to 330us Sets the pulse width to lus TRIG COUN CONTINUOUS Enables continuous pulsing mode OUTP ON Turns Output ON SYST KEY 20 Begins continuous pulsing SDC Stops continuous pulsing OUTP OFF Turns Output OFF SDC Selected Device Clear SDC is a GPIB Bus Command see Table 10 1 Implementing this command depends on the GPIB controller driver Refer to GPIB controlled documentation for specific syntax Where Example For Keithley GPIB transmit UNL LISTEN lt addr gt SDC status For NI GPIB Dev Clear lt Boardnum gt lt addr gt lt addr gt is the GPIB address of the 2520 and lt Boardnum gt is the GPIB controller board number usually 0 Related modes There are three choices in the 2520 Trigger Count menu 1 Trigger count Finite This mode will output up to 5000 pulses with a fixed source current Measurements are taken at each pulse which means that the minimum pulse delay time is about 2 milliseconds 400us In addition the minimum pulse delay is constrained by the maximum duty cycle of 4 above 1A source levels This means that requesting a duty cycle gt 4 will cause the pulse delay to be increased to give a duty cycle 4 For I lt 1A the maximum duty cycle is about 15 Trigger count Inf This mode will output an infini
123. S aeee ea a ara ies e oes 14 37 STOP SIS hree e a a S RETON 14 37 CENTET lt M e aae e E 14 38 SPAN AIS aeree e a a a ERETON 14 38 STEPS I n R ese seetnan ae soe thease 14 39 POINtS lt K gt sifnctdtinieingiieluitidsinaiiethee 14 40 DIRection lt name gt ceeeeesessceeeeeceseeeeeeeeseeeeeeeeanees 14 40 Configure list ereire n a oS 14 41 CURRent lt NRf list ooo eeeeseeneeneeneceeseeaeeneeaes 14 41 APPend lt NRf list oo eeeeeeeseeneeseeeeeeeeeseeneeatees 14 41 POINTS oss seed enon iis hehe eee ities aii 14 42 WIDThH lt NR List wo ee eeeeeeeeceeeeeeeeeeseeaeeneeaes 14 42 APPend lt NRf list wo eeeeeeeeeeneeseeeeeeeeeseeaeeaeees 14 42 POUINGS ose coss func iai ea aaa eects 14 42 DELay lt NR f list pesitses ereere 14 43 APPend lt NRf list oo eee eeeeeeeneeteeseeeeeeseeaeeaeens 14 43 POINGS innein deel bea oles 14 43 Sweep and list program examples ce ceeeeeeeeeeeeerees 14 44 Linear staircase sweep eseeecceeseesseeeeeeeetreeseeeeees 14 44 List SWEEP cissicesieciee dideestens E E T E 14 44 Logarithmic staircase sweep sseseseereseereeeereerrseeeeses 14 45 SOURce2 and SOURce3 sossesesssssseseseressersreresesresessreessee 14 46 Set amplitudes useisiin iiaei 14 47 IMMediate AMPLitude lt n gt ce eeesseeeeees 14 47 SOURCE secstcvisucedtseesrevesdeieh vectivvasundenel icessitpiserpepeteateetes 14 47 Setting digital output oo eee ceeesereeeeseteeeteeneeeaees 14 47 LEVel lt NRf g
124. SCPI Command Reference 14 39 CENTer and SPAN are coupled to STARt and STOP Thus when cen ter and span values are changed the values for start and stop are affected as follows Start Center Span 2 Stop Center Span 2 STEP lt n gt SOURce 1 CURRent STEP lt n gt Specify step size for sweep Parameters lt n gt 0 to 5 0 Set source level amps DEFault OA MINimum 0A MAXimum 5 0A Query STEP Query step size for sweep STEP DEFault Query RST default level STEP MINimum Query lowest allowable level STEP MAXimum Query highest allowable level Description This command is used to specify a step size for a linear sweep When the sweep is started the source level changes in equal steps from the start level to the stop level A measurement is performed at each source step including the start and stop levels NOTE This command cannot be used for a logarithmic sweep Use the POINts com mand to set the source and measure points for a log sweep To avoid a setting conflicts error make sure the step size is greater than the start value and less than the stop value The number of source and measure points in a linear sweep can be cal culated as follows Points Stop Start Step 1 Points Span Step 1 An alternate way to set the source and measure points in a linear sweep is to simply specify the number of source and measure points in the sweep using the POINts command Note that the STEP a
125. SCPI based programs ooo ee eeeeeeseeeeeeseeeeeeeeees G 3 Bus hold off os 5 sen scaissesesecsadvanoneciaccbinesoaettbeaseasecanestoasyGasenie G 4 Triggeron talk a seasicss cess oeesasiesenceissonsstensesavesoensucoysel ons Weaseaie G 4 Message available irii innsnevre reiros G 4 General operation notes eee eeeeeeseeceseeeeeeeeeeeeaeeeeeeaeees G 4 Example Programs IntrOdUctiOny siirrt ae e E E REER H 2 Hardware requirements insssscisiisriccsicissiisiiisicniriessassesi H 2 Software requireMent ssiisressiiciiniror inie H 2 General program instructions esessesesesseseesesessesesesresrssesee H 2 Laser diode test program sssseseseesesseseesestsresreserrestrsreresreseereses H 3 Linear staircase sweep program e sessessessssessesssesstsserssessessessees H 4 List sWeep PLO STAM soc p sabes eb eeecuarseodeladefe a TAE aa EE r EEE A H 5 Continuous Pulse Mode Continuous pulse mode se eeeeesceeeseeesceeeaeceseeceaeeeeeeeaeeeeeeeeaees I 2 Pulse test advantage s sssseeseeeeeeseeessessessssssessresresrereresresees I 2 IDIS CY CIE ecsccesdecevendvecectesvecsicedeeasvesscesevevsstecstesceteaseestece ines I 2 Configuring the 2520 to use Continuous Pulse Mode 1 3 Pront panelene resen ts sescesaiveiasestesstisvecastent inns 1 3 Remote configuration over GPIB TEEE 488 0 0 cee 1 4 Related MOdeS cccccssssccceesssscceccesssseecceesssceeecceeessseeeeees 1 4 List of Illustrations 1 F
126. SOURce 1 CURRent RANGe lt range gt Set laser diode current source range 0 5 or 5 6 4 Range Filter and Math Filter Model 2520 User s Manual Range programming example Table 6 5 shows a programming example for controlling range The Model 2520 is set up as follows e Laser diode voltage measure range 5V e Laser diode current source range 500mA e Detector current range 10mA Detector 2 current range 100mA Table 6 5 Range programming example Command Description RST SENS1 VOLT RANG 5 SOURI CURR RANG 0 5 SENS2 CURR RANG 10e 3 SENS3 CURR RANG 100e 3 Restore GPIB defaults 5V laser diode measure range 500mA laser diode source range 10mA detector current range 100mA detector 2 current range OUTP1 ON Turn on outputs READ Trigger and acquire readings OUTP1 OFF Turn off outputs Filtering stabilizes noisy measurements caused by noisy input signals The Model 2520 uses an averaging type filter for all three measurements The number of readings averaged can be set between 1 and 100 However the more filtering that is used higher number of readings averaged the slower the measurement process becomes Averaging filter overview When the averaging filter is enabled the unit cycles through the complete delay pulse cycle for each filter sample measurement See Section 5 for delay pulse details The measurement results for all delay pulse cycles are
127. SWEEPS menu select SWEEP COUNT press ENTER then choose FINITE or INFINITE as desired Press EXIT to return to normal display Step 3 Turn outputs on Press the ON OFF OUTPUT key to turn the outputs on blue OUTPUT indicator turns on The Model 2520 will output the photodiode bias voltages Step 4 Run sweep To run the sweep press the SWEEP key After the sweep is completed turn the output off by pressing the ON OFF OUTPUT key Step 5 Read buffer Use the RECALL key to access the readings stored in the buffer 7 8 Sweep Operation Model 2520 User s Manual Remote sweep operation Staircase sweep commands Table 7 2 summarizes remote commands used for linear and log staircase sweep opera tion See Section 14 Configure sweeps for more details on these commands Table 7 2 Linear and log staircase sweep commands Command Description SOURce 1 CURRent MODE SWEep Select staircase sweep mode SOURce 1 CURRent STARt lt current gt Specify sweep start current 0 to 5 0 SOURce 1 CURRent STOP lt current gt Specify sweep stop current 0 to 5 0 SOURce 1 CURRent STEP lt current gt Specify sweep step current 0 to 5 0 SOURce 1 CURRent CENTer lt current gt Specify sweep center current 0 to 5 0 SOURce 1 CURRent SPAN lt current gt Specify sweep span current 0 to 5 0 SOURce 1 SWEep SPACing lt type gt Select staircase sweep type LINear or LOGarithmic SOURce 1 SWEep POINts lt
128. T 1 OUTPUT 25 SOUR1 LIST PRINT 1 OUTPUT 25 SOUR2 VOLT PRINT 1 OUTPUT 25 SOUR3 VOLT PRINT 1 OUTPUT 25 OUTP1 ON CLS PRINT 1 OUTPUT 25 READ PRINT 1 ENTER 25 LINE INPUT 2 R PRINT Custom sweep data R PRINT 1 OUTPUT 25 OUTP1 OFF END Laser diode custom sweep program 1 1 FORM ELEM VOLT1 CURR2 CURR3 MODE LIST i CURR 0 2 0 1 0 4 0 3 0 5 DEL 7e 3 4e 3 2e 3 8e 3 le 3 Open IEEE 488 output path Open IEEE 488 input path Set input terminator Set output terminator Put 2520 in remote Restore GPIB defaults Voltage current data Custom sweep mode I list D list WIDT 10e 6 50e 6 35e 6 20e 6 602 6 5 5 1 1 1 Detector 1 bias 5V Detector 2 bias 5V Turn on outputs Trigger sweep and read data Address 2520 to talk Input sweep data Turn off outputs Continuous Pulse Mode l 2 Continuous Pulse Mode Model 2520 User s Manual Continuous pulse mode In addition to LIV characterization laser diodes typically require some type of wavelength or spectrum measurement In these cases the 2520 can be used as a current pulse generator driving the laser diode with a current pulse train while a spectrometer or other instrument makes measurements As a pulse generator the 2520 provides a fixed pulse current level with control over pulse width and pulse off time to provide a desired duty cycle As with conventi
129. TA query See below When dis abled the CALC1 DATA CALC2 DATA CALC3 DATA and gt CALC4 DATA queries will return the NAN not a number value of 9 91e37 Model 2520 User s Manual SCPI Command Reference 14 17 DATA CALCulate 1 DATA2 Read laser diode math CALC1 result CALCulate2 DATA Read detector 1 math CALC2 result CALCulate3 DATA Read detector 2 math CALC3 result CALCulate4 DATA Read delta math CALC4 result Description These query commands are used to read the result of the CALC1 CALC2 CALC3 or CALC4 calculation The largest valid calculation result can be 9 9e37 which defined by SCPI is infinity An invalid NAN not a number result of 9 91e37 indicates that CALC1 CALC2 CALC3 or CALC4 is disabled or that a division by zero error has occurred See STATe lt b gt page 14 16 LATest CALCulate 1 DATA LATest2 Read latest CALC1 result CALCulate2 DATA LATest Read latest CALC2 result CALCulate3 DATA LATest Read latest CALC3 result CALCulate4 DATA LATest Read latest CALC4 result Description These commands work exactly like CALC1 DATA CALC2 DATA CALC3 DATA and CALC4 DATA except that they return only the latest CALC1 CALC2 CALC3 or CALC4 result DISPlay subsystem The display subsystem controls the display of the Model 2520 and is summarized in Table 14 2 Control display ENABle lt b gt DISPlay ENABle lt b gt Control display circuitry Parameters lt b gt
130. Terlock Path to interlock status TRIPped Interlock tripped 1 yes or 0 no Model 2520 User s Manual SCPI Command Reference 14 7 Table 14 5 SENSe command summary Default Command Description parameter SCPI SENSe 1 Sense subsystem to control laser diode voltage measurement J VOLTage DC Path to configure voltage v RANGe Configure measurement range v UPPer lt n gt Select range by specifying the expected voltage reading 10 v 0 to 10 5 Ranges 5 or 10 UPPer Query range Jv POLarity lt name gt Select polarity Name POSitive or NEGative POS POLarity Query polarity PROT TRIPped Query if voltage compliance limit is exceeded 1 yes 0 no y AVERage Path to configure digital filter 10 v COUNt lt n gt Specify filter count 1 to 100 v COUNt Query filter count OFF v STATe lt b gt Enable or disable digital filter Jv STATe Query state of digital filter DATA LATest Query latest reading only when trigger model is in IDLE SENSe2 Sense 2 subsystem to control detector 1 current measurement y CURRent DC Path to configure current y RANGe Configure measurement range v UPPer lt n gt Select range by specifying the expected current reading 0 1 v 0 to 0 105 Ranges 0 01 0 02 0 05 0 1 UPPer Query range y POLarity lt name gt Select polarity Name POSitive or NEGative POS POLarity Query polarity AVERage Path to configure d
131. Testing Circuit configuration for laser diode testing 0 ee 4 3 Source Measure Concepts Delay pulse Cycle csecsen 5 2 Front panel fixed mode pulse parameters s sseeeeseeeereeeereee 5 4 Front panel staircase sweep mode pulse parameters 5 5 Front panel staircase sweep mode DC parameters 5 5 Remote fixed mode pulse parameters 0 0 ee eeeeeeeeeeeeeeeees 5 6 Remote staircase sweep mode pulse parameters 5 7 PUISC CharacterSties 225 ccecescsaeisedesascazensvenasst sasezsaseaussonsarsaaatenes 5 7 Sweep waveform types oo eeceseseesecseseeessecesesseeeseeeeeeaeeseees 5 9 Custom sweep waveform 00 cceeeeeeseeseeeseeeeeeaseneeeaeeeeeeaeesaes 5 9 Current source limit Lines 0 eee eseeseeseeeseeeeeeaeeeeens 5 10 Loading effects secs ccciiccaeeeseads adagei seseug cpasbs xsdeses naas 5 11 Data flow front panel oo eee eee eeeeeeeeeeeeeseeeaeeeeeeaeeeeens 5 13 Range Filter and Math Averaging filter during SWEEP ee eeeeseeeseereceeeeeeeeeeeeeenees 6 5 7 Sweep Operation Figure 7 1 Linear staircase sweep eeseeeeseesseeseeeseeseeesecseeeaeeneeeaeeneeeaes 7 2 Figure 7 2 Logarithmic staircase sweep oo ee eeeeseeeeeeeceeeeseeneeeseeeseeaes 7 3 Figure 7 3 Custom pulse sweep esceseeeesecesceeeeecesceceeeceaeeceeeeeaeeeseeeeaeers 7 4 Figure 7 4 Sweep configuration Menu tree oo eee eee eee eeeeeeeeereeeeeenees 7 5 8 Triggering Figure 8 1 Trigger model front panel operati
132. This command is used to select the scale for the sweep With LINear selected the source and measure points in the sweep will be performed on a linear scale With LOGarithmic selected the source and measure points will be performed on a logarithmic scale STARt lt n gt STOP lt n gt SOURce 1 CURRent STARt lt n gt Specify start current level SOURce 1 CURRent STOP lt n gt Specify stop current level Parameters lt n gt 0 to 5 0 Set source level amps DEFault OA MINimum OA MAXimum 5 0A Query STARt Query start level for sweep STARt DEFault Query RST default level STARt MINimum Query lowest allowable level STARt MAXimum Query highest allowable level STOP Query start level for sweep STOP DEFault Query RST default level STOP MINimum Query lowest allowable level STOP MAXimum Query highest allowable level 14 38 SCPI Command Reference Model 2520 User s Manual Description CENtTer lt n gt SPAN lt n gt These commands are used to specify the start and stop levels for a sweep When the sweep is started the source will output the specified start level and measurements are performed The sweep continues until the source outputs the specified stop level At this level the instrument again performs another series of measurements and then stops the sweep The source and measure points in a sweep can be set by specifying a step size or by specifying the number of source and measure points in the swee
133. UR is set to manual the TRIG key will be active in remote TALK This indicator is on when the instrument is in the talker active state Place the unit in the talk state by addressing it to talk with the correct MTA My Talk Address command TALK is off when the unit is in the talker idle state Place the unit in the talker idle state by sending a UNT Untalk command addressing it to listen or sending the IFC Interface Clear command LSTN This indicator is on when the Model 2520 is in the listener active state which is activated by addressing the instrument to listen with the correct MLA My Listen Address com mand LSTN is off when the unit is in the listener idle state Place the unit in the listener idle state by sending UNL Unlisten addressing it to talk or sending IFC Interface Clear command over the bus SRQ You can program the instrument to generate a service request SRQ when one or more errors or conditions occur When this indicator is on a service request has been generated This indicator stays on until the serial poll byte is read or all the conditions that caused SRQ have been cleared See Section 11 for more information LOCAL key The LOCAL key cancels the remote state and restores local operation of the instrument Pressing the LOCAL key also turns off the REM indicator and returns the display to nor mal if a user defined message was displayed If the LLO Local Lockout command is in effect the LOC
134. URR2 Ipp VOLT2 V82 CURR3 Ipp3 VOLT3 Vp 3 5 0A maximum pulse mode only 1A maximum in DC mode 4 Settings affected by maximum duty cycle See Section 5 Model 2520 User s Manual Table 4 2 continued Laser diode test commands Laser Diode Testing 4 7 Command Description SOURce 1 CURRent MODE FIXed SOURce 1 CURRent RANGe lt range gt SOURce 1 CURRent lt current gt SOURce 1 CURRent POLarity lt polarity gt SOURce 1 VOLTage PROTection lt limit gt SOURce 1 FUNCtion lt function gt SOURce 1 PULSe DELay lt delay gt SOURce 1 PULSe WIDTh lt width gt SOURce 1 CURRent LOW lt low_current gt SOURce2 VOLTage lt voltage gt SOURce3 VOLTage lt voltage gt Select fixed not sweep laser diode current source mode Select laser diode source range 0 5 or 5 Set laser diode source current 0 to 5 0 3 Set laser diode source polarity POSitive or NEGative Set laser source voltage compliance limit 3 to 10 5 Select laser diode current source function DC or PULSe Set laser diode source pulse delay 20e 6 to 0 5 4 Set laser diode source pulse width 500e 9 to 5e 3 4 Set low pulse amplitude for pulse mode 0 to 0 015 500mA range 0 to 0 150 5A range Set detector 1 source voltage 0 to 20 Set detector 2 source voltage 0 to 20 COND I V RES V I POWER Vy I 2 CURRI IL VOLT1 V CURR2 Ipp VOLT2 Vg2 CURR3 Ipp3 VOLT3 Vp
135. V lt NRi gt Save uo eeseseeceeeeecceensescentsoereneeeersnteees 12 4 RCL lt NRf gt recall ee eeeeseeseeeeceeeeseeeeeeseeeeeaes 12 4 SAV RCL programming example eee 12 5 RSW TOS Gl iss oses pets evciecsen teeyasebeuive ciasascvadiuemelearcsines 12 5 UI RG WB BOR icy ect cictecew eves ii R 12 5 TRG programming example eee eeeeseeeeeeees 12 5 TST self test QUery soucient 12 6 WAIT wait to COntimue oo eee eeeeeeeseeeeeeeeeeeeseeeeeeeees 12 6 SCPI Signal Oriented Measurement Commands Command SUMIMALY visioen tisis rrii senaisiais sinoi 13 2 ACQUITING TCACINGS 3 cocci teneiessieestdesescceacssesactesecvaciesenaccuuerabesces 13 2 FETON intinck atest atiicids cies e lenestees 13 2 SENSe 1 DATA LATest oossoo 13 3 SENSe2 DATA LATest oo ec eeeseeeceeeneeeeeeeseeeeeeees 13 3 SENSe3 DATA LATest oeer 13 3 READ soissssaccectecstgieGaelesaelelealenstceessichobedtsbenseraleseeteucediacn 13 3 MEASURE aunen in ER RR 13 3 SCPI Command Reference Reference tables nenn ESS 14 2 Calculate subsystems 00 eee eeeeseeeeeseceeeeseceeeeaeseeeeeeeneesees 14 14 Select laser diode math function cccessececeeessseeeeee 14 15 FORMat lt name gt oo cccccccccceeeesesesesssesssssesstseeeeees 14 15 Set MX B parameters oo eee eeseeseeseceeeeneeeneeeeeeaeeees 14 15 MBF actor lt 1 sccecdss sseseccessscadcaetas AE 14 15 MMBactor lt i gt asiasana a 14 15 UNITs lt aMme gt
136. YSTem PRESet defaults loaded into the available setup memory If a recall error occurs the setup memory defaults to the SYSTem PRESet values Model 2520 User s Manual Common Commands 12 5 SAV RCL programming example Table 12 3 summarizes the basic command sequence for saving and recalling a setup The present setup is stored in memory location 2 GPIB defaults are restored and the memory location 2 setup is recalled Table 12 3 SAV RCL programming example Command Description SAV 2 Save present setup in memory location 2 RST Restore GPIB defaults RCL 2 Recall location 2 setup RST reset Return Model 2520 to GPIB defaults When the RST command is sent the Model 2520 performs the following operations e Returns the Model 2520 to the GPIB default conditions Refer to Default parame ters column of SCPI tables in Section 14 e Cancels all pending commands e Cancels response to any previously received OPC and OPC commands TRG trigger Send bus trigger to Model 2520 Use the TRG command to issue a GPIB trigger to the Model 2520 It has the same effect as a group execute trigger GET Use the TRG command as an event to control operation The Model 2520 reacts to this trigger if BUS is the programmed arm control source using the TRIG SOUR BUS com mand NOTE Details on triggering are covered in Section 8 TRG programming example The command sequence in Table 12 4 configures the M
137. a nied AA iei B 2 Status and error MESSAES isisisi ii ieii eias B 2 Eliminating common SCPI errors eee eeeeeeseceeeeeeeeeeeeeees B 7 113 Undefined header c cc ccccsecccceesssseccceesssseeeeeees B 7 410 Query INTERRUPTED 0 000 eceeceeseeeteeteeeseeereees B 7 420 Query UNTERMINATED 0 0 ceeceeceeteeteeeeeeesees B 8 Data Flow TntrOductiOn serce pieri EE a S E C 2 Butler S preesens oereear ani peene E EE TAG C 2 SENS1 SENS2 and SENS3 cecccccccessccessteceeseeesseeees C 3 INED aeea aeboebis ese S hanes a a E C 3 BET GW meneen enre aea E wees C 3 READ and MEASure ooo cccceecccceesssseceeeesessseeeeeeesseeeees C 4 CALCulate1 DATA CALCulate2 DATA CAL Culate3 DATA siseses tnr C 4 CAL Culate4 DATA noiire iiher i eisi C 4 TRACe DATA and TRACe DATA VALue ooieoe C 4 IEEE 488 Bus Overview Introduction cccccssccccccsssscsecceeessseceeceeseseecccecsssseeeceessseeeeeeess D 2 Bus CeSCTiption ceeeeseeseceseessceeeeeeeaeecseeeeaeeesaeeeaeeeseeeseeeneees D 2 BUS NES arsa oio ernaten ni ee e EE O E TETES D 5 IDETE E Ni E E EE E E E E oda eeeeees D 5 Bus management lines ssessssseseseesesresessesresesrrsresrsresesresrese D 5 Handshake lines sssonnnnnoononnoeesseneesssssseessseseoesssseneesssssereesss D 5 Bus commands cccccccccessssecceeessseceeccesessseeceeessnseeeceessstseeeeeess D 7 Uniline commands c ccccccccsssccccessssscecceeessnsceeceesessaeeees D 8 Universal m
138. about 100nH while a typical 2 inch square loop has an inductance on the order of 170nH Figure F 4 Effects of open loop area Current Output HI Voltage Sense HI Connecting Large Cables Exposed Loop Area Sense LO Current Output LO A Large exposed loop area Current Output HI Voltage Sense HI Small Exposed Loop Area Connecting Cables Voltage Sense LO Current Output LO B Small exposed loop area Model 2520 User s Manual Measurement Considerations F 7 Figure F 5 shows ideal response of a 2A pulse for short 10 inch properly connected cables Figure F 6 shows the same setup except for the addition of a two square inch loop in the source connection Figure F 5 Ideal response of 2A pulse using 10 inch cables 2S 2 0 1 5 Current A 1 0 0 5 0 0 0 0 6 0 8 1 1 2 1 4 1 6 1 8 2 2 2 Figure F 6 Response of 2A pulse with two square inch loop 2 5 2 0 1 5 Current A 1 0 0 5 0 0 0 0 6 08 1 1 2 1 4 1 6 1 8 2 2 2 2 4 Time us F 8 Measurement Considerations Model 2520 User s Manual Sense lead connections Proper sense lead connections to the laser diode are important to good measurements Figure F 7 shows a comparison of correct and incorrect sense connections With the incor rect connections shown in Figure F 7A sense and current leads are not connected together at the DUT In contrast the correct connections shown in Figure F 7B show sense connec tions made
139. all three measurement functions laser diode voltage and both detector current measurements Model 2520 User s Manual Range Filter and Math 6 7 Conductance This math function computes the conductance from the ratio between the laser diode cur rent source value and the measured voltage Conductance I V where I laser diode source current VL measured laser diode voltage Resistance This math function computes the resistance using the ratio between the measured laser diode voltage and the source current Resistance V1 iL where Vj laser diode voltage measurement Ig laser diode source current Power This math function calculates power using the measured voltage and source current values as follows Power V xf where Vj laser diode voltage measurement Ig laser diode source current MX B This math function multiplies the measured laser diode voltage or photodiode detector current by an offset factor and adds an offset value as follows Reading MX B where M gain slope factor X measured laser diode voltage V1 or photodiode current Ipp B offset value Delta remote only This math function computes the difference between detector 1 and detector 2 current Delta Ipp 5 Ipp2 The calculation is performed point by point on individual A D samples not on the final current measurement Delta is available using the CALC4 subsystem See Section 14 6 8 Range Filter and Math
140. alues Use the following keys to edit source values LASER IL DETECTOR 1 VB and DETECTOR 2 VB selects the laser diode photodiode 1 or photodiode 2 source for editing EDIT edits the last selected source A blinking cursor will appear in the field to be edited and the EDIT annunciator will turn on while in the edit mode If no key is pressed within a few seconds the edit mode will be cancelled automatically COMPL allows editing of the laser diode current source voltage compliance EDIT lt and places the display cursor on the display digit to be changed EDIT a or y increments or decrements the source value Note that pressing either of these keys will automatically enable the source edit mode RANGE a or y selects the laser diode source range 500mA or 5A while in edit mode ENTER Completes source editing without waiting for time out period Numeric keys 0 9 allow you to directly enter source values EXIT exits the edit mode without waiting for the time out period 3 10 Basic Operation Model 2520 User s Manual Configuring laser diode source The basic procedure for setting up laser diode current source values for both DC and pulse modes is outlined below DC mode 1 2 3 SON oe 10 11 Press CONFIG then LASER I to access the source configuration menu Choose POLARITY then press ENTER Select POSITIVE or NEGATIVE as desired then press ENTER See Figure 3 2
141. anode is connected to the center conductor conversely select positive current source polarity if the laser diode anode is connected to the shield This method decreases rise time because it eliminates one of the two cables that connect the current source to the laser diode effectively cutting the cable inductance in half How ever the disadvantage is that one terminal of the laser diode is connected to analog com mon and you must be careful to properly set the polarity as covered above Also this connection method should not be used for the VOLTAGE SENSE terminals F 6 Measurement Considerations Model 2520 User s Manual Exposed loop area The open loop area Figure F 4 also affects the rise time of the measurements because of added inductance With the relatively large open loop area in Figure F 4A the shields are not carried through to the DUT and the exposed signal lines form a current loop This loop effectively increases the inductance and affects the rise time in the same manner as cable inductance outlined above To minimize the exposed loop area carry all shields as close to the DUT as possible as shown in Figure F 4B Doing so will reduce the distributed induc tance and decrease the rise time of the current pulse Inductance for a loop of wire X inches by Y inches with a diameter D inches can be calcu lated as follows 9 Y x L 10 16x 10 xin 255 in 25 Thus a typical 1 inch square loop has an inductance of
142. aser diode source and measure capabilities The Model 2520 has the following laser diode current source and voltage measurement capabilities Source Current The Model 2520 can source DC current to the laser diode from 8uA to 1A DC or pulse mode 5 0A pulse mode only In the pulse mode pulse on time pulse width is adjustable from 500ns to 5ms in 100ns increments and pulse off time pulse delay is adjustable from 20us to 500ms in 10us increments NOTE Pulse width and delay settings are affected by maximum duty cycle See Section 5 e Measure Voltage The Model 2520 can measure laser diode DC voltage from 0 33mV to 10 5V on two ranges 5V and 10V WARNING Itis the responsibility of the customer to operate instruments in a safe manner Follow all applicable safety regulations for installing config uring and using the Model 2520 The Model 2520 as installed should be approved by the appropriate safety personnel such as the responsi ble Laser Safety Officer or equivalent Suggested starting points for workplace regulations and standards ANSIZ136 1 IEC 825 OSHA 29 CFR 1910 In short always be aware of workplace hazards strive to minimize them and work safely Laser diode source and measure ranges Table 3 1 summarizes laser diode current source ranges resolutions and maximum output values while Table 3 2 lists voltage measurement ranges resolutions and maximum volt ages See Section 6 for more details on rangin
143. ata bus Step Command ATN state Hex Decimal 1 UNL Set low 63 2 LAG Stays low 58 3 SDC Stays low 4 4 Returns high Assumes primary address 26 Table D 4 gives a typical common command sequence In this instance ATN is true while the instrument is being addressed but it is set high while sending the common command string Table D 4 Typical addressed common command sequence Data bus Step Command ATN state Decimal 1 UNL Set low 63 2 LAG Stays low 58 3 Data Set high 4 Data Stays high 5 Data Stays high 6 Data Stays high Assumes primary address 26 Model 2520 User s Manual IEEE command groups IEEE 488 Bus Overview D 13 Command groups supported by the Model 2520 are listed in Table D 5 Common com mands and Table D 5 SCPI commands are not included in this list IEEE command groups UNIVERS LISTEN TALK HANDSHAKE COMMAND GROUP NDAC NOT DATA ACCEPTED NRFD NOT READY FOR DATA DAV DATA VALID AL COMMAND GROUP ATN ATTENTION DCL DEVICE CLEAR IFC INTERFACE CLEAR REN REMOTE ENABLE SPD SERIAL POLL DISABLE SPE SERIAL POLL ENABLE ADDRESS COMMAND GROUP LAG LISTEN ADDRESS GROUP MLA MY LISTEN ADDRESS UNL UNLISTEN TAG TALK ADDRESS GROUP MTA MY TALK ADDRESS UNT UNTALK OTA OTHER TALK ADDRESS ADDRESSED COMMAND GROUP ACG ADDRESSED COMMAND GROUP GTL GO TO LOCAL SDC SELECTIVE DEVICE CLEAR STATUS COMMAND
144. ated when the sweep is completed Remote trigger commands Table 8 1 summarizes remote trigger commands These commands are covered in more detail in Section 14 Trigger subsystem except for TRG a common command covered in Section 12 8 14 Triggering Model 2520 User s Manual Table 8 1 Remote trigger commands Command Description INITiate Take Model 2520 out of idle state ABORt Reset trigger system TRIGger COUNt lt count gt Set trigger count 1 to 5000 TRIGger ILINe lt line gt Select trigger link input line 1 to 6 TRIGger OLINe lt line gt Select trigger link output line 1 to 6 TRIGger OUTPut lt event gt Enable disable output trigger TRIGger or NONB TRIGger SOURce lt source gt TRIGger TIMer lt time gt TRG Select trigger input source IMMediate TIMer BUS TLINK PSTest NSTtest or BSTest Set trigger timer 0 to 99999 99s Trigger Model 2520 if BUS source selected Remote trigger example Table 8 2 summarizes the command sequence for basic trigger operation These com mands set up Model 2520 triggering as follows Trigger input source bus Output trigger enabled Trigger link output line 1 After the unit is set up INIT is sent to take the unit out of idle TRG is sent to trigger the unit after which it performs one measurement cycle Table 8 2 Remote triggering example Command Description RST Restore GPIB defaults SOURI CURR
145. b gt Enable or disable digital filter OFF y STATe Query state of digital filter v SWEep Path to sweep abort commands CABort LEVel lt n gt Set detector 2 current level for sweep abort 0 to 0 105 0 105 LEVel Query detector 2 sweep abort current threshold STATe lt b gt Enable or disable detector 2 sweep abort function OFF STATe Query state of detector 2 sweep abort function DATA LATest Query latest reading only when trigger model is in IDLE AVERage filter commands are global and affect all three measurements SENS1 SENS2 and SENS3 simultaneously Model 2520 User s Manual SCPI Command Reference 14 9 Table 14 6 SOURce command summary Default Command Description parameter SCPI SOURce 1 Path to control laser diode current source Jv CLEar MMediate Turn all three sources off CURRent Path to configure current v MODE lt name gt Select mode FIXed SWEep or LIST FIX A MODE Query mode v RANGe lt n gt Select fixed range 0 to 5 0 Range 0 5 or 5 0 5 v RANGe Query range setting v LEVel Set source level in amps y IMMediate Set specified current level immediately v AMPLitude lt n gt Specify current level for FIXed mode 0 to 5 0 v AMPLitude Query current level Jv LOW lt n gt Specify low current pulse level 0 to 0 015 0 500mA range 0 to 0 15 5A range LOW Query low current pulse level POLarity lt name gt Specify polarity POSit
146. ble Raxture clamp Data flow Data flow for front panel operation is summarized by the block diagrams provided in Figure 5 12 NOTE See Appendix C for remote operation data flow information as well as a diag nostic tool that allows you to access raw samples Basic reading display With sweeps and math disabled Figure 5 12A the Model 2520 displays the configured laser diode voltage and detector current readings Math function display With a math function enabled Figure 5 12B the Model 2520 displays the configured math functions Laser diode math functions include V I resistance I V conductance power and MX B while only MX B is available for the two photodiode detector chan nels Sweep data storage Figure 5 12C shows data flow when a sweep is enabled All data is stored in the buffer while the sweep is in process When the recall mode is activated by pressing the RECALL key data comes from the buffer Data includes laser diode source current and voltage mea surement detector current measurements and buffer location number If the math function is enabled math readings will be processed and displayed for each buffer location instead of basic voltage and current readings Model 2520 User s Manual Figure 5 12 Data flow front panel Laser Voltage and Detector Current Functions A Math Function and Sweeps Disabled Math Function B Math Function Enabled Laser Voltage and Detector Cu
147. case sweep from 10mA to 100mA in 20 points RST SOURI SWE SPAC LOG SOUR1 CURR STAR 10e 3 SOUR1 CURR STOP 100e 3 SOURI SWE POIN 20 SOUR1 CURR MODE SWE OUTP1 ON INIT To determine the current source values that will be generated Start 10 Log o Start 1 Stop 100 Logjo Stop 2 LogStep Log Start Log 9 Stop SWE POIN 1 2 1 20 1 1 19 0 105263 14 46 SCPI Command Reference Model 2520 User s Manual Now add the LogStep value to Log Start and to each subsequent result This will create a list of Log g Values Next take the anti log of each Log Value to get the actual sweep values Value Log Value Sweep Value mA 1 1 0000000 10 000000 2 1 0526316 11 288379 3 1 1052632 12 742751 4 1 1578948 14 384501 5 1 2105263 16 237767 6 1 2631579 18 329807 7 13157895 20 691382 8 1 3684211 23 357217 9 1 4210527 26 366513 10 1 4736842 29 763514 11 1 5263158 33 598184 12 1 5789474 37 926905 13 1 6315790 42 813329 14 1 6842105 48 329299 15 1 7368421 54 555947 16 1 7894737 61 584823 17 1 8421053 69 519286 18 1 8947369 78 476007 19 1 9473684 88 586675 20 2 0000000 100 00000 SOURce2 and SOURce3 The SOURce2 and SOURce3 commands control the detector 1 and detector 2 voltage sources respectively Model 2520 User s Manual Set amplitudes IMMediate AMPLitude lt n gt SCPI Command Reference 14 47 SOURce2 VOLTage LEVel IMMediate AMPLitude lt n gt Set detector 1 sour
148. ce Noise can seriously affect sensitive current measurements This section discusses how DUT device under test resistance and capacitance affect noise performance DUT resistance The resistance of the DUT will affect the noise performance of the ammeters As the DUT resistance is reduced the noise gain of the ammeter will increase Noise gain can be given by the following equation Output VNorsE Input Vyorse 1 Re Rpur where Output Vyorseg is noise seen at the output of the ammeter Input Vyorsg 18 the noise seen at the input of the ammeter e Rg is the internal feedback resistance for the ammeter e Rpur is the resistance of the DUT Table F 1 summarizes minimum recommended source resistance values for various mea surement ranges for the Model 2520 ammeters Note that the recommended source resis tance varies by measurement range because the R value also depends on the measurement range Table F 1 Minimum recommended source resistance values Minimum recommended I measure range source resistance 10mA and 20mA 250Q 50mA and 100mA 509 F 18 Measurement Considerations Model 2520 User s Manual Source capacitance DUT source capacitance will also affect the noise performance of the Model 2520 amme ters In general as source capacitance increases the noise gain also increases The elements of interest for this discussion are the capacitance Cpyr of the DUT and the internal feedback capa
149. ce results in voltage drops that can affect the measurement Even if the ground loop currents are small magnetic flux cutting across the large loops formed by the ground leads can induce sufficient voltages to disturb sensitive measurements To prevent ground loops instruments should be connected to ground at only a single point as shown in Figure F 19 Note that only a single instrument is connected directly to power line ground Experimentation is the best way to determine an acceptable arrangement For Model 2520 User s Manual Light Measurement Considerations F 21 this purpose measuring instruments should be placed on their lowest ranges The configu ration that results in the lowest noise signal is the one that should be used Figure F 18 Eliminating ground loops Signal Leads Instrument 1 Instrument 2 Instrument 3 a Grounds Loop 3 _ Current Saas nee Power Line Ground Figure F 19 Power line ground loops Instrument 1 Instrument 2 Instrument 3 Power Line Ground Some components such as semiconductor junctions and MOS capacitors on semiconduc tor wafers are excellent light detectors Consequently these components must be tested in a light free environment While many test fixtures provide adequate light protection oth ers may allow sufficient light penetration to affect the test results Areas to check for light leaks include doors and door hinges tubing entry points and connector
150. ce to send the entire response message including the line feed EOI terminator The most likely causes are e Sending a query to the instrument and then sending another command or query before reading the response to the first query For example the following sequence of commands will cause an error 410 iSYST ERR OPC This sequence generates an error because you must read the response to SYST ERR before sending the OPC query B 8 Status and Error Messages Model 2520 User s Manual Incorrectly configured IEEE 488 driver The driver must be configured so that when talking on the bus it sends line feed with EOI as the terminator and when lis tening on the bus it expects line feed with EOI as the terminator See the reference manual for your particular IEEE 488 interface 420 Query UNTERMINATED This error occurs when you address the instrument to talk and there is no response mes sage to send The most likely causes are Not sending a query You must send a valid query to the instrument before address ing it to talk Sending an invalid query If you have sent a query and still get this error make sure that the instrument is processing the query without error For example sending an ill formed query that generates an error 113 Undefined header and then addressing the instrument to talk will generate an error 420 Query UNTERMI NATED as well Valid query following an invalid command This situation can occu
151. ce amplitude SOURce3 VOLTage LEVel IMMediate AMPLitude lt n gt Set detector 2 source amplitude Parameters lt n gt 20 to 20 Set source amplitude volts DEFault OV MINimum 20V MAXimum 20V Query VOLTage Query programmed source amplitude VOLTage DEFault Query RST default amplitude VOLTage MINimum Query lowest allowable amplitude VOLTage MAXimum Query highest allowable amplitude Description These commands are used to immediately update the amplitude of the detector 1 and detector 2 voltage bias sources if the outputs are on If the outputs are off when either of these commands is sent the source value will be updated to the most recently programmed value when the outputs are turned on Note that the maximum output current for both voltage sources is 100mA SOURce4 The following commands are used to set control the number of bits Setting digital output LEVel lt NRf gt lt NDN gt SOURce4 TTL LEVel lt NRf gt lt NDN gt Parameters lt NRf gt lt NDN gt Bx Hx Qx Query TTL the logic levels of the digital output lines and to Set digital output pattern 0 to 15 Decimal format Binary format x 0000 to 1111 Hexadecimal format x 0 to F Octal format x 0 to 17 Query digital output value 14 48 SCPI Command Reference Model 2520 User s Manual Description This command is used to set the logic levels of the output lines of the Digital I O port When set
152. ce polarity eee 3 6 Laser diode voltage measurement polarity 0 3 7 Detector measurement polarity eee eeeeseeeeeees 3 8 Voltage bias polarity cece eee eee eeeeseeeeeeseeeeeseeeaees 3 8 Configuring SOUNCES sicie prereset aiei aeia 3 9 Editing source Values sss sseresvssrssssesessessssrssrisesiscsssesssresosss 3 9 Configuring laser diode source sseeesseeeeseseeeresrerrsrerrsreee 3 10 DC Mode aiseee sececntess Hees cdatsseancesestcorsocs r cients 3 10 PUlS Mod sarei ennen a n r 3 11 Setting photodiode detector source values 00 0 0 eee 3 11 Configuring measurements 0 0 ee eee eeeseeeeeseeeseeeeeeeeseeeaeeees 3 12 Configuring laser diode measurements eeeeeeeeeees 3 12 Configuring photodiode measurements 1 0 0 0 eee 3 12 Remote source and measure configuration cceeeeeeeeeeeeeeee 3 13 Source and measure configuration commands 3 13 Programming example ceecceesccesteeeseceeeeeeseeeneeee 3 14 Laser Diode Testing Source and measure configuration MENUS 0 00 eee eeeereeeeeeee 4 2 Front panel laser diode testing eee eee ceeeeseeeeeeereeeeaeeeeees 4 3 Test Circuit configuration oo eee eeeteeeeeeeceeeeaeeneeeseeeaes 4 3 Front panel test procedure ee eeeeeeeeeseeeeeseceeeeeeeseeseeeaes 4 4 Step 1 Configure laser diode measurement Dinie Ceno n 555255 E 4 4 Step 2 Configure photodiode detector measurement FUNCHONS ise scsescessisescssvsieonss
153. ciniesevsssevsndesaciviseseusteraseeoenveneseeaiers 1 13 Status and error MESSAGES oo eee eee eeeeeseeteeereeeeeeaeeeeeees 1 13 Remote display programming sce eeseeeseeseeereeeeeeeees 1 14 Front panel display tests cee eseeeeseeeeeneeeeeteeeeeeeseeeees 1 14 Dealt Sete Sasraningrat rn arra E EE e aes 1 14 Saving and restoring user setups eesesssesseessrssessersseseese 1 14 Saving SOUMIPS secesie n ei irni o o a 1 14 Restoring SQMIPS sornes rokeris 1 15 Power on configuration essseeesesesseesseeresesresteresreseereseneeses 1 15 Factory default settings 0 0 eeeesereeeeeeeeeesetseeeaees 1 15 Remote setups sorcen nnna oi E 1 17 Menys sessen eiet ebacsebascenesncocened sesandesdeecstesedis cetaveeieees 1 17 Main Menu siiinsiesser aee ee e e EN EE ET E 1 18 Rules to navigate menus sseessssessseeseereseerrsreresreserresreeses 1 18 Main operation Menus s ssesessesesesessrsrrsrsrreresrsrrsreresrrsesees 1 19 Configuration MENUS csiissscicioeeeiiecsirsinis onesies resins 1 21 Connections Connection precautions 0 eeeeeeseeseeeceeseceeceseeeeeeseeeeeeeeeeees 2 2 Testhead preparation cesccesccssscceseeeseeceseecececeaceceaeeeatesseeeeaeees 2 3 Testhead mounting 0 eeeeseceseeesseceseeeeeceseeeeaeceseeeeeeeeaees 2 3 Testhead connections 00 eee eeeeseeeeeeseeseeeseeseeeseeseeeaeeseeens 2 3 Signal connectors 20 cceseeceecceseeeseeeseeseeeeseeceaeeesaeseaeeesaeeeeeeeaeees 2 5 Signal con
154. citance Cp for the ammeter Taking into account the capacitive reactance of these two elements our previous noise gain formula must be modified as fol lows Output Vyorse Input Vyorse 1 Zp Zpur where Output Vyorsg 1s the noise seen at the output of the ammeter Input Vyorsg 18 the noise seen at the input of the ammeter e Zpis the internal feedback impedance for the ammeter that is formed by Cp and Rp e Zpur is the internal impedance of the DUT that is formed by Cpyr and Rpyr Furthermore R Zs oes Sn 2nfR_Cp 1 and Rg Zour 2nfRgCg 1 Note that as Cg increases in value Zp decreases in value thereby increasing the noise gain Again at the point where Zpuyr Zp the input noise is amplified by a factor of two High source capacitance can also cause overshoot ringing and in the extreme oscillation of the feedback ammeter Whenever possible use low capacitance photodiodes and short cables Generated currents Any extraneous generated currents in the test system will add to the measured detector current causing errors Currents can be internally generated as in the case of instrument input offset current or they can come from external sources such as insulators cables and leaky photodiodes Model 2520 User s Manual Measurement Considerations F 19 Offset currents Internal offset current The ideal ammeter should read zero when its input terminals are left open Practical ammeters s
155. clears any pending operation discards any pending output and returns a DCL Baud rate The baud rate is the rate at which the Model 2520 and the programming terminal commu nicate Choose one these available rates e 57600 e 38400 e 19200 Model 2520 User s Manual Remote Operations 10 17 e 9600 e 4800 e 2400 e 1200 e 600 e 300 The factory selected baud rate is 9600 When you choose a baud rate make sure the programming terminal or printer that you are connecting to the Model 2520 can support the baud rate you selected Both the Model 2520 and the other device must be configured for the same baud rate Data bits and parity The RS 232 interface can be configured to send receive data that is 7 or 8 bits long using even odd or no parity No parity is only valid when using 8 data bits Terminator The Model 2520 can be configured to terminate each program message that it transmits to the controller with any of the following combinations of lt CR gt and lt LF gt lt CR gt Carriage return lt CR LF gt Carriage return and line feed lt LF gt Line feed lt LF CR gt Line feed and carriage return Flow control signal handshaking Signal handshaking between the controller and the instrument lets the two devices com municate with each other about readiness to receive data The Model 2520 does not sup port hardware handshaking flow control Software flow control is in the form of XON and XOFF characters
156. ction 11 Generally the serial polling sequence is used by the controller to determine which of several instru ments has requested service with the SRQ line However the serial polling sequence may be performed at any time to obtain the status byte from the Model 2520 Front panel GPIB operation This section describes aspects of the front panel that are part of GPIB operation including messages status indicators and the LOCAL key Error and status messages See Appendix B for a list of status and error messages associated with IEEE 488 program ming The instrument can be programmed to generate an SRQ and command queries can be performed to check for specific error conditions Model 2520 User s Manual Remote Operations 10 9 GPIB status indicators The REM remote TALK talk LSTN listen and SRQ service request annunciators show the GPIB bus status Each of these indicators is described below REM This indicator shows when the instrument is in the remote state REM does not necessarily indicate the state of the bus REN line as the instrument must be addressed to listen with REN true before the REM indicator turns on When the instrument is in remote all front panel keys except for the LOCAL key are locked out When REM is turned off the instrument is in the local state and front panel operation is restored NOTE IfLLO is in effect LOCAL will be locked out OUTPUT ON OFF is still opera tional in remote If TRIG SO
157. ction provides several complete functional listings for example programs through out this manual These programs include e Laser diode test program from Section 4 e Linear staircase sweep program from Section 7 e List custom sweep program from Section 7 Hardware requirements The following computer hardware is required to run the example programs IBM PC compatible computer e Keithley KPC 488 2 KPS 488 2 or KPC 488 2AT or CEC PC 488 IEEE 488 interface for the computer Shielded IEEE 488 connecting cable Keithley Model 7007 Software requirements In order to use the example programs you will need the following computer software e Microsoft QBasic supplied with MS DOS 5 0 or later or Quick Basic e MS DOS version 5 0 or later or Windows 95 98 e HP style Universal Language Driver CECHP EXE supplied with Keithley and CEC interface cards listed above General program instructions 1 With the power off connect the Model 2520 to the IEEE 488 interface of the com puter Be sure to use a shielded IEEE 488 cable for bus connections Turn on the computer and the Model 2520 Make sure the Model 2520 is set for its default primary address of 25 Use the front panel COMM key to check or change the address 4 Make sure that the computer IEEE 488 bus driver software CECHP EXE is prop erly initialized 5 Enter the Basic editor and type in the desired program 6 Check thoroughly for errors then save i
158. ctional elements required for SCPI commands Contained in SCPI command sub systems tables see Table 14 1 through Table 14 10 7 Buffer size limitations for block data Block display messages 32 characters max 8 Syntax restrictions See Section 10 Programming syntax 9 Response syntax for every query command See Section 10 Programming syntax 10 Device to device message transfer that does not follow None rules of the standard 11 Block data response size See Section 14 FORMat subsystem 12 Common Commands implemented by Model 2520 See Section 12 Common Commands 13 Calibration query information See Service Manual 14 Trigger macro for DDT Not applicable 15 Macro information Not applicable 16 Response to IDN identification See Section 12 Common Commands 17 _ Storage area for PUD and PUD Not applicable 18 Resource description for RDT and RDT Not applicable 19 Effects of RST RCL and SAV See Section 12 Common Commands 20 TST information See Section 12 Common Commands 21 Status register structure See Section 11 Status Structure 22 Sequential or overlapped commands All are sequential 23 Operation complete messages OPC OPC and WAT see Section 12 Common Commands IEEE 488 and SCPI Conformance Information Table E 2 Coupled commands Model 2520 User s
159. ctor 1 MX B CALCulate3 KMATh MUNits lt name gt Specify units for detector 2 MX B Parameters lt name gt One ASCII character enclosed in single or double quotes Query MUNits Query units for MX B Description These commands are used to specify the units suffix name for the MX B math function for CALC1 through CALC3 Use one upper or lower case ASCII character for the units suffix name no numbers spaces dashes etc Enable and read math function result STATe lt b gt CALCulate 1 STATe lt b gt Control laser diode math function CALCulate2 STATe lt b gt Control detector 1 math function CALCulate3 STATe lt b gt Control detector 2 math function CALCulate4 STATe lt b gt Control delta detector 1 detector 2 math function Parameters lt b gt 0 or OFF Disable CALC1to CALC4 math function Parameters 1 or ON Enable CALC1 to CALC4 math function Query STATe Query state on or off of CALC1 to CALC4 Description These commands are used to enable or disable the CALC1 CALC2 CALC3 and CALC4 math function for the laser diode detector 1 and detector 2 respectively When enabled the selected math function cal culation will be performed when the Model 2520 is triggered to perform the programmed source and measure operations use INIT After the Model 2520 returns to idle you can read the result of the selected math function using the CALC1 DATA CALC2 DATA gt CALC3 DATA or CALC4 DA
160. d 10 5V limit Model 2520 User s Manual Figure 5 11 Loading effects Voltage Limit Load Line 10 5V Output Voltage V Operating av Point lt Current Source Load Line 100mA Output Current mA V eleR 100mA 50Q 5V A Normal Current Source Operation Voltage Limit Load Line Operating Point 10 5V Output Voltage V Current Source Load Line 80mA 100mA Output Current mA V R 10V 125Q 80mA B Current Source in Compliance Source Measure Concepts 5 11 5 12 Source Measure Concepts Model 2520 User s Manual Notice that as resistance increases the slope of the DUT load line increases As resistance approaches infinity open output the Model 2520 will source virtually OmA at 10 5V Conversely as resistance decreases the slope of the DUT load line decreases At zero resistance shorted output the Model 2520 will source virtually 100mA at OV Regardless of the load voltage will never exceed the programmed compliance of 10 5V In the constant current mode the output impedance is extremely high When the compli ance voltage is exceeded however the source operates more like a voltage source with a finite output impedance The open circuit compliance voltage is programmable from 3V to 10 5V and the nominal output impedance is 0 1Q As a result the clamping voltage at the DUT will be lower than the compliance value by the following amount V at DUT Iip X 0 1Q Rea
161. d mode DUT resistance F 17 Front panel pulse parameters 5 4 Duty cycle 5 3 1 2 Remote pulse parameters 5 6 Flow control see signal handshaking 10 17 FORMat subsystem 14 19 Electromagnetic Interference EMI F 23 Front panel Electrostatic interference F 22 Summary mainframe 1 6 Equivalent circuit 2 8 Summary testhead 1 9 Error and status messages 10 8 Front panel operation Error messages see Messages 1 13 Data flow 5 12 Event detection 8 11 Digital output control 9 4 Examples Display tests 1 14 OPC programming example 12 4 SAV RCL programming example 12 5 TRG programming example 12 5 Basic source and measure configuration programming example 3 14 Custom sweep programming 7 10 Display 1 13 Filter programming example 6 6 Laser diode test program H 3 Laser diode test programming example 4 7 Linear staircase sweep program H 4 List sweep program H 5 Math function programming example 6 10 Program and read register set 11 19 Programs H 1 Range programming example 6 4 Read error queue 11 21 Remote trigger 8 14 RS 232 programming example 10 20 Staircase sweep programming 7 9 Status byte programming example 11 10 Sweep and list program examples 14 44 GPIB 10 8 Laser diode test procedure 4 4 Laser diode testing 4 3 Math functions 6 8 Pulse parameters 5 4 Sweep 7 5 Trigger model 8 2 Fuse replacement 1 12 General information 1 2 General program instructions H 2 GET group execute trigger 10 8 Getting Started 1 1 GPIB
162. d state VSTEST When Digital I O SOT is pulsed low TSTEST When Digital I O SOT line is pulsed high TLSTEST When Digital I O SOT line is pulsed either high or low TIMER Set trigger timer interval TRIGGER OUT Configure output triggers LINE Select trigger link output line 1 6 EVENTS Enable disable output events TRIG LAYER DONE Enable ON or disable OFF on exiting trigger layer CONFIG FILTER AVG 10 RDGS 1 100 Program number of averaged filter readings 1 100 1 24 Getting Started Model 2520 User s Manual Table 1 9 SWEEP and MATH configuration menus Configuration menu item Description CONFIG SWEEP Configure sweeps for laser diode current source lq CONFIGURE SWEEPS TYPE Select sweep type NONE Disable sweeps STAIR Linear staircase sweep program START STOP and STEP LOG Log staircase sweep program START STOP NO OF POINTS SWEEP COUNT Set sweep count FINITE Program sweep count value INFINITE Never ending sweep CONFIG MATH Configure math functions CONFIGURE MATH CHANNEL1 Program V laser diode voltage math function I V Select conductance function I V1 V I Select resistance function V I MX B_UNIT Select MX B function program M B and units Pf Select power function V x I CHANNEL2 Program Ipp detector 1 MX B M B and units CHANNEL3 Program Ipp detector 2 MX B M B and units Connections Connection precautions Summarizes precautions that should
163. de it will process one set of readings per trigger If the unit is in the sweep mode it will process one sweep per trigger The number of readings per sweep depends on programmed sweep parameters The data that is output by the read commands FETCh and READ depend on which data elements are selected With all elements selected available data includes both voltage and current measurements source values as well as the timestamp and status information See Section 14 FORMat ELEMents SCPI Command Reference for details After all source and measure operations are completed the Model 2520 returns to the idle state The data stored in the reading buffer will remain there until data from another source measure cycle overwrites the buffer Data in the reading buffer is lost if the Model 2520 goes to the local state REM annunciator off NOTE With no data in the reading buffer sending the FETCh and CALCulateX DATA commands to read data will display the message Data corrupt or stale FETCh 2 This command is used to read processed data from the reading buffer If for example there are 20 data sets stored in the reading buffer in the sweep mode then all 20 data sets will be sent to the computer when FETCh is executed Note that FETCh does not affect processed data in the reading buffer Thus subsequent executions of FETCh acquire the same data Ca Data Flow Model 2520 User s Manual READ and MEASure The READ
164. de the current source can output a maximum of 1A 9 9V In the pulse mode the current source can output 5A 9 5V The voltage compliance limit can be set over a range of 3V to 10 5V The compliance voltage is sensed at the pulser circuit board so any I R drops in the cables or connections is not sensed and no corrections are made for these resistances Figure 5 10 Current source limit lines Voltage Compliance Limit Line 10 5V Max 9 9V 9 5V Output Voltage Current Source Limit Line 1A DC 5A Pulse Max Max Output Current Loading effects Where within the boundaries each Model 2520 current source operates depends on the resistance of the load DUT that is connected to the output Figure 5 11 shows operation examples for resistive loads that are 50Q and 125Q respectively For these examples the Model 2520 current source is programmed to source 100mA with a voltage limit of 10 5V In Figure 5 11A the Model 2520 is sourcing 100mA into the 50Q load and subsequently develops 5V across the load resistance As shown the load line for 50Q intersects the 100mA current source line at 5V Figure 5 11B shows what happens if the resistance of the load is increased to 125Q The DUT load line for 125Q intersects the 10 5V compliance limit line placing the Model 2520 in compliance In compliance the Model 2520 will not be able to source its pro grammed current 100mA For the 125Q DUT the unit will output only 80mA at the programme
165. del 2520 to talk the displayed data message or reading will be sent to the computer Define TEXT messages DATA lt a gt DISPlay WINDow 1 TEXT DATA lt a gt Define message top display DISPlay WINDow2 TEXT DATA lt a gt Define message bottom display Parameters lt a gt ASCII characters for message Types String aa a or aa a Indefinite Block 0aa a Definite Block X Yaa a where Y number of characters in message Up to 20 for top display Up to 32 for bottom display X number of digits that make up Y 1 or 2 Query DATA Query the defined text message Description These commands define text messages for the display A message can be as long as 20 characters for the top display and up to 32 characters for the bottom display A space is counted as a character Excess message characters result in an error Model 2520 User s Manual SCPI Command Reference 14 19 An indefinite block message must be the only command in the program message or the last command in the program message If you include a command after an indefinite block message on the same line it will be treated as part of the message and is displayed instead of executed STATe lt b gt DISPlay WINDow 1 TEXT STATe lt b gt Control message top display DISPlay WINDow2 TEXT STATe lt b gt Control message bottom display Parameters lt b gt 0 or OFF Disable message for specified display 1 or ON Enable message for specified display Quer
166. detector measure SENS2 CURR POL NEG Det 1 negative polarity SENS3 CURR POL NEG Det 2 negative polarity FORM ELEM CURR3 Det 2 current data SENS2 CURR RANG 0 01 Det 1 10mA range SENS3 CURR RANG 0 05 Det 2 50mA range 3 Configure laser source SOURI CURR RANG 0 5 0 5A LD source range SOURI CURR 0 5 LD source output 0 5A SOURI VOLT PROT 5 5V LD source voltage limit SOUR1 CURR POL POS LD source positive polarity SOURI FUNC PULS LD source pulse mode SOURI PULS DEL 200e 6 200usec pulse delay SOURI PULS WIDT 10e 6 10usec pulse width SOURI CURR LOW 10e 3 10mA low current pulse 4 Configure detector bias sources SOUR2 VOLT 20 Det 1 source output 20V SOUR3 VOLT 10 Det 2 source output 10V 5 Configure math functions gt CALC1 FORM POWER1 Select LD power math gt CALC2 KMAT MBF 2 Det 1 B 2 gt CALC2 KMAT MME 0 5 Det 1 M 0 5 CALC1 STAT ON Enable LD math function gt CALC2 STAT ON Enable Det 1 math 6 Turn on outputs OUTP1 ON All source outputs on 7 Trigger and read data READ Trigger get readings CALC1 DATA Acquire LD math data CALC2 DATA Acquire Det 1 math data 8 Turn off outputs OUTP1 OFF Outputs off after measuring Steps correspond to front panel steps previously in Front panel laser diode testing page 4 3 2Commands must be sent in order given 3Instrument must be addressed to talk after READ CALC1 DATA and CALC2 DATA to acquir
167. diode 1 Measure Bit Be D DETECTOR 2 Photodiode 2 Tove l Measure i pa 2 10 Connections Model 2520 User s Manual Connection considerations When making connections to the laser diode observe the following considerations to avoid pulse degradation due to distributed inductance and other effects Use only the supplied 15Q coaxial cables Keep cable lengths to a minimum Connect the four cable shields together at the DUT Carry cable shields as close to the DUT as possible Minimize the length of exposed unshielded signal lines Dress the VOLTAGE SENSE cables as far away from the CURRENT OUTPUT cables to avoid magnetic coupling Twist the SENSE cables together to further reduce magnetic coupling Connect the VOLTAGE SENSE leads as close to the body of the DUT as possible NOTE See Appendix F Measurement Considerations for information on these and other possible measurement problems and how to avoid them Basic Operation e Operation overview Discusses current and voltage source and measure capabil ities ranges compliance and fundamental measurement and voltage bias circuit configuration Configuring sources Covers setting up the laser diode current source and photodiode voltage bias source values Configuring measurements Covers setting up both laser diode voltage and photodiode current measurements 3 2 Basic Operation Model 2520 User s Manual Operation overview L
168. dress value sent out over the bus is obtained by ORing the primary address with H20 For example if the primary address is decimal 26 H1A the actual listen address is H3A H3A H1A H20 In a similar manner the talk address is obtained by ORing the primary address with H40 With the present example the talk address derived from a primary address of 26 decimal would be H5A H5A H1A H40 The IEEE 488 standards also include another addressing mode called secondary address ing Secondary addresses lie in the range of H60 H7F Note however that many devices including the Model 2520 do not use secondary addressing Once a device is addressed to talk or listen the appropriate bus transactions take place For example if the instrument is addressed to talk it places its data string on the bus one byte at a time The controller reads the information and the appropriate software can be used to direct the information to the desired location D 4 IEEE 488 Bus Overview Model 2520 User s Manual Figure D 1 IEEE 488 bus configuration To Other Devices Device 1 Able to Talk Listen and Control C t ai q Device 2 Able to gt Talk and e Data B Listen ata Byte 2520 O iransiet Control Device 3 Only Able e suet H General rinter Interface Management Device 4 i Only Able B DIO 1 8 Data to Talk H 8 Lines DAV NRFD NDAC Handshake IFC ATN Bus SRQ REN Management EOI Model 2520 U
169. dth list Description These commands are used to determine the length of the specified pulse width list The response message indicates the number of pulse width values in the list Model 2520 User s Manual SCPI Command Reference 14 43 DELay lt NRf list gt SOURce 1 LIST DELay lt NRf list gt Define pulse delay list Parameters lt NRf list gt NRf NRf NRf NRf 20e 6 to 0 5 Pulse delay seconds Query DELay Query pulse delay list Description This command is used to define a list of pulse delays up to 100 for the list sourcing mode of operation When operation is started the instru ment will sequentially source each current pulse value in the list see CURRent lt NRf list gt page 14 41 with the programmed pulse width and delay Each pulse delay point in the list corresponds to the equiva lent point in the current and width lists The following command shows the proper format for defining a list using pulse delay values of 200us 400us and 500us SOURce 1 LIST DELay 200e 6 400e 6 500e 6 NOTE Ifthe pulse delay list is shorter than the current list the last pulse delay value will be used for all subsequent current list points If delay is not programmed a default value of 1 5ms will be used but the query will return 0 APPend lt NRf list gt SOURce 1 LIST DELay APPend lt NRf list gt Add value s to pulse delay list Parameters lt NRf list gt NRf NRf NRf NRf 20e 6 to 0 5 Pulse delay
170. e STATe lt b gt SENSe2 AVERage STATe lt b gt SENSe3 AVERage STATe lt b gt Enable disable digital filter Enable disable digital filter Enable disable digital filter Disable digital filter Enable digital filter 0 or OFF 1 or ON Parameters lt b gt Abort sweep Query STATe Query state of average digital filter Description These commands are used to enable or disable the average digital filter When enabled voltage and current readings are filtered according to how may readings are averaged see COUNt lt n gt page 14 30 When disabled the digital filter stage is bypassed CABort LEVel lt n gt Set detector 1 sweep abort current SENSe2 SWEep CABort LEVel lt n gt Set detector 2 sweep abort current SENSe3 SWEep CABort LEVel lt n gt Parameters lt n gt 0 to 0 105 Sweep abort current in amps DEFault 0 105 MINimum 0 MAXimum 0 105 Query CABort LEVel Query sweep abort current threshold Description These commands provide means to set a maximum detector current for detector 1 or detector 2 that will cause a sweep to be aborted if the corresponding detector current threshold is reached Sweep abort must be enabled with the STATe command see below The Sweep Aborted bit Bit 7 in the Measurement Event Register will be set if the sweep aborts early because of reaching the maximum detec tor current threshold for a particular channel The Model 2520 can be programmed to g
171. e 1 POWER 1 or RESistance 1 Request laser diode math reading Enable disable laser diode math ON or OFF Set laser diode MX B B offset parameter Set laser diode MX B M slope parameter Define laser diode MX B units 1 character ASCII string Request detector 1 math reading Enable disable detector 1 math ON or OFF Set detector 1 MX B B offset parameter Set detector 1 MX B M slope parameter Define detector 1 MX B units 1 character ASCII string Request detector 2 math reading Enable disable detector 2 math ON or OFF Set detector 2 MX B B offset parameter Set detector 2 MX B M slope parameter Define detector 2 MX B units 1 character ASCII string Request delta detector 1 detector 2 current reading Enable disable delta measurement ON or OFF Select READ data elements CURRent 1 VOLTage 1 CURRent2 VOLTage2 CURRent3 VOLTage3 STATus or TIME Select CALC data elements CALCulate STATus or TIME Trigger readings Turn all sources ON or OFF Trigger and acquire readings Set laser diode voltage measure range 5 or 10 Set laser diode measure polarity POSitive or NEGative Set detector 1 measure range 0 01 0 02 0 05 0 1 Set detector 1 measure polarity Set detector 2 measure range 0 01 0 02 0 05 0 1 Set detector 2 measure polarity COND I V RES V I POWER Vy I 2 CURRI IL VOLTI V C
172. e 11 2 To determine the exact nature of the error you will have to read the Error Queue Refer to Queues page 11 19 Table 11 4 Status byte programming example Command Description CLS Clear Error Queue SRE 4 Enable EAV FORM SREG BIN __ Select binary format XYZ Generate error STB Read Status Byte Register Model 2520 User s Manual Status Structure 11 11 Status register sets As shown in Figure 11 1 there are four status register sets in the status structure of the Model 2520 Standard Event Status Operation Event Status Measurement Event Status and Questionable Event Status NOTE See Appendix B for details on which register bits are set by specific error and status conditions Register bit descriptions Standard event register The used bits of the Standard Event Register shown in Figure 11 4 are described as fol lows Bit BO Operation Complete Set bit indicates that all pending selected device operations are completed and the Model 2520 is ready to accept new commands This bit only sets in response to the OPC query command See Section 12 for details on OPC and OPC Bit B1 Not used Bit B2 Query Error QYE Set bit indicates that you attempted to read data from an empty Output Queue Bit B3 Device Dependent Error DDE Set bit indicates that an instrument operation did not execute properly due to some internal condition Bit B4 Execution Error EXE Se
173. e 11 3 Serial polling and SRQ Any enabled event summary bit that goes from 0 to 1 will set bit B6 and generate an SRQ service request In your test program you can periodically read the Status Byte to check if an SRQ has occurred and what caused it If an SRQ occurs the program can for exam ple branch to an appropriate subroutine that will service the request Typically SRQs are managed by the serial poll sequence of the Model 2520 If an SRQ does not occur bit B6 RQS of the Status Byte Register will remain cleared and the pro gram will simply proceed normally after the serial poll is performed If an SRQ does occur bit B6 of the Status Byte Register will set and the program can branch to a service subroutine when the SRQ is detected by the serial poll The serial poll automatically resets RQS of the Status Byte Register This allows subse quent serial polls to monitor bit B6 for an SRQ occurrence generated by other event types After a serial poll the same event can cause another SRQ even if the event register that caused the first SRQ has not been cleared The serial poll does not clear MSS The MSS bit stays set until all Status Byte summary bits are reset SPE SPD serial polling The SPE SPD General Bus Command sequence is used to serial poll the Model 2520 Serial polling obtains the serial poll byte status byte Typically serial polling is used by the controller to determine which of several instruments has requ
174. e 5 4 5 6 Syntax 10 10 System identification 1 12 SYSTem subsystem 14 51 Terminator 10 17 Testhead Connections 2 3 Mounting 2 3 Signal connectors 2 5 Testhead front panel 1 9 Testhead rear panel 1 10 Tests Front panel display 1 14 Front panel laser diode 4 3 Laser diode 4 1 Remote laser diode 4 5 Timestamp Reset 14 55 TRACe subsystem 14 56 Transmission line model F 14 Trigger link 8 5 Connector 1 8 Trigger model Program 14 58 Trigger subsystem 14 57 AY Triggering 8 1 Voltage Configuring 8 7 Burden F 20 Front panel operation 8 2 Voltage measurement circuit model F 15 Remote 8 9 Triggers Input 8 3 8 6 8 11 Ww w infi ion 1 2 Output 8 13 arranty information 1 User setups see Setups 1 14 TEquipment An Interworld Highway LLC Company Specifications are subject to change without notice All Keithley trademarks and trade names are the property of Keithley Instruments Inc All other trademarks and trade names are the property of their respective companies KENT HLEY Keithley Instruments Inc Sales Offices BELGIUM CHINA FINLAND FRANCE GERMANY GREAT BRITAIN INDIA ITALY JAPAN KOREA NETHERLANDS SWEDEN TAIWAN 28775 Aurora Road Cleveland Ohio 44139 440 248 0400 Fax 440 248 6168 1 888 KEITHLEY 534 8453 e www keithley com Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 Yuan Chen Xin Building Room 705 12 Yumin Road
175. e Fuse rating Keithley part no 100 240V 1 6A slow blow 250V 5 X 20mm FU 106 1 6 Model 2520 User s Manual Getting Started 1 13 Display Display format The Model 2520 display is used primarily to display measured readings and source values The top line displays source values and the bottom line shows measured values Display example The following example shows the unit displaying the laser diode source value on the top line and the laser diode voltage detector 1 current and detector 2 current from left to right on the bottom line Ipulse 100 00mA 1 0000 V 05 000mA 10 000mA Display units Measurement reading information can be displayed using either engineering units or sci entific notation in either fixed or floating point format Use the NUMBERS selection of the main MENU to select the display format as discussed under Menus page 1 17 Engineering units example 12 345mA Scientific notation example 1 23e 2A Annunciators which are located along the top of the reading message display indicate various states of operation as covered previously in Front panel summary page 1 6 Status and error messages Status and error messages are displayed momentarily During Model 2520 operation and programming you will encounter a number of front panel messages Typical messages are either status or error in nature and are listed in Appendix B 1 14 Getting Started Model 2520 User s Manual
176. e Sync Output Digital 1 O port wo eceeescsccseeseceecseeseeseeseeaeeaeeesaeeeeseseeeeeeeeaees 9 2 Port configuration 20 eee eteeeeeereeeeeesececeeaecneeeaeeseeeaeenaes 9 2 Digital output limes oo ee eeeeseeeeeeeeeseeseeeseeeees 9 2 Start of test SOT line ccc eeeeseessseeeseseeeesseessseeees 9 3 5V output 00 ceeccsresssccsnrcesssssnscerescnssessessnrcersessnnsons 9 3 Digital output configuration 0 0 eee eeeeeeceeeeseeeeeseeeees 9 3 Sink Operation 00 eeceeceeseeseneeeeeeeeeceseeeeeeeseeeeteeeseeees 9 3 Source operation eee eeceesceeeneceneeeeaeceseeeeeeceteeeeeeeeeees 9 4 10 Controlling digital output lines oo eee eeeeeeeeeeeeeeeee 9 4 Front panel digital output control eee 9 4 Remote digital output control oo eee eeeeeeeeeeeeeees 9 5 Interlock scoireann ei eiae EEE AA EEE 9 5 Interlock operation sariserscrieiisiiisiiiiiiii ii 9 6 Interlock status indicator test sequence oe eeeeeeeee 9 7 Reading interlock state 0 eee eeeeseeeeeseeeeeeneeeeeeeeeeeees 9 7 Pulse Syne OUtpUE 2 2 ise eie eeesciee seed oesy cade Hesieneiede desesuedee seta vanes 9 8 Pulse sync waveform eeeeceeeeesesseeeeeseeeseeseeeaeeneeeaeeeeens 9 8 Pulse sync connections 000 eeeeeeeereeeeeeseeseeeaeeeeeaeeseeens 9 9 Remote Operations Differences remote vs local Operation cece eeeeeeeeeeeeeeees 10 2 Local to remote transition 0 0 eee eee eeeeeeeeeeeseeeeeeseeeeeeaees 10 2 Remote to local transition elec
177. e appropriate enable command i e STATus OPERation ENABle 0 Table 11 7 Event enable registers commands Command Description Default ESE lt NDN gt or lt NRf gt Program Standard Event Enable Register See Parameters Note ESE Read Standard Event Enable Register STATus STATus Subsystem OPERation Operation Event Enable Register ENABle lt NDN gt or lt NRf gt Program enable register See Parameters ENABle Read enable register MEASurement Measurement Event Enable Register ENABle lt NDN gt or lt NRf gt Program enable register See Parameters ENABle Read enable register QUEStionable Questionable Event Enable Register ENABle lt NDN gt or lt NRf gt Program enable register See Parameters ENABle Read Measurement Event Enable Register Parameters lt NDN gt BXx x Binary format each x 1 or 0 Hx Hexadecimal format x 0 to FFFF Qx Octal format x 0 to 177777 lt NRf gt Oto 65535 Decimal format Note Power up and STATus PRESet resets all bits of all enable registers to 0 CLS has no effect Model 2520 User s Manual Status Structure 11 19 Programming example program and read register set The command sequence in Table 11 8 programs and reads the measurement register set Registers are read using the binary format which directly indicates which bits are set The command to select format FORMat SREGister is documented in Table 11 2
178. e commands and give a simple programming example Laser diode test commands Table 4 2 summarizes commands used for basic laser diode testing including those for the two photodiode detectors See Section 14 for more information on using these and other commands for laser diode testing 4 6 Laser Diode Testing Table 4 2 Laser diode test commands Model 2520 User s Manual Command Description CALCulate 1 FORMat lt format gt CALCulate 1 DATA CALCulate 1 STATe lt state gt CALCulate 1 KMATh MBFactor lt B gt CALCulate 1 KMATh MMFactor lt M gt CALCulate 1 KMATh MUNits lt units gt CALCulate2 DATA CALCulate2 STATe lt state gt CALCulate2 K MATh MBFactor lt B gt CALCulate2 KMATh MMFactor lt M gt CALCulate2 KMATh MUNits lt units gt gt CALCulate3 DATA CALCulate3 STATe lt state gt CALCulate3 K MATh MBFactor lt B gt CALCulate3 KMATh MMFactor lt M gt CALCulate3 KMATh MUNits lt units gt CALCulate4 DATA CALCulate4 STATe lt state gt FOR Mat ELEMents lt elements gt FORMat ELEMents CALCulate lt elements gt INIT OUTPut 1 lt state gt READ SENSe 1 VOLTage RANGe lt range gt SENSe 1 VOLTage POLarity lt polarity gt SENSe2 CURRent RANGe lt range gt SENSe2 CURRent POLarity lt polarity gt SENSe3 CURRent RANGe lt range gt SENSe3 CURRent POLarity lt polarity gt Define laser diode math format MXB 1 CONDuctanc
179. e data 3 source Measure Concepts e Pulse concepts Describes the various aspects of the laser diode current source pulse mode e Sweep operation Covers the various types of sweeps that can be performed Operating boundaries Covers output and limit operating boundaries for the laser diode current source Data flow Describes measurement readings and how data is stored in the buffer during a sweep 5 2 Source Measure Concepts Model 2520 User s Manual Pulse concepts Overview The Model 2520 laser diode current source can output either DC or pulse waveforms Maximum current is as follows e DC 1A e Pulse mode 5A In addition the current source can be operated in either the fixed or sweep mode In the fixed mode the source simply outputs the programmed DC level DC mode or pulses at a fixed amplitude pulse mode In the sweep mode the source DC or pulse amplitude can be swept across a series of steps at given increments In addition you can design your own sweep waveforms by using the custom list sweep mode See Sweep waveforms page 5 8 for more sweep information Delay pulse cycle Model 2520 laser diode current source and voltage measurements consist of a series of delay pulse cycles Figure 5 1 During each cycle the following occurs 1 Wait for the programmed delay period Output the programmed current pulse 3 During the current pulse the LOMHz A D converter processes a
180. e event occurs when SOT start of test high pulse is received via the Digital I O port SOT line With BSTest selected the event occurs when SOT start of test high or low pulse is received via the Digital I O port SOT line TRIGger SEQuence 1 LAYer 1 TIMer lt n gt Set interval for trigger layer timer Parameters Query Description lt n gt 0 to 99999 99 Specify timer interval in seconds DEFault Sets timer to 0 1 MINimum Sets timer to 0 MAXimum Sets timer to TIMer Queries programmed timer interval TIMer DEFault Queries RST default interval TIMer MINimum Queries lowest allowable interval TIMer MAXimum Queries largest allowable interval This command is used to set the interval for the timer Note that the timer is in effect only if the timer is the selected control source 14 60 SCPI Command Reference Model 2520 User s Manual ILINe lt NRf gt STRIGger SEQuence 1 TCONfigure ILINe lt NRf gt Select Trigger Link input line Parameters lt NRf gt 1 Line 1 2 Line 2 3 Line 3 4 Line 4 5 Line 5 6 Line 6 Query ILINe Query input trigger line Description This command is used to select input lines for the Trigger Link For nor mal operation Trigger Link input and output see OLINe lt NRf gt should not share the same line OLINe lt NRf gt TRIGger SEQuence 1 TCONfigure OLINe lt NRf gt Select Trigger Link output line Parameters lt NRf gt 1 Line 1 2 Line 2 3 Line
181. e of your own user setups using the following proce dures Saving setups Select the various instrument operating modes you wish to save Press the SETUP key From the SAVESETUP MENU select SAVE then press ENTER Select the setup position 0 4 to save then press ENTER to complete the process fe ge T Model 2520 User s Manual Getting Started 1 15 Restoring setups 1 Press the SETUP key 2 From the SAVESETUP MENU select RESTORE then press ENTER 3 Select the setup position 0 4 to restore then press ENTER to complete the pro cess Power on configuration You can also define which of the stored setups factory default or user the instrument assumes as the power on configuration as follows Press the SETUP key 2 From the SAVESETUP MENU select POWERON then press ENTER 3 From the SET POWER ON DEFAULT menu choose the power on configuration BENCH or GPIB see below or USER SETUP NUMBER 4 Ifyou chose to use a user setup as the power on configuration select the user setup number 0 4 then press ENTER Factory default settings Table 1 3 summarizes BENCH front panel and GPIB remote factory defaults for oper ating modes available from the front panel Some features are available only via remote see Section 14 You can restore either of these default conditions from the front panel as follows Press the SETUP key 2 From the SAVESETUP menu select RESET then press ENTER 3 Select BENCH or
182. e width in the fixed and sweep modes but it does not control pulse widths for the list mode which are programmed separately see Configure list page 14 41 Description TRANsition STATe lt b gt SOURce 1 PULSe TRANsition STATe lt b gt 0 or OFF 1 or ON Parameters lt b gt Query STATe Control pulse transition control state Disable transition control Enable transition control Query state of transition control This command enables or disables pulse transition rise time control When off 0 the leading edge is as fast as the system hardware allows When on 1 the turn on is intentionally slowed down to a fixed setting of 5e 6 The output will not fully settle to its final value for Sus Description Model 2520 User s Manual SCPI Command Reference 14 37 Configure sweeps There are two methods to configure the start and stop levels of a sweep You can use either the STARt and STOP commands or you can use the CENTer and SPAN commands See Sweep and list program examples page 14 44 NOTE In order to run a sweep the source must be in the sweep sourcing mode Use the CURRent MODE command to select the SWEep sourcing mode See Select sourcing mode page 14 32 SPACing lt name gt SOURce 1 SWEep SPACing lt name gt Select scale for current sweep Parameters lt name gt LINear Linear scale LOGarithmic Logarithmic scale Query SPACing Query scale for sweep Description
183. ead is at a digital low asserted Outputs can be turned on Bit B2 MSR1 Overflow M10 Set bit indicates that the laser diode voltage measurement is in an overflow condition Bit B3 MSR2 Overflow M20 Set bit indicates that the photodiode detector 1 current measurement is in an overflow condition Bit B4 MSR3 Overflow M30 Set bit indicates that the photodiode detector 2 current measurement is in an overflow condition Bit BS Not used Bit B6 Reading Available RAV Set bit indicates that a reading has been pro cessed and is available Bit B7 Sweep Aborted SWA Set bit indicates that the sweep was aborted before being completed Bit B8 Sweep Done SWD Set bit indicates a sweep was completed success fully Bits B9 to B11 Not used Bit B12 Over Temperature OT Set bit indicates that safe operating tempera ture of the testhead has been exceeded Outputs cannot be turned on Bit B13 Not used Bit B14 Source 1 Compliance S1C Set bit indicates that the laser diode cur rent source is in compliance Bit B15 Not used Model 2520 User s Manual Status Structure 11 15 Figure 11 6 Measurement event status Measurement Condition stat meas cond Register S1C OT SWD SWA RAV M3O M20 M10 INT B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 Bo S1C OT L 4 RAV L L INT B15 B14 B13 B12 B11 B10 B9
184. ead version of SCPI standard ces eeeeeseeseeeeneeeneees 14 54 VERSIONA Y sestsisefsani sis eagsrtiea tics serene 14 54 RS 23 2 terface sinss erien ns AREA EEE 14 55 LOCal dtearn e a ea R ie 14 55 REM te rupesin a a e nee eee 14 55 Reset timestamp 20 c e ces ene cinsceen esceesieetsasteseevesasectvece 14 55 RESEGE eciecss cisteccssscdiceettesscvevecisnecacveciivaseensbaciacsertaatvens 14 55 TRAC SUDSYSEDL viepi asiad a 14 56 Read sample buffer wscsisscsscndstdseseccavenseseaysavssaienarssoetucnsenenss 14 56 DATA secerni O OA 14 56 VALue KNR gt niione 14 56 Configure sample buffer ssesseeseeesersresresesrerrsreerrsrserses 14 57 POUNGS lt I gt aiian naeia aeisi 14 57 Trigger SUBSYSTEM ws seseetescd eeescsnces ia ecsaeteaveecssbes sadveasendaleecbeseeas 14 57 Initiate source Measure cycle oo eee eseeeeseeeeeeeeeeeeseeees 14 57 DINU AG isisi a letleices aaa evans nada eects 14 57 Abort source measure cycle oo eeeeeeeseeseeseereeeeeeeneentens 14 58 ABORD sgsisc sts ceencsteessesastva senna sduiniseentevgavendcsenestenyeteas 14 58 Program trigger model oo ee eee eseeeeeeeeeeeteeeeeeaeees 14 58 COUN eierniie 14 58 SOURCE lt MaMe gt sisirin streini eeina 14 58 TIMer lt in iee aoia ea ANERE 14 59 TING lt NR E oireena a 14 60 OLINE lt NRE gt eteina ae 14 60 OUTP t lt 0amMeS iser eisie r n ii 14 60 Specifications Status and Error Messages Tntrod CtiON ssscesecsbiitis ceeds Riad a ii
185. eaees 7 4 Configuring and running a SWEEP 0 00 ee eeeeseceeeeseeeeeeeeeeeeeeeeees 7 5 Front panel sweep Operation 00 ee eeeeeeseeeeeeseeeeeeseeeeeeaes 7 5 Configuring a SWEEP ceeseeseeceeeceseeeeeeeteeceaeeeteeeeaees 7 5 Performing SWEEPS ee eeeeseeseeeseeseceseeseeeseeseeesecseeesecaeenaes 7 6 Performing a linear staircase sweep 0 00 cee eeeeeeeeeeeees 7 6 Performing a log staircase SWEEP 2 0 0 eee eeeeeseeeeeeeees 7 7 Remote sweep Operation eee seeeeseceeeeeeeseeseeeeeeseeeeeeaes 7 8 Staircase sweep commands 0 eee ese eeeeteeeeereeeeeee 7 8 Staircase sweep programming example ee 7 9 Custom sweep commands ee eeeeeeeeeeseeeeeeeeeeeeees 7 10 Custom sweep programming example ee 7 10 8 Triggering Trigger model front panel operation 0 0 eee eeeeseeeeeereeeeees 8 2 Idlelayer oo aeriene ioniese etor ies irse SETS 8 3 Input triggers oo eee eseceeeeseeseeeseeseeesecseeeaecseeeaeesseeaeenaes 8 3 Delay and pulse phases 00 eee eeeeseeseceeeeseeeeeeeeseeeseenees 8 3 Delay phase ces 8sccbesecbecseesdeceges iensor aaie nE e ea 8 3 Pulse PASC isis iennpseersoecceieorerieoisorirae Aae Ee eet 8 4 Filtern Ee ainnise eee E eet 8 4 SWEEP points sseseessersscsessoeesroserssocsensosesonesosiesoisosesneesi 8 4 Co nter sisstin rira orrea si es eaor NA ettare sia a noai 8 4 Output TTI BEL savevics coidceszevzesdevscecdecteacdetgestaeevegiessesbseededevendess 8 4 Bench Getaults sc
186. ececeeseeceeeeeaeeeeeens 10 17 Terminator aise sirsiran esa ae i 10 17 Flow control signal handshaking seeeeseeeeeeeeeeeeeee 10 17 RS 232 Connections wissscieicccsscssescossesssosendsocssconactsssedavvrests 10 18 Error MESSAGES saion io eiaeia n R ia ees 10 20 Programming example sesessesesseesssreresresreesrsresresesreseses 10 20 Status Structure VERVIEW saccsesczasesvcsesucbeccstessvoeaseasctavsscbecsdbenssnsutensoessnavsasstersondees 11 2 Status byte and SRQ wo eee eeecseceseeseeeseeseeeseeseeeaeeseeens 11 2 Status register sets oo eee eee eseceeeeeeseeeseeeeeeseeeeeeaeeeaeees 11 2 Queues oasa eena ee eee 11 2 Clearing registers and queues sesesseesesesseseeresresrsrrsreresresrees 11 4 Programming and reading registers eeeeseeeeeeeeeeereeerrseerrereee 11 5 Programming enable registers esesseeseeeeseserresreersrsrrereee 11 5 Reading registers 0 eeeeecesccesseeeseceececeseeeeaeeeaeeseaeeeaeeeees 11 6 Status byte and service request SRQ eeceeseeeeeeeseeeeeeeneeeeees 11 7 Status byte register 0 eee eeeeesecsseeeeeeeeeeeseeeeaeeeseeeeaeeesees 11 8 Service request enable register 0 0 0 eee eeeeseeseeeeeeeeeeeees 11 8 Serial polling and SRQ wo ec eeeeeseeeeeeeeseeeaeeseeeaeeseeens 11 9 SPE SPD serial polling eee ee eeeeeeeseeeeeeeeneeeeees 11 9 Status byte and service request commands eee 11 10 Programming example set MSS B6 when SLOP OCCULS sevetei opiniii i aea R ENE 1
187. ed so that an operator is not exposed to any radiation The test fix ture interlock must not be defeated The testhead key control must be used to prevent operation unless authorized by the responsible body This requirement must be part of the facilities administrative controls for laser safety When servicing the test system any required personnel protection equipment e g laser safety goggles must be provided by the cus tomer s responsible body The customer s laser safety officer LSO must review and approve all installations before being put into operation Any safety concerns must be immediately reported to the customer s LSO If at any time the indicators provided on the testhead for INTER LOCK STATUS or LASER POWER ON should fail to light or properly indicate status immediately contact a Keithley service rep resentative for repair Failure to do so may expose the user to haz ards without proper warnings See Interlock status indicator test sequence page 9 7 for details on testing the indicator lights Maximum isolation from earth ground is 10V Exceeding this value may result in a shock hazard When making connections do not leave any exposed connections Be sure that all external circuits are properly insulated Model 2520 User s Manual Connections 2 3 Testhead preparation Testhead mounting The Model 2520 has a mounting ear with two holes 2 5 inches on center that allow the unit to be mounted
188. ed to set or clear the appropriate bits BO B2 B3 B4 B5 and B7 of the Status Byte Register These summary bits do not latch and their states 0 or 1 are solely dependent on the summary messages 0 or 1 For example if the Standard Event Register is read its register will clear As a result its summary message will reset to 0 which in turn will reset the ESB bit in the Sta tus Byte Register The bits of the Status Byte Register are described as follows Bit BO Measurement Summary Bit MSB Set summary bit indicates that an enabled measurement event has occurred Bit B1 Not used Bit B2 Error Available EAV Set summary bit indicates that an error or status message is present in the Error Queue Bit B3 Questionable Summary Bit QSB Set summary bit indicates that an enabled questionable event has occurred Bit B4 Message Available MAV Set summary bit indicates that a response message is present in the Output Queue Bit BS Event Summary Bit ESB Set summary bit indicates that an enabled standard event has occurred Bit B6 Request Service RQS Master Summary Status MSS Set bit indi cates that an enabled summary bit of the Status Byte Register is set Bit B7 Operation Summary OSB Set summary bit indicates that an enabled operation event has occurred Depending on how it is used Bit B6 of the Status Byte Register is either the Request for Service RQS bit or t
189. eeeeeees 14 3 Table 14 2 DISPlay command summary cc eeeceeeeeeeeeeeeeeeeeeeeeees 14 5 Table 14 3 FORMat command summary 0 0 0 0 eeeeceeeeeeeeeeeeeeeeeeeeees 14 6 Table 14 4 OUTPut command summary 0 eee eeeeeeeeeeeeeeeeeeees 14 6 Table 14 5 SENSe command summary occ eeceseceeceseeeeeeseeeeeeseeees 14 7 Table 14 6 SOURce command summary eee eeeeeeceseeeeeeeeeeeeeeeeees 14 9 Table 14 7 STATus command summary cece ceecsseeeeeeseeeeeneees 14 12 Table 14 8 Table 14 9 Table 14 10 B Table B 1 D Table D 1 Table D 2 Table D 3 Table D 4 Table D 5 Table D 6 E Table E 1 Table E 2 F Table F 1 SYSTem command suMMAry 0 ce eee eeeeeeeeeeeeeseeeeeees 14 13 TRACe command summary ce eeeeseeeeeeeeseeeeeeeeeeneeees 14 13 TRIGger command SUMMATY 0 00 eee eeeeeeeeeeeeeeeeeeeeeees 14 14 Status and Error Messages Status and error MESSAGES oo ee eee eee eee eeeeseeeaeceeeeseeeeeeaeeeees B 3 IEEE 488 Bus Overview TEEE 488 bus command summary sceeeseeeeeseeeseeeeees D 7 Hexadecimal and decimal command codes 0 0 eee D 10 Typical addressed multiline command sequence D 12 Typical addressed common command sequence D 12 TEEE command groups 0 eeeeseeseeseeeseeeeeeeeeeneeaeeneeeseesees D 13 Model 2520 interface function codes eee eeeeeeeeeeeeeees D 14 IEEE 488 and SCPI Conformance Information TEEE 488 documentation requireme
190. eeeeeeeseenseeseenaes F 6 Ideal response of 2A pulse using 10 inch cables 0 0 0 F 7 Response of 2A pulse with two square inch loop 4 F 7 Sense lead CONNECTIONS ee eee seeseeseeeseceeeeseteeeeseeeeeeaeeseees F 8 Response of 2A pulse with sense leads 1 4 inch away trom DUT esse ba ssecs isc seneese EEE r e EET n E aiia F 9 Magnetic coupling ssessseseessssssssesssssessrssressrssressessrssesseessese F 10 Optical pulse propagation through differing indices of TEfTACHOM ssisescerseiortroseriterisnssk isesi doa nee rosvoina Siae on Eiaa F 11 Model 2520 output circuit model sssseeeseeeeeseeeesreersrsrreeee F 13 Minimal impedance mismatch sesssseseeseseeresreresrrerrsrereereee F 14 Compromised shield provides laser diode access F 14 Voltage measurement circuit model ol eect eee eee tees F 15 Pulse source and forward voltage cable interconnections F 15 Model 2520 photo current measurement channels with dual bias supplies eee eee eeeeseeeeeseeeseeseeeaeeseeeaeeseeens F 16 Voltage DUTGED int kserscioseseaiessssdceagecesd danavecusteaes a F 20 Eliminating ground lOOpS ceeesseceeseeeeeeseeeeeeeeeeeeaeeeeeens F 21 Power line ground loops eseeeesseeceeseeeeeeseeeeeeaeeeeeeseenaees F 21 List of Tables 1 Table 1 1 Table 1 2 Table 1 3 Table 1 4 Table 1 5 Table 1 6 Table 1 7 Table 1 8 Table 1 9 3 Table 3 1 Table 3 2 Table 3 3 Table 3 4 Table 3 5 4 Table
191. een PRINT Set COM2 baud rate to 9600 PRINT Set no flow control and CR as terminator Configure serial port parameters The following values are the default settings for the Model 2520 ComOpen COM2 9600 N 8 1 ASC CD0 CS0 DS0 LF OP0 RS TB8192 RB8192 OPEN ComOpen FOR RANDOM AS 1 Model 2520 setup commands PRINT 1 RST Reset instrument to default parame ters PRINT 1 SENS1 VOLT RANG 3 Set 3V measure range PRINT 1 SOUR1 CURR 0 1 Set laser source to output 100mA PRINT 1 FORM ELEM VOLT1 Set to output voltage readings to PC 1 Initiate a reading and print results PRINT 1 READ Trigger and acquire one reading LINE INPUT 1 RDS RD Voltage RDS PRINT RDS 1 Clean up and quit finish CLOSE 1 Close file CLEAR Interface clear END 11 Status Structure Overview Provides an operational overview of the status structure for the Model 2520 Clearing registers and queues Covers the actions that clear reset registers and queues Programming and reading registers Explains how to program enable registers and read any register in the status structure Status byte and service request SRQ Explains how to program the Status Byte to generate service requests SRQs Shows how to use the serial poll sequence to detect SRQs Status register sets Provides bit identification and command information for t
192. eep points cannot exceed 5000 Model 2520 User s Manual Triggering 8 13 Output trigger As shown in Figure 8 6 the Model 2520 can be programmed to output a trigger when operation leaves the Trigger Layer This output trigger is typically sent to another instru ment to signal the end of a sweep The TRIG OUTPut command is used to control this output trigger The TRIGger parameter enables the trigger on exiting the Trigger Layer and the NONE parameter disables the output trigger GPIB defaults The GPIB defaults are listed as follows They are also denoted in Figure 8 6 by the symbol Trigger In Source Immediate Trigger Count 1 Timer 0 1s Enabled output trigger None With outputs turned ON OUTP1 ON the Model 2520 will perform one measurement cycle when the INITiate command is sent After the measurement the Model 2520 returns to the idle state Operation summary The trigger model is designed to offer versatility for the various source and measure appli cations It allows you to specify input and output triggers for both single reading and sweep operation as follows When sweeps are disabled the unit will process one set of readings per Trigger In Event and provide one output trigger per reading If the unit is in the Immediate trigger mode it will process readings continuously e When a sweep is enabled the unit will perform one sweep per Trigger In Event One output trigger will be gener
193. ement control and data I O connections are for connection to Category I sourc es unless otherwise marked or described in the Manual Exercise extreme caution when a shock hazard is present Lethal voltage may be present on cable connector jacks or test fixtures The American National Standards Institute ANSI states that a shock hazard exists when voltage levels greater than 30V RMS 42 4V peak or 60VDC are present A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring Operators of this product must be protected from electric shock at all times The responsible body must ensure that operators are prevented access and or insulated from every connection point In some cases connections must be exposed to potential human contact Product operators in these circumstances must be trained to protect themselves from the risk of electric shock If the circuit is capable of operating at or above 1000 volts no conductive part of the circuit may be exposed Do not connect switching cards directly to unlimited power circuits They are intended to be used with impedance limited sourc es NEVER connect switching cards directly to AC mains When connecting sources to switching cards install protective de vices to limit fault current and voltage to the card Before operating an instrument make sure the line cord is connected to a properly grounded power receptacle Inspect the con necting cables test
194. ements The unit has 0 3 basic laser diode voltage measurement accuracy and 0 3 basic photodiode current measure ment accuracy A separate remote testhead allows versatility for signal connections The Model 2520 has the following source and measure capabilities Source DC laser diode current from 10UA to 1A Source laser diode current pulses from 10uA to 5 0A Measure laser diode voltage from 0 33mV to 10 5V Measure photodiode current from 0 7uUA to 105mA on each of two channels Source photodiode bias voltage on each of two channels from 0 to 20V Some additional capabilities of the Model 2520 include Sweep capabilities linear and logarithmic staircase and custom sweeps for the laser diode current source Digital I O port to control other instruments Programming language and remote interfaces The Model 2520 uses the SCPI programming language and two remote interface ports IEEE 488 GPIB and RS 232C Trigger Link interface to Keithley Series 7000 switching hardware Pulse sync out Allows synchronizing external instruments with current pulse Math functions V I I V power and MX B functions Reading and setup storage Voltage and current readings and seven setups five user defaults factory default RST default can be stored and recalled Closed cover calibration The instrument can be calibrated either from the front panel or remote interface 1 6 Getting Started Model 2520 User s Manual Mai
195. enerate an SRQ under these conditions See Section 11 for register and SRQ details CABort STATe lt b gt SENSe2 SWEep CABort STATe lt b gt SENSe3 SWEep CABort STATe lt b gt Parameters lt b gt 0 or OFF 1 or ON Query STATe Description Enable disable detector 1 sweep abort Enable disable detector 2 sweep abort Disable sweep abort Enable sweep abort Query sweep abort state These commands enable or disable sweep abort when the programmed current threshold is reached see LEVel above 14 32 SCPI Command Reference Model 2520 User s Manual SOURce subsystem This subsystem is used to configure and control the laser diode current source the two detector voltage bias sources and to set the logic level high or low of each digital output line The commands for this subsystem are summarized in Table 14 6 SOURce 1 Use the following commands to configure and control the laser diode current source NOTE See Section 5 for pulse and sweep waveform definitions Control source outputs on off IMMediate SOURce 1 CLEar IMMediate Turn source outputs off Description This command is used to turn off all three sources and performs the same function as the OUTPut OFF command NOTE The SOURI CLEar command is global and turns off all three source outputs Select sourcing mode MODE lt name gt SOURce 1 CURRent MODE lt name gt Select laser diode sourcing mode Parameters lt name gt FIXed Selec
196. ening takes up bus time Through the use of control lines a handshake sequence takes place in the transfer process of information from a talker to a listener This handshake sequence helps ensure the credi bility of the information transfer The basic handshake sequence between an active con troller talker and a listener is as follows 1 The listener indicates that it is ready to listen 2 The talker places the byte of data on the bus and indicates that the data is available to the listener 3 The listener aware that the data is available accepts the data and then indicates that the data has been accepted 4 The talker aware that the data has been accepted stops sending data and indicates that data is not being sent 5 The listener aware that there is no data on the bus indicates that it is ready for the next byte of data Bus description The IEEE 488 bus which is also frequently referred to as the GPIB General Purpose Interface Bus was designed as a parallel transfer medium to optimize data transfer with out using an excessive number of bus lines In keeping with this goal the bus has only eight data lines that are used for both data and with most commands Five bus manage ment lines and three handshake lines round out the complement of bus signal lines A typical set up for controlled operation is shown in Figure D 1 Generally a system will contain one controller and a number of other instruments to which the c
197. ent register 11 13 Program event enable registers 14 49 Programming enable registers 11 5 Questionable event register 11 16 Read condition registers 14 50 Read event registers 14 49 Reading 11 6 Select default conditions 14 50 Service request enable register 11 8 Standard event register 11 11 Status byte register 11 8 Status register sets 11 11 Related modes 1 4 Remote configuration over GPIB IEEE 488 I 4 Remote operation 10 1 Differences to local operation 10 2 Selecting an interface 10 2 Trigger model 8 9 Remote programming Digital output control 9 5 Display 1 14 Filter 6 5 Laser diode testing 4 5 Math functions 6 9 Pulse parameters 5 6 Range 6 3 Setups 1 17 Sweeps 7 8 Trigger commands 8 13 REN remote enable 10 7 Resistance math function 6 7 RS 232 Connector 1 8 RS 232 interface 10 2 14 55 Connections 10 18 Connector 10 18 Data bits and parity 10 17 Operation 10 16 Sending and receiving data 10 16 Safety Symbols and terms 1 2 SCPI Command reference 14 1 Eliminating common errors B 7 Reference tables 14 2 SCPI commands D 10 SCPI commands see Command reference Command summary Common commands and Signal oriented measurement commands 14 1 SCPI conformance information E 1 SDC selective device clear 10 8 SENSe subsystem 14 27 Serial polling 11 9 Settings Factory default 1 15 Setups Remote 1 17 Restoring 1 15 Saving 1 14 Signal handshaking 10 17 Signal oriented measurement commands 13 1 SENSe
198. erse byte order the data format for each element is sent as fol lows Byte4 Byte3 Byte2 Byte1 Single precision 14 26 SCPI Command Reference Model 2520 User s Manual The 0 header is not affected by this command The header is always sent at the beginning of the data string for each measurement conver sion The ASCII data format can only be sent in the normal byte order The SWAPped selection is simply ignored when the ASCII format is selected NOTE The SWAPped byte order must be used when transmitting binary data to any IBM PC compatible computer Status register format SREGister lt name gt FORMat SREGister lt name gt Set data format for reading status registers Parameters lt name gt ASCii Decimal format Hexadecimal Hexadecimal format OCTal Octal format BINary Binary format Query SREGister Query format for reading status registers Description Query commands are used to read the contents of the status event regis ters This command is used to set the response message format for those query commands When a status register is queried the response message is a value that indicates which bits in the register are set For example if bits B5 B4 B2 B1 and BO of a register are set 110111 the following values will be returned for the selected data format ASCii 55 decimal value Hexadecimal H37 hexadecimal value OCTal Q67 octal value BINary B110111 binary value See Section 11 and
199. es the Error Queue STATus PRESet has no effect 2 Power up enables error messages and disables status messages CLS and STATus PRESet have no effect Programming example read error queue The following command reads the error queue STAT QUE 12 Common Commands Command summary Lists the IEEE 488 2 common commands used by the Model 2520 e Command reference Provides a detailed reference for all common commands except for those associated with the status structure which are discussed in Section 11 12 2 Common Commands Command summary Model 2520 User s Manual Common commands summarized in Table 12 1 are device commands that are common to all devices on the bus These commands are designated and defined by the IEEE 488 2 standard Most of these commands are described in detail in this section NOTE The following common commands associated with the status structure are cov ered in Section 11 CLS ESE ESE ESR SRE SRE and STB Table 12 1 IEEE 488 2 common commands and queries Mnemonic Name Description CLS Clear status Clears all event registers and Error Queue ESE lt NRf gt Event enable command Program the Standard Event Enable Register ESE Event enable query Read the Standard Event Enable Register ESR Event status register query Read and clear the Standard Event Enable Register IDN Identification query Returns the manufacturer model number serial number
200. esenesteteveays cose savessdnoncetenss 4 4 Step 3 Configure laser diode current source 4 4 Step 4 Configure photodiode detector voltage bias SOUICOS siisii oa ie ei ar a 4 4 Step 5 Configure math functions sssr 4 5 Step 6 Turn source outputs on and trigger readings 4 5 Step 7 Observe readings on the display 0 0 00 4 5 Step 8 Turn source outputs Off s es 4 5 Remote laser diode testing eee eeeeseeseeeneeeeeeeeeeeeseeeeeeaeenaes 4 5 Laser diode test commands ei eeeeseeseeseeseeeeeeeeeneeeeees 4 5 Programming example 0 eee eeeeeeeseeeeeeeeeeeeeeees 4 7 Source Measure Concepts PUlSe concepts eienenn pairere aeeie saeia a Ta 5 2 OVETVIEW aiioa oeae aaea EEEa E ETE EE EAE 5 2 Delay pulse CYCIE c sccssseseesseessscsersecenustsvscasessesenrecersees 5 2 Delay phase incccucintehsisaicashestesiaset sissagecsbeetaiedeapstnertesetzauy 5 3 Pulse phase niorit eiieeii eTa 5 3 DULY CY Cle sirarne era a a aTe 5 3 Front panel pulse parameters 00 0 ee eeeeseeeeeeteeseeeeeeeeees 5 4 Fix d mode erstens eisir ia ER 5 4 Staircase sweep mode ooo eee eee eseeeeeseeeseereeeaeeeeees 5 4 Remote pulse parameters sees eeseeeeeeeeseeeseeseeeseeeeeees 5 6 FIX Mod ess coca shosesaahcaslasteshessacdcnazeesseivesseds a aa 5 6 Staircase sweep MOE oo eee ee eseeeeeseeeseereeeseeseeees 5 6 Pulse rise and fall times oo eee eseeseceeeeseeeseeseeeaeeseeees 5 7 SWEEP Waveforms 2 ivsis saceseiesaved oi eean e e
201. est readings only when the unit is in the idle layer of the trigger model see Section 8 for triggering information SENS1 DATA requests the latest laser diode voltage measurement while SENS2 DATA and SENS3 DATA request the latest detector 1 and detector 2 current readings respectively Configure and control filter NOTE Detailed information on the filter is provided in Section 6 Filter Filter commands are global and affect all three measurement functions simultaneously COUNt lt n gt SENSe 1 AVERage COUNt lt n gt Set average filter count SENSe2 AVERage COUNt lt n gt Set average filter count SENSe3 AVERage COUNt lt n gt Set average filter count Parameters lt n gt 1 to 100 Specify average filter count DEFault 10 MINimum 1 MAXimum 100 Query COUNt Query filter count COUNt DEFault Query the RST default filter count COUNt MINimum Query the lowest allowable filter count COUNt MAXimum Query the largest allowable filter count Description These commands are used to specify the average filter count The filter count is the number of readings that are acquired and stored in the filter buffer for the averaging calculation Each aquired group of readings yields a single set of filtered readings The larger the filter count the more filtering that is performed but at the expense of measurement speed Model 2520 User s Manual SCPI Command Reference 14 31 STATe lt b gt SENSe 1 AVERag
202. ested service with the SRQ line Status Structure Model 2520 User s Manual Status byte and service request commands The commands to program and read the Status Byte Register and Service Request Enable Register are listed in Table 11 3 For details on programming and reading registers see Programming enable registers page 11 5 and Reading registers page 11 6 NOTE To reset the bits of the Service Request Enable Register to 0 use 0 as the param eter value for the SRE command i e SRE 0 Table 11 3 Status byte and service request enable register commands Command Description Default STB Read Status Byte Register SRE lt NDN gt or lt NRf gt Program the Service Request Enable Register Note lt NDN gt Bxx x Binary format each x 1 or 0 Hx Hexadecimal format x 0 to FF Qx Octal format x 0 to 377 lt NRf gt 0 to 255 Decimal format Read the Service Request Enable Register Note CLS and STATus PRESet have no effect on the Service Request Enable Register Programming example set MSS B6 when error occurs The first command of sequence in Table 11 4 enables EAV error available When an invalid command is sent line 4 bits B2 EAV and B6 MSS of the Status Byte Register set to 1 The last command reads the Status Byte Register using the binary format which directly indicates which bits are set The command to select format FORMat SREGister is documented in Tabl
203. eue Service Status Request Byte Enable Register Register Sweep Done Over Temperature Src 1 Compliance Always Zero MSB MSB STB SRE SRE Master Summary Status MSS MSB Measurement Summary Bit EAV Error Available QSB Questionable Summary Bit MAV Message Available ESB Event Summary Bit RQS MSS Request for Service Master Summary Staus OSB Operation Summary Bit Note RQS bit is in serial poll byte MSS bit is in STB response Calibrating Waiting for Trigger Idle Always Zero Operation Operation Operation Event Condition Event Enable Register Register Register Trig T CICICICIC GOOG Eef 11 4 Status Structure Model 2520 User s Manual Clearing registers and queues When the Model 2520 is turned on the bits of all registers in the status structure are cleared reset to 0 and the two queues are empty Commands to reset the event and event enable registers and the Error Queue are listed in Table 11 1 In addition to these com mands any enable register can be reset by sending the 0 parameter value with the individ ual command to program the register NOTE SYSTem PRESet and RST have no effect on status structure registers and queues Table 11 1 Common and SCPI com
204. fe manner Follow all applicable safety regulations for installing config uring and using the Model 2520 The Model 2520 as installed should be approved by the appropriate safety personnel such as the responsi ble Laser Safety Officer or equivalent Table 4 1 Source and measure configuration menus Configuration menu item Description CONFIG LASER V Configure laser diode voltage measurement CHANNEL POLARITY Select laser diode measurement polarity POSITIVE Select positive measurement polarity NEGATIVE Select negative polarity CONFIG DETECTOR 1 Ipp Configure detector 1 current measurement CHANNEL2 POLARITY Select detector 1 measurement polarity POSITIVE Select positive measurement polarity NEGATIVE Select negative polarity CONFIG DETECTOR 2 Ipp Configure detector 2 measurement CHANNEL3 POLARITY Select detector 2 measurement polarity POSITIVE Select positive measurement polarity NEGATIVE Select negative polarity CONFIG LASER I Configure laser diode voltage current source CONFIGURE I SOURCE POLARITY Select source polarity POSITIVE Select positive polarity NEGATIVE Select negative polarity SHAPE Select current source output mode DC DC current output PULSE Pulse current output LOW Set pulse low amplitude O 15mA 500mA range 0 to 150mA 5A range Model 2520 User s Manual Laser Diode Testing 4 3 Front panel laser diode testing Test circuit configuration The basic circuit configuration fo
205. ference Model 2520 User s Manual Table 14 3 FORMat command summary Default Command Description parameter SCPI FORMat SREGister lt name gt Select data format for reading status event registers ASC v ASCii HEXadecimal OCTal or BINary SREGister Query format for reading status event registers DATA lt type gt lt length gt Specify data format ASCii REAL 32 or SREal ASC y DATA Query data format y BORDer lt name gt Specify byte order NORMal or SWAPped Note v BORDer Query byte order v ELEMents lt item list gt Specify FETCh and READ data elements VOLTI CURRent 1 VOLTage 1 CURRent2 VOLTage2 CURR2 CURRent3 VOLTage3 TIME and STATus CURR3 CALCulate lt item list gt Specify CALCulate data elements CALCulate CALC TIME and STATus CALCulate Query CALCulate data elements TRACe lt item list gt Specify TRACe data elements VOLTage 1 VOLTI CURRent2 CURRent3 and TIME CURR2 CURR3 TRACe Query TRACe data elements ELEMents Query FETCh and READ data format elements SOURce4 lt name gt Specify SOURce4 data format ASCii HEXadecimal ASC OCTal or BIN SOURce4 Query SOURce4 data format Note RST default is NORMal SYST PRES default is SWAPPed Table 14 4 OUTPut command summary Default Command Description parameter SCPI OUTPut 1 Path to control all three outputs v STATe lt b gt Turn all three sources on or off OFF v STATe Query state of sources v IN
206. g Table 3 1 Laser diode current source ranges Current Maximum Maximum range resolution output 500mA 10uA 500mA 5A 100A 5 0A Pulse mode only Maximum DC current is 1A Model 2520 User s Manual Table 3 2 Laser diode voltage measurement ranges Voltage Maximum range Resolution reading 5V 0 33mV 5 25V 10V 0 66mV 10 5V Basic Operation Laser diode source compliance The laser diode current source has a maximum DC output level of 1A 9 9V for a maxi mum power of 9 9W Maximum pulse output level is 5A 9V for a maximum pulse power of 45W If the load resistance is high enough so that the unit exceeds the pro grammed voltage limit the unit is considered to be in compliance and the source display field will blink See Section 5 Source Measure Concepts for more information The unit can be programmed to generate an SRQ under compliance conditions over the GPIB Section 11 The compliance voltage is sensed at the pulser circuit board so any I R drops in the cables or connections is not sensed and no corrections are made for these resistances Photodiode source and measure capabilities Each Model 2520 photodiode channel has the following current measurement and voltage bias capabilities e Measure Current Each Model 2520 photodiode channel can measure DC cur rents from 0 7uA to 105mA Each channel has four current ranges 10mA 20mA 50mA and 100mA Source
207. g Caused by Exposed Leads Connecting Cables Voltage Sense LO Current Output LO A Coupling caused by exposed leads Current Output HI Voltage Sense HI Connecting Ae apn Cables Shielding Voltage Sense LO Current Output LO B Coupling reduced by shielding Model 2520 User s Manual Measurement Considerations F 11 Increasing laser diode pulse measurement speed Overview The index of refraction of a given optical media is the ratio of the speed of light in a vacuum divided by the speed of light through the media As a ray of light passes through optical media of differing indices of refraction reflections and coupling losses will result These reflections will act to generate constructive or destructive interference with other reflections and desired wave fronts These undesired reflections may strongly affect the performance of the optics system Measures must be taken to prevent the effects of unwanted reflection in an optical system Optical engineers have developed design methodologies to identify and control the negative side effects of differing indices of refraction while capturing the desired optical mechanisms Figure F 10 shows an optical pulse propagating through an optical media of differing indices of refraction In this example multiple reflections combine to form a second image of the pulse trailing behind the first Preventing the reflections would help maintain the fidelity of the original
208. g of connector shell and outer cable shield chassis ground Figure 2 3 DETECTOR connector terminals Voltage Detector Bias Current Output Input Chassis Ground CURRENT OUTPUT and VOLTAGE SENSE connectors CURRENT OUTPUT and VOLTAGE SENSE are BNC jacks used for making connec tions to the laser diode under test CURRENT OUTPUT HI and LO provide current source connections to the DUT while VOLTAGE SENSE HI and LO sense the voltage across the DUT Note that the center pin of each connector is signal while the outer shell is chassis ground Interlock connections The Model 2520 has two interlock circuits a remote interlock and a key interlock NOTE Both interlocks must be enabled to operate Otherwise the source outputs will not turn on Remote interlock connections A remote interlock switch should be wired to pins 1 and 9 of the REMOTE INTERLOCK connector as shown in Figure 2 4 Connections can also be made between pins 1 and 5 The switch must be configured to close contacts enabled to operate See Section 9 for more information Model 2520 User s Manual Connections 2 7 Figure 2 4 Remote interlock connections REMOTE INTERLOCK DISABLED 1 eo 0e9 ENABLED Pin 1 Pin 9 Key interlock The key must be inserted into KEY INTERLOCK and rotated to the ENABLED position to operate the unit Rotate the key to the DISABLED position and remove the key to inhibit the source outputs Laser diode test connections Connec
209. ge is removed the separated charges generate a decaying current through circuits connected to the insulator as they recombine To minimize the effects of dielectric absorption on current measurements avoid applying voltages greater than a few volts to insulators being used for sensitive current measure ments In cases where this practice is unavoidable it may take minutes or even hours in some cases for the current caused by dielectric absorption to dissipate F 20 Measurement Considerations Model 2520 User s Manual Voltage burden The input resistance of the ammeter causes a small voltage drop across the input terminals This voltage is known as the voltage burden and it can cause measurement errors Refer to Figure F 17 to see how voltage burden affects detector current measurements Note that voltage burden Vp reduces the measured current Iy due to the effects of the ammeter input resistance Ryn Figure F 17 Voltage burden Model 2520 Rout i Ve General measurement considerations The following measurement considerations apply to all precision measurements Ground loops Ground loops that occur in multiple instrument test setups can create error signals that cause erratic or erroneous measurements The configuration shown in Figure F 18 intro duces errors in two ways Large ground currents flowing in one of the wires will encounter small resistances either in the wires or at the connecting points This small resistan
210. ger Out BNC 5V 50Q output impedance output trigger corresponding to current source pulse pulse to trigger delay lt 100ns See Figure 3 MAINS INPUT 100V to 240V rms 50 60Hz 140VA WARRANTY year EMC Conforms to European Union Directive 89 336 EEC EN61326 1 SAFETY Conforms to European Union Directive 73 23 EEC EN61010 1 CAT 1 VIBRATION MIL PRF 28800F Class 3 Random WARM UP hour to rated accuracy DIMENSIONS WEIGHT Main Chassis bench configuration with handle amp feet 105mm high x 238mm wide x 416mm deep 4 1 8 in x 9 3 8 in x 16 3 8 in 2 67kg 5 90 Ibs Remote Test Head 95mm high x 178mm deep with interlock key installed x 216mm wide 3 1 2 in x 7 in x 8 1 2 in 1 23kg 2 70 Ibs ENVIRONMENT Operating 0 50 C 70 R H up to 35 C Derate 3 R H C 35 50 C Storage 25 to 65 C HW Rev D 2 26 03 2520 Pulsed Laser Diode Test System Notes 1 year 23 C 5 C TF Duty Cycle 1 exceeds 0 2 accuracy specifications must be derated with an additional error term as follows 500mA Range 0 1 rdg yD 1 5A Range 40 3 rdg yD 1 where I current setting D duty cycle This derating must also be applied for a period equal to the time that JD T was gt 0 2 w Not including overshoot and setting time Pulse mode only Output 500mA DC on 500mA range and 1A DC on SA range Refer to 2520 Service Manual for test setup of current accuracy Fig
211. gnificance of each status bit is explained as follows Bit O OFLO1 Set to 1 if the laser diode voltage measurement was made while in over flow Cleared to 0 otherwise Bit 1 OFLO2 Set to 1 if the detector 1 current measurement was made while in over flow Cleared to 0 otherwise Bit 2 OFLO3 Set to 1 if the detector 2 current measurement was made while in over flow Cleared to 0 otherwise Bit 3 COMPL Set to 1 if the laser diode current source is in voltage compliance limit Cleared to 0 otherwise Bit 4 FILT Set to 1 if any measurement was made with the averag ing filter on Cleared to 0 otherwise Calculate data elements CALCulate lt item list gt FORMat ELEMents CALCulate lt item list gt Specify CALC data string elements Parameters lt item list gt CALCulate Includes CALC data element TIME Includes timestamp STATus Includes status information NOTE Each item in the list must be separated by a comma i e CALC TIME Query CALCulate Query elements in CALC data string 14 24 SCPI Command Reference Description Model 2520 User s Manual This command is used to specify the data elements returned by the CALCn DATA and CALCn DATA LATest queries You can specify from one to all three elements Each element in the list must be separated by a comma These elements are explained as fol lows NOTE An overflow reading reads as 9 9E37 CALCulate This element provides the CAL
212. he Master Summary Status MSS bit e When using the serial poll sequence of the Model 2520 to obtain the status byte a k a serial poll byte B6 is the RQS bit See Serial polling and SRQ page 11 9 for details on using the serial poll sequence e When using the STB command Table 11 3 to read the status byte B6 is the MSS bit Service request enable register The generation of a service request is controlled by the Service Request Enable Register This register is programmed by you and is used to enable or disable the setting of bit B6 RQS MSS by the Status Summary Message bits BO B2 B3 B4 B5 and B7 of the Status Byte Register As shown in Figure 11 3 the summary bits are logically ANDed amp with the corresponding enable bits of the Service Request Enable Register When a set 1 summary bit is ANDed with an enabled 1 bit of the enable register the logic 1 output Model 2520 User s Manual Status Structure 11 9 is applied to the input of the OR gate and therefore sets the MSS RQS bit in the Status Byte Register The individual bits of the Service Request Enable Register can be set or cleared by using the SRE common command To read the Service Request Enable Register use the SRE query command The Service Request Enable Register clears when power is cycled or a parameter value of 0 is sent with the SRE command i e SRE 0 The commands to pro gram and read the SRQ Enable Register are listed in Tabl
213. he end of each table SCPI A checkmark V indicates that the command and its parameters are SCPI con firmed An unmarked command indicates that it is a SCPI command but does not conform to the SCPI standard set of commands It is not a recognized command by the SCPI con sortium SCPI confirmed commands that use one or more non SCPI parameters are explained by notes Model 2520 User s Manual SCPI Command Reference 14 3 Table 14 1 CALCulate command summary Default Command Description parameter SCPI CALCulate 1 Path to configure and control laser diode math DATA Path to CALC1 data LATest Return only most recent math result DATA Read result of math generated by INIT v FOR Mat lt name gt Select math format MXB 1 CONDuctance 1 RES y RESistance 1 or POWER 1 FORMat Query math format v KMATh Configure MX B parameters MBFactor lt n gt Set B parameter 9 99999e20 to 9 99999e20 0 MBFactor Query B parameter MMFactor lt n gt Set M parameter 9 99999e20 to 9 99999e20 1 MMFactor Query M parameter MUNits lt string gt Set MX B units 1 character ASCII string X MUNits Query M parameter STATe lt b gt Enable or disable CALC1 math OFF v STATe Query state of math y CALCulate2 Path to configure and control detector 1 math DATA Path to CALC2 data LATest Return only most recent math result DATA Read result of math generated by INIT v KMATh Configure MX
214. he following are some of the more common parameter types lt b gt Boolean Used to enable or disable an instrument operation 0 or OFF dis ables the operation and 1 or ON enables the operation Example CALCulate1 STATe ON Enable Calc 1 math lt name gt Name parameter Select a parameter name from a listed group Model 2520 User s Manual Remote Operations 10 11 Example lt name gt NONE TRIGger OUTPut NONE lt NRf gt Numeric representation format This parameter is a number that can be expressed as an integer e g 8 a real number e g 23 6 or an exponent 2 3E6 Example SOURce1 VOLTage PROTection 5 Sets protection to 5V lt n gt Numeric value A numeric value parameter can consist of an NRf number or one of the following name parameters DEFault MINimum MAXimum When the DEFault parameter is used the instrument is programmed to the RST default value When the MINimum parameter is used the instrument is programmed to the lowest allowable value When the MAXimum param eter is used the instrument is programmed to the largest allowable value Ex amples SOURce1 PULSe DELay 0 05 Sets pulse delay to 50ms SOURce1 PULSe DELay DEFault Sets pulse delay to 10ms SOURce1 PULSe DELay MINimum Sets pulse delay to 20ps SOURce1 PULSe DELay MAXimum Sets pulse delay to 100msec lt numlist gt Numlist Specify one or more numbers for a list Example STATus QUEue ENABIle 110 222 Enable errors 110
215. he four status register sets Standard Event Status Operation Event Status Mea surement Event Status and Questionable Event Status Queues Provides details and command information on the Output Queue and Error Queue 11 2 Status Structure Model 2520 User s Manual Overview The Model 2520 provides a series of status registers and queues allowing the operator to monitor and manipulate the various instrument events The status structure is shown in Figure 11 1 The heart of the status structure is the Status Byte Register This register can be read by the user s test program to determine if a service request SRQ has occurred and what event caused it Status byte and SRQ The Status Byte Register receives the summary bits of four status register sets and two queues The register sets and queues monitor the various instrument events When an enabled event occurs it sets a summary bit in the Status Byte Register When a summary bit of the Status Byte is set and its corresponding enable bit is set as programmed by the user the RQS MSS bit will set to indicate that an SRQ has occurred Status register sets A typical status register set is made up of a condition register an event register and an event enable register A condition register is a read only register that constantly updates to reflect the present operating conditions of the instrument When an event occurs the appropriate event register bit sets to 1 The bit remain
216. herwise a DCL or IFC must be sent to reset the output task Empty command strings terminator only should not be sent Using SCPI based programs In general an existing SCPI based program will run properly and faster in the 488 1 pro tocol as long as it meets the above guidelines and limitations G 4 GPIB 488 1 Protocol Model 2520 User s Manual Bus hold off OPC OPC and WAI are still functional but are not needed for the 488 1 protocol When sending commands the GPIB is automatically held off when it detects a terminator The hold off is released when all the commands have finished executing or if there is some parser or command error An exception is an initiate command which releases the hold off immediately and does not wait for all of the readings to be acquired This imme diate release of bus hold off is done to support GET SDC IFC TRG RCL RST SYSTem PRESet and ABORt during data acquisition Trigger on talk Trigger on talk functionality has been added for the 488 1 protocol If a query has not been received by the instrument the Model 2520 will automatically assume a READ command has been sent when it is addressed to talk This technique increases GPIB speed by decreasing the transmission and parser times for the command Trigger on talk is extremely useful in the single shot reading mode RST default and is the main reason for a gt 2x speed improvement over the SCPI protocol Remember that the outputs mu
217. ias 5V Turn on source outputs Trigger sweep request data Turn off source outputs 1 This command should normally be sent after START STOP and STEP to avoid delays caused by rebuilding sweep when each command is sent 7 10 Sweep Operation Model 2520 User s Manual Custom sweep commands Table 7 4 summarizes remote commands used for custom sweep operation See Section 14 Configure list for more details on these commands Table 7 4 Custom sweep commands Command Description SOURce 1 CURRent MODE LIST SOURce 1 LIST CURRent lt I list gt SOURce 1 LIST CURRent APPend lt I list gt SOURce 1 LIST CURRent POINts SOURce 1 LIST DELay lt D list gt SOURce 1 LIST DELay APPend lt D list gt SOURce 1 LIST DELay POINts SOURce 1 LIST WIDTh lt W list gt SOURce 1 LIST WIDTh APPend lt W list gt SOURce 1 LIST WIDTh POINts SOURce 1 LIST DIRection lt direction gt Select current list custom sweep mode Define I source list 11 I2 In 0 to 5 0 100 max points Add I source list value s 11 I2 In 0 to 5 0 100 max Query length of I source list Define pulse delay D1 D2 Dn 20e 6 to 0 5 Add pulse delay list value s D1 D2 Dn 20e 6 to 0 5 Query length of pulse delay list Define pulse width list W1 W2 Wn 500e 9 to 5e 3 Add pulse width list value s W1 W2 Wn 500e 9 to Se 3 Query length of pulse width list
218. iggering Trigger model Discusses the trigger model including various layers input trig gers and output trigger Trigger link Discusses the trigger link including input triggers and output trig gers Configuring triggering Details how to configure the various triggering aspects from the front panel Remote triggering Details the remote trigger model summarizes trigger com mands and gives a basic triggering example 8 2 Triggering Model 2520 User s Manual Trigger model front panel operation The flowchart in Figure 8 1 summarizes triggering for front panel operation The trigger model is modeled after the remote commands used to control triggering Refer to Trigger model remote operation page 8 9 Key trigger model settings are included in the flow chart Note that the BENCH defaults are denoted by the symbol The trigger model consists of an Idle Layer and a Trigger Layer to provide versatility A programmable counter allows operations to be repeated and various input and output trig ger options are available to provide synchronization between the Model 2520 and other instruments via the Trigger Link Unless otherwise noted the programmable aspects of the trigger model are performed from the CONFIGURE TRIGGER menu See Configuring triggering page 8 7 Figure 8 1 Trigger model front panel operation Idle Turn On Outputs Trigger Layer Immediate GPIB Timer
219. igital filter v COUNt lt n gt Specify filter count 1 to 100 10 v COUNt Query filter count v STATe lt b gt Enable or disable digital filter OFF y STATe Query state of digital filter y SWEep Path to sweep abort commands CABort LEVel lt n gt Set detector 1 current level for sweep abort 0 to 0 105 0 105 LEVel Query detector 1 sweep abort current threshold STATe lt b gt Enable or disable detector 1 sweep abort function OFF STATe Query state of detector 1 sweep abort function DATA LATest Query latest reading only when trigger model is in IDLE AVERage filter commands are global and affect all three measurements SENS1 SENS2 and SENS3 simultaneously 14 8 SCPI Command Reference Model 2520 User s Manual Table 14 5 continued SENSe command summary Default Command Description parameter SCPI SENSe3 Sense 3 subsystem to control detector 2 current measurement y CURRent DC Path to configure current y RANGe Configure measurement range v UPPer lt n gt Select range by specifying the expected current reading 0 1 v 0 to 0 105 Ranges 0 01 0 02 0 05 0 1 UPPer Query range y POLarity lt name gt Select polarity Name POSitive or NEGative POS POLarity Query polarity AVERage Path to configure digital filter v COUNt lt n gt Specify filter count 1 to 100 10 v COUNt Query filter count v STATe lt
220. igital output lines sink operation and source operation Sink operation Figure 9 2 shows the basic output configuration for sink operation Note that the external relay coil is connected between the digital output line pins 1 to 4 and 5V pin 7 With this configuration the digital output line must be set LO to energize the relay and the maximum sink current is 500mA Model 2520 External Be ey ee oe Pie Relay Circuits I I To Other I I I I I Maximum Sink Current 500mA Digital I O Port 9 4 Digital I O Port Interlocks and Pulse Sync Output Model 2520 User s Manual Source operation Figure 9 3 shows the basic output configuration for source operation In this case the external relay coil is connected between the digital output line pins 1 to 4 and ground pin 9 With this configuration the digital output line must be set HI to energize the relay and the maximum source current is 2mA l External Relay Figure 9 3 Source operation Model 2520 BE Maximum Source Current 2mA 1 5VO O I 1 I I I I I 1 I I l O To Other i i Circuits I I I 1 I I Q I I I Digital 1 O Port Controlling digital output lines The Digital I O lines can be used to control external relays or indicator lights You can control these lines either from the front panel or via remote as covered below Front panel digital output control Set digital output line logic levels from the front panel as follows
221. igure 1 1 Figure 1 2 Figure 1 3 Figure 1 4 2 Figure 2 1 Figure 2 2 Figure 2 3 Figure 2 4 Figure 2 5 Figure 2 6 3 Figure 3 1 Figure 3 2 Figure 3 3 Figure 3 4 4 Figure 4 1 5 Figure 5 1 Figure 5 2 Figure 5 3 Figure 5 4 Figure 5 5 Figure 5 6 Figure 5 7 Figure 5 8 Figure 5 9 Figure 5 10 Figure 5 11 Figure 5 12 6 Figure 6 1 Getting Started Mainframe front panel 0 0 cee eeeeesceeenecesreceeeeeeeeeeeeeseeeteeees 1 6 Mainframe rear panel 0 eee eseeeeseeseeeseeseeeaeeeeeeseeseeeaeenaes 1 8 Testhead front panel 0 0 eee cece eeeeseeseeeeeseeeaeeeeecseenseeseeeas 1 9 Testhead rear panel oo eee eeeeeseceeeeseeseeeeeeseeseeeeeeaeeeaeees 1 10 Connections Testhead COMMeCtIONS sisses eee eeeeeeeneeeseeseeeaeeeeeeaeeeseeseenaes 2 4 Testhead signal connectors 0 00 eee eeseeseeseeeceeaeeeeeeaeeeeeeaeenees 2 5 DETECTOR connector terminals ee seeeeeeeeeeseeeeeeeeeees 2 6 Remote interlock CONNECTIONS 0 0 lee eeeeseeeeereeeeeeeeteeeeaeeeees 2 7 Laser diode test CONNECTIONS 0 0 ee ees eeeeseeeceeeeeeeeaeteeeeaeeeees 2 8 Equivalent circuit of laser diode test connections 2 9 Basic Operation Basic Circuit configuration 0 0 eee ee eeeereeeeeeaeeeeeeaeteeetaeeeees 3 5 Laser diode current source polarity ec eeeeeeseeseeeeeeeeeees 3 6 Laser diode measure polarity ices eeeeseeseeseeeeeeeteeeeeeeees 3 7 Detector current measurement polarity s src 3 8 Laser Diode
222. igure 14 2 does not show the byte for the terminator that is attached to the end of each data string Model 2520 User s Manual SCPI Command Reference 14 21 Figure 14 2 IEEE 754 single precision data format 32 data bits Header Byte 1 Byte 2 Byte 3 Byte 4 s sign bit 0 positive 1 negative e exponent bits 8 f fraction bits 23 Normal byte order shown For swapped byte order bytes sent in reverse order Header Byte 4 Byte 3 Byte 2 Byte 1 The header and terminator are sent only once for each READ During binary transfers never un talk the Model 2520 until after the data is read input to the computer Also to avoid erratic operation the readings of the data string and terminator should be acquired in one piece The header 0 can be read separately before the rest of the string NOTE The Model 2520 terminates the binary data string with LF EOI If your pro gram is set to terminate on CR andlor LF data transfer may terminate prema turely because one or more data bytes has a CR or LF value To avoid the problem set your computer program to terminate on EOI only The number of bytes to be transferred can be calculated as follows Bytes 2 Rdgs x 4 1 where 2 is the number of bytes for the header 0 Rdgs is the product of the number of selected data elements arm count and trigger count 4 is the number of bytes for each reading is the byte for the terminator For example assume the Model
223. in Number Description Rear Panel Pinout Trigger Link 1 Trigger Link 2 00 Trigger Link 3 ae Trigger Link 4 Trigger Link 5 Trigger Link 6 Ground Ground ON DOO BWNH 8 6 Triggering Model 2520 User s Manual Input trigger requirements An input trigger is used to satisfy event detection for a trigger model layer that is config ured for the TRIGGER LINK event See Trigger model front panel operation page 8 2 The input requires a falling edge TTL compatible pulse with the specifications shown in Figure 8 3 Figure 8 3 Trigger link input pulse specifications Triggers on Leading Edge TTL High 2V 5V TTL Low 0 8V le atin Output trigger specifications The Model 2520 can be programmed to output a trigger after various trigger model actions See Trigger model front panel operation page 8 2 The output trigger provides a TTL compatible output pulse that can be used to trigger other instruments The specifi cations for this trigger pulse are shown in Figure 8 4 A trigger link line can source ImA and sink up to 50mA Figure 8 4 Trigger link output pulse specifications End of Measurement or Sweep TTL High 3 4V Typical TTL Low 0 25V Typical 5s gt Model 2520 User s Manual Triggering 8 7 Configuring triggering Triggering is configured from the CONFIGURE TRIGGER menu and is structured as fol lows NOTE See Trigger model front panel operation
224. ing and type are the same Other components that are not safety related may be purchased from other suppliers as long as they are equivalent to the original component Note that selected parts should be purchased only through Keithley Instruments to maintain accuracy and functionality of the product If you are unsure about the applicability of a replacement component call a Keithley Instruments office for information To clean an instrument use a damp cloth or mild water based cleaner Clean the exterior of the instrument only Do not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument Products that consist of a circuit board with no case or chassis e g data acquisition board for installation into a computer should never require cleaning if handled accord ing to instructions If the board becomes contaminated and operation is affected the board should be returned to the factory for proper cleaning servicing Table of Contents 1 Getting Started General information 00 0 0 eeeeeseeeeeeeceeeceeeeesseeeaeseeeeaeeseees 1 2 Warranty information ceeeeeeesceseeeceseeceeeceeeeseeseneeeeneees 1 2 Contact information eee eeeeeseeeeeeseeeeeeeeceeeeseseneeaeenees 1 2 Manual addenda 000 eee eeseeseeseeeseeseeeseeseeeseceeeesesseeeaeenees 1 2 Specifications cnc ccisecicesuescouds shencdecessnses oi aa a r E E a 1 2 Safety symbols and terms sesssseesesssesrsesessesrsssessrssrssresees 1 2
225. ing that the equip ment is operated within its specifications and operating limits and for ensuring that operators are adequately trained Operators use the product for its intended function They must be trained in electrical safety procedures and proper use of the instrument They must be protected from electric shock and contact with hazardous live circuits Maintenance personnel perform routine procedures on the product to keep it operating properly for example setting the line voltage or replacing consumable materials Maintenance procedures are described in the manual The procedures explicitly state if the operator may perform them Otherwise they should be performed only by service personnel Service personnel are trained to work on live circuits and perform safe installations and repairs of products Only properly trained service personnel may perform installation and service procedures Keithley products are designed for use with electrical signals that are rated Installation Category I and Installation Category II as described in the International Electrotechnical Commission IEC Standard IEC 60664 Most measurement control and data T O signals are Installation Category I and must not be directly connected to mains voltage or to voltage sources with high tran sient over voltages Installation Category II connections require protection for high transient over voltages often associated with local AC mains connections Assume all measur
226. ing the pulse delay unless the pulse amplitude is below the low level in which case the level is set to OA Model 2520 User s Manual Source Measure Concepts 5 5 Figure 5 3 Front panel staircase sweep mode pulse parameters Stop Start e PW gt Delay gt Returns to OA because pulse is less than Low OA Figure 5 4 shows how various front panel programming parameters control various stair case sweep DC waveform aspects These parameters are programmed by pressing the appropriate key e Pulse amplitudes determined by the programmed START STOP and STEP or POINTS parameters in the CONFIG SWEEP menu e DELAY PW determines the time at each step Figure 5 4 Front panel staircase sweep mode DC parameters OA lt Delay gt lt Pw gt No Readings Readings Taken Taken and Averaged 5 6 Source Measure Concepts Model 2520 User s Manual Remote pulse parameters Fixed mode Figure 5 5 shows how various remote commands control various fixed pulse waveform aspects These parameters are programmed as follows e SOUR1 CURR sets the pulse amplitude e SOUR1 PULS DEL sets the pulse delay time between pulses e SOUR1 PULS WIDT sets the pulse width Figure 5 5 Remote fixed mode pulse parameters SOUR1 PULS WIDT SOUR1 CURR gt lt gt SOUR1 PULS DEL Staircase sweep mode Figure 5 6 shows how various front panel programming parameters control various
227. ings measurements Sweep points When a sweep is enabled the unit cycles through the complete delay pulse process including filtering if enabled for the programmed number of sweep points For linear staircase sweeps the number of points depends on the start stop and step current values For log staircase sweeps the number of points depends on the start and stop current values and the programmed number of points Counter The programmable counter is used to repeat operations within the Trigger Layer For example to repeat a sweep three times the trigger counter would be set to 3 If the sweep has a total of 10 points a total of 30 measurements will be made The maximum finite trigger counter value is 5000 However the product of the trigger count and the number of sweep points cannot exceed 5000 Output trigger The Model 2520 can be programmed to output a trigger via rear panel Trigger Link con nector after various trigger model operations An output trigger is used to trigger another instrument to perform an operation See Trigger link page 8 5 for more information When enabled the unit outputs a trigger when operation leaves the Trigger Layer and enters back into the Idle Layer This output trigger is typically sent to another instrument to signal the end of a sweep Model 2520 User s Manual Triggering 8 5 Bench defaults The bench defaults are listed as follows They are also denoted in Figure 8 1 by the
228. iode power measurement R PRINT 1 OUTPUT 25 CALC2 DATA Read detector 1 MX B data PRINT 1 ENTER 25 Address 2520 to talk LINE INPUT 2 R Input detector 1 math reading PRINT Detector 1 MX B measurement RS PRINT 1 OUTPUT 25 OUTP1 OFF Turn off outputs END H 4 Example Programs Model 2520 User s Manual Linear staircase sweep program The program listing below performs a linear sweep as covered in Section 7 This program sets up the following operating modes e Measure range 5V e Source mode sweep e Source current range 5 00mA e Start current 1OmA e Stop current 100mA e Step current 10mA e Detector bias voltages 5V Linear staircase sweep program 2520 primary address 25 1 OPEN IEEE FOR OUTPUT AS 1 Open IEEE 488 output path OPEN IEEE FOR INPUT AS 2 Open IEEE 488 input path PRINT 1 INTERM CRLF Set input terminator PRINT 1 OUTTERM LF Set output terminator PRINT 1 REMOTE 25 Put 2520 in remote PRINT 1 OUTPUT 25 RST Restore GPIB defaults PRINT 1 OUTPUT 25 FORM ELEM VOLT1 CURR2 CURR3 Voltage current data PRINT 1 OUTPUT 25 SENS1 VOLT RANG 5 5V measure range PRINT 1 OUTPUT 25 SOUR1 CURR RANG 0 5 500mA source range PRINT 1 OUTPUT 25 SOUR1 CURR STAR 10e 3 10mA start current PRINT 1 OUTPUT 25 SOUR1 CURR STOP 100e 3 100mA stop current PRINT 1
229. ion Command processing will halt until the trigger model returns to the idle state with the following exceptions ABORt SDC DCL IFC SYSTem PRESet RST or RCL TRG or GET with TRIG SOUR BUS If any other command is sent after an INIT only SDC IFC and DCL will work 14 58 SCPI Command Reference Model 2520 User s Manual Abort source measure cycle ABORt Abort operation Description When this action command is sent the Model 2520 aborts operation and returns to the idle state A faster way to return to idle is to use the DCL or SDC command Program trigger model COUNt lt n gt STRIGger SEQuence 1 COUNt lt n gt Set trigger count Parameters lt n gt 1 to 5000 Specify count DEFault Sets count to 1 MINimum Sets count to 1 MAXimum 5000 INFinite Run continuously NOTE The product of the trigger count and the number of sweep points SOURI SWE POIN cannot exceed 5000 Query COUNt Queries programmed count COUNt DEFault Queries RST default count COUNt MINimum Queries lowest allowable count COUNt MAXimum Queries largest allowable count Description This command is used to specify how many times the unit cycles through the trigger layer For example if the trigger count is set to 2 the unit will cycle through the trigger layer twice TRIGger COUNt INFinite can be used for repetitive source waveforms or for long tests where only the last reading is important SOURce lt name gt TRIGger
230. is disabled and the 488 1 protocol is enabled To summarize 1 SCPI protocol 0 488 1 protocol Model 2520 User s Manual GPIB 488 1 Protocol G 3 Protocol differences The following information covers the differences between the 488 1 protocol and the SCPI protocol Message exchange protocol MEP When the 488 1 protocol is selected the MEP is disabled to speed up GPIB operation The following guidelines limitations must be followed when using the 488 1 protocol If a query is sent it must be the only command on the line this limitation also means no multiple queries can be sent Otherwise full SCPI command syntax is still supported including long form and short form commands multiple com mands and MIN MAX DEF parameter definitions For example the following command strings are invalid SENS 1 VOLT RANG 10 OPC SENS2 CURR RANG READ READ READ The following command strings are valid SOURI CURRent STARt 0 1 STOP 0 5 STEP 0 1 SENS2 CURR RANG MAX READ When a query is sent either the data must be read back or a Device Clear DCL or Interface Clear IFC must be performed to reset the query When sending a command or query do not attempt to read data from the Model 2520 until the terminator has been sent usually Line Feed with EOI Otherwise a DCL or IFC must be sent to reset the input parser When receiving data all data up to and including the terminator LF with EOD must be accepted Ot
231. ister Description These query commands are used to read the contents of the status event registers After sending one of these commands and addressing the Model 2520 to talk a value is sent to the computer This value indicates which bits in the appropriate register are set Program event enable registers ENABle lt NDN gt or lt NRf gt STATus MEASurement ENABle lt NDN gt or lt NRf gt Program Measurement Event Enable Register STATus QUEStionable ENABle lt NDN gt or lt NRf gt Program Questionable Event Enable Register STATus OPERation ENABle lt NDN gt or lt NRf gt Program Operation Event Enable Register Parameters lt NDN gt Bxx x Binary format each x 1 or 0 Hx Hexadecimal format x 0 to FFFF Qx Octal format x 0 to 177777 lt NRf gt 0 to 65535 Decimal format Query ENABle Read an enable register Description These commands are used to program the enable registers of the status structure The binary equivalent of the parameter value that is sent deter mines which bits in the register gets set See Section 11 for details 14 50 SCPI Command Reference Model 2520 User s Manual Read condition registers CONDition STATus MEASurement CONDition Read Measurement Condition STATus QUEStionable CONDition Read Questionable Register STATus OPERation CONDition Read Operation Condition Description These query commands are used to read the contents of the condition registers Select default condi
232. ith low induc tance such as the supplied CA 290 BNC cables which have a nominal characteristic impedance of 15Q and an inductance of 27nH ft F 4 Measurement Considerations Model 2520 User s Manual Figure F 2 A comparison of operating conditions is shown in Figure F 2 and Figure F 3 Figure F 2 shows the settled response for 4A into 1 6Q using 3m of cable Inductance is excessive in this case resulting in the first settled reading at 1 7us as opposed to 1 5us a lus delay was used before the pulse Figure F 3 shows the settled response of 0 45A into 16Q also using 3m of cable The response is clean because di dt is much lower Rise time of 4A current pulse Current A 4 5 4 0 3 5 3 0 2 5 2 0 0 5 0 0 0 0 5 1 1 5 2 2 5 Time us Model 2520 User s Manual Measurement Considerations F 5 Figure F 3 Rise time of 0 45A current pulse 0 50 0 45 0 40 0 35 0 30 Current A 0 25 0 20 0 15 0 10 0 05 0 00 0 0 5 1 1 5 2 2 5 Time us Increasing cable length To double the effective recommended cable length without significantly degrading pulse characteristics connect the laser diode to the CURRENT OUTPUT HI jack only To use this method connect one laser diode terminal to the center cable conductor connect the other terminal to the cable shield and install a BNC shorting cap on the CURRENT OUT PUT LO jack Select negative current source polarity if the laser diode
233. ity for both laser diode and photodiode measurements NOTE The pulse width setting affects not only the source but the measurement as well The larger the pulse width the more A D samples that will be averaged to gener ate a measurement which decreases noise but increases test time In the DC mode the pulse width setting effectively becomes the aperture sample time for the entire measurement Configuring laser diode measurements 1 ae eS Press CONFIG then LASER Vj to access the laser diode measurement configura tion menu Choose POLARITY then press ENTER Select POSITIVE or NEGATIVE as desired then press ENTER Figure 3 3 Press the LASER V key Use the RANGE A and y keys to select the desired measurement range 5V or 10V Use the lowest range possible for best accuracy Configuring photodiode measurements 1 SV ee ate Press CONFIG then either DETECTOR 1 Ipp or DETECTOR 2 Ipp to access the photodiode measurement configuration menu Choose POLARITY then press ENTER Select POSITIVE or NEGATIVE as desired then press ENTER Figure 3 4 Press the DETECTOR 1 Ipp or DETECTOR 2 Ipp key Use the RANGE 4A and y keys to select the desired measurement range 10mA 20mA 50mA or 100mA Use the lowest range possible for best accuracy Repeat steps through 6 for the other photodiode detector channel Model 2520 User s Manual Basic Operation 3 13 Remote source and measure configuration Source and mea
234. ive or NEGative POS POLarity Query polarity STARt lt n gt Specify start level for I sweep 0 to 5 0 0 v STARt Query start level for current sweep v STOP lt n gt Specify stop level for I sweep 0 to 5 0 0 v STOP Query stop level for current sweep y STEP lt n gt Specify step value for I sweep 0 to 5 0 0 STEP Query step value for current sweep v SPAN lt n gt Specify span 0 to 5 0 0 v SPAN Query span v CENTer lt n gt Specify center point 0 to 5 0 0 v CENTer Query center point v FUNCtion SHAPe lt name gt Select source shape PULSe or DC PULS y SHAPe Query source shape y PULSe Path to control pulse generation for FIXed and SWEep DELay lt n gt Set delay between pulses 20e 6 to 0 5 1 10e 3 v DELay Query delay between pulses v WIDTh lt n gt Set pulse width 500e 9 to 5e 3 10e 6 v WIDTh Query pulse width v TRANsition Control pulse leading edge time STATe lt b gt Enable or disable transition control OFF v STATe Query transition control state v 1 Minimum and default pulse delay and width values depend on pulse duty cycle See Duty cycle in Section 5 14 10 SCPI Command Reference Model 2520 User s Manual Table 14 6 continued SOURce command summary Default Command Description parameter SCPI SOURce 1 Path to control laser diode current source continued VOLTage Path to set compliance level PROTecti
235. l 2520 User s Manual Interlock operation Figure 9 4 shows typical connections to the REMOTE INTERLOCK connector If the fix ture switch is closed Figure 9 4A the three source outputs are enabled and can be turned on If the lid of the test fixture opens Figure 9 4B the switch opens and the three source outputs are disabled and cannot be turned on Figure 9 4 Interlock operation Model 2520 Testhead Test Fixture Pin 1 Remote i i Interlock Switch Interlock i Closed Pin 9 e T A Model 2520 outputs can be turned on Model 2520 Testhead Test Fixture Pin 1 i Remote i Interlock Switch Interlock Open B Model 2520 outputs cannot be turned on Model 2520 User s Manual Digital I O Port Interlocks and Pulse Sync Output 9 7 Interlock status indicator test sequence Perform the following steps to verify the operation of the indicator lights l Remove any connections from the testhead CURRENT OUTPUT VOLTAGE SENSE or DETECTOR terminals Connect the testhead to the mainframe and follow the steps for power connection and power up sequence in Section 1 Bypass the interlock switch on the remote testhead with a bypass plug or cable connected as shown in Figure 9 4A Insert the key provided into the key interlock and verify it is in the DISABLED position At this point the INTERLOCK STATUS indicator should be BLUE and the LASER POWER ON indicator should be OFF on the testhead The OUTPUT ON OFF indicator on the
236. leads and jumpers for possible wear cracks or breaks before each use When installing equipment where access to the main power cord is restricted such as rack mounting a separate main input pow er disconnect device must be provided in close proximity to the equipment and within easy reach of the operator For maximum safety do not touch the product test cables or any other instruments while power is applied to the circuit under test ALWAYS remove power from the entire test system and discharge any capacitors before connecting or disconnecting ca 5 02 bles or jumpers installing or removing switching cards or making internal changes such as installing or removing jumpers Do not touch any object that could provide a current path to the common side of the circuit under test or power line earth ground Al ways make measurements with dry hands while standing on a dry insulated surface capable of withstanding the voltage being measured The instrument and accessories must be used in accordance with its specifications and operating instructions or the safety of the equipment may be impaired Do not exceed the maximum signal levels of the instruments and accessories as defined in the specifications and operating in formation and as shown on the instrument or test fixture panels or switching card When fuses are used in a product replace with same type and rating for continued protection against fire hazard Chassis connections mus
237. llowing notes Event Registers Power up and CLS clears all bits STATus PRESet has no effect Enable Registers Power up and STATus PRESet clears all bits CLS has no effect Accepts the SCPI 1995 0 mandated non decimal numeric format H Q or B Error Queue Power up and CLS clears all bits of the registers 1 Error Queue Messages Power up clears list of messages CLS and STATus PRESet have no effect Register Query Commands The format for the response messages ASCII hexadecimal octal or binary depend on which data format is presently selected See the FORMat SREGister command Model 2520 User s Manual SCPI Command Reference 14 13 Table 14 8 SYSTem command summary Default Command Description parameter SCPI SYSTem PRESet Return to SYSTem PRESet defaults Jv POSetup lt name gt Select power on setup RST PRESet or SAV 0 4 POSetup Query power on setup VERSion Query revision level of SCPI v ERRor Path to read messages in error queue v NEXT Return and clear oldest error code and message ALL Return and clear all errors codes and messages COUNt Return the number of errors CODE Path to return error code numbers only NEXT Return and clear oldest error code only ALL Return and clear all errors codes only CLEar Clears messages from error queue KEY lt n gt Simulate key press 1 to 31 v KEY Query the last pressed key v
238. lower case The lt NRf gt numeric representation for mat parameter type is used to send decimal values and does not use a header The follow ing examples show the proper parameter syntax for setting Bits B5 B3 and B2 b101100 Binary format lt NDN gt parameter type h2C Hexadecimal format lt NDN gt parameter type q54 Octal format lt NDN gt parameter type 44 Decimal format lt NRf gt parameter type Valid characters for the non decimal parameter values are shown as follows lt NDN gt format Valid characters Binary 1s and Os Hexadecimal O through 9 and A through F Octal O through 7 Reading registers Any register in the status structure can be read by using the appropriate query com mand The following explains how to interpret the returned value response message The actual query commands are covered later in this section Table 11 3 through Table 11 7 The response message will be a value that indicates which bits in the register are set That value if not already binary will have to be converted to its binary equivalent For exam ple for a binary value of 100101 bits B5 B2 and BO are set The returned value can be in the binary decimal hexadecimal or octal format The FOR Mat SREGister command is used to select the data format for the returned value Table 11 2 For non decimal formats one of the following headers will accompany the returned value to indicate which format i
239. lowing SCPI commands e Save and recall user setups using SAV and RCL Section 13 e Restore GPIB defaults using RST Section 13 e Restore BENCH defaults using SYSTem PRESet Section 14 e Save the power on configuration using SYSTem POSetup Section 14 1 17 The following paragraphs discuss the main menu operation menus configuration menus and rules to navigate menus 1 18 Getting Started Model 2520 User s Manual Main menu Use the MENU key to access the Main Menu to select configure and or perform various instrument operations These include default setup conditions communications GPIB or RS 232 calibration front panel tests digital output states auto zero timestamp and numeric display format The Main Menu structure is summarized in Table 1 4 Use the Rules to navigate menus to check and or change menu options Table 1 4 Main menu Menu item Description CAL Calibrate Model 2520 UNLOCK Unlock calibration EXECUTE Execute calibration VIEW DATES View last and next calibration dates SAVE Save calibration constants CHANGE PASSWORD Change password TIMESTAMP Reset timestamp YES or NO TEST Perform tests on Model 2520 DISPLAY TESTS Test front panel keys and display digits KEYS Test front panel keys DISPLAY PATTERNS Test display pixels and annunciators CHAR SET Test special display characters SERIAL Display serial number firmware revision SCPI version NUMBERS Select EN
240. ly see below Set MX B parameters MBFactor lt n gt CALCulate 1 KMATh MBFactor lt n gt CALCulate2 KMATh MBFactor lt n gt CALCulate3 KMATh MBFactor lt n gt Set laser diode B offset value Set detector 1 B offset value Set detector 2 B offset value Parameters lt n gt 9 99999e20 to Specify B offset value for MX B 9 99999e20 MINimum 9 99999e20 MAXimum 9 99999e20 DEFault 0 Query MBFactor Query B offset value for MX B Description These commands program the B offset value for the MX B math function Use CALC1 for the laser diode CALC2 for detector 1 and CALC3 for detector 2 MM Factor lt n gt CALCulate 1 KMATh MMFactor lt n gt CALCulate2 KMATh MMFactor lt n gt CALCulate3 KMATh MMFactor lt n gt Parameters 9 99999e20 to 9 99999e20 MINimum MAXimum DEFault lt n gt Select laser diode M slope value Select detector 1 M slope value Select detector 2 M slope value Specify M slope value for MX B 9 99999e20 9 99999e20 1 14 16 SCPI Command Reference Model 2520 User s Manual Query MMFactor Query M slope value for MX B Description These commands program the M slope value for the MX B math function Use CALC1 for the laser diode CALC2 for detector 1 and CALC3 for detector 2 UNITs lt name gt CALCulate 1 KMATh MUNits lt name gt Specify units for laser diode MX B CALCulate2 KMATh MUNits lt name gt Specify units for dete
241. mance Information Model 2520 User s Manual Introduction The IEEE 488 2 standard requires specific information about how the Model 2520 imple ments the standard Paragraph 4 9 of the IEEE 488 2 standard Std 488 2 1987 lists the documentation requirements Table E 1 provides a summary of the requirements and pro vides the information or references the manual for that information Table E 2 lists the coupled commands used by the Model 2520 The Model 2520 complies with SCPI version 1996 0 Table 14 1 through Table 14 10 in Section 14 lists the SCPI confirmed commands and the non SCPI commands implemented by the Model 2520 Model 2520 User s Manual IEEE 488 and SCPI Conformance Information E 3 Table E 1 IEEE 488 documentation requirements Requirements Description or reference 1 IEEE 488 Interface Function Codes See Appendix D 2 Behavior of Model 2520 when the address is set outside Cannot enter an invalid address the range 0 30 3 Behavior of Model 2520 when valid address is entered Address changes and bus resets 4 Power On Setup Conditions Determine by SYSTem POSetup See Section 14 5 Message Exchange Options a Input buffer size 2048 bytes b Queries that return more than one response message None unit c Queries that generate a response when parsed All queries Common Commands and SCPI d Queries that generate a response when read None e Coupled commands See Table E 2 6 Fun
242. mands to reset registers and clear queues Commands Description Ref To Reset Registers CLS Reset all bits of the following event registers to 0 Note 1 Standard Event Register Operation Event Register Measurement Event Register Questionable Event Register STATus PRESet Reset all bits of the following enable registers to 0 Note 1 Operation Event Enable Register Measurement Event Enable Register Questionable Event Enable Register To Clear Error Queue CLS Clear all messages from Error Queue Note 2 STATus QUEue CLEar Clear messages from Error Queue Note 3 Notes 1 The Standard Event Enable Register is not reset by STATus PRESet or CLS Send the 0 parameter value with ESE to reset all bits of that enable register to 0 See Status byte and service request commands page 11 10 2 STATus PRESet has no effect on the Error Queue 3 Use either of the two clear commands to clear the Error Queue Model 2520 User s Manual Status Structure 11 5 Programming and reading registers Programming enable registers The only registers that can be programmed by the user are the enable registers All other registers in the status structure are read only registers The following explains how to ascertain the parameter values for the various commands used to program enable registers The actual commands are covered later in this section Table 11 3 and Table 11 6 A command to program an event enable register is sent
243. ments that use the standard BNC trigger connectors Model 8503 DIN to BNC trigger cable Lets you connect Trigger Link lines one Volt meter Complete and two External Trigger of the Model 2520 to instruments that use BNC trigger connectors The Model 8503 is 1m long Rack mount kits Model 4288 1 single fixed rack mount kit Mounts a single Model 2520 in a standard 19 inch rack Model 4288 2 side by side rack mount kit Mounts two instruments Models 182 428 486 487 2000 2001 2002 2010 2015 2016 2400 2410 2420 2430 2500 2510 2520 6430 6517 7001 side by side in a standard 19 inch rack Model 4288 3 side by side rack mount kit Mounts a Model 2520 and a Model 199 side by side in a standard 19 inch rack Model 4288 4 side by side rack mount kit Mounts a Model 2520 and a 5 25 inch instrument Models 195A 196 220 224 230 263 595 614 617 705 740 775 etc side by side in a standard 19 inch rack Model 4288 5 dual fixed rack mounting kit Mounts a Model 2520 and another 34 inch high instrument Model 182 428 486 487 2000 2010 2400 2410 2420 2430 or 7001 side by side in a standard 19 inch rack Model 2520 User s Manual Getting Started 1 5 Product overview The Model 2520 Pulsed Laser Diode Test System combines high current laser diode pulse and voltage measurement capabilities and two stable DC bias voltage sources with two low noise ammeters for dual channel photodiode measur
244. message must be terminated with an LF line feed EOI end or identify or an LF EOI The bus will hang if your computer does not provide this termination The following example shows how a multiple command program message must be terminated outpl1 on lt PMT gt Command execution rules e Commands execute in the order that they are presented in the program message An invalid command generates an error and of course is not executed Valid commands that precede an invalid command in a multiple command program message are executed Valid commands that follow an invalid command in a multiple command program message are ignored Response messages A response message is the message sent by the instrument to the computer in response to a query command program message Sending a response message After sending a query command the response message is placed in the Output Queue When the Model 2520 is then addressed to talk the response message is sent from the Output Queue to the computer Multiple response messages If you send more than one query command in the same program message Multiple com mand messages the multiple response messages for all the queries are sent to the com puter when the Model 2520 is addressed to talk The responses are sent in the order the query commands were sent and are separated by semicolons Items within the same query are separated by commas The following example shows the respo
245. mmand is not an addressed command so all instruments equipped to implement DCL will do so simultaneously 10 8 Remote Operations Model 2520 User s Manual When the Model 2520 receives a DCL command it clears the Input Buffer and Output Queue cancels deferred commands and clears any command that prevents the processing of any other device command A DCL does not affect instrument settings and stored data SDC selective device clear The SDC command is an addressed command that performs essentially the same function as the DCL command However since each device must be individually addressed the SDC command provides a method to clear only selected instruments instead of clearing all instruments simultaneously as is the case with DCL GET group execute trigger GET is a GPIB trigger that is used as a trigger event to control operation The Model 2520 reacts to this trigger if it is the programmed trigger control source The following com mand selects the GPIB trigger control source TRIG SOURce BUS NOTE With TRIG SOURce BUS selected and an INITiate command sent do not send any commands except GET DCL SDC IFC TRG and ABORt while per forming source and measure operations ARM annunciator on If you do erratic operation will occur SPE SPD serial polling Use the serial polling sequence to obtain the Model 2520 serial poll byte The serial poll byte contains important information about internal functions See Se
246. mmed timer interval elapses The timer resets to its initial state when the instrument goes into idle MANual Event detection occurs when the TRIG key is pressed The Model 2520 must be in LOCAL mode for it to respond to the TRIG key Press the LOCAL key or send GTL over the bus to take the Model 2520 out of remote TLINk Event detection occurs when an input trigger via the Trigger Link input line is received see Trigger link page 8 5 for more information NSTest Event detection occurs when the start of test SOT line of the Digital I O port is pulsed low See Section 9 PSTest Event detection occurs when the start of test SOT line of the Digital I O port is pulsed high See Section 9 BSTest Event detection occurs when the start of test SOT line of the Digital I O port is pulsed either high or low See Section 9 8 12 Triggering Model 2520 User s Manual Delay and pulse phases The delay pulse cycle consists of two phases Delay and Pulse See Section 5 for details Delay phase The programmable delay is the time period between current pulses The delay is set with the DELay commands and can be programmed in the range of 20us to 500ms Note how ever that the programmed delay is the minimum delay and the actual delay depends on the pulse duty cycle see Section 5 Pulse phase During the pulse phase the unit outputs one current pulse with the programmed pulse width set to between 500ns a
247. mote Custom sweep The custom sweep lets you construct your own sweep by specifying the number of source measure points 100 maximum and the current source level pulse width and pulse delay at each point Figure 5 9 The SOURI LIST commands program various custom sweep parameters including e SOUR1 LIST CURR Sets up a custom sweep list with up to 100 current values e SOUR1 LIST WIDT Specifies up to 100 pulse width values for a custom sweep e SOUR1 LIST DEL Specifies up to 100 pulse delay values for a custom sweep NOTE Ifthe delay or width list is shorter than the current list the last delay or width value will be used for the remainder of the current list points See the custom sweep information in Section 7 and the LIST commands under SOURce subsystem page 14 32 for details Model 2520 User s Manual Source Measure Concepts 5 9 Figure 5 8 Sweep waveform types lt Stop Start Linear Staircase Sweep Logarithmic scale shown for staircase steps Logarithmic Staircase Sweep First Point Last Point Custom Sweep Note DC mode waveforms shown Figure 5 9 Custom sweep waveform SOURT1 LIST CURR SOUR1 CURR LOW SOUR1 LIST DEL SOUR1 LIST WIDT 5 10 Source Measure Concepts Model 2520 User s Manual Current source operating boundaries Limit lines Figure 5 10 shows the operating boundaries or limit lines for the laser diode current source In the DC mo
248. mplitude determined by the SOUR1 CURR AMPL command see Set amplitudes page 14 34 PULSe In this mode the source will output a current pulse The high and low amplitudes are set with the SOUR1 CURR AMPL and SOUR1 CURR LOW commands covered in Set amplitudes page 14 47 The pulse width and delay are set with the SOUR1 PULS WIDT and SOUR1 PULS DEL commands see Set pulse times page 14 36 Select source range RANGe lt n gt SOURce 1 CURRent RANGe lt n gt Select range for laser diode current source Parameters lt n gt 0 to 5 0 Specify source level amps DEFault 500mA range MINimum 500mA range MAXimum 5A range UP Select next higher range DOWN Select next lower range Query RANGe Query range for specified source RANGe DEFault Query RST default source range RANGe MINimum Query lowest source range RANGe MAXimum Query highest source range Description This command is used to select the range for the laser diode current source Range is selected by specifying the approximate current magni tude that you will be using The instrument will then go to the lowest range that can accommodate that level 14 34 SCPI Command Reference Model 2520 User s Manual For example if you expect to source levels around 300mA send the fol lowing command SOURce1 CURRent RANGe 0 3 The above command will select the 5 00mA range for the laser diode current source As listed in Parameters
249. n occurs after the timer interval elapses After selecting this arm event you will be prompted to specify the timer interval in seconds MANUAL Event detection occurs when the TRIG key is pressed TLINK After selecting this arm event you will be prompted to select the input line for the Trigger Link 1 to 6 8 8 Triggering Model 2520 User s Manual JSTEST Event detection occurs when the SOT line of the Digital I O port is pulsed low See Section 9 TSTEST Event detection occurs when the SOT line of the Digital I O port is pulsed high TJSTEST Event detection occurs when the SOT line of the Digital I O port is pulsed either high or low TRIGGER OUT Use to configure the output trigger e LINE Select the Trigger Link line for the output trigger line 1 2 3 4 5 or 6 e EVENTS Enable ON or disable OFF the arm layer output triggers TRIG LAYER DONE ON enables an output trigger on exiting the trigger layer Figure 8 5 Configure trigger menu tree CONFIG TRIG COUNT INIT HALT TRIGGER TRIGGER IN OUT FINITE INFINIE LINE EVENTS IMMEDIATE GPIB TIMER MANUAL TLINK IMSTEST IUSTEST M STEST Model 2520 User s Manual Triggering 8 9 Remote triggering Trigger model remote operation The trigger model flowchart in Figure 8 6 summarizes remote trigger operation Operation is controlled by SCPI commands from the Trigger Subsystem Key remote command
250. n unaffected The laser diode current source is placed in the FIXed mode Remote to local transition When changing from remote to local operation the following takes place If the laser diode current source is in the DC mode and the output is turned on the continuous init mode is turned on Otherwise the Model 2520 is placed into the Idle layer of the Trigger Model All user defined displays are disabled The display is re enabled if it was previously turned off The laser diode current source is placed in the FIXed mode Selecting an interface The Model 2520 supports two built in remote interfaces GPIB General Purpose Interface Bus RS 232 interface You can use only one interface at a time The factory default interface selection is the GPIB bus You can select the interface only from the front panel The interface selection is stored in non volatile memory it does not change when power has been off or after a remote interface reset The GPIB bus is the IEEE 488 interface You must select a unique address for the Model 2520 The address is displayed when the instrument is turned on At the factory the address is set to 25 The IEEE 488 address can only be changed from the front panel while the IEEE 488 bus is enabled Model 2520 User s Manual Remote Operations 10 3 The RS 232 interface is a serial interface Programmable aspects of this interface include the following factory default settings are shown in parentheses
251. nated on the other end CA 290 1A Cable This 1m BNC cable is terminated at one end with a male BNC con nector and is unterminated on the other end Model 7078 TRX Triax Cables These low noise triax cables are terminated at both ends with 3 slot male triax connectors The Model 7078 TRX is available in 0 3m 1ft 0 9m 3ft 1 5m 5ft and 3m 10ft lengths Model 7078 TRX BNC Adapter This is a 3 slot male triax to female BNC adapter This adapter lets you connect a BNC cable to the triax detector inputs of the Model 2520 testhead Model 237 TRX TBC Connector This is a 3 lug female triax bulkhead connector with cap for assembly of custom panels and interface connections 1 4 Getting Started Model 2520 User s Manual Interface cables Models 7007 1 and 7007 2 shielded GPIB cables Connect the Model 2520 to the GPIB bus using shielded cables and connectors to reduce Electromagnetic Interference EMI The Model 7007 1 is 1m long the Model 7007 2 is 2m long Model 7009 5 shielded RS 232 cable Connect the Model 2520 to computer serial port using shielded cables and connectors to reduce EMI Models 8501 1 and 8501 2 trigger link cables Connect the Model 2520 to other instruments with Trigger Link connectors e g Model 7001 Switch System The Model 8501 1 is 1m long the Model 8501 2 is 2m long Model 8502 trigger link adapter Lets you connect any of the six Trigger Link lines of the Model 2520 to instru
252. nd POINts commands are coupled Changing the step size also changes the number of source and measure points Con versely changing the number of source and measure points changes the step size 14 40 SCPI Command Reference Model 2520 User s Manual POINts lt n gt SOURce 1 SWEep POINts lt n gt Set number of points for sweep Parameters lt n gt 2 to 1000 Specify number of source measure points MINimum 2 MAXimum 1000 DEFault 1000 Query POINts Query number of sweep points POINts DEFault Query RST default number of sweep points POINts MINimum Query lowest allowable number of sweep points POINts MAXimum Query highest allowable number of sweep points Description The POINts command specifies the total number of source and measure points in a sweep For a linear sweep the source and measure points are equally spaced stepped between the start level and the stop level For a log sweep the source and measure points are equally spaced on a loga rithmic scale Note that the start and stop levels are source and measure points Step size for a linear sweep can be calculated as follows Step Size Stop Start Points 1 Step Size Span Points 1 Step size for a logarithmic sweep can be calculated as follows log 10 Stop log10 Start Points 1 An alternate way to set the source and measure points in a sweep is to specify the step size using the STEP command Note that the POINts and STEP comma
253. nd 5ms with the WIDTh commands If the unit is in the fixed non sweep mode the pulse amplitude is the same for each cycle through the loop However if the unit is the sweep mode the pulse amplitude is set to the programmed value for that sweep point 1 OMHz samples are taken during the pulse phase and one set of voltage and current readings is DSP processed for each pulse Filtering If the filter is enabled the instrument cycles through the delay pulse loop for the pro grammed filter count and averages the specified number of readings to yield a single set of filtered readings measurements Sweep points When a sweep is enabled the unit cycles through the complete delay pulse process including filtering if enabled for the programmed number of sweep points For linear staircase sweeps the number of points depends on the start stop and step current values For log staircase sweeps the number of points depends on the start and stop current values and the programmed number of points For custom sweeps the number of points depends on the length of the sweep current list Counter The programmable counter is used to repeat operations within the Trigger Layer For example to repeat a sweep three times the trigger counter would be set to 3 If the sweep has a total of 10 points a total of 30 measurements will be made The maximum finite trigger counter value is 5000 However the product of the trigger count and the number of sw
254. nd does not affect the instrument setup This command does not trigger source and measure operations it sim ply requests the last available readings Note that this command can repeatedly return the same readings Until there are new readings this command continues to return the old readings For example assume that the Model 2520 performed 20 source and measure operations The FETCh command will request the readings for those 20 source and measure operations If FETCh is sent while performing source and measure operations ARM annunciator on it will not be executed until the Model 2520 goes back into idle NOTE The FETCh command is automatically asserted when the READ or MEA Sure command is sent The readings that are acquired depend on which data elements are selected Section 14 FORMat subsystem Data elements Measure readings take priority over source readings and data from channels not sourced or measured are assigned the NAN not a number value of 9 91e37 Model 2520 User s Manual SCPI Signal Oriented Measurement Commands 13 3 NOTE See Appendix C for a detailed explanation on how data flows through the vari ous operation blocks of the Model 2520 It clarifies the types of readings that are acquired by the various commands to read data SENSe 1 DATA LATest SENSe2 DATA LATest SENSe3 DATA LATest Description READ Description These commands work exactly like FETCh
255. nds are coupled Changing the number of source and measure points also changes the step size Con versely changing the step size changes the number of source and mea sure points Log Step Size DiRection lt name gt SOURce 1 SWEep DIRection lt name gt Set direction of sweep Parameters lt name gt UP Run sweep from start to stop DOWN Run sweep from stop to start Query DIRection Query direction of sweep Description Normally a sweep is run from the start level to the stop level The STARt and STOP or CENTer and SPAN commands are used to set these levels Model 2520 User s Manual Configure list SCPI Command Reference 14 41 This command lets you change the execution direction of the sweep With DOWN selected the sweep will begin at the stop level and end at the start level Selecting UP restores sweep operation to the normal start to stop direction The list commands allow you to program a custom sweep of up to 100 points Each point can be individually programmed for pulse amplitude pulse width and pulse delay CURRent lt NRf list gt SOURce 1 LIST CURRent lt NRf list gt Define current list Parameters Query Description lt NRf list gt NRf NRf NRf NRf 0 to 5 0 Pulse high amplitude amps CURRent Query current list This command is used to define a list of current pulse values up to 100 for the list sourcing mode of operation When operation is started the instrument will seque
256. nectors 0 eeeceeseeeseceseeceeeeseeceaeeesaeceaeeetaeeeeeeteeees 2 5 Triax DETECTOR connectors oo eee eeceeseeeeseeeeeeseeeeeeaes 2 6 CURRENT OUTPUT and VOLTAGE SENSE COMMECLONS diers asirese ee a oesie eE EE EE ARE NRE 2 6 Interlock connections sssesesessesesreeesrerrsrssreresreresreresrerrrsreresreeese 2 6 Remote interlock connections sssseseseeseeeeereresrerrsrereereerrees 2 6 Key interlock si ciccees saecitededvncieseiens dea cians A 2 7 Laser diode test connections 0 0 0 ee eeseeeeeseeeeeeseeecetaeeeeeeseeeeeaes 2 7 Connecting Cables vss cccccvestiiecsessssce dives estessevassseervecoeaesnee 2 7 Typical connections 000 eee seeseeseeeeeeaeeeeeeseeeaeeeeeeeesaeenaes 2 7 Equivalent circ it c cc cecssessccinceieeccsseesacecessndenevaseeeiveseneneueas 2 8 Polarity considerations 00 0 cece eeeeeeeseeeeeseeseeeneeneeeeeeetees 2 8 Connection Considerations 00 0 ee ceeeeeeeeeseeeeseeeeeeeeseeeaees 2 10 Basic Operation Operation OVETVICW ceeecesceessecesceceaeeeseeceaeeeseeceaeeeaeseaeeeteeeeaees 3 2 Laser diode source and measure capabilities 0 3 2 Laser diode source and measure ranges s 3 2 Laser diode source Compliance eee eeeeeeeseeereeees 3 3 Photodiode source and measure capabilities 0 ee 3 3 Photodiode source and measure range s es 3 4 Basic circuit configuration oo eee eee eeeeeeceeeeeeeeeeeeteeeeaes 3 5 Polarity Sinsc setae acriashasitguntel raa EEE 3 6 Laser diode current sour
257. nfigure trigger lines and output trigger v ILINe lt n gt Select input trigger line 1 2 3 4 5 or 6 1 ILINe Query input trigger line OLINe lt n gt Select output trigger line 1 2 3 4 5 or 6 2 OLINe Query output trigger line OUTPut lt name gt Output trigger TRIGger or NONB NONE OUTPut Query output trigger status Calculate subsystems There are a total of four CALCulate subsystems e CALCI Laser diode math I V V I V x I or MX B e CALC2 Detector 1 math MX B only e CALC3 Detector 2 math MX B only e CALC4 Detector 1 current detector 2 current The commands in these subsystems are summarized in Table 14 1 NOTE See Appendix C for a detailed explanation on how data flows through the vari ous CALC operation blocks of the Model 2520 It clarifies the type of readings that are acquired by the various commands to read data Model 2520 User s Manual Select laser diode math function FORMat lt name gt CALCulate 1 FORMat lt name gt SCPI Command Reference 14 15 Select laser diode math function Parameters lt name gt MXB 1 MX B CONDuctance 1 I1 V1 POWER 1 VIxiil RESistance 1 ViI ll Query FORMat Query selected math function Description This command selects the laser diode math function The laser diode current source value I1 and measured voltage V1 are used to calcu late CONDuctancel POWER1 and RESistancel while MX B parameters are programmed separate
258. nframe front and rear panel familiarization Front panel summary The front panel of the Model 2520 mainframe is shown in Figure 1 1 Figure 1 1 Mainframe front panel 2520 PULSED LASER DIODE TEST SYSTEM LASER DETECTOR 1 DETECTOR2 gt 9OOOOOO 2e o 1 2 3 4 5 eir MATH LOCAL RECALI FILTER D OUT TRIG SWEEP Ca cou RANGE 6 7 8 9 0000 PW DELAY COMM SETUP CONFIG MENU EXIT ENTER Q OUTPUT r N LASER keys VL Configure laser diode voltage measure IL Control laser diode current source DETECTOR 1 keys VB Control photodiode detector 1 bias voltage source lpp Configure photodiode detector 1 current measure DETECTOR 2 keys VB Control photodiode detector 2 bias voltage source Ipp Configure photodiode detector 2 current measure EDIT keys Increase value Decrease value Move cursor left va dp Move cursor right COMPL and RANGE keys COMPL Set laser diode source voltage compliance limit RANGE A Increase range RANGE Y Decrease range Model 2520 User s Manual Operation keys EDIT MATH LOCAL RECALL FILTER DIG OUT TRIG SWEEP PW DELAY COMM SETUP CONFIG MENU EXIT ENTER Annunciators EDIT ERR MATH REM TALK LSTN SRQ FILT ARM TRIG Output control Getting Started 1 7 Enter EDIT mode Enable math function Cancel remote operation Display stored readings and timestamp Control digital filter Set Digital I O port output val
259. nge sending UP is a No Op no operation When on the lowest range sending DOWN is a NO Op Select detector current measurement range UPPer lt n gt SENSe2 CURRent DC RANGe UPPer lt n gt l UPIDOWN Select detector 1 current range SENSe3 CURRent DC RANGe UPPer lt n gt l UPIDOWN Select detector 2 current range Parameters lt n gt 0 to 0 105 Expected reading in amps DEFault 0 1 MINimum 0 MAXimum 0 105 UP Select next higher measurement range DOWN Select next lower measurement range Query RANGe Query measurement range RANGe DEFault Query RST default range RANGe MINimum Query lowest range returns 0 RANGe MAXimum Query highest range Model 2520 User s Manual SCPI Command Reference 14 29 Description These commands are used to select the current measurement range for detector 1 and detector 2 The range is selected by specifying the expected reading The instrument will then go to the most sensitive reading that will accommodate that reading For example if you expect a reading of approximately 60mA then simply let lt n gt 0 06 or 6e 2 in order to select the 100mA range You can also use the UP and DOWN parameters to select range Each time UP or DOWN is sent the next higher or lower measurement range is selected When on the maximum range sending UP is a No Op no operation When on the lowest range sending DOWN is a NO Op Select polarity POLarity lt name gt SENSe 1
260. nout oo eee cee eee eee eeeeeeeeeeeeseesaee 10 19 Table 10 3 PC serial port pinout 00 eee cece ceeeeeceeeeeeeeseeeeeeneesaes 10 19 11 Status Structure Table 11 1 Common and SCPI commands to reset registers and CLEAR GUCUES niione ee eee 11 4 Table 11 2 Data format commands for reading status registers 11 7 Table 11 3 Status byte and service request enable register COMMANDS scsciieeenscesscolesadevseeeswetlevetieieeecesrs senda E SE 11 10 Table 11 4 Status byte programming example eee eee eeeees 11 10 Table 11 5 Condition register commands 0 0 ee eee eeeeeseeeeeeseeeeee 11 17 Table 11 6 Event register commands 00 0 ee eeeeeeeeeceeeeeeeeeeeeeeneenaee 11 17 Table 11 7 Event enable registers commands 00 0 0 eceeeeeeeseeeeeereeeeee 11 18 Table 11 8 Program and read register programming example 11 19 Table 11 9 Error queue commands 00 eee eee ceeeeeeeeeeeeeeeeeeeeeneenaee 11 21 12 Common Commands Table 12 1 TEEE 488 2 common commands and queries 12 2 Table 12 2 OPC programming example 0 00 0 eee eeeeeeeeeeeeeeeseeeaeeeees 12 4 Table 12 3 SAV RCL programming example ou eee eeeeeeee 12 5 Table 12 4 TRG programming example eee eeeeeeeeeeeeeeeseeeaeeeees 12 6 13 SCPI Signal O riented Measurement Commands Table 13 1 Signal oriented measurement command summary 13 2 14 SCPI Command Reference Table 14 1 CALCulate command summary 2 0 0 0 cee eeceeeeeeeeee
261. nse message for a program message that contains four single item query commands 0 1 1 0 10 16 Remote Operations Model 2520 User s Manual Response message terminator RMT Each response is terminated with an LF Line Feed and EOI end or identify The fol lowing example shows how a multiple response message is terminated 0 1 1 0 lt RMT gt Message exchange protocol Two rules summarize the message exchange protocol Rule 1 You must always tell the Model 2520 what to send to the computer The following two steps must always be performed to send information from the instru ment to the computer 1 Send the appropriate query command s in a program message 2 Address the Model 2520 to talk Rule 2 The complete response message must be received by the computer before another program message can be sent to the Model 2520 RS 232 interface operation NOTE The programmable aspects of RS 232 operation baud rate data bits parity and terminator are configured from the COMMUNICATIONS SETUP menu accessed with the COMM key Sending and receiving data The RS 232 interface transfers data using 8 data bits 1 stop bit and no parity Make sure the device you connect to the Model 2520 also uses these settings You can break data transmissions by sending a C decimal 3 or X decimal 18 charac ter string to the instrument or by sending an RS 232 break condition holding the transmit line low for gt 11 bits This
262. nt Conductor Back Model 2520 Testhead Output Ne Photodiode A Detector Triax Cable Optional Earth Ground Connection Za m Laser Diode Ly Forward Photodiode Detector Center Conductor Ss Coax Cables Triax Cable Detector 1 Detector 2 Voltage Sense Inner Shield FN Shield Outer Shield Chassis Ground Equivalent circuit Figure 2 6 shows an equivalent circuit for the connection scheme shown in Figure 2 5 The circuit includes the current source and voltmeter to excite and measure the laser diode two ammeters to make photodiode current measurements and two voltage sources to bias the photodiodes Polarity considerations All measurements are unipolar If a particular measurement polarity is set up incorrectly the Model 2520 will display the OVERFLOW message For detector Ipp measure ments current flowing into the ammeter center conductor of the DETECTOR triax con nector is negative while current flowing out is positive For laser diode voltage V1 measurements the measurement is positive when the HI terminal is at a higher polarity than the LO terminal and negative when the HI terminal is at a lower polarity than the LO terminal Model 2520 User s Manual Connections 2 9 Figure 2 6 Equivalent circuit of laser diode test connections Reverse CURRENT Optional Relay OUTPUT Earth Ground HI Cables Current Source VOLTAGE SENSE DETECTOR 1 Photo
263. nt panel HL cuRRENT_LO OUTPUT coma CAT I DETECTOR 1 DETECTOR 2 A L vortace Hi SENSE Lo ISOLATION FROM EARTH 10V MAX DETECTOR connectors DETECTOR 1 Use to bias and measure photodiode detector 1 DETECTOR 2 Use to bias and measure photodiode detector 2 Triax connector terminals Center conductor Current input Inner shell Voltage bias source output Outer shell Chassis ground WARNING Isolation from earth is 10V maximum Exceeding this value may result in a shock hazard Laser diode connectors CURRENT OUTPUT Current source HI and LO output terminals to laser diode VOLTAGE SENSE HI and LO sense terminals to measure laser diode voltage BNC connector terminals Center conductor Signal input or output Outer shell Chassis ground 1 10 Getting Started Model 2520 User s Manual Rear panel summary The rear panel of the Model 2520 testhead is shown in Figure 1 4 Figure 1 4 Testhead rear panel DISABLED PULLTO BOTH INTERLOCKS MUST BE ENABLED TO OPERATE FMOVE KEY REMOTE INTERLOCK INTERLOCK DISABLED e e9 ENABLED 1 GREEN ENABLED a RED DISABLED O INTERLOCK STATUS OCA MAINFRAME CONN 2 CR MAINFRAME MAINFRAME connectors MAINFRAME CONN 1 Connects to mainframe TESTHEAD CONN 1 connector MAINFRAME CONN 2 Connects to mainframe TESTHEAD CONN 2 connector INTERLOCKS REMOTE I
264. nt3 This element provides the detector 2 current reading If no current reading is available the NAN not a number value of 9 91e37 is used TIME This element returns the timestamp value The first reading taken during the pulse will be given a TIME value of 0 The TIME value is then incremented by 100ns for each successive reading NOTE Inthe pulse mode the current source pulse will not necessarily start at the first reading and may be delayed by up to five readings 500ns To determine when the pulse actually occurs you must look at the measurement data SOURce4 lt name gt FORMat SOURce4 lt name gt Set SOUR4 TTL response format Parameters lt name gt ASCii ASCII format HEXadecimal Hexadecimal format OCTal Octal format BINary Binary format Query SOURce4 Query response format Description This command controls the response format for the SOUR4 TTL query in a manner similar to formats set by the FORM SREG command See SOURce subsystem page 14 32 for details Byte order BORDer lt name gt FORMat BORDer lt name gt Specify binary byte order Parameters lt name gt NORMal Normal byte order for binary formats SWAPped Reverse byte order for binary formats Query BORDer Query byte order Description This command is used to control the byte order for the IEEE 754 binary formats For normal byte order the data format for each element is sent as follows Byte 1 Byte2 Byte3 Byte4 Single precision For rev
265. ntially source each current pulse value in the list A set of measurements are performed at each current pulse level The pulse width and delay are set with the WIDTh and DELay commands see below The pulse low level is set with the LOW command see Set amplitudes page 14 34 The following command shows the proper format for defining a list using source values of 1A 2A and 5A SOURce 1 LIST CURRent 1 2 5 In order to execute a source list the selected source must be in the list sourcing mode Use the SOUR1 CURR MODE command to select the LIST sourcing mode See Select sourcing mode page 14 32 APPend lt NRf list gt SOURce 1 LIST CURRent APPend lt NRf list gt Add value s to current list Parameters Description lt NRf list gt NRf NRf NRf NRf 0 to 5 0 Source value amps This command is used to add one or more values up to 100 to a source list that already exists The source values are appended to the end of the list By using multiple appended lists up to 1000 points can be in a list 14 42 SCPI Command Reference Model 2520 User s Manual POINts SOURce 1 LIST CURRent POINts Query length of current list Description These commands are used to determine the length of the specified cur rent list The response message indicates the number of source values in the list WIDTh lt NRf list gt SOURce 1 LIST WIDTh lt NRf list gt Define pulse width list Parameters lt NRf li
266. nts 0 0 0 ee eeeeeeeeeeeee E 3 Coupled commands oc eeeeeeseeeeeeseeseeeeeeeeeseceeeeeenseeseeees E 4 Measurement Considerations Minimum recommended source resistance values F 17 Getting Started General information Covers general information that includes warranty infor mation contact information safety symbols and terms inspection and available options and accessories Product overview Summarizes the features of the Model 2520 Pulsed Laser Diode Test System Familiarization Summarizes the controls and connectors on the unit Power up Covers line power connection line voltage settings fuse replace ment and the power up sequence Display Provides information about the Model 2520 display Default settings Covers factory default setups and saving and recalling user set ups Menus Covers the main and configuration menus as well as rules to navigate menus 1 2 Getting Started Model 2520 User s Manual General information Warranty information Warranty information is located at the front of this manual Should your Model 2520 require warranty service contact the Keithley representative or authorized repair facility in your area for further information When returning the instrument for repair be sure to fill out and include the service form at the back of this manual to provide the repair facility with the necessary information Contact information Worldwide phone
267. numbers are listed at the front of this manual If you have any questions please contact your local Keithley representative or call one of our Application Engineers at 1 800 348 3735 U S and Canada only Additional information may be obtained at www keithley com Manual addenda Any improvements or changes concerning the instrument or manual will be explained in an addendum included with the manual Be sure to note these changes and incorporate them into the manual Specifications Model 2520 specifications shown throughout the body of this manual and the detailed specifications listed in Appendix A were current at the time of printing but they are sub ject to change without notice For the most recent specifications refer to the web site at www keithley com Safety symbols and terms The following symbols and terms may be found on the instrument or used in this manual The J symbol on an instrument indicates that the user should refer to the operating instructions located in the manual The A symbol on the instrument shows that high voltage may be present on the termi nal s Use standard safety precautions to avoid personal contact with these voltages The WARNING heading used in this manual explains dangers that might result in per sonal injury or death Always read the associated information very carefully before per forming the indicated procedure The CAUTION heading used in this manual explains hazards that could damage
268. o 10 SOURce 1 FUNCtion lt function gt Select laser diode current source function DC or PULSe SOURce 1 PULSe DELay lt delay gt Set laser diode source pulse delay 20e 6 to 0 5 2 SOURce 1 PULSe WIDTh lt width gt Set laser diode source pulse width 500e 9 to 5e 3 2 SOURce 1 CURRent LOW lt low_current gt Set low pulse amplitude for pulse mode 0 to 15e 3 500mA range 0 to 150e 3 5A range SOURce2 VOLTage lt voltage gt Set detector 1 source voltage 0 to 20 SOURce3 VOLTage lt voltage gt Set detector 2 source voltage 0 to 20 5 0A maximum pulse mode only 1A maximum in DC mode Settings affected by maximum duty cycle See Section 5 3 14 Basic Operation Model 2520 User s Manual Programming example Table 3 5 summarizes the command sequence for basic source and measure configuration NOTE See Section 4 for complete test procedures These commands set up the Model 2520 as follows Laser diode voltage measurement range and polarity 10V positive Photodiode measurement polarity negative both detectors Laser diode source 0 5A range 0 5A amplitude 5V voltage limit positive polarity Laser diode source mode pulse delay 100usec width 10usec low I 10mA Detector 1 source 20V amplitude Detector 2 source 10V amplitude Table 3 5 Basic source and measure configuration example Commands Comments SENS1 VOLT RANG 10 SENS1 VOLT POL POS SENS2 CUR
269. odel 2520 to be controlled by bus triggers The last command which sends a bus trigger triggers one measurement Each subsequent bus trigger will also trigger a single measurement NOTE With TRIG SOURce BUS selected do not send any commands except TRG GET DCL SDC IFC and ABORt while performing source measure opera tions Otherwise erratic operation will occur 12 6 Common Commands Model 2520 User s Manual Table 12 4 TRG programming example Command Description RST Restore GPIB defaults TRIG SOUR BUS Select BUS trigger control source TRIG COUN INF __ Set trigger layer count to infinite OUTP1 ON Turn on output INIT Take Model 2520 out of idle TRG Trigger one measurement TST self test query Run self test and read result Use this query command to perform a checksum test on ROM The command places the coded result 0 or 1 in the Output Queue When the Model 2520 is addressed to talk the coded result is sent from the Output Queue to the computer A returned value of zero 0 indicates that the test passed and a value of one 1 indicates that the test failed WAI wait to continue Wait until previous commands are completed Effectively the WAI command is a No Op no operation for the Model 2520 and thus does not need to be used Two types of device commands exist e Sequential commands A command whose operations are allowed to finish before the next command i
270. of math Model 2520 User s Manual SCPI Command Reference 14 5 Table 14 2 DISPlay command summary Default Command Description parameter SCPI DISPlay ENABle lt b gt Turn on or turn off front panel display Note 1 Jv ENABle Query state of display WINDow 1 Path to locate message to top display line Jv TEXT Control user test message Note 2 v DATA lt a gt Define ASCII message a up to 20 characters v DATA Query text message v STATe lt b gt Enable or disable message mode Note 3 Jv STATe Query text message state v DATA Query data on top portion of display WINDow2 Path to locate message to bottom display line TEXT Control user test message Note 2 v DATA lt a gt Define ASCII message a up to 32 characters v DATA Query text message v STATe lt b gt Enable or disable message mode Note 3 v STATe Query text message state v DATA Query data on bottom portion of display Jv Notes 1 RST and SYSTem PRESet has no effect on the display circuitry Pressing LOCAL or cycling power enables ON the display circuit 2 RST and SYSTem PRESet has no effect on a user defined message Pressing LOCAL or cycling power cancels all user defined messages 3 RST and SYSTem PRESet has no effect on the state of the message mode Pressing LOCAL or cycling power disables OFF the message mode 14 6 SCPI Command Re
271. ommands are given Device operation is categorized into three operators controller talker and listener The controller does what its name implies it controls the instruments on the bus The Model 2520 User s Manual IEEE 488 Bus Overview D 3 talker sends data while a listener receives data Depending on the type of instrument any particular device can be a talker only a listener only or both a talker and listener There are two categories of controllers system controller and basic controller Both are able to control other instruments but only the system controller has the absolute authority in the system In a system with more than one controller only one controller may be active at any given time Certain protocol is used to pass control from one controller to another The IEEE 488 bus is limited to 15 devices including the controller Thus any number of talkers and listeners up to that limit may be present on the bus at one time Although sev eral devices may be commanded to listen simultaneously the bus can have only one active talker or communications would be scrambled A device is placed in the talk or listen state by sending an appropriate talk or listen com mand These talk and listen commands are derived from an instrument s primary address The primary address may have any value between 0 and 30 and is generally set by rear panel DIP switches or programmed from the front panel of the instrument The actual lis ten ad
272. ommon commands Model 2520 User s Manual Common commands are commands that are common to all devices on the bus These com mands are designated and defined by the IEEE 488 2 standard Generally these commands are sent as one or more ASCII characters that tell the device to perform a common operation such as reset The IEEE 488 bus treats these commands as data in that ATN is false when the commands are transmitted SCPI commands SCPI commands are commands that are particular to each device on the bus These com mands are designated by the instrument manufacturer and are based on the instrument model defined by the Standard Commands for Programmable Instruments SCPI Consor tium s SCPI standard Generally these commands are sent as one or more ASCII characters that tell the device to perform a particular operation such as setting a range or closing a relay The IEEE 488 bus treats these commands as data in that ATN is false when the commands are transmit ted Command codes Command codes for the various commands that use the data lines are summarized in Figure D 3 Hexadecimal and the decimal values for the various commands are listed in Table D 2 Table D 2 Hexadecimal and decimal command codes Command GTL SDC GET LLO DCL SPE SPD LAG TAG SCG UNL UNT Hex value Decimal value 01 04 08 11 14 18 19 20 3F 40 5F 60 7F 3F 5F D 11 IEEE 488 Bus Overview Model 252
273. ommon commands 12 1 Condition register 11 17 Coupled E 4 Custom sweep 7 10 Error queue 11 21 Event enable registers 11 18 Event register 11 17 Filter 6 5 6 6 General bus 10 6 GPIB D 7 Laser diode test 4 5 Math functions 6 9 Range 6 3 Remote trigger 8 13 Source and measure configuration 3 13 Staircase sweep 7 8 Status byte and service request 11 10 Unaddress D 9 Uniline D 8 Universal multiline D 8 Common commands 12 1 D 10 IDN 12 3 OPC 12 3 OPC 12 3 OPT 12 4 RCL 12 4 RST 12 5 SAV 12 4 TRG 12 5 TST 12 6 WAI 12 6 Compliance Laser diode source 3 3 Conductance math function 6 7 Configuration Buffer 14 57 Circuit See Circuit configuration 3 5 Detector 1 22 Digital I O port 9 2 Digital output 9 3 Filter 1 23 6 5 14 30 GPIB D 4 Laser diode current source 4 4 Laser diode measurement function 4 4 Laser diode measurements 3 12 Laser diode source 3 10 Laser diode voltage measurement 1 22 MATH functions 1 24 Math functions 4 5 Measurements 3 12 Menus 1 21 Photodiode detector measurement functions 4 4 Photodiode detector voltage bias sources 4 4 Photodiode measurements 3 12 Power on 1 15 Remote source and measure 3 13 Source 3 9 Sweep 7 5 SWEEPS 1 24 Sweeps 14 37 Triggering 1 23 8 7 Configuring the 2520 to use Continuous Pulse Mode I 3 Front panel I 3 Connections Considerations 2 10 GPIB 10 4 IEEE 488 10 4 Interlock 2 6 Laser diode test
274. on LEVel lt NRf gt Set voltage limit 3 to 10 5 10 LEVel Query voltage limit SWEep Configure staircase sweep mode SPACing lt name gt Select sweep spacing type LINear or LOGarithmic LIN v SPACing Query sweep spacing v POINts lt n gt Specify number of sweep points 2 to 1000 1000 POINts Query number of points in sweep DIRection lt name gt Sweep from start to stop UP or from stop to UP start DOWN DIRection Query sweep direction LIST Configure list sweep mode CURRent lt NRf gt Create list of up to 100 source values 0 to 5 0 Note 1 APPend lt NRf gt Add up to 100 source values to end of list Note 1 POINts Query number of source values in list Note 2 CURRent Query all points in source list WIDTh lt NRf gt Create list of pulse width values 500e 9 to 5e 3 3 Note 1 APPend lt NRf gt Add up to 100 pulse width values to end of list Note 1 POINts Query number of pulse width values in list Note 2 WIDTh Query all points in pulse width list DELay lt NRf gt Create list of pulse delay values 20e 6 to 0 5 3 Note 1 APPend lt NRf gt Add up to 100 pulse delay values to end of list Note 1 POINts Query number of pulse delay values in list Note 2 DELay Query all points in pulse delay list DIRection lt name gt Specify direction of list sweep UP or DOWN UP DIRection Query direction of list sweep Notes 1 Not affected by RST or SYSTem PRESet 2 1 on power u
275. on 0 0 eee cess eeeeeee 8 2 Figure 8 2 Rear panel pimout siirre isansa 8 5 Figure 8 3 Trigger link input pulse specifications ssssseeeseeeeeeereeerreereee 8 6 Figure 8 4 Trigger link output pulse specifications 0 0 lee eeeeeeeee 8 6 Figure 8 5 Configure trigger Menu tree el eee eee eeeeeeeeeeeeseteeeeaes 8 8 Figure 8 6 Trigger model remote Operation 2 0 0 eeeeeeseeeeereeeeeeeees 8 10 9 Digital I O Port Interlocks and Pulse Sync Output Figure 9 1 Digital 1 O port sorcen annii e AE 9 2 Figure 9 2 Sink operation sessioissa eson iisensnio sirsat aaia 9 3 Figure 9 3 Source Operation ssis iin as aaee aia i E EEE 9 4 Figure 9 4 Interlock operation esssssesesesessesresesresrsresresrerestesrerrsrerenresenees 9 6 Figure 9 5 Pulse sync output waveform ssesesesseeseseseeesesesresreresreeesreserees 9 8 Figure 9 6 Pulse sync out connections ssessesesseesssesreesesesresreresreresreserees 9 9 10 Remote Operations Figure 10 1 TEEE 488 COnmector 0 0 eee eeeeeeeeeeeeeseeeaeeseeeaeeeeeaeeseeeaeees 10 4 Figure 10 2 TEEE 488 multi unit test system connections 0 0 0 0 eee 10 4 Figure 10 3 TEEE 488 and RS 232 connector location s es 10 5 Figure 10 4 RS 232 interface Connector 0 eee eseeseeeeteeeeeeeeeeeaeeees 10 18 11 Status Structure Figure 11 1 Model 2520 status register structure seses 11 3 Figure 11 2 16 bit Status register scimisce cacsecsesnessuaupecendecaeaeossenes 11 5 Figure 11 3 Status byte and service request SRQ
276. onal single purpose pulse generators no measurements are made when using the 2520 in the continuous pulse mode Ensure that the 2520 is using the latest firmware B07 DSP B06 as of this writing before using the continuous pulse mode Pulse test advantage Testing in the pulse regime is done to minimize the heating of the diode junction so duty cycles are typically 1 or less By minimizing the heating testing can be performed on the laser diode as soon as the lasing cavity is defined at the wafer level for VCSELs and at the bar level for edge emitting laser diodes This early testing permits pass fail and other grading decisions to be performed before any additional process or packaging costs are added to the device Duty cycle The 2520 supports a wide range of duty cycles There are two different maximum duty cycles based on the current source level For I gt 1 00A Maximum Duty Cycle 4 For I lt 1 00A Maximum Duty Cycle 99 6 The duty cycle DC is controlled by adjusting the pulse width PW and pulse delay PD values The pulse delay is the pulse off time This gives DC PW x100 PW PD where DC duty cycle PW pulse width s 500ns to 5ms PD pulse delay s 20us to 5 00ms For example the maximum duty cycle for I lt 1 A PW 5ms PD 20us DC 5 x100 99 6 5 02 Model 2520 User s Manual Continuous Pulse Mode l 3 Minimum Duty Cycle PW 500ns PD 500ms DC 500x10 x100 0 0
277. onstruct a pulse to determine pulse parameters such as settling times overshoot and undershoot These samples can be requested by the TRACe DATA query which acquires all raw samples and the TRACe DATA VALue query which requests specific samples See Section 14 TRACe subsystem for details D IEEE 488 Bus Overview D 2 IEEE 488 Bus Overview Model 2520 User s Manual Introduction Basically the IEEE 488 bus is a communication system between two or more electronic devices A device can be either an instrument or a computer When a computer is used on the bus it serves to supervise the communication exchange between all the devices and is known as the controller Supervision by the controller consists of determining which device will talk and which device will listen As a talker a device will output information and as a listener a device will receive information To simplify the task of keeping track of the devices a unique address number is assigned to each one On the bus only one device can talk at a time and is addressed to talk by the controller The device that is talking is known as the active talker The devices that need to listen to the talker are addressed to listen by the controller Each listener is then referred to as an active listener Devices that do not need to listen are instructed to unlisten The reason for the unlisten instruction is to optimize the speed of bus information transfer since the task of list
278. ontrols if they were previously locked out with the LLO command GET Group Execute Trigger The GET command is used to trigger devices to per form a specific action that depends on device configuration for example take a reading Although GET is an addressed command many devices respond to GET without address ing Address commands Addressed commands include two primary command groups and a secondary address group ATN is true when these commands are asserted The commands include LAG Listen Address Group These listen commands are derived from an instru ment s primary address and are used to address devices to listen The actual command byte is obtained by ORing the primary address with H20 TAG Talk Address Group The talk commands are derived from the primary address by ORing the address with H40 Talk commands are used to address devices to talk SCG Secondary Command Group Commands in this group provide additional addressing capabilities Many devices including the Model 2520 do not use these com mands Unaddress commands The two unaddress commands are used by the controller to remove any talkers or listeners from the bus ATN is true when these commands are asserted UNL Unlisten Listeners are placed in the listener idle state by the UNL command UNT Untalk Any previously commanded talkers will be placed in the talker idle state by the UNT command D 10 IEEE 488 Bus Overview C
279. or sample time of the system Duty cycle The pulse duty cycle is defined as the ratio between the pulse on time pulse phase and the pulse off time delay phase expressed as a percentage PW DC PwsPD x 100 Where DC duty cycle PW pulse width s PD pulse delay s NOTE The Model 2520 will not output pulses at a duty cycle larger than 4 for cur rents more than 1A 5 4 Source Measure Concepts Model 2520 User s Manual Front panel pulse parameters Fixed mode Figure 5 2 shows how various front panel programming parameters control various fixed pulse waveform aspects These parameters are programmed by pressing the appropriate key e LASER I sets the pulse amplitude e DELAY sets the pulse delay time period between pulses e PW sets the pulse width Figure 5 2 Front panel fixed mode pulse parameters PW Laser gt Delay gt Staircase sweep mode Figure 5 3 shows how various front panel programming parameters control various stair case sweep pulse waveform aspects These parameters are programmed by pressing the appropriate key e Pulse amplitudes determined by the programmed START STOP and STEP or POINTS parameters in the CONFIG SWEEP menu e DELAY sets the pulse delay time between pulses e PW sets the pulse width e LOW This parameter accessible in the CONFIG LASER I menu sets the pulse low level The pulse amplitude returns to this level dur
280. ort Interlocks and Pulse Sync Output Model 2520 User s Manual Pulse sync output The Model 2520 has a pulse sync output that allows synchronization of external equip ment to the laser diode current source pulse Pulse sync waveform Figure 9 5 shows the pulse sync waveform which is a 5V pulse with 50Q output imped ance The pulse timing and duration are approximately the same as those for the laser diode current source pulse however there is a certain amount of latency between the pulse sync and the laser diode current pulse Figure 9 5 Pulse sync output waveform Pulse Sync Output High 5V Typical Low i OV Typical 1 gt lt Latency gt lt Laser Diode Current Pulse Model 2520 User s Manual Digital I O Port Interlocks and Pulse Sync Output 9 9 Pulse sync connections Figure 9 6 shows typical pulse sync connections Use quality BNC 50Q RG 58 cable to avoid pulse distortion that could cause timing and jitter problems Figure 9 6 Pulse sync out connections Pulse Sync Out Coax Cable WARNINE No INTERNAL OPERATOR SERVICABLE PARTS SERVICE BY QUALIFIED PERSONNEL ONLY KEITHLEY MADE IN USA carr IEEE 488 hA CHANGE IEEE ADDRESS PULSE ITH FRONT PANEL MENU SYNC A DIGITAL 1 0 C once oe TRIGGER LINK RS 232 LINE FUSE SLOWBLOW 1 6A 250V A LINE RATING 100 240VAC 50 60Hz TESTHEAD r CONN 2 140VA MAX ic OF s CAUTION
281. other wired straight through not null modem Figure 10 4 RS 232 interface connector RS 232 5432 1 Uy 9876 Rear Panel Connector Model 2520 User s Manual Table 10 2 RS 232 connector pinout Pin number Description 1 Not used 2 TXD transmit data 3 RXD receive data 4 Not used 5 GND signal ground 6 Not used 7 RTS ready to send 8 CTS clear to send 9 Not used Note CTS and RTS are tied together Pins 1 4 and 6 are tied together Remote Operations 10 19 Table 10 3 provides pinout identification for the 9 pin DB 9 or 25 pin DB 25 serial port connector on the computer PC Table 10 3 PC serial port pinout DB 9 pin DB 25 pin Signal number number DCD data carrier detect 1 8 RXD receive data 2 3 TXD transmit data 3 2 DTR data terminal ready 4 20 GND signal ground 5 T DSR data set ready 6 6 RTS request to send 7 4 CTS clear to send 8 5 RI ring indicator 9 22 10 20 Remote Operations Model 2520 User s Manual Error messages See Appendix B for RS 232 error messages Programming example The following QuickBasic 4 5 programming example will control the Model 2520 via the RS 232 COM2 port Place the Model 2520 into the RS 232 mode from the front panel main menu press COMM then select RS 232 When the communication setting is changed the Model 2520 will reset into that mode RD SPACES 1500 Set string space CLS Clear scr
282. p Refer to STEP and POINts STARt and STOP are coupled to CENTer and SPAN Thus when start and stop values are changed the values for center and span are affected as follows Center Start Stop 2 Span Stop Start SOURce 1 CURRent CENTer lt n gt Specify center point of sweep SOURce 1 CURRent SPAN lt n gt Specify span of sweep Parameters Query Description lt n gt 0 to 5 0 Set SPAN source level amps 0 to 5 0 Set CENT source level amps DEFault OA MINimum OA SPAN 0A CENT MAXimum 5 0A SPAN 5 0A CENT CENTer Query center point for sweep CENTer DEFault Query RST default level CENTer MINimum Query lowest allowable level CENTER MAXimum Query highest allowable level SPAN Query span for sweep SPAN DEFault Query RST default level SPAN MINimum Query lowest allowable level SPAN MAXimum Query highest allowable level A sweep can be configured by specifying center and span parameters By specifying a center point you can sweep through the operating point of a device The span determines the sweep width with the operating point at the center of the sweep For example assume you are testing a device that operates at 100mA and you want to sweep from 80mA to 120mA To do this you would specify the center to be 100mA and the span to be 40mA 120 80 Use the STEP or POINts command to specify the number of source and measure points in the sweep Model 2520 User s Manual
283. p otherwise not affected by RST or SYSTem PRESet 3 Minimum and default pulse delay and width values depend on pulse duty cycle See Section 5 Duty cycle If delay and width are not programmed default values of 1 5ms delay and 500ns width will be used and queries will return 0 Model 2520 User s Manual SCPI Command Reference 14 11 Table 14 6 continued SOURce command summary Default Command Description parameter SCPI SOURce2 Path to control detector 1 voltage bias source y VOLTage LEVel Set source level in volts y IMMediate Set specified voltage level immediately v AMPLitude lt n gt Specify voltage level 20 to 20 0 v AMPLitude Query voltage level Jv SOURce3 Path to control detector 2 voltage bias source y VOLTage LEVel Set source level in volts y IMMediate Set specified voltage level immediately v AMPLitude lt n gt Specify voltage level 20 to 20 0 v AMPLitude Query voltage level Jv SOURce4 Path to control digital output lines BSIZe lt n gt Set Digital I O bit size 4 or 16 No effect BSIZe Query Digital I O bit size TTL LEVel lt NRf gt Specify digital output pattern 0 to 15 15 lt NDN gt LEVel Query pattern on digital output port 16 bit size available only with 2499 DIGIO option 20 to 65535 with 2499 DIGIO option 365535 with 2499 DIGIO option 14 12 SCPI Command Reference Model 2520 User s Manual
284. programmed and stop after the last current point The size of the current list determines the custom sweep size Normally the pulse width list and delay list should be the same size as the current list However if the pulse width and or pulse delay list is shorter than the current list the last pulse width and or delay point will be used for all subsequent current values Figure 7 3 Custom pulse sweep Pulse 2 Pulse 1 Pulse 3 Model 2520 User s Manual Sweep Operation 7 5 Configuring and running a sweep Front panel sweep operation Configuring a sweep The sweep configuration menu is structured as follows and shown in Figure 7 4 Note that bullets indicate the primary items of the sweep menu and dashes indicate the options of each menu item Using Section 1 Rules to navigate menus go through the following menu to select and configure the desired sweep CONFIGURE SWEEPS menu Press CONFIG then SWEEP to display the sweep configuration menu TYPE Use this menu item to select the type of sweep e NONE Disables all sweeps e STAIR When the linear staircase sweep is selected you will be prompted to enter the START STOP and STEP levels e LOG When the logarithmic staircase sweep is selected you will be prompted to enter the START and STOP levels and specify the NO OF POINTS number of measurement points e SWEEP COUNT Use this menu item to specify how many sweeps to perform e FINITE Use
285. r diode positive terminal is connected to the VOLTAGE SENSE LO terminal while the negative laser diode terminal is connected to the VOLTAGE SENSE LO terminal NOTE Laser diode voltage measurements are essentially unipolar and the polarity set ting must agree with the polarity connections of the laser diode If the polarity is set incorrectly an overflow reading will be displayed In order to reduce common mode errors in voltage measurements connect the HI voltage measurement terminal to the same terminal as current source HI and connect the LO volt age measurement terminal to current source LO Figure 2 6 In this situation set the voltage measurement polarity to the same setting POSITIVE or NEGATIVE as the cur rent source polarity Figure 3 3 Laser diode measure polarity Voltage Sense HI Voltage Sense HI Measure Laser Measure Voltage Diode Voltage Voltage Sense LO Voltage Sense LO A POSITIVE polarity connections B NEGATIVE polarity connections Note Incorrect polarity setting will result in overflow voltage reading 3 8 Basic Operation Model 2520 User s Manual Detector measurement polarity Figure 3 4 shows the basic configuration for detector current measurement polarity With connections shown in Figure 3 4A current will flow into the current input center conduc tor of the triax connector Under these conditions the measured current is negative and the polarity setting must also be NEGATIVE Conversely if
286. r the laser diode current source POSitive selects normal polarity while NEGative selects reversed polarity See Section 3 Configuring measurements for more information on polarity 14 36 SCPI Command Reference Set pulse times Model 2520 User s Manual DELay lt n gt SOURce 1 PULSe DELay lt n gt Set current source pulse delay Parameters lt n gt 20e 6 to 0 5 Specify pulse delay in seconds MINimum 20e 6 seconds MAXimum 0 5 seconds DEFault 10e 3 seconds Query DELay Query pulse delay DELay DEFault DELay MINimum DELay MAXimum Query RST default pulse delay Query lowest allowable pulse delay Query highest allowable pulse delay Description This command is used to set the delay time between current pulses in the pulse function It sets the pulse delay in the fixed and sweep modes but it does not control pulse delays for the list mode which are pro grammed separately see Configure list page 14 41 WIDTh lt n gt SOURce 1 PULSe WIDTh lt n gt Set current source pulse width Parameters lt n gt 500e 9 to 5e 3 Specify pulse width in seconds MINimum 500e 9 seconds MAXimum Se 3 seconds DEFault 10e 6 seconds Query WIDTh Query pulse width WIDTh DEFault Query RST default pulse width WIDTh MINimum Query lowest allowable pulse width WIDTh MAXimum Query highest allowable pulse width This command is used to set the current pulse width in the pulse func tion It sets the puls
287. r the laser diode test procedures in this section is shown in Figure 4 1 See Figure 2 5 for a more detailed drawing Note that connections for laser diode as well as both photodiode detectors are included but the required interlock connections are not shown See Section 2 Connections for detailed signal connection information as well as interlock connections Figure 4 1 Circuit configuration for laser diode testing Optional Earth Ground Measure VL Measure Ipp K y Detector 1 Source VB S Measure Ipp Source VB y Detector 2 Model 2520 4 4 Laser Diode Testing Model 2520 User s Manual Front panel test procedure Step 1 Configure laser diode measurement function Configure the laser diode measurement function as follows l 2 3 Press CONFIG then LASER VL Choose POSITIVE or NEGATIVE polarity as desired then press ENTER Press LASER V4 then use the RANGE 4A and W keys to choose the measurement range 5V or 10V based on the expected voltage measurement Use the lowest range possible for best accuracy Step 2 Configure photodiode detector measurement functions Configure the photodiode detector measurement functions as follows 1 2s 3 4 Press CONFIG then DETECTOR 1 Ipp Choose POSITIVE or NEGATIVE polarity as desired then press ENTER Press DETECTOR 1 Ipp then use the RANGE 4A and keys to choose the mea surement range 10mA 20mA 50mA or 100mA based on
288. r when you send multiple commands or queries program message units within one command string program message When the Model 2520 detects an error in a program message unit it discards all further program message units until the end of the string for example SENS1 DATE SOUR1 CURR In the above program message the program message unit SENS1 DATE will generate error 113 Undefined header and the Model 2520 will discard the second program mes sage unit SOUR1 CURR even though it is a valid query Data Flow C 2 Data Flow Model 2520 User s Manual Introduction Data flow for remote operation is summarized by the block diagram shown in Figure C 1 Refer to this block diagram for the following discussion Figure C 1 Data flow block diagram i CALC1 DATA DATA A i Three Independent i K a Simultaneous 10MHz i Disabled Measurements SENS1 Laser Diode CALC1 SENS1 odie R G P M A D CALC2 DATA DATA A A Bypass if i CALC2 Disabled SENS2 Sample SENS2 Buffer Detector 1 iede A D Raw Current Buffer Samples Reading p l A CALC3 DATA i DATA 4 A Bypass if CALC3 SENS3 i STE Disabled READ ND y TRAC DATA Detector 2 CALC3 FETC Current MX B MEAS If CALC4 ac Reading Enabled Y CALC4 DATA Buffers There are two types of buffers used in the Model 2520 e Sample buffer stores individual raw samples from the three 14 bit 1 OMHz A D converters one each for SENS1 SENS2 and SE
289. ree commands in this structure can be executed by sending three separate program messages as follows 10 14 Remote Operations Model 2520 User s Manual stat oper enab lt NRf gt stat oper enab stat pres In each of the above program messages the path pointer starts at the root command stat and moves down the command levels until the command is executed Multiple command messages You can send multiple command messages in the same program message as long as they are separated by semicolons The following is an example showing two commands in one program message stat oper stat oper enab lt NRf gt When the above is sent the first command word is recognized as the root command stat When the next colon is detected the path pointer moves down to the next command level and executes the command When the path pointer sees the colon after the semicolon it resets to the root level and starts over Commands that are on the same command level can be executed without having to retype the entire command path Example stat oper enab lt NRf gt enab After the first command enab is executed the path pointer is at the third command level in the structure Since enab is also on the third level it can be typed in without repeating the entire path name Notice that the leading colon for enab is not included in the pro gram message If a colon were included the path pointer would reset to the root level and
290. rement ranges 0 00 eee eee eeeeeee 6 2 Photodiode current measurement ranges sses 6 2 Laser diode current source ranges ees eeeeseeeeeeeeeeeeeeeeeeees 6 3 Range COMMMANAS icciessciceisccnssscsesseeizasssdisessseesoosiecacsconsbeeueeases 6 3 Range programming example ee eeeeeeseeseeeeeeeeeeteeeeaes 6 4 Filte commands siise rsrsr sssrini an EE E IEEE 6 6 Filter programming example 0 cece eeeeseeeeeeeeeeeeeseeeneeaes 6 6 Math configuration menu o eee eeeeeeeseeeeeeeeceeetaeeeeeeaeeeeeeaes 6 8 Math function commands 000 eee eeeeeeseeseeeseeeeeeaeeeeeeseseeeeaes 6 9 Math function programming example sses 6 10 Sweep Operation Logarithmic sweep points oo ee eeeeeeeeeeeeceeetaeeeeeeaeeeeeeaes 7 4 Linear and log staircase sweep commands ce eeeeeeeeeeee 7 8 Linear staircase sweep programming example ee 7 9 Custom sweep commands 0 0 eee eseeseeseeseeeseereeeaeeeeeeatees 7 10 Custom sweep programming example ceeeeeeeeseeeereeees 7 11 8 Triggering Table 8 1 Remote trigger commands 00 0 eeeeeeeeeeeeeeeeeeeeeeseeene 8 14 Table 8 2 Remote triggering example ec eeeeeeeeeeeeeeeeeeeeeeeeeeene 8 14 9 Digital I O Port Interlocks and Pulse Sync O utput Table 9 1 Digital output line settings ee eee eeeeeeeeeeeeeeeeenees 9 5 10 Remote O perations Table 10 1 General bus commands 00 0 cece eeeececeeeeeeeeeeeeeeeeeeeneeaeeens 10 6 Table 10 2 RS 232 connector pi
291. rong fields Note however that shielding can increase capacitance in the measuring cir cuit possibly slowing down response time 2 Reduction of electrostatic fields Moving power lines or other sources away from the experiment reduces the amount of electrostatic interference seen in the measurement Magnetic fields A magnetic field passing through a loop in a test circuit will generate a magnetic EMF voltage that is proportional to the strength of the field the loop area and the rate at which these factors are changing Magnetic fields can be minimized by following these guidelines e Locate the test circuit as far away as possible from such magnetic field sources as motors transformers and magnets e Avoid moving any part of the test circuit within the magnetic field e Minimize the loop area by keeping leads as short as possible and twisting them together Model 2520 User s Manual Measurement Considerations F 23 Electromagnetic Interference EMI The electromagnetic interference characteristics of the Model 2520 comply with the elec tromagnetic compatibility EMC requirements of the European Union as denoted by the CE mark However it is still possible for sensitive measurements to be affected by exter nal sources In these instances special precautions may be required in the measurement setup Sources of EMI include e Radio and TV broadcast transmitters e Communications transmitters including cellular phone
292. rrent Readings Sweep Buffer C Sweep Enabled Source Measure Concepts Display Normal Voltage and Current Readings Display Math Function Readings Display Buffer Readings with Recall Active 5 13 6 Range Filter and Math e Range Discusses available ranges maximum readings and source values and ranging limitations e Filter Provides information on the filtering process that can be used to reduce reading noise e Math Outlines the math functions that can be performed on laser diode voltage measurement and photodiode current measurement data 6 2 Range Filter and Math Model 2520 User s Manual Range Measurement ranges The selected measurement range affects the accuracy of the laser diode voltage measure ments photodiode detector current measurements as well as the maximum signal that can be measured Laser diode voltage ranges Table 6 1 summarizes laser diode voltage ranges resolution and maximum readings Table 6 1 Laser diode voltage measurement ranges Voltage Maximum range Resolution reading Photodiode detector current ranges Table 6 2 lists the available current measurement ranges resolution values and maximum readings for each Model 2520 photodiode detector NOTE The current measurement range can be individually set for each detector Table 6 2 Photodiode current measurement ranges Current Maximum range Resolution reading 10mA 0 7HA
293. ry location 4 POSetup Query power on setup This command is used to select the power on defaults With RST selected the instrument powers up to the RST default conditions With PRES selected the instrument powers up to the S YStem PRESet default conditions Default conditions are listed in the SCPI tables Table 14 1 through Table 14 10 With the SAVO 4 parameters specified the instrument powers on to the setup that is saved in the specified location using the SAV command NOTE See Section 11 for details on the error queue NEXT SYSTem ERRor NEXT Read oldest error code and message Description As error and status messages occur they are placed in the Error Queue The Error Queue is a first in first out FIFO register that can hold up to 10 messages After sending this command and addressing the Model 2520 to talk the oldest message is sent to the computer and is then removed from the queue NOTE The STATus Queue command performs the same function as SYSTem ERRor NEXT See STATus subsystem page 14 49 ALL SYSTem ERRor ALL Description Read all errors codes and messages This query command is similar to the NEXT command except that all messages in the Error Queue are sent to the computer when the Model 2520 is addressed to talk All messages are removed from the queue Model 2520 User s Manual SCPI Command Reference 14 53 COUNT SYSTem ERRor COUNt Return the number of error
294. s Description After sending this command and addressing the Model 2520 to talk a decimal number will be sent to the computer That is the number of mes sages in the Error Queue CODE NEXT 2 SYSTem ERRor CODE NEXT Read oldest error code only Description This command is identical to the NEXT command except only the code is returned The message itself is not returned The error is cleared from the queue CODE ALL SYSTem ERRor CODE ALL Read all errors codes only Description This query command is identical to the ALL command except only the codes are returned The actual messages are not returned All errors are cleared from the queue CLEar SYSTem CLEar Clear Error Queue Description This action command is used to clear the Error Queue of messages Simulate key presses KEY SYSTem KEY lt NRf gt Simulate key press RANGE A key EDIT w key EDIT 4 key MENU key DETECTOR 1 Ipp key FILTER key DELAY key EDIT key COMPL key EDIT gt key EXIT key DETECTOR 2 Vg key DIG OUT key COMM key Parameters lt NRf gt AANADNKRWN KH Re Ke RK OO BRWNrF CO 14 54 SCPI Command Reference Query Description Model 2520 User s Manual 15 LASER V key 16 MATH key 17 RANGE yw key 18 ENTER key 19 DETECTOR 2 Ipp key 20 TRIG key 21 SETUP key 22 LASER I key 23 LOCAL key 24 ON OFF OUTPUT key 250 wenn 26 EDIT a key 27 SWEEP key 28 CONFIG key 29 DETECTOR 1 Vg key 30 RE
295. s front panel keys are opera tional However the user may wish to lock out front panel keys during RS 232 communications See RWLock This action command is used to remove the Model 2520 from the remote state and enables the operation of front panel keys in a manner similar to the GPIB GTL command Place the Model 2520 in remote This action command is used to place the Model 2520 in the remote state in a manner similar to the GPIB REN command In remote the front panel keys will be locked out if local lockout is asserted See RWLock Disable or enable front panel keys This command is used to enable local lockout in a manner similar to the GPIB LLO command See Section 10 When enabled the front panel keys except OUTPUT OFF are locked out not operational when the instrument is in remote See REMote When disabled the front panel LOCAL key is operational in remote Removing the instrument from remote SYST LOCal restores front panel keys operation Reset timestamp This action command is used to reset the absolute timestamp to 0 sec onds The timestamp also resets to 0 seconds every time the Model 2520 is turned on 14 56 SCPI Command Reference Model 2520 User s Manual TRACe subsystem The TRACe subsystem is mostly a diagnostic tool for debugging connections and setup In normal operation a 14 bit A D converter in the Model 2520 samples at 1OMHz rate and then an internal Digital Signal Processor
296. s ENTER At the prompts enter the desired START STOP and STEP values From the CONFIGURE SWEEPS menu select SWEEP COUNT press ENTER then choose FINITE or INFINITE as desired 6 Press EXIT to return to normal display Pi he Step 3 Turn outputs on Press the ON OFF OUTPUT key to turn the outputs on blue OUTPUT indicator turns on The Model 2520 will output the photodiode bias voltages Step 4 Run sweep To run the sweep press the SWEEP key After the sweep is completed turn the output off by pressing the ON OFF OUTPUT key Step 5 Read buffer Use the RECALL key to access the readings stored in the buffer Model 2520 User s Manual Sweep Operation 7 7 Performing a log staircase sweep Step 1 Configure source and measure Configure the Model 2520 source and measure functions as follows 1 Select the current source range by pressing LASER I then EDIT then use the RANGE keys Press LASER V_ then choose the desired measurement range Use the DETECTOR 1 Vg and DETECTOR 2 Vp keys and EDIT keys to set the photodiode bias voltages to the desired values Set the current measurement ranges by pressing the DETECTOR 1 Ipp DETECTOR 2 Ipp and RANGE keys Step 2 Configure sweep Configure the sweep as follows Pe ei 6 Press CONFIG then SWEEP Select TYPE then press ENTER Select LOG then press ENTER At the prompts enter the desired START STOP and NO OF POINTS values From the CONFIGURE
297. s Model 2520 User s Manual OPC programming example The command sequence in Table 12 2 will perform 10 measurements After the measure ments are completed in approximately 10 seconds an ASCII 1 will be placed in the Output Queue and displayed on the computer CRT Note that additional codes must be added to query the instrument for the presence of the ASCII 1 in the Output Queue Table 12 2 OPC programming example Command Description RST Return Model 2520 to GPIB defaults idle TRIG COUN 10 Program for 10 measurements and stop OUTP1 ON Turn on output INIT Start measurements OPC Send OPC to query Output Queue Additional code required to test for 1 in Output Queue OPT option query Return list of installed options When OPT is sent Model 2520 returns a list of any installed options SAV lt NRf gt save Save present setup in memory RCL lt NRf gt recall Return to setup stored in memory Parameters 0 Memory location 0 1 Memory location 1 2 Memory location 2 3 Memory location 3 4 Memory location 4 Use the SAV command to save the present instrument setup configuration in memory for later recall Any control affected by RST can be saved by the SAV command The RCL command is used to restore the instrument to the saved setup configuration Five setup configurations can be saved and recalled The Model 2520 ships from the factory with S
298. s and handheld radios e Devices incorporating microprocessors and high speed digital circuits Impulse sources as in the case of arcing in high voltage environments The effect on instrument performance can be considerable if enough of the unwanted sig nal is present The effects of EMI can be seen as an unusually large offset or in the case of impulse sources erratic variations in the displayed reading The instrument and experiment should be kept as far away as possible from any EMI sources Additional shielding of the instrument experiment and test leads will often reduce EMI to an acceptable level In extreme cases a specially constructed screen room may be required to sufficiently attenuate the troublesome signal External filtering of the input signal path may be required In some cases a simple one pole filter may be sufficient In more difficult situations multiple notch or band stop fil ters tuned to the offending frequency range may be required Connecting multiple capac itors of widely different values in parallel will maintain a low impedance across a wide frequency range Keep in mind however that such filtering may have detrimental effects such as increased response time on the measurement G GPIB 488 1 Protocol G 2 GPIB 488 1 Protocol Model 2520 User s Manual Introduction The Model 2520 supports two GPIB protocols SCPI and 488 1 The 488 1 protocol is included to significantly increase speed over the G
299. s are included in the trigger model Also note that the GPIB defaults are denoted by the symbol The trigger model consists of two layers Idle Layer and Trigger Layer to provide versa tility A programmable counter allows operations to be repeated and various input and output trigger options are available to provide synchronization between the Model 2520 and other instruments via the Trigger Link Idle and initiate The instrument is considered to be in the idle state when it is not operating within the trig ger layer While in the idle state the instrument cannot perform any measurements An ini tiate command is required to take the instrument out of idle The following commands perform an initiate operation e INITiate e READ e MEASure Conversely if the unit is taking readings most commands except DCL SDC IFC and ABORt are queued up and will not be executed until the unit returns to idle The MEASure command will automatically turn the output on Note that after the instru ment returns to the idle state the output will remain on 8 10 Triggering Model 2520 User s Manual Figure 8 6 Trigger model remote operation See Note Note The following commands place the Model 2520 into idle DCL SDC ABORt RST SYSTem PREset and RCL Idle Turn On Outputs Trigger Layer TRIGger SOURce Another TRIGger COUNt IMMediate Trigger lt n gt INF BUS 1 TIMer MANual TLINK TRIGger OUT
300. s executed e Overlapped commands A command that allows the execution of subsequent commands while device operations of the Overlapped command are still in progress The WAI command is used to suspend the execution of subsequent commands until the device operations of all previous Overlapped commands are finished The WAI command is not needed for Sequential commands 13 SCPI Signal Oriented Measurement Commands Command summary Summarizes those commands used to acquire readings e Acquiring readings Describes commands to acquire post processed readings both trigger and acquire readings and to perform a single measurement 13 2 SCPI Signal Oriented Measurement Commands Model 2520 User s Manual Command summary The signal oriented measurement commands are used to acquire readings You can use these high level instructions to control the measurement process These commands are summarized in Table 13 1 Table 13 1 Signal oriented measurement command summary Command Description FETCh Requests latest readings READ Performs an INITiate and a FETCh MEASure If output is off turns output on Performs an INITiate and a FETCh Acquiring readings FETCh Description This query command requests the latest post processed readings stored in the reading buffer After sending this command and addressing the Model 2520 to talk the readings are sent to the computer This com ma
301. s latched to 1 until the register is reset When an event register bit is set and its corresponding enable bit is set as programmed by the user the output summary of the register will set to 1 which in turn sets the summary bit of the Status Byte Register Queues The Model 2520 uses an Output Queue and an Error Queue The response messages to query commands are placed in the Output Queue As various programming errors and sta tus messages occur they are placed in the Error Queue When a queue contains data it sets the appropriate summary bit of the Status Byte Register Model 2520 User s Manual Figure 11 1 Model 2520 status register structure Questional Questionable Questionable Event Condition Event Enable Register Register Registe le Calibration Summary Command Warning Always Zero Output Queue Standar Standard Event Event Status Status Enable Register Register Operation Complete Query Error Device Specific Error Execution Error Command Error User Request Logical Power O 8 ower On BR Always Zero ESR ESE ESE Measurement Measurement Measurement Event Condition Event Enable Register Register Register HW Interlock MSR 1 Overflow MSR 2 Overflow MSR 3 Overflow Reading Available Logical Sweep Aborted BR Status Structure Error Qu
302. s or connector panels F 22 Measurement Considerations Model 2520 User s Manual Electrostatic interference Electrostatic interference occurs when an electrically charged object is brought near an uncharged object thus inducing a charge on the previously uncharged object Usually effects of such electrostatic action are not noticeable because low impedance levels allow the induced charge to dissipate quickly However the high impedance levels of many mea surements do not allow these charges to decay rapidly and erroneous or unstable readings may result These erroneous or unstable readings may be caused in the following ways e DC electrostatic field can cause undetected errors or noise in the reading e AC electrostatic fields can cause errors by driving the input preamplifier into satu ration or through rectification that produces DC errors Electrostatic interference is first recognizable when hand or body movements near the experiment cause fluctuations in the reading Means of minimizing electrostatic interfer ence include 1 Shielding Possibilities include a shielded room a shielded booth shielding the sensitive circuit and using shielded cable The shield should always be connected to a solid connector that is connected to signal low If circuit low is floated above ground observe safety precautions and avoid touching the shield Meshed screen or loosely braided cable could be inadequate for high impedances or in st
303. s selected B Header for binary values H Header for hexadecimal values Q Header for octal values Model 2520 User s Manual Status Structure 11 7 Table 11 2 Data format commands for reading status registers Command Description Default FOR Mat SREGister lt name gt Select data format for reading status registers ASCii lt name gt ASCii Decimal format HEXadecimal Hexadecimal format OCTal Octal format BINary Binary format Status byte and service request SRQ Service request is controlled by two 8 bit registers the Status Byte Register and the Ser vice Request Enable Register Figure 11 3 shows the structure of these registers Figure 11 3 Status byte and service request SRQ Status Summary Message OSB RGS ESB MAV QSB EAV MSB B6 B77 mss 85 B4 B3 B2 B1 BO lt Read by Serial Poll Status Byte Register Service STB Request i Seral Poll Generation lt Read by STB Service Request Enable B4 Register B3 B2 OSB Operation Summary Bit QSB Questionable Summary Bit MSS Master Summary Status EAV Error Available RQS Request for Service MSB Measurement Summary Bit ESB Event Summary Bit amp Logical AND MAV Message Available OR Logical OR 11 8 Status Structure Model 2520 User s Manual Status byte register The summary messages from the status registers and queues are us
304. s that program the following math function parameters e Laser diode math function power Detector 1 MX B slope M 0 5 e Detector 1 MX B offset B 5e 3 Table 6 10 Math function programming example Command Description gt CALC1 FORM POWER1 CALC1 KMAT MUN W CALC1 STAT ON CALC2 KMAT MBF 5e 3 CALC2 KMAT MMF 0 5 CALC2 STAT ON OUTP1 ON INIT CALC1 DATA CALC2 DATA OUTP1 OFF Select laser diode power function Set W math units Enable laser diode math Detector 1 MX B offset B 5e 3 Detector 1 slope M 0 5 Enable detector 1 math Turn on outputs Trigger math readings Request laser diode power result Request detector 1 MX B result Outputs off 7 Sweep Operation e Sweep types Describes the three basic sweep types Linear staircase logarith mic staircase and custom sweep Configuring and running a sweep Discusses the procedure for setting up and performing sweeps including selecting and configuring a sweep and performing a sweep 7 2 Sweep Operation Model 2520 User s Manual Sweep types The three basic sweep types described in the following paragraphs include e Linear staircase e Logarithmic staircase e Custom NOTE Linear and logarithmic staircase sweeps are available both from the front panel and via remote Custom sweeps can be performed only via remote Linear staircase sweep As shown in Figure 7 1 this sweep s
305. s used by devices when they require service from the controller Handshake lines The bus handshake lines operate in an interlocked sequence This method ensures reliable data transmission regardless of the transfer rate Generally data transfer will occur at a rate determined by the slowest active device on the bus One of the three handshake lines is controlled by the source the talker sending informa tion while the remaining two lines are controlled by accepting devices the listener or lis teners receiving the information The three handshake lines are DAV DATA VALID The source controls the state of the DAV line to indicate to any listening devices whether or not data bus information is valid D 6 IEEE 488 Bus Overview Model 2520 User s Manual NRED Not Ready For Data The acceptor controls the state of NRFD It is used to signal to the transmitting device to hold off the byte transfer sequence until the accepting device is ready NDAC Not Data Accepted NDAC is also controlled by the accepting device The state of NDAC tells the source whether or not the device has accepted the data byte The complete handshake sequence for one data byte is shown in Figure D 2 Once data is placed on the data lines the source checks to see that NRFD is high indicating that all active devices are ready At the same time NDAC should be low from the previous byte transfer If these conditions are not met the source must wait un
306. same GPIB bus controller addresses are usually 0 or 21 The primary address can be checked and or changed from the COMMUNICATIONS SETUP menu accessed with the COMM key This menu option also allows you to select the 488 1 or SCPI protocol Appendix G To set the primary address Press the COMM key Select GPIB then press ENTER 3 Use the EDIT keys to set the primary address to the desired value then press ENTER 4 Select GPIB or 488 1 protocol then press ENTER See Appendix G for details 5 Press EXIT to return to normal display General bus commands General commands are those commands such as DCL that have the same general mean ing regardless of the instrument Table 10 1 lists the general bus commands Table 10 1 General bus commands Command Effect on Model 2520 REN IFC LLO GTL DCL SDC GET SPE SPD Goes into remote when next addressed to listen Goes into talker and listener idle states LOCAL key locked out Cancel remote restore Model 2520 front panel operation Returns all devices to known conditions Returns Model 2520 to known conditions Initiates a trigger Serial polls the Model 2520 Model 2520 User s Manual Remote Operations 10 7 REN remote enable The remote enable command is sent to the Model 2520 by the controller to set up the instrument for remote operation Generally the instrument should be placed in the remote mode before you attempt to program it o
307. ser s Manual IEEE 488 Bus Overview D 5 Bus lines The signal lines on the IEEE 488 bus are grouped into three different categories data lines management lines and handshake lines The data lines handle bus data and com mands while the management and handshake lines ensure that proper data transfer and operation takes place Each bus line is active low with approximately zero volts represent ing a logic 1 true The following paragraphs describe the operation of these lines Data lines The IEEE 488 bus uses eight data lines that transfer data one byte at a time DIO1 Data Input Output through DIO8 Data Input Output are the eight data lines used to transmit both data and multiline commands and are bidirectional The data lines operate with low true logic Bus management lines The five bus management lines help to ensure proper interface control and management These lines are used to send the uniline commands ATN Attention The ATN line is one of the more important management lines The state of this line determines how information on the data bus is to be interpreted IFC Interface Clear As the name implies the IFC line controls clearing of instru ments from the bus REN Remote Enable The REN line is used to place the instrument on the bus in the remote mode EOI End or Identify The EOI is usually used to mark the end of a multi byte data transfer sequence SRQ Service Request This line i
308. set the bias source value to the desired value Step 5 Configure math functions Set up your math functions as desired For example these steps will set up the unit for laser diode power and detector 1 MX B math Press CONFIG then MATH Select CHANNEL then press ENTER Select P for power then press ENTER Press CONFIG then MATH Choose CHANNEL2 then press ENTER At the subsequent prompts set the MX B parameters M B and units to the desired values Oy Oak a Step 6 Turn source outputs on and trigger readings Turn all three source outputs on by pressing the ON OFF OUTPUT key The blue OUT PUT indicator on the mainframe and the testhead POWER ON indicators will turn on to indicate the outputs are on Press the TRIG key to trigger readings NOTE _ Interlocks must be enabled before outputs can be turned on See Section 2 Step 7 Observe readings on the display Observe the measurement readings on the display For this example the unit will display laser diode power detector 1 MX B math and detector 2 current on the lower line Step 8 Turn source outputs off When finished making measurements turn all three source outputs off by pressing the ON OFF OUTPUT key The blue OUTPUT and POWER ON indicator lights will turn off Remote laser diode testing Laser diode test procedures can also be performed via remote by sending appropriate com mands in the right sequence The following paragraphs summarize th
309. specified by FORM ELEM TRAC see FORMat subsystem page 14 19 Model 2520 User s Manual SCPI Command Reference 14 57 Configure sample buffer POINts lt n gt TRACe POINts lt n gt Specify number of samples Parameters lt n gt 1 to 3000 Specify number of samples MINimum 1 MAXimum 32000 DEFault 100 Query POINts Query number of samples POINts MINimum Query smallest allowable sample number POINts MAXimum Query largest allowable sample number POINts DEFault Query RST default sample number Description This command sets the number of samples to return for the Trigger subsystem TRAC DATA query Every time the pulse width SOUR PULS WIDTh is changed the TRAC POINts value defaults to either the Pulse Width x 10e6 in DC mode or Pulse Width x 10e6 5 in pulse mode or 3000 whichever is less For example if the pulse width is 10us the number of points will default to 100 in DC mode or 105 in the pulse mode The Trigger subsystem is made up of a series of commands and subsystems to configure the Trigger Model These commands and subsystems are summarized in Table 14 10 NOTE See Section 8 for more details on triggering and the trigger model Initiate source measure cycle INITiate INITiate IMMediate Take Model 2520 out of idle state Description This command is used to initiate source and measure operation by tak ing the Model 2520 out of idle The READ and MEASure com mands also perform an initiat
310. ssrsossesesresserons 14 31 CABort STATE lt gt senare inica 14 31 SOURCE subsystem soucient eis i i ia 14 32 SOURCE I risna e a ei 14 32 Control source outputs On Off eseeeseeeeseeseereerereerrererrses 14 32 IMMediate soisisiiiisiyitieiiisearaaiii 14 32 Select sourcing mode oo eee eseeseeeeeeeeeaeeeneeeteeeeaes 14 32 MODE lt name gt eeccesceesneeseeeeseecsseeeeeeeenneseaeeeaeers 14 32 Select source function ooo eee eeeeeteeeteeeeneeeneeeeeeeseeeeeeeeee 14 33 FUNCtion SHAPe lt name gt ccccccssseessreeesees 14 33 SELECESOULCE TANSE sesicc scseenctvesdhensnsdsisdervessesiscesseenseisenierese 14 33 RANGE KHS eoan eraann aa ee a EE TaS 14 33 Set amplitudes sosisini 14 34 IMMediate AMPLitude lt n gt eeceesseeeeeeees 14 34 LOW SI gt sinri tate etn EEEa ER 14 34 Set Voltage limit occ cioscasccciessteeesssscaadee siovicnctese vaseseermevoaes 14 35 PROTection LEVel lt NRf gt eeesceeesseeeeteeessnees 14 35 Select source polarity 0 0 ee eesceeseeestecseeeeeeeeeeeeseeeeneeeee 14 35 POLarity lt name gt eonenni en e E oze 14 35 Set pulse times cece eseeeseeceseeeeeeeeseeseaeeeeeeeeaeeeteeeeeeeeee 14 36 DELAY lt en e a ere e TERT 14 36 WIDTH RAS binsin aiina saes e eis 14 36 TRANsition STATe lt b gt n nsosssssssssssssssessesessssssssessse 14 36 Configure SWEEPS eeeeeeccesecseceeseeeeeeceeeeeeeceeeseneeeaeees 14 37 SPACING lt NaMe gt nnee n n a a 14 37 S PARC SD
311. st be on OUTput 1 STATe ON before you can take readings The TRIG SOUR BUS and TRIG COUN INF commands are not supported by READ with the 488 1 protocol selected If you send one of these commands a DCL or IFC may be required to reset the GPIB Message available The MAV message available bit in the Serial Poll byte will be set when the query is fin ished being processed not when there is data available in the output buffer as with the SCPI protocol For the 488 1 protocol output data will not be formatted until the first request for data is received This delay may cause unexpected time outs when using SRQ on MAV for queries that take a long time to execute General operation notes The TALK LSTN and SRQ annunciators are not functional in the 488 1 protocol This speeds up data throughput greatly The REM annunciator still operates since it is critical to fundamental GPIB operation If the unit is in REMote the GTL command may not put the Model 2520 into the local mode Only the front panel LOCAL key is guaranteed to operate if not in local lockout LLO GTL will still disable LLO e JEEE 488 bus commands and features GET IFC SDC DCL LLO Serial Poll and SRQ are still fully supported e Multiple TALKs on the same query are supported as in the SCPI protocol This fea ture is useful when reading back long ASCII strings Example Programs H 2 Example Programs Model 2520 User s Manual Introduction This se
312. st gt NRf NRf NRf NRf 500e 9 to 5e 3 Pulse width seconds Query WIDTh Query pulse width list Description This command is used to define a list of pulse widths up to 100 for the list sourcing mode of operation When operation is started the instru ment will sequentially source each current pulse value in the list see CURRent lt NRf list gt page 14 41 with the programmed pulse width and delay see DELay lt NRf list gt below Each pulse width point in the list corresponds to the equivalent point in the current and delay lists The following command shows the proper format for defining a list using pulse width values of 10us 30us and 60us SOURce 1 LIST WIDTh 10e 6 30e 6 60e 6 NOTE If the width list is shorter than the current list the last width value will be used for all subsequent current list points If the width is not programmed a default value of 500ns will be used but the query will return 0 APPend lt NRf list gt SOURce 1 LIST WIDTh APPend lt NRf list gt Add value s to pulse width list Parameters lt NRf list gt NRf NRf NRf NRf 500e 9 to 5e 3 Pulse width seconds Description This command is used to add one or more values up to 100 to a pulse width list that already exists The pulse width values are appended to the end of the list By using multiple appended lists up to 1000 points can be in a list POINts SOURce 1 LIST WIDTh POINts Query length of pulse wi
313. sure configuration can also be performed via remote by sending appropri ate commands The following paragraphs summarize these commands and give a simple programming example Source and measure configuration commands Table 3 4 summarizes commands used for source and measure configuration See Section 14 for more information on using these and other commands Table 3 4 Source and measure configuration commands Command Description Configure measurements SENSe 1 VOLTage RANGe lt range gt Set laser diode voltage measure range 5 or 10 SENSe 1 VOLTage POLarity lt polarity gt Set laser diode measure polarity POSitive or NEGative SENSe2 CURRent RANGe lt range gt Set detector 1 measure range 0 01 0 02 0 05 0 1 SENSe2 CURRent POLarity lt polarity gt Set detector 1 measure polarity SENSe3 CURRent RANGe lt range gt Set detector 2 measure range 0 01 0 02 0 05 0 1 SENSe3 CURRent POLarity lt polarity gt Set detector 2 measure polarity Configure sources SOURce 1 CURRent MODE FIXed Select fixed not sweep laser diode current source mode SOURce 1 CURRent RANGe lt range gt Select laser diode source range 0 5 or 5 SOURce 1 CURRent lt current gt Set laser diode source current 0 to 5 0 SOURce 1 CURRent POLarity lt polarity gt Set laser diode source polarity POSitive or NEGative SOURce 1 VOLTage PROTection lt limit gt Set laser source voltage compliance limit 1 t
314. t lt NDN gt 00 eee eeeeteeteeeeeeeeeeee 14 47 Setting DICSIZE c sic cieesecesaccestibiisastssssoeaanebedeseasepececvioeeny 14 48 BSES iiaa a ra i el 14 48 STAT s s bs stenmi oo eee eeeeseceseeseeeseeseeeeeeseesaeeseeeaeeeeeeetees 14 49 Read event registers ciiin cini 14 49 GEVENG asides iatienandiohinaneieiiiny 14 49 Program event enable registers selec eeeeereeeeeeeeeees 14 49 ENABle lt NDN gt or lt NRf gt o eeeeeeseeseereeeeeeeeeeeeees 14 49 Read condition registers cceeceescceseeeeseceneeeeneeeeseeeaeers 14 50 CONDition siessen eia ais 14 50 Select default conditions 0 0 eee eeseeeteeeseeeeeeeeteeeteeeeee 14 50 PRESEI aaa T taeonneaes 14 50 Error QUe Sierpie eini a i i A aE 14 50 EINEXU 2 iriran ieee 14 50 CLEA reece oper errr epe cree e A aS 14 50 ENABI lt list gt iiinn nnn 14 51 DSable lt list gt E EEA 14 51 SY STem Subsystem s pises eiiie idiari ien e E 14 51 Default conditions 5 ccs5 ic cc eciesvssesosaeserssvstaverterdacsssteveces 14 51 PRESET 3200 Ssteivsrs ata siube dese ckarsad ts etwas 14 51 POSED aeniea eaer e E ee ES 14 52 Error gueu ioon oe E REA 14 52 NEXT en a E E ER 14 52 ADE ren a E 14 52 COUN eriekin eaae o E 14 53 CODE NEXT sorsisicoriicesiisiesninerastseasissssastesoie aeai 14 53 CODE ALL dinoan ene a eE 14 53 CLEAT sch a iere e e a nirai oE 14 53 Simulate key presses cceecessseeseceeseeeseeeeseeeeeeeeseeeneeeees 14 53 KEY aeeiio ina E hohe 14 53 R
315. t bit indicates that the Model 2520 detected an error while trying to execute a command Bit B5 Command Error CME Set bit indicates that a command error has occurred Command errors include JTEEE 488 2 syntax error Model 2520 received a message that does not fol low the defined syntax of the IEEE 488 2 standard e Semantic error Model 2520 received a command that was misspelled or received an optional IEEE 488 2 command that is not implemented The instrument received a Group Execute Trigger GET inside a program message Bit B6 User Request URQ Set bit indicates that the LOCAL key on the Model 2520 front panel was pressed Bit B7 Power ON PON Set bit indicates that the Model 2520 has been turned off and turned back on since the last time this register has been read 11 12 Status Structure Model 2520 User s Manual Figure 11 4 Standard event status ESR Standard Event Status Register ET PON URQ CME EXE DDE QYE OPC B15 B8 B7 B6 B5 B4 B3 B2 B1 BO To Event Summary Bit ESB of Status Byte Register Figure 11 3 Standard Event Status Enable Register PON Power On QYE Query Error URQ User Request OPC Operation Compete amp Logical AND OR Logical OR CME Command Error EXE Execution Error DDE Device Dependent Error Model 2520 User s Manual Status Structure 11 13 Operation event register The used bits of the
316. t fixed sourcing mode LIST Select list sourcing mode SWEep Select sweep sourcing mode Query MODE Query sourcing mode Description This command is used to select the sourcing mode for the laser diode current source The three modes are explained as follows FIXed In this sourcing mode the source will output a fixed level Use the RANGe and AMPLitude commands to specify the fixed source level See Select source range page 14 33 and Set amplitudes page 14 34 LIST In this mode the source will output current pulses that are spec ified in a list See Configure list page 14 41 for commands to define and control the execution of the list SWEep In this mode the source will perform a staircase current sweep See Configure sweeps page 14 37 for commands to define the sweep Model 2520 User s Manual SCPI Command Reference 14 33 NOTE The sourcing mode will default to FIXed whenever the Model 2520 goes to the local state Select source function FUNCtion SHAPe lt name gt SOURce 1 FUNCtion SHAPe lt name gt Select laser diode source function Parameters lt name gt DC Select DC source function PULSe Select pulse source function Query FUNCtion SHAPe Query source function Description This command is used to select the source function for the laser diode current source The two functions are DC With this source function the source will output a DC level with the a
317. t only be used as shield connections for measuring circuits NOT as safety earth ground connections If you are using a test fixture keep the lid closed while power is applied to the device under test Safe operation requires the use of a lid interlock If or 4 is present connect it to safety earth ground using the wire recommended in the user documentation The VAN symbol on an instrument indicates that the user should refer to the operating instructions located in the manual The JN symbol on an instrument shows that it can source or measure 1000 volts or more including the combined effect of normal and common mode voltages Use standard safety precautions to avoid personal contact with these voltages The WARNING heading in a manual explains dangers that might result in personal injury or death Always read the associated information very carefully before performing the indicated procedure The CAUTION heading in a manual explains hazards that could damage the instrument Such damage may invalidate the war ranty Instrumentation and accessories shall not be connected to humans Before performing any maintenance disconnect the line cord and all test cables To maintain protection from electric shock and fire replacement components in mains circuits including the power transformer test leads and input jacks must be purchased from Keithley Instruments Standard fuses with applicable national safety ap provals may be used if the rat
318. t set EE Standard Event 3 502 Calibration data invalid EE Standard Event 3 503 DAC calibration overflow EE Standard Event 3 504 DAC calibration underflow EE Standard Event 3 505 Source offset data invalid EE Standard Event 3 506 Source gain data invalid EE Standard Event 3 507 Measurement offset data invalid EE Standard Event 3 508 Measurement gain data invalid EE Standard Event 3 509 Not permitted with cal locked EE Standard Event 3 510 Not permitted with cal unlocked EE Standard Event 3 B 6 Status and Error Messages Model 2520 User s Manual Table B 1 continued Status and error messages Number Error message Event Status register Bit Lost data errors 601 Reading buffer data lost EE Standard Event 3 602 GPIB address lost EE Standard Event 3 603 Power on state lost EE Standard Event 3 604 Calibration data lost EE Standard Event 3 605 Calibration dates lost EE Standard Event 3 606 GPIB communication language lost EE Standard Event 3 Communication errors 700 Invalid system communication EE Standard Event 3 701 ASCII only with RS 232 EE Standard Event 3 702 DSP communication timeout EE Standard Event 3 Additional command execution errors 4 802 OUTPUT blocked by interlock EE Standard Event 4 803 Not permitted with OUTPUT off EE Standard Event 810 OUTPUT blocked by over temp EE Standard Event 4 830 Invalid with INF TRIG COUNT EE Standard Event 4 900 Internal System Error EE Standard Event 3
319. t to send data over the bus to other devices is provided by the T function Instrument talker capabilities T5 exist only after the instrument has been addressed to talk L Listener Function The ability for the instrument to receive device dependent data over the bus from other devices is provided by the L function Listener capabilities L4 of the instrument exist only after it has been addressed to listen SR Service Request Function SR1 defines the ability of the instrument to request service from the controller RL Remote Local Function RL1 defines the ability of the instrument to be placed in the remote or local modes Model 2520 User s Manual IEEE 488 Bus Overview D 15 PP Parallel Poll Function The instrument does not have parallel polling capabilities PPO DC Device Clear Function DC1 defines the ability of the instrument to be cleared initialized DT Device Trigger Function DT1 defines the ability of the Model 2520 to have readings triggered C Controller Function The instrument does not have controller capabilities CO TE Extended Talker Function The instrument does not have extended talker capa bilities TEO LE Extended Listener Function The instrument does not have extended listener capabilities LEO E Bus Driver Type The instrument has open collector bus drivers E1 E IEEE 488 and SCPI Conformance Information E 2 IEEE 488 and SCPI Confor
320. t using a convenient filename 7 Run the program and note any display messages and data on the screen NOTE _ Interlocks must be enabled and laser diode and photodiode connections must be made See Section 2 Model 2520 User s Manual Example Programs H 3 Laser diode test program The program listing below performs laser diode testing as covered in Section 4 This pro gram sets up the following operating modes e Laser diode measurement 10V range power math function e Laser diode source range and amplitude 500mA e Laser diode pulse delay width 200s 10us e Detector 1 detector 2 source values 10V 20V Laser diode test program 2520 primary address 25 1 1 OPEN IEEE FOR OUTPUT AS 1 Open IEEE 488 output path OPEN IEEE FOR INPUT AS 2 Open IEEE 488 input path PRINT 1 INTERM CRLF Set input terminator PRINT 1 OUTTERM LF Set output terminator PRINT 1 REMOTE 25 Put 2520 in remote PRINT 1 OUTPUT 25 RST Restore GPIB defaults PRINT 1 OUTPUT 25 SENS1 VOLT RANG 10 10V LD measure range PRINT 1 OUTPUT 25 SENS1 VOLT POL POS Positive LD measure polarity PRINT 1 OUTPUT 25 SENS2 CURR POL NEG Negative D 1 measure polarity PRINT 1 OUTPUT 25 SENS3 CURR POL NEG Negative D 2 measure polarity PRINT 1 OUTPUT 25 FORM ELEM CURR3 Detector 2 current data PRINT 1 OUTPUT 25 SOUR1 CURR RANG 0 5 500mA L
321. tage ranges 6 2 Light F 21 Limit lines 5 10 Limits Query voltage 14 29 Set voltage limit 14 35 Line fuse 1 12 Line power connection 1 11 Line voltage 1 11 Linear staircase sweep 7 2 14 44 Performing 7 6 List sweep 14 44 LLO local lockout 10 7 Loading effects 5 10 LOCAL key 10 9 Logarithmic staircase sweep 7 3 14 45 Performing 7 7 Loop area F 6 Magnetic coupling F 10 Magnetic fields F 22 Mainframe front panel 1 6 Mainframe rear panel 1 8 Math function Display 5 12 Math functions 6 6 Commands 6 9 Conductance 6 7 Delta 6 7 Front panel 6 8 Laser diode 14 15 MX B 6 7 Power 6 7 Programming 6 8 Programming example 6 10 Remote 6 9 Resistance 6 7 Measurement Considerations F 1 General considerations F 20 Math functions 6 6 Ranges 6 2 Measurements Configuration 3 12 Menus COMM 1 20 COMPL 1 21 Configuration 1 21 CONFIGURE TRIGGER 8 7 DELAY 1 21 DETECTOR configuration 1 22 DIG OUT 1 20 FILTER configuration 1 23 LASER configuration 1 22 Main 1 18 Main operation 1 19 MATH configuration 1 24 6 8 PW 1 21 Rules to navigate 1 18 SETUP 1 20 Source and measure configuration 4 2 SWEEP configuration 1 24 TRIG configuration 1 23 Messages Define TEXT 14 18 Error and status 10 8 Status and error 1 13 B 1 MX B math function 6 7 Set parameters 14 15 Noise Source Impedance F 17 Operating boundaries see Limit lines 5 10 Operation overview 3 2 Options 1 3 Output circuit model F 13 OUTPut subsystem
322. tatus and error messages Number Error message Event Status register Bit 440 Query UNTERMINATED after EE Standard Event 2 indefinite response 430 Query DEADLOCKED EE Standard Event 2 420 Query UNTERMINATED EE Standard Event 2 410 Query INTERRUPTED EE Standard Event 2 363 Input buffer overrun EE Standard Event 3 362 Framing error in program message EE Standard Event 3 361 Parity error in program message EE Standard Event 3 360 Communications error EE Standard Event 3 350 Queue overflow SYS Standard Event 3 330 Self test failed EE Standard Event 3 314 Save recall memory lost EE Standard Event 3 315 Configuration memory lost EE Standard Event 3 285 Program syntax error EE Standard Event 4 284 Program currently running EE Standard Event 4 282 Ilegal program name EE Standard Event 4 281 Cannot create program EE Standard Event 4 260 Expression error EE Standard Event 4 241 Hardware missing EE Standard Event 4 230 Data corrupt or stale EE Standard Event 4 225 Out of memory EE Standard Event 4 224 Ilegal parameter value EE Standard Event 4 223 Too much data EE Standard Event 4 222 Parameter data out of range EE Standard Event 4 221 Settings conflict EE Standard Event 4 220 Parameter error EE Standard Event 4 215 Arm deadlock EE Standard Event 4 214 Trigger deadlock EE Standard Event 4 213 Init ignored EE Standard Event 4 212 Arm ignored EE Standard Event 4 211 Trigger ignored EE Standard Event 4 210 Trigger error EE
323. te stream of fixed current pulses It is different from the Continuous Pulse mode because it offers measure ments VLD Detector current Detector 2 current The measurement process takes additional time meaning that the minimum pulse delay time is about 2ms Trigger count Continuous Pulse This mode is explained above It is similar to count Inf but there are no measurements in this mode and the set pulse width equals the actual pulse width Index Accessories 1 3 Adapters 1 3 Annunciators 1 7 LSTN 10 9 REM 10 9 SRQ 10 9 TALK 10 9 Baud rate 10 16 Bench defaults 8 5 Bit size Setting 14 48 Buffer C 2 Configure sample buffer 14 57 Read sample buffer 14 56 Bus management lines D 5 Byte order 14 25 Cable Increasing length F 5 Cable inductance F 3 Cables Interface 1 4 Signal 1 3 Calculate subsystems 14 14 Circuit configuration Basic 3 5 Laser diode testing 4 3 Command codes D 10 Command reference Calculate subsystems 14 14 DISPlay subsystem 14 17 FORMat subsystem 14 19 OUTPut subsystem 14 27 SENSe subsystem 14 27 SOURce subsystem 14 32 SOURce 1 14 32 SOURce2 and SOURce3 14 46 SOURce4 14 47 STATus subsystem 14 49 SYSTem subsystem 14 51 TRACe subsystem 14 56 Trigger subsystem 14 57 Command summary CALCulate 14 3 DISPlay 14 5 FORMat 14 6 OUTPut 14 6 SENSe 14 7 SOURce 14 9 STATus 14 12 SYSTem 14 13 TRACe 14 13 TRIGger 14 14 Commands Address D 9 Addressed multiline D 9 Common see c
324. tep size for the sweep in Figure 7 2 is calculated as follows Log Step Size log10 stop log10 start Points 1 _ log10 10 log10 1 5 1 0 0 4 0 25 7 4 Sweep Operation Model 2520 User s Manual Thus the five log steps for this sweep are 0 0 25 0 50 0 75 and 1 00mA The actual cur rent source levels at these points are listed in Table 7 1 the current level is the anti log of the log step Table 7 1 Logarithmic sweep points Measure point Log step Current level mA Point 1 0 1 Point 2 0 25 1 7783 Point 3 0 50 3 1623 Point 4 0 75 5 6234 Point 5 1 0 10 When this sweep is triggered to start the output will go to the start source current level 1mA and sweep through the symmetrical log points The time duration at each step is determined by the time it takes to perform the measurement which includes the pulse delay time Custom sweep This sweep type lets you configure a customized sweep via remote only Programmable sweep list parameters include the number of measurement points in the sweep the current source level at each point pulse width and pulse delay Figure 7 3 shows an example of a custom sweep When this sweep is started the output goes to the first current level in the sweep after the delay period The pulse period and time between pulses is determined by the programmed pulse and delay parameters The sweep will continue through the points in the order they were
325. teps from a start current source value to an ending stop current source value Programmable parameters include the start stop and step source current levels This example shows the DC mode of operation When this sweep is triggered to start the current source output will go to the start source current level The output will then change in equal steps until the stop source level is reached The time duration at each step is determined by the time it takes to perform the measurement which includes both the pulse width and the pulse delay Figure 7 1 Linear staircase sweep PW Delay gt lt Stop Step PwW lt Delay gt Note DC Mode Shown Model 2520 User s Manual Sweep Operation 7 3 Logarithmic staircase sweep This sweep is similar to the linear staircase sweep The steps however are done on a loga rithmic scale as shown in the example sweep in Figure 7 2 This is a 5 point log sweep from ImA to 10mA As with the staircase sweep the measurement time is the same for all steps Again DC mode waveforms are shown Figure 7 2 Logarithmic staircase sweep Lo Scale PW e Delay gt 10 Sto 10 5 6234 mA 3 1623 1 7783 Log Points 5 Note DC Mode Shown The programmable parameters for a log sweep include the start and stop levels and the number of measurement points for the sweep The specified start stop and point parame ters determine the logarithmic step size for the sweep S
326. tering the queue DiSable lt list gt STATus QUEue DISable lt list gt Disable messages for Error Queue Parameters lt list gt numlist where numlist is a specified list of messages that you wish to disable for the Error Queue Query DISable Query list of disabled messages Description On power up all error messages are enabled and will go into the Error Queue as they occur Status messages are not enabled and will not go into the queue This command is used to specify which messages you want disabled Disabled messages are prevented from going into the Error Queue SYSTem subsystem The SYSTem subsystem contains miscellaneous commands that are summarized in Table 14 8 Default conditions PRESet SYSTem PRESet Return to SYSTem PRESet defaults Description This command returns the instrument to states optimized for front panel operation SYSTem PRESet defaults are listed in the SCPI tables Table 14 1 through Table 14 10 14 52 SCPI Command Reference POSetup Model 2520 User s Manual SYSTem POSetup lt name gt Program power on defaults Parameters Query Description Error queue lt name gt RST Power up to RST defaults PRESet Power up to SYSTem PRESet defaults SAVO Power up to setup stored at memory location 0 SAV1 Power up to setup stored at memory location 1 SAV2 Power up to setup stored at memory location 2 SAV3 Power up to setup stored at memory location 3 SAV4 Power up to setup stored at memo
327. the instrument Such damage may invalidate the warranty Model 2520 User s Manual Getting Started 1 3 Inspection The Model 2520 was carefully inspected electrically and mechanically before shipment After unpacking all items from the shipping carton check for any obvious signs of physi cal damage that may have occurred during transit There may be a protective film over the display lens which can be removed Report any damage to the shipping agent immedi ately Save the original packing carton for possible future shipment The following items are included with every Model 2520 order e Model 2520 mainframe with line cord e Model 2520 testhead with two connecting cables e Two triax connecting cables for detector signal connections Four unterminated 15Q BNC coaxial connecting cables for laser diode signal connections e Accessories as ordered e Certificate of calibration e User s Manual e Manual addenda containing any improvements or changes to the instrument or manual If an additional user s manual is required order the appropriate manual package for example 2520 900 00 The manual packages include a manual and any pertinent addenda Options and accessories The following options and accessories are available from Keithley for use with the Model 2520 Signal cables and adapters CA 289 1A Cable This 1m low noise triax cable is terminated at one end with a 3 slot male triax connector and is untermi
328. the POLARITY selections in the corresponding configuration menus see Configuring sources page 3 9 and Configur ing measurements page 3 12 for procedures to set the polarity Laser diode current source polarity Figure 3 2 shows a comparison of positive and negative current source polarity With the positive polarity shown in A current across the DUT develops a voltage such that the pos itive DUT terminal is connected to CURRENT OUTPUT HI and the negative DUT termi nal is connected to CURRENT OUTPUT LO With the negative polarity shown in B the negative DUT terminal is connected to CURRENT OUTPUT HI and the positive termi nals is connected to CURRENT OUTPUT LO Figure 3 2 Laser diode current source polarity Current Output HI Optional Earth Ground Current Source Current Output LO A Positive Polarity Current Output HI Current Source Current Output LO Optional Earth Ground B Negative Polarity Model 2520 User s Manual Basic Operation 3 7 Laser diode voltage measurement polarity Figure 3 3 shows the basic configuration for laser diode voltage measurement polarity Figure 3 3A shows correct connections for POSITIVE polarity In this case the laser diode positive terminal is connected to the VOLTAGE SENSE HI terminal while the neg ative laser diode terminal is connected to the VOLTAGE SENSE LO terminal Figure 3 3B shows correct connections for NEGATIVE polarity In this case the lase
329. the bus Only the ASCII format is allowed over the RS 232 inter face This command only affects the output of READ FETCh MEA Sure TRACe DATA CALCx DATA over the GPIB All other queries are returned in the ASCII format NOTE Regardless of which data format for output strings is selected the Model 2520 will only respond to input commands using the ASCII format Figure 14 1 ASCII format The ASCII data format is in a direct readable form for the operator Most BASIC languages easily convert ASCII mantissa and exponent to other formats However some speed is compromised to accommodate the conversion Figure 14 1 shows an example ASCII string that includes current voltage time and status data elements Data elements not specified by the ELEMents command are simply not included in the string See ELEMents lt item list gt page 14 22 ASCII data format 1 000206E 03 1 000000E 01 7 282600E 01 4 813200E 04 ee eee wees ee Current Voltage Time Status TEEE 754 single precision format REAL 32 or SREal will select the binary IEEE 754 single precision data format Figure 14 2 shows the normal byte order format for each data element For example if three valid elements are specified the data string for each reading conversion is made up of three 4 byte data blocks Note that the data string for each reading conversion is preceded by a 2 byte header that is the binary equivalent of an ASCII sign and 0 F
330. then averaged to give one filtered reading If the filter is enabled in sweep mode See Section 7 each step of the sweep will effec tively be repeated for the filter count number of times Figure 6 1 shows an example of a sweep from 10mA to 30mA with a filter count of 3 Note that three delay pulse cycles are performed at each step In this example three readings per measurement channel will be returned by a READ query Model 2520 User s Manual Range Filter and Math 6 5 Figure 6 1 Averaging filter during sweep Start 10mA 30mA Step Stop 30mA eS _ Step 10mA 20mA Step 10mA Step With filter count 3 three delay pulse cycles are performed at each sweep step Filter configuration NOTE The average filter setting is global and affects all three measurements laser diode voltage and both detector current measurements 1 Press the CONFIG key and then the FILTER key to access the filter configuration menu 2 Use the EDIT lt gt A and W keys to set the display to the desired count 1 to 100 and press ENTER Filter control When filtering is being applied to the measured signals the FILT annunciator will be on The FILTER key is used to control filtering Pressing FILTER turns on the FILT annuncia tor to indicate that the filter configuration is being applied to all three measurements Pressing FILTER a second time turns the FILT annunciator off to indicate that filtering is turned off Remote
331. til NDAC and NRFD have the correct status If the source is a controller NRFD and NDAC must be stable for at least 100nsec after ATN is set true Because of the possibility of a bus hang up many control lers have time out routines that display messages in case the transfer sequence stops for any reason Once all NDAC and NRED are properly set the source sets DAV low indicating to accept ing devices that the byte on the data lines is now valid NRFD will then go low and NDAC will go high once all devices have accepted the data Each device will release NDAC at its own rate but NDAC will not be released to go high until all devices have accepted the data byte The sequence just described is used to transfer both data talk and listen addresses as well as multiline commands The state of the ATN line determines whether the data bus con tains data addresses or commands as described in the following paragraph Figure D 2 IEEE 488 handshake sequence DAV Source Valid i All Ready Acceptor NRFD All Accepted NDAC Acceptor Model 2520 User s Manual Bus commands IEEE 488 Bus Overview D 7 The instrument may be given a number of special bus commands through the IEEE 488 interface This section briefly describes the purpose of the bus commands which are grouped into the following four categories 1 Uniline commands Sent by setting the associated bus lines true For example to assert REN Remote Enable the R
332. ting cables For optimum performance use only the supplied connecting cables or the equivalent Be sure the connector insulating boots are in place and properly seated to assure ESD elec tro static discharge protection Typical connections Figure 2 5 shows typical connections to the laser diode the back detector photodiode and the front detector photodiode in a laser diode test setup interlock connections are not shown see Figure 2 4 Connections are as follows The center conductors of the CURRENT OUTPUT and VOLTAGE SENSE HI and LO terminals connect to the laser diode under test Current is applied to the laser diode through the CURRENT OUTPUT HI and LO terminals and voltage across the DUT is measured through the VOLTAGE SENSE HI and LO terminals e DETECTOR 1 connects to the forward detector photodiode The CURRENT INPUT center conductor is connected to one photodiode terminal while the BIAS terminal inner shield is connected to the other photodiode terminal e DETECTOR 2 connects to the back detector photodiode The CURRENT INPUT center conductor is connected to one photodiode terminal while the BIAS termi nal inner shield is connected to the other photodiode terminal NOTE The BNC cable shields should be connected as shown if possible If one terminal of the laser diode is to be earth grounded it must be the anode 2 8 Connections Model 2520 User s Manual Figure 2 5 Laser diode test connections Center Curre
333. tions PRESet STATus PRESet Return registers to default conditions Description When this command is sent the following SCPI event registers are cleared to zero 0 1 Operation Event Enable Register 2 Event Enable Register 3 Measurement Event Enable Register NOTE The Standard Event Register is not affected by this command Error queue NEXT STATus QUEue NEXT Read Error Queue Description As error and status messages occur they are placed into the Error Queue This query command is used to read those messages See Appendix B for a list of messages NOTE The STATus QUEue NEXT query command performs the same function as the SYSTem ERRor query command See SYSTem subsystem page 14 51 CLEar STATus QUEue CLEar Clear Error Queue Description This action command is used to clear the Error Queue of messages Model 2520 User s Manual SCPI Command Reference 14 51 ENABle lt list gt STATus QUEue ENABle lt list gt Enable messages for Error Queue Parameters lt list gt numlist where numlist is a specified list of messages that you wish to enable for the Error Query ENABle Query list of enabled messages Description On power up all error messages are enabled and will go into the Error Queue as they occur Status messages are not enabled and will not go into the queue This command is used to specify which messages you want enabled Messages not specified will be disabled and prevented from en
334. to command words that exceed four letters Ifthe fourth letter of the command word is a vowel including y delete it and all the letters after it Example e immediate imm Ifthe fourth letter of the command word is a consonant retain it but drop all the letters after it Example e format form Ifthe command contains a question mark query or a non optional number included in the command word you must include it in the short form version Example e delay del Command words or characters that are enclosed in brackets are optional and need not be included in the program message NOTE For fastest response to commands always use short forms Program messages A program message is made up of one or more command words sent by the computer to the instrument Each common command is a three letter acronym preceded by an asterisk SCPI commands are categorized in the STATus subsystem and are used to explain how command words are structured to formulate program messages STATus Path Root OPERation Path ENABle lt NRf gt Command and parameter ENABle Query command PRESet Command Single command messages The above command structure has three levels The first level is made up of the root com mand STATus and serves as a path The second level is made up of another path OPERation and a command PRESet The third path is made up of one command for the OPERation path The th
335. transmitted As with all multiline commands these commands are transmitted with ATN true LLO Local Lockout LLO is sent to the instrument to lock out the LOCAL key and thus all the front panel controls DCL Device Clear DCL is used to return instruments to some default state Usually instruments return to the power up conditions SPE Serial Poll Enable SPE is the first step in the serial polling sequences which is used to determine which device has requested service SPD Serial Poll Disable SPD is used by the controller to remove all devices on the bus from the serial poll mode and is generally the last command in the serial polling sequence Model 2520 User s Manual IEEE 488 Bus Overview D 9 Addressed multiline commands Addressed commands are multiline commands that must be preceded by the device listen address before that instrument will respond to the command in question Note that only the addressed device will respond to these commands Both the commands and the address preceding it are sent with ATN true SDC Selective Device Clear The SDC command performs essentially the same function as the DCL command except that only the addressed device responds Generally instruments return to their power up default conditions when responding to the SDC com mand GTL Go To Local The GTL command is used to remove instruments from the remote mode With some instruments GTL also unlocks front panel c
336. uch as those in the Model 2520 do have some small current that flows when the input is open This current is known as the input offset current and it is caused by bias currents of active devices as well as by leakage currents through insulators within the instrument The internal input offset current adds to the photodiode detector current so that the meter measures the sum of the two currents Im Ipp lio where I is the measured current Ipp is the photodiode current Ijo is the internal input offset current The offset current of the Model 2520 is sufficiently low so as to be negligible in most mea surement situations Use the lowest measurement range possible to minimize offset cur rent effects External offset current Offset currents can also be generated from external effects The external offset current also adds to the desired current and the ammeter again mea sures the sum of the currents Im Ipp lio lgo where Igo is the external offset current The two main sources for external offset currents are leaky photodiodes and increased photodiode leakage current caused by bias voltage Generally lower voltage bias values result in lower photodiode leakage currents Dielectric absorption Dielectric absorption in an insulator can occur when a voltage across that insulator causes positive and negative charges within the insulator to polarize because various polar mole cules relax at different rates When the volta
337. ue Trigger a measurement from the front panel Start configured sweep Set laser diode current source pulse width Set laser diode current source pulse delay period Select remote interface set GPIB and RS 232 operating parameters Save recall default or user instrument setup configurations Press CONFIG and then appropriate key to configure function or operation Access and configure Main Menu selections When entering numeric data use to clear reading to minimum absolute value Cancels selection Use to back out of menu structures Accepts selection Instrument in edit mode Questionable reading invalid cal step Math function enabled Instrument in GPIB remote mode Instrument addressed to talk over GPIB Instrument addressed to listen over GPIB Service request over GPIB Digital filter enabled Source measure operations being performed External trigger source selected ON OFF OUTPUT Turns the source outputs on or off Handle Pull out and rotate to desired position Rear panel summary The rear panel of the Model 2520 mainframe is shown in Figure 1 2 1 8 Getting Started Figure 1 2 Mainframe rear panel MADE IN CAT I re PULSE SYNC CE ouT A TRIGGER LINK lt TESTHEAD CONN 1 A aC TESTHEAD CONN 2 WARNING NO INTERNAL OPERATOR SERVICABLE PARTS SERVICE BY QUALIFIED PERSONNEL ONLY 1 6A 250V A LINE RATING Model 2520 User s Manual IEEE 488 CHANGE
338. ultiline commands cccccccccessssteeeeeeesseeees D 8 Addressed multiline commands sssseeseeeereeesseesssssesssssrsere D 9 Address commands seeeeeeesesssesesserererererrrresrersssssssesserrereee D 9 Unaddress commands cccccccccccceceseseeseeessseeesssssssnesseeeees D 9 Common commands ssssssesessessssesesrerereererrersrnesssssssrsesrrere D 10 SCPI commands ccccccccessssceceeesssseceeceessseeeceeessnneeeeeees D 10 Command codes cccssseccecesssceceeeessseeeeccesssnseeeeeesesseeees D 10 Typical command sequences sssssesesseessseereseeresrrseerrserreses D 12 TEEE command groups sssssssseesesresesreresrrerrreeresersesrrseereses D 13 Interface function codes eeeeeeeeeesesesssessecescecscececeeeeseeeeeeeeees D 14 IEEE 488 and SCPI Conformance Information Introduction sovas E iaia E 2 Measurement Considerations Optimizing laser diode connections 0 0 Lele eee eeeeeseeeeeeeeeeees F 2 Current pulse output circuit model eee eeeeeeeeees F 2 Cable MGuctance i scssescscosscsnsersescocorsvscvsnessvseassestsuseneonesetey F 3 Increasing cable length oo eee eeeeeseeeeeeeeeeeeeseeeseeeeeaes F 5 Exposed loop area eee eseeceesseseeeseeseeeseeeeeeaeceeeesessaeeseenaes F 6 Sense lead connections oo eee eeseeseeeseeseeeseeeeeseeeeeeaeenees F 8 Magnetic coupling oe eee eeceesneceneceseeceaeeeseeceaeeeeneeeaeeses F 10 Increasing laser diode pulse measurement speed F 11 OV
339. ures 1 and 2 are typical pulse outputs into resistive loads Typical Per ANSI IEEE Std 181 1977 0 Per ANSI IEEE Std 181 1977 10 to 90 DC accuracy 700mV output terminal 0 2Q typical output impedance At DC 101s measurement pulse width Filter off Standard deviation of 10 000 readings with 10s pulse width filter off with I source set to 0 amps DC 14 The useful resolution is Useful Resolution Range ________________ _ Averaging Filter Setting Excluding total programmed Pulse ON time Pulse OFF time Front panel off calc off filter off duty cycle lt 10 binary communications Returning 1 voltage and 2 current measurements for each source point Sweep mode Valid for both continuous pulse and sweep modes Shown is the Power Distribution based on current settings Timing Cycle P pw pd 4 max Specifications are subject to change without notice Pulse Waveform Flatness 500mA Into 20 Ohms The A D converter has 14 bit resolution The useful resolution is improved by reading averaging 0 6 T 0 515 Full Pulse 0 5 0 51 0 4 0 505 Current Healt HN te Expanded Pulse Top Current a 03 05 A 0 2 0 495 0 1 0 49 0 0 485 0 5 10 15 20 25 Time us Figure 1 Pulse Waveform Flatness 5A into 2 ohms 6 T 5 06 Full Pulse 5 5 04 4
340. ver the bus Setting REN true does not place the instrument in the remote state You must address the instrument to listen after setting REN true before it goes into remote The Model 2520 must be in remote in order to use the following commands to trigger and acquire readings e INITiate and then FETCh e READ e MEASure IFC interface clear The IFC command is sent by the controller to place the Model 2520 in the local talker lis tener idle states The unit responds to the IFC command by cancelling front panel TALK or LSTN lights if the instrument was previously placed in one of these states Note that this command does not affect the status of the instrument Settings data and event registers are not changed To send the IFC command the controller need only set the IFC line true for a minimum of 100us LLO local lockout Use the LLO command to prevent local operation of the instrument After the unit receives LLO all of its front panel controls except OUTPUT OFF are inoperative In this state pressing LOCAL will not restore control to the front panel The GTL command restores control to the front panel Cycling power will also cancel local lockout GTL go to local Use the GTL command to put a remote mode instrument into local mode The GTL com mand also restores front panel key operation DCL device clear Use the DCL command to clear the GPIB interface and return it to a known state Note that the DCL co
341. when the start of test SOT line of the Digital I O port is pulsed low See Section 9 TSTEST Event detection occurs when the SOT line of the Digital I O port is pulsed high See Section 9 TLSTEST Event detection occurs when the SOT line of the Digital I O port is pulsed either high or low See Section 9 Delay and pulse phases The delay pulse cycle consists of two phases Delay and Pulse See Section 5 for com plete details Delay phase The programmable delay set to between 20us and 500ms with the DELAY key is the time period between current pulses Note however that the programmed delay is the min imum delay and the actual delay depends on the pulse duty cycle see Section 5 8 4 Triggering Model 2520 User s Manual Pulse phase During the pulse phase the unit outputs one current pulse with the programmed pulse width set to between 500ns and 5ms with the PW key If the unit is in the fixed non sweep mode the pulse amplitude is the same for each cycle through the loop However if the unit is in the sweep mode the pulse amplitude is set to the programmed value for that sweep point 10MHz samples are taken during the pulse phase and one set of voltage and current readings is DSP processed for each pulse Filtering If the filter is enabled the instrument cycles through the delay pulse loop for the pro grammed filter count and averages the specified number of readings to yield a single set of filtered read
342. xxxx yyyyyyy zzzzz mmm ddd yyyy aaa bbb c d e Where XXXXXXxX is the mainframe serial number yyyyyyy is the testhead serial number ZZZzz is the main microprocessor firmware revision Mmm dd yyyy is the month day and year of the firmware release aaa is the display board revision level bbb is the DSP firmware revision level c is the mainframe board revision level d is the testhead measurement board revision level e is the testhead pulser board revision level OPC operation complete Sets OPC bit OPC operation complete query Places a 1 in output queue When OPC is sent the OPC bit in the Standard Event Register will set after all pending command operations are complete When OPC is sent an ASCII 1 is placed in the Output Queue after all pending command operations are complete Typically either one of these commands is sent after the INITiate command The INITiate command is used to take the instrument out of idle in order to perform measurements While operating within the trigger model layers all sent commands except DCL SDC IFC SYSTem PRESet RST RCL TRG GET and ABORt will not execute After all programmed operations are completed the instrument returns to the idle state at which time all pending commands including OPC and or OPC are executed After the last pending command is executed the OPC bit and or an ASCII 1 is placed in the Output Queue 12 4 Common Command
343. y STATe Query state of message mode for specified display Description These commands enable and disable the text message modes When enabled a defined message is displayed When disabled the message is removed from the display GPIB Operation A user defined text message remains displayed only as long as the instrument is in remote Taking the instrument out of remote by pressing the LOCAL key or sending LOCAL 26 cancels the message and disables the text message mode RS 232 Operation A user defined test message can be cancelled by sending the SYSTem LOCal command or pressing the LOCAL key FORMat subsystem The commands for this subsystem are used to select the data format for transferring instru ment readings over the bus These commands are summarized in Table 14 3 Data format DATA lt type gt length FORMat DATA lt type gt lt length gt Select data format Parameters lt type gt lt length gt ASCii ASCII format REAL 32 IEEE754 single precision format SREal TEEE754 single precision format NOTE lt length gt is not used for the ASCii or SREal parameters It is optional for the REAL parameter If you do not use lt length gt with the REAL parameter the lt length gt defaults to 32 single precision format Query DATA Query data format 14 20 SCPI Command Reference Description Model 2520 User s Manual This command is used to select the data format for transferring readings over
344. y forms are used to deter mine the RST default value and the upper and lower limits for the fundamental command Examples are SOURce1 PULSe DELay DEFault Queries the RST default value SOURcel PULSe DELay MINimum Queries the lowest allowable value SOURce1 PULSe DELay MAXimum Queries the largest allowable value Case sensitivity Common commands and SCPI commands are not case sensitive You can use upper or lower case and any case combination Examples RST rst DATA data SYSTem PRESet system preset NOTE Using all upper case will result in slightly faster command response times Long form and short form versions A SCPI command word can be sent in its long form or short form version The command subsystem tables in Section 14 provide the long form version However the short form version is indicated by upper case characters Examples SYSTem PRESet long form SYST PRES short form SYSTem PRES long form and short form combination Note that each command word must be in long form or short form and not something in between For example SYSTe PRESe is illegal and will generate an error The command will not be executed Model 2520 User s Manual Remote Operations 10 13 Short form rules Use the following rules to determine the short form version of any SCPI command Ifthe length of the command word is four letters or less no short form version exists Example feed feed These rules apply

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