Isolated Voltage Source - Stanford Research Systems
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1. Min Typ Max Units Output Output range 20 20 V Floating output 40 40 V common mode to ground Noise 10 UVrms 1 kHz BW Settable resolution 1 mV Display resolution 1 mV V lt 1 999 V 10 mV V lt 19 99 V Max output current 10 10 mA before dropout Short circuit current 15 mA Short circuit duration indefinite Batteries Number of batteries 2 1 operating 1 charging standby Chemistry Nickel metal hydride Charge time 5 h Discharge time 12 h 10 mA load Lifetime 1000 charge cycles 2 yr shelf life Battery switching Automatic when active battery is fully discharged Switchover glitch lt 1 mV for lt 1 ms Battery charge override Allows manual switching of batteries Triggered when Battery Override is held for 5s or more Only armed when standby battery is in ready state Operating Temperature 0 40 C Power 15 5 24 V DC Supply current 250 mA 5 V 40 mA 15 24 V General Characteristics Interface Serial RS 232 through SIM interface Connectors Banana binding posts and chassis ground DB 15 male SIM interface Weight 3lbs Dimensions 1 5 W x 3 6 H x 7 0 D ASRS SIM928 Isolated Voltage Source 1 Getting Started This chapter gives you the necessary information to get started quickly with the SIM928 Isolated Voltage Source In This Chapt2. 2 2 Alphabetic List of Commands 2 3 Introduction 0 00 eee eee eee 24 Commander BS eee LOS 2 5 Status Model 0000200 ae 3 Circuitry Onl Circuit Description ar in m ok AE Sw Seg 32 Parts Blister Get Mee eee ee eed 3 3 Schematic Diagrams es Ea a a ii Contents ASRS SIM928 Isolated Voltage Source General Information The SIM928 Isolated Voltage Source part of Stanford Research Sys tems Small Instrumentation Modules family is a low noise pro grammable voltage source intended for sensor biasing and other demanding low power applications Dual auto switching inter nal nickel metal hydride batteries provide continuous uninterrupted operation at the isolated output which can deliver up to 20 V bias at up to 10 mA current load Safety and Preparation for Use A WARNING The front panel binding post outputs and are isolated from the Earth the power line outlet ground and the metal chassis of the module No dangerous voltages are generated by the SIM928 However if a dangerous voltage is externally applied to the module it may be present on either binding post connector the chassis or the SIM interface connector and may cause injury or death Do not exceed 40 V to the Earth at either binding post terminal The SIM928 ships from the factory with the internal battery pack installed and ready for operation Do not install substitute parts or perform any unauthori
3. U604 drives a current mirror 0610 0608 used to translate its limited output voltage swing into a gt 20 V signal which can drive the volt age follower made of Q601 and Q602 The biased low current output stage is built with bipolar transistors and diodes that are specified for 400 V operation Current and voltage sense transistors QN603 Q604 limit the maximum output current of this stage to lt 18 mA and make sure that overvoltages can not damage the output stage On detec tion of a permanent overvoltage the microcontroller disconnects the SIM928 Isolated Voltage Source 4 SRS Circuitry A WARNING 3 1 5 Display and buttons module s output from the source While the circuit is designed to be safe for higher voltages a set of gas discharge arrestors will limit any potential difference between the SIM chassis and the output ter minals to approx 60 V 80 V DO NOT ATTEMPT TO EXCEED THE 40 V EARTH OUTPUT PO TENTIAL An active floating ground reference made of U607 and Q613 Q614 creates a virtual 1 5 V grounding point relative to the battery cath ode which allows the regulator to reduce the output voltage all the way to 0V without loosing linearity and precision Dual pre regulators Q502 D503 and U506 increase common mode rejection and stability of the reference voltage source the DAC and the feed back opamp The DAC s output voltage is programmed by the microcontroller through an optically isolated U501 U504 s
4. Power supply return 9 CHASSIS_GND Chassis ground 10 TXD MF gt SIM Async data start bit 0 5 V 1 GND 11 RXD SIM gt MF Async data start bit 0 5 V 1 GND 12 REF_10MHz MF gt SIM 10 MHz reference optional connection 13 5V MF gt SIM Power supply digital circuitry 14 15V MF gt SIM Power supply no connection in SIM928 15 24V MF gt SIM Power supply battery charger 1 3 2 Direct interfacing 1 3 2 1 Table 1 1 SIM Interface Connector Pin Assignments DB 15 The SIM928 is intended for operation in the SIM900 Mainframe but users may wish to directly interface the module to their own systems without the use of additional hardware The mating connector needed is a standard DB 15 receptacle such as Amp part 747909 2 or equivalent Clean well regulated supply voltages of 15 5 24 VDC must be provided following the pin out specified in Table 1 1 Ground must be provided on pins 1 and 8 with chassis ground on pin 9 The STATUS signal may be monitored on pin 2 for a low going TTL compatible output indicating a status message Direct interface cabling If the user intends to directly wire the SIM928 independent of the SIM900 Mainframe communication is usually possible by directly connecting the appropriate interface lines from the SIM928 DB 15 plug to the RS 232 serial port of a personal computer Connect RXD from the SIM928 directly to RD o
5. Thus the only possible responses to the TOKN query are ON and 9 At power on TOKN OFF is set TOKN OFF TERM z Example Response Termination Set query the term sequence to Z NONE 0 CR 1 LF 2 CRLF 3 LFCR 4 The term sequence is appended to all query responses sent by the module and is constructed of ASCII character s 13 carriage return and or 10 line feed At power on TERM CRLF is set TERM 3 ASRS SIM928 Isolated Voltage Source 2 5 Status Model 2 5 Status Model The SIM928 status registers follow the hierarchical IEEE 488 2 for mat A block diagram of the status register array is given in Figure 2 1 There are three categories of registers in the SIM928 status model Condition Registers Event Registers Enable Registers These read only registers correspond to the real time condi tion of some underlying physical property being monitored Queries return the latest value of the property and have no other effect Condition register names end with CR These read only registers record the occurrence of defined events When the event occurs the corresponding bit is set to 1 Upon querying an event register any set bits within it are cleared These are sometimes known as sticky bits since once set a bit can only be cleared by reading its value Event register names end with SR These read write registers define a bitwise mask for their cor responding e
6. 01050 200 C106 C108 C114 C126 5 00102 4 7U R101 R103 R115 R116 4 01503 10K R635 4 01590 33 2K C110 C112 5 00102 4 7U R201 R202 R215 R605 R636 4 00326 200 C111 C113 5 00299 1U R609 R611 R622 R627 R637 4 01067 301 C501 5 00041 220U R628 R648 R638 4 01021 100 C503 5 00025 100P R102 R104 R655 4 01479 1 0K R639 4 00296 604 C504 5 00298 01U R105 4 01057 237 R640 R641 4 00217 1 000K C505 5 00192 22U MIN R106 4 01405 1 00M R642 4 01650 10 00K C506 C507 5 00599 10uF 50V R107 R213 R214 4 01455 100 R643 4 01651 100 0K C601 5 00267 1000U R108 R301 R302 R619 4 01495 4 7K R644 4 01479 1 0K C603 C610 C612 C615 5 00525 1U R109 4 01511 22K R645 4 01557 1 8M C617 R110 4 01431 10 R646 4 01515 33K C604 C613 C614 5 00526 22U T16 R111 R120 R216 4 01213 10 0K R651 4 01462 200 C605 5 00545 3 3N R113 R114 R117 R124 4 01527 100K R652 4 00012 20K C606 5 00572 330P R626 R653 4 01535 220K C607 C608 5 00525 1U R118 R206 R222 4 01483 1 5K R654 4 01519 47K C619 5 00319 10U T35 R119 4 01244 21 0K RN101 RN108 RN403 4 00442 1 2K CN101 CN106 5 00594 4x1000pF R121 4 00849 100K RN404 4 00442 1 2K CN107 CN108 5 00594 4x1000pF R122 R123 4 01455 100 RN112 RN602 RN604 4 00906 100X4D CN112 5 00600 4x100pF R125 R503 R610 R612 4 01551 1 0M RN113 4 00908 270X4D D101 D103 D613 3 00945 BAT54S R203 R204 4 01487 2 2K RN201 RN203 RN501 4 00912 10KX4D D205 D209 D211 D501 3 00544 BAV70LT1 R205 4 00997 56 2 RN503 D502 D603 D606 D608 R207 R208 R209 4 01675 100 OHM 5 5W RN405 RN413 4 0
7. 2005 05 16 2 4 6 Serial communication commands ASRS SIM928 Isolated Voltage Source 2 4 Commands BAUD i Example Baud Rate Set query the baud rate to At power on the baud rate defaults to 9600 Actual baud rate settings depend on implementation details of the SIM928 based on modulo prescalars of the 10 MHz system clock As aresult queries of BAUD will in general be slightly different from the set values For example after setting BAUD 9600 the query BAUD will respond 9470 The functional requirement for successful asyn chronous serial communication is no greater than 5 mismatch in baud rates BAUD 9600 FLOW z Example Flow Control Set query flow control to Z NONE 9 RTS 1 XON 2 At power on the SIM928 defaults to FLOW RTS flow control FLOW 0 PARI z Example 2 4 7 Status commands Parity Set query parity to z NONE 0 ODD 1 EVEN 2 MARK 3 SPACE 4 At power on the SIM928 defaults to PARI NONE PARI EVEN The Status commands query and configure registers associated with status reporting of the SIM928 See Section 2 5 for more details CLS Example Clear Status CLS immediately clears the ESR CESR and the OVSR CLS SIM928 Isolated Voltage Source 4 SRS Remote Operation STB 1 Example Status Byte Reads the Status Byte register bit Execution of the STB query without the optional bit i always ca
8. Query OVSR to clear the Battery Switch flag 2 Issue the BCOR command 3 Wait at least one second 4 Query OVSR again to check for the Battery Switch flag BCOR BATS Example Battery State Query the battery status of the SIM928 The response is return in the format lt a gt lt b gt lt x gt where lt a gt and lt b gt correspond to batteries A and B and are equal to 1 for in use 2 for charging and 3 for ready standby The third parameter lt x gt is normally 0 it is set to 1 if the service batteries indicator is lit BATS 2 1 0 BIDN z Example Battery Identification Query the battery identification parameter Z Valid parameters to query are Value Definition PNUM 0 Battery pack part number SERIAL 1 Battery pack serial number MAXCY 2 Design life of charge cycles CYCLES 3 charge cycles used PDATE 4 Battery pack production date YYYY MM DD The MAXCY parameter returns the estimated maximum number of charge discharge cycles that each battery in the pack can sustain be fore suffering a significant reduction in charge capacity The CYCLES parameter reports the actual number of cycles used by the most used battery in the pack Typically both batteries in the pack will have the same number of cycles within 1 but it is possible through power cycling at odd times to have one battery see more overall use than the other BIDN PDATE
9. driver operates without interuption When the discharged battery is first connected to the charger circuit a resistive load is briefly applied to complete the discharge of the cell to a known starting voltage From that point the charger applies a fixed charging current for 5 hours to completely charge the battery If power is interrupted while the battery is charging the charge cy cle will not resume rather the power on system check will select the most depleted battery for initial operation and place the other battery in the Ready state assuming neither battery appears fully discharged This algorithm ensures that a battery cannot be over charged by an unfortunate series of power cycles 1A small glitch may appear at the output when the fresh battery switches in ASRS SIM928 Isolated Voltage Source 1 2 Front Panel Operation 1 5 1 2 2 2 Battery charge override For some applications it may be important to insure that the SIM928 will not begin a battery switch over during a particularly sensitive experiment The Battery Override can be used to force the Ready battery to be switched to On immediately ensuring a 12 hour period of un switched operation The Battery Override is only armed when one of the batteries is in the Ready state while a battery is in the Charge state this key is temporarily disabled To initiate a forced swich over press and hold Battery Override for at least 5 seconds Over the ne
10. error code Valid codes are Value Definition 0 No execution error since last LEXE 1 Illegal value 2 Wrong token 3 Invalid bit STB 12 LEXE LEXE 3 0 The error 3 Invalid bit is because STB only allows bit specific queries of 0 7 The second read of LEXE returns 0 ASRS SIM928 Isolated Voltage Source 2 4 Commands LCME Device Error Query the last command error code Valid codes are Value Definition 0 No command error since last LCME 1 Illegal command 2 Undefined command 3 Illegal query 4 Illegal set 5 Missing parameter s 6 Extra parameter s 7 Null parameter s 8 Parameter buffer overflow 9 Bad floating point 10 Bad integer 11 Bad integer token 12 Bad token value 13 Bad hex block 14 Unknown token Example IDN LCME 4 The error 4 Illegal set is due to the missing LBTN Button Query the last button press code Valid codes are Value Definition 0 no button pressed since last LBTN 1 On Off 2 100mV 4 3 100mV 1 4 10mV 1 5 10mV I 6 mV 7 1mVY 8 Battery Override Example LBTN 1 SIM928 Isolated Voltage Source ASRS Remote Operation Example Token Mode Set query the Token Query mode to Z OFF 0 ON 1 If TOKN ON is set then queries to the SIM928 that return tokens will return the text keyword otherwise they return the decimal integer value
11. output is loaded with close to 10mA current The initialization algorithm tries to ensure the best possible availability by comparing the battery voltages toa minimum ASRS SIM928 Isolated Voltage Source 3 1 Circuit Description 3 3 threshold and giving the user access to the batteries in such an order that operation disruptions are minimized 3 1 2 1 Discharge Charge circuit Batteries are discharged with a 50mA constant current discharge circuit made of Q205 U205 and current sense resistors R213 214 Power resistors R207 R209 dissipate excess heat during discharge to keep transistor Q205 within its max power dissipation limits It usually takes only a few minutes to deplete the battery from the 24 2 V useful end voltage to the discharge termination voltage of 23 0V After discharge the charger current source made up of Q202 Q203 U201 and current sense resistor R205 delivers 45 mA current into the battery A fully depleted battery of 150 mAh can be safely recharged in approx 1 4 x 150 mAh 45 mA 4 7 hours The charge and discharge circuits are essentially current sinks and sources referenced to the 15 V and 24 V power supply rails The maximum voltage difference of 39 V available to a SIM module is required to charge the NiMH battery stacks which can have as much as 21 cells x 1 5 V cell 31 5 V potential accross them while leaving enough headroom for transistor and sense resistor voltage drops 3 1 2 2 Thermal co
12. 0407 2 7K D401 D404 D409 3 00424 GREEN MINI R217 4 01320 130K RT301 RT302 4 00766 RXE030 D410 D412 3 00426 YELLOW MINI R218 R221 4 00131 1 00M 401 S406 S408 S409 2 00053 B3F 1052 D413 3 00425 RED MINI R223 4 01720 47K U101 3 01378 74HCU04 D503 3 00134 1N759A R224 R231 R649 4 01519 47K U102 3 00903 MAX6348 D601 D602 D604 D605 3 01148 SiM R225 R229 R232 4 01706 1 0M U103 3 01379 68HC912B32 D609 D610 R226 R233 4 01719 470k U104 3 00662 74HC14 D611 3 01357 MMBZ5230 R227 4 01401 909k U105 U201 U203 3 01133 TL431CDB D612 3 01149 1SMA5913BT3 R228 4 00617 100K U204 U205 3 01156 AQW216A J201 1 00281 HEADER10_POL5DIM R230 4 01720 47K U206 U501 U504 3 01413 MOCD213 M J202 J503 J504 1 00473 2 PIN WHITE R234 R235 4 01708 220K U207 U608 3 01159 TLV431CDB J301 1 00281 10 PIN DI R236 R237 4 01264 34 0K U301 3 01458 24LC16B J401 1 01071 SMS 112 01 G S R238 4 01242 10 0K U402 U406 3 00672 74HC595ADT J501 1 01074 TMS 112 01 G S RA R239 4 01184 4 99K U407 3 01424 HDSP A107 J502 JP104 1 00008 20PINDI R240 R501 R502 4 01535 220K U408 U410 3 00290 HDSP A101 JP101 1 00302 6 PIN DIF CES R401 4 01489 2 7K U411 3 01157 74HC165 JP103 1 00367 15 PIN D R402 R403 4 01480 1 1K U412 3 01158 74HC133 K201 K204 K501 K502 3 01009 TX2SA 5V R508 4 01548 750K U506 3 01415 LP2951CMM L101 L106 6 00174 BEAD R509 R510 4 01536 240K U601 3 01451 ADR421AR L501 L502 6 00640 500uH 10mA R511 4 01435 15 U602 3 01160 AD5541 Q201 Q204 3 00580 MMBT3906LT1 R601 R602 4 00620 10 U604 3 01370 OPA277UA Q202 Q2
13. 05 Q601 Q608 3 01150 FZT658 R603 R604 R647 4 01443 33 U606 3 01161 OPA336N Q610 R613 4 01467 330 U607 3 01162 OPA244N Q207 Q208 Q613 3 00927 MMBT2907 R614 R616 4 01491 3 3K Y101 6 00571 10 000MHz 3 3 Schematic Diagrams Schematic diagrams follow this page SIM928 Isolated Voltage Source SRS
14. Operation and Service Manual Isolated Voltage Source SIM928 SRS Stanford Research Systems Revision 1 9 e May 19 2006 Certification Stanford Research Systems certifies that this product met its published specifications at the time of shipment Warranty This Stanford Research Systems product is warranted against defects in materials and workman ship for a period of one 1 year from the date of shipment Service For warranty service or repair this product must be returned to a Stanford Research Systems authorized service facility Contact Stanford Research Systems or an authorized representative before returning this product for repair Information in this document is subject to change without notice Copyright Stanford Research Systems Inc 2005 2006 All rights reserved Stanford Research Systems Inc 1290 D Reamwood Avenue Sunnyvale CA 94089 USA Phone 408 744 9040 e Fax 408 744 9049 www thinkSRS com e e mail info thinkSRS com Printed in U S A SRS SIM928 Isolated Voltage Source Contents General Information Safety and Preparation for Use SYM cian is See ee Sake as Das Notaio uta ehh ol de a he Oe win whe oh we oh A eA SPCCHICAMONS Z ESE baa Ae econ Si 1 Getting Started 1 1 Introduction to the Instrument 1 2 Front Panel Operation 4 0 3 4 Ed eh ete Gt 1 3 SIM Interface 200000084 2 Remote Operation 2 1 Index of Common Commands
15. a few picofarads depending on the actual charger configration Since the batteries can be connected to different absolute potentials these changes in potentials and capacitance can generate small cur rent spikes during battery switching events Similar but smaller spikes can occur when the charge discharge circuits are activated The module has a set of opticaly isolated Mosfet switches U204 205 with 1 MQ series resistors R218 R221 which pre charge the battery s stray capacitance to minimize these current spikes However user s who are very sensitive to charge transfers on the order of a few nanocoulombs need to take precations against these unavoidable ar tifacts by either shunting these charges against ground with a capac itor or by stretching them out with series resistors Alternatively the ASRS SIM928 Isolated Voltage Source 3 1 Circuit Description 3 5 3 1 3 Battery pack SIM928 can be forced to switch in a fresh battery see section 1 2 2 2 prior to connecting to the sensitive user system A fully charged unloaded battery has a terminal voltage several volts higher than that of a loaded almost fully discharged battery During switch over both batteries are connected to the isolated user regulator for approx 30 seconds to ensure that the output voltage never drops out Two discrete low drop voltage regulators with Q207 and Q208 as series elements equalize the battery voltages to 23 5 V and make sure that th
16. able OVSE 2 22 2 2 Remote Operation 2 1 Index of Common Commands symbol definition ij Integers f Floating point values Z Literal token Required for queries illegal for set commands var Parameter always required var Required parameter for set commands illegal for queries var Optional parameter for both set and query forms Output VOLT f 2 9 Voltage OPON 2 9 Output On OPOF 2 9 Output Off EXON z 2 9 Excitation On Off Battery BCOR 2 9 Battery charger override BATS 2 10 Battery State BIDN z 2 10 Battery Identification Serial Communications BAUD i 2 11 Baud Rate FLOW z 2 11 Flow Control PARI z 2 11 Parity Status CLS 2 11 Clear Status STB 1 2 12 Status Byte SRE i j 2 12 Service Request Enable ESR i 2 12 Standard Event Status ESE 1 1 j 2 12 Standard Event Status Enable CESR i 2 12 Communication Error Status CESE i j 2 12 Communication Error Status Enable OVCR 1 2 13 Overload Condition OVSR i 2 13 Overload Status OVSE LIU 2 13 Overload Status Enable PSTA z 2 13 Pulse STATUS Mode Interface RST 2 13 Reset CONS z 2 14 Console Mode IDN 2 14 Identify ASRS SIM928 Isolated Voltage Source 2 1 Index of Common Commands 2 3 OPC 2 14 Operation Complete LEXE 2 14 Execution Error LCME 2 15 Device Error LBTN 2 15 Button TOKN 2 2 16 Token Mode TERM z 2 16 Response Ter
17. ains two identical 25 2 V NiMH batter ies During normal operation at least one battery is connected at any time to the isolated voltage regulator circuit The other battery is either idle disconnected or connected to the charger circuit Once the microcontroller detects that the battery in use is running low on charge via opto U502A it swaps the two batteries and connects the now depleted battery to the charger circuit Constant charge and discharge currents are used to maximize battery life and minimize electronics noise on the isolated voltage output First the charger algorithm discharges a depleted battery to a fixed voltage endpoint 23 0 V to ensure a well defined discharge state It then charges the battery with a constant current until the charge termination endpoint is reached Charging terminates on either total charge time or a zero of the NiMH dV dt curve The charger algo rithm is designed to maximize battery life and ensure several years of uninterrupted operation with a single battery pack A complex state machine driven by a timer and battery monitoring signals implements the discharge charge idle cycle for each battery in such a way that the module is always available after an initial charge cycle NiMH batteries suffer from self discharge on the order of 1 per day If the module has been powered down for several months insufficient charge might remain in either battery to assure continuous operation especially if the
18. ake discrete 1 mV steps using 1 mV AY by counting key taps the user can determine the sub display voltage setting When V gt 2 00 V the display always corresponds to the truncated value of the programmed voltage For instance if V 2 120V through 2 129 V the display will show t2 le similarly if V 12 730 V through 12 739 V the display will show 7c 13 The BATTERY block of the front panel shows the present state of the SIM928 s internal battery system The two batteries labeled A and B correspond to the two shaded rows while the available bat tery states On Charge and Ready correspond to the three columns A battery is On when it is switched to power the output stage Ready corresponds to a battery in the nominally fully charged state that is ready for operation when the On battery is depleted The Charge state indicates that the battery is connected to the charger circuit Under typical operation a fully charged battery should run for 12 18 hours before being depleted When the On battery is nearly dis charged an internal threshold circuit signals the SIM928 controller to begin a battery switch over The stand by battery which at this point is typically in the Ready state is switched onto the output circuit after which the discharged battery is switched to the charger cir cuit A diode or circuit effectively prevents the discharged battery from loading down the fresh battery and the output
19. aud rates 62500 78125 104167 156250 Note that these rates are typically not accessible on a standard PC RS 232 port but can be used between the SIM928 and the SIM900 Mainframe ASRS SIM928 Isolated Voltage Source 2 Remote Operation In This Chapter This chapter describes operating the SIM928 over the serial interface 2 1 2 2 2 3 2 4 2 5 Index of Common Commands 2 2 Alphabetic List of Commands 2 4 Introductions X vs ia PN eR 2 6 2 3 1 Power on configuration 2 6 23 2 BUPEES ss ra a be bw ok a ek 2 6 2 3 3 Device Clear 2 6 Commands saosa see a Ged Be R 2 7 2 4 1 Command syntax es ie sle die Re ee 2 7 24 27 Notation i ssis 4 420 ace 6 be a 2 8 2 4 3 Examples o tr goth a ee ae so 2 8 2 44 Output commands 2 9 2 4 5 Battery commands vs tne A ee 2 9 2 4 6 Serial communication commands 2 10 2 4 7 Statuscommands 2 11 2 4 8 Interface commands 2 13 Status Model vos as eo PRES ee AS 2 17 2 5 1 Status Byte SB pps ea ote ae SE 2 18 2 5 2 Service Request Enable SRE 2 19 2 5 3 Standard Event Status ESR 2 19 2 5 4 Standard Event Status Enable ESE 2 20 2 5 5 Communication Error Status CESR 2 20 2 5 6 Communication Error Status Enable CESE 2 21 2 5 7 Overload Status OVCR 2 21 2 5 8 Overload Status OVSR 2 21 2 5 9 Overload Status En
20. command Reading a single bit with the CESR i query clears only bit i Weight Bit Flag 1 0 PARITY 2 1 FRAME 4 2 NOISE 8 3 HWOVRN 16 4 OVR 32 5 RTSH 64 6 CTSH 128 7 DCAS PARITY FRAME NOISE HWOVRN OVR RTSH CTSH DCAS Parity Error Set by serial parity mismatch on incoming data byte Framing Error Set when an incoming serial data byte is missing the STOP bit Noise Error Set when an incoming serial data byte does not present a steady logic level during each asynchronous bit period window Hardware Overrun Set when an incoming serial data byte is lost due to internal processor latency Causes the Input Buffer to be flushed and resets the command parser Input Buffer Overrun Set when the Input Buffer is overrun by incoming data Causes the Input Buffer to be flushed and resets the command parser Undefined for the SIM928 Command Error Indicates a parser detected error Undefined for the SIM928 Device Clear Indicates the SIM928 received the Device Clear signal an RS 232 break Clears the Input Buffer and Output Queue and resets the command parser ASRS SIM928 Isolated Voltage Source 2 5 Status Model 2 5 6 Communication Error Status Enable CESE The CESE acts as a bitwise AND with the CESR register to produce the single bit CESB message in the Status Byte Register SB It can be set and queried with the CESE command This re
21. e maximum voltage jump at the output regulator power supply rail stays well below a few hundred millivolts Each SIM928 battery pack contains two sets of three 9 V NiMH batter ies each Each 9 V battery contains seven NiMH cells with a nominal voltage of 1 2 V A fully charged battery will produce a voltage of approx 21x 1 2 V 1 3 V 25 2 V 27 3 V Under load this voltage quickly settles to a slowly falling ramp until the battery is nearly empty At approx 1 15 V per cell the battery quickly starts losing voltage and the voltage detection circuitry signals the microcontroller through U502A that the battery needs to be switched over Each battery pack carries a non volatile EEPROM with information about cell type voltage capacity production date charge cycles and serial number This information is used by the microcontroller to determine the optimum charging time and when to turn on the Sevice Battery indicator 3 1 4 Isolated voltage regulator stage The output stage is built around the low power precision volt age reference U601 a 16 bit serial digital to analog converter U602 and a gain 10 output stage containing U604 as the central precision opamp Precision is ensured by using a low temperature coefficient adjustable precision voltage divider network R634 R642 Offset voltage compensation is partially digital by adding a digital offset word to the DAC code and partially analog by trimming of U604 s offset voltage
22. enient starting point for user program ming ASRS SIM928 Isolated Voltage Source 2 4 Commands 2 4 4 Output commands These commands directly query and control the output state of the SIM928 VOLT f Example Voltage Set query the programmed voltage to f VOLT 1 012e 1 VOLT 10 120 OPON Example Output On Turn the output on The output state can be queried with the EXON command below OPON OPOF Example Output Off Turn the output off The output state can be queried with the EXON command below OPOF EXON z Example 2 4 5 Battery commands Excitation On Off Set query the output to Z OFF 0 ON 1 The output can also be turned on with the OPON command and turned off with the OPOF command EXON ON These commands directly query and control the battery system of the SIM928 BCOR Battery charger override Forces the SIM928 to switch the active output battery BCOR follows the same rules as the front panel Battery Override button see section 1 2 2 2 In particular the command will only be operative if one of the batteries is in the ready state see BATS below Furthermore the SIM928 may delay initiating BCOR by up to 1s for internal synchronization To verify that BCOR has actually initiated a battery switch the user program should SIM928 Isolated Voltage Source 4 SRS Remote Operation Example 1
23. er 1 1 Introduction to the Instrument 1 2 LEI COVEIVIEW ceres enok eS R es de 1 2 1 1 2 Power on State 1 2 1 2 Front Panel Operation 1 2 TZI SACUUSE arara Ee AAA 1 3 1 22 Battery s oe ccd mas aes ee eo eee 1 4 127 Diputada e Sob e a Boke A 1 5 1 3 SIM Interface o 1 6 1 3 1 SIM interface connector 1 6 1 3 2 Direct interfacing gt 1 7 1 2 Getting Started 1 1 Introduction to the Instrument 1 1 1 Overview 1 1 2 Power on State first use after extended storage The SIM928 Isolated Voltage Source is ideally suited for applications demanding flexibility and low noise from a programmable voltage source The basic function of the SIM928 is to generate a user specified volt age between 20V and 20 V between the and front panel terminals The architecture of the SIM928 uses an internal battery to power the output stage This provides an ideal voltage source free of power supply ripple Two independent batteries are used while one is powering the output circuitry the second is either be ing recharged or held in standby When the output battery nears its fully discharged state the standby battery is seamlessly switched into the output circuit and the depleted battery switched to the inter nal charger With this arrangement essentially continuous isolated bias voltage is available to the user Note that although the output stage is e
24. eration of the SIM928 is through the front panel ADJUST block 1 2 1 1 On Off toggle The output circuit of the SIM928 is toggled between enabled and disabled with On Off In the event of an overvoltage Trip see section 1 2 3 2 press On Off to clear the Trip indicator 1 2 1 2 Changing the programmed voltage The remaining 6 adjust keys allow changing the programmed voltage from the front panel Brief taps on 100 mV 11 increment or decre ment the setting by 100 mV similarly the 10 mV 11 and 1 mV 41 step the setting by 10mV and 1mV respectively Holding any of these keys for 1 second begins an accelerating auto repeat for faster voltage changes Note that the auto repeat function will not scroll across 0 V when decreasing a positive setting or increasing a nega tive setting the auto repeat will stop at 0 V To reverse the polarity the key must be released and then re pressed to resume auto repeat Note that the programmed voltage can be modified independent of the on off state of the SIM928 Adjusting the voltage while in the On SIM928 Isolated Voltage Source SRS Getting Started 1 2 2 Battery 1 2 2 1 Battery cycle state causes the output voltage to change in real time When the programmed voltage V lt 1 999 V the display shows the full settable resolution of the SIM928 At greater voltages V gt 1 999 V the least significant digit shown corresponds to 10 mV It is still possible to m
25. erial interface Since the batteries can only supply unipolar 24 V polarity inversion is implemented with a relay switch K501 K502 by commutating the output terminals The module s firmware makes sure that polarity switching only happens when the regulator output voltage is 0 V A passive output filter L501 L502 C506 C507 limits output noise and increases stability for passive capacitive and inductive loads The SIM928 display is fully static to minimize noise Display and LEDs are driven and buttons are read by shift registers which hold their state without firmware update The microcontroller only reads from and writes to these registers when display updates are necessary or the user presses one of the buttons ASRS SIM928 Isolated Voltage Source 3 2 Parts List 3 2 Parts List Reference SRS P N Value Reference SRS P N Value Reference SRS P N Value B301 B306 6 00635 NiMH 9V 8cell Q209 3 00601 MMBT3904LT1 R615 4 01464 240 C101 5 00106 9 0 50P Q501 Q503 Q614 3 01421 MMBT2222 R617 R620 4 00849 100K C102 5 00366 18P Q602 Q607 Q609 3 01152 FZT758 R618 4 01544 510K C103 5 00376 120P QN201 QN204 3 01153 NDC7002N R621 4 01489 2 7K C104 5 00368 27P QN205 QN207 QN502 3 01154 MBT3904DW1T1 R623 4 00859 150K C105 C107 C109 C115 5 00299 1U QN602 QN604 QN606 R629 4 01447 47 C119 C125 C127 C129 QN611 R630 R631 4 01463 220 C301 C401 C404 C502 QN206 QN208 QN503 3 01419 MBT3906DW1T1 R632 R633 4 01406 0 C602 C616 QN603 QN605 R634 4
26. gister is cleared at power on 2 5 7 Overload Status OVCR The Overload Condition Register consists of 3 single bit monitors of conditions within the SIM928 Bits in the OVCR reflect the real time values of their corresponding signals Reading the entire register or individual bits within it does not affect the OVCR Weight Bit Flag 1 0 Overload 2 1 Overvoltage TRIP 4 2 Battery Switch 8 3 Battery Fault 16 4 undef 0 32 5 undef 0 64 6 undef 0 128 7 undef 0 Overload The output driver reached its current limit 15 mA Overvoltage TRIP The protection circuitry tripped off This happens if the voltage across the outputs exceeds 25 V and typically can only occur if an external voltage is applied to the instrument Battery Switch Indicates a battery switch over event has occured either due to the On battery being depleted or a user initiated Battery Over ride event Battery Fault Indicates a gross battery failure such as no battery installed Detected at power on only 2 5 8 Overload Status OVSR The Overload Status Register consists of latching event flags that correspond one to one with the bits of the OVCR see above Upon the transition 0 gt 1 of any bit within the OVCR the corresponding bit in the OVSR becomes set Bits in the OVSR are unaffected by the 1 0 transitions in the OVCR and are cleared only by reading or with the CLS command Reading a sin
27. gle bit with the OVSR i query clears only bit i SIM928 Isolated Voltage Source ASRS 2 22 Remote Operation 2 5 9 Overload Status Enable OVSE The OVSE acts as a bitwise AND with the OVSR register to produce the single bit OVSB message in the Status Byte Register SB It can be set and queried with the OVSE command This register is cleared at power on SRS SIM928 Isolated Voltage Source 3 Parts Lists and Schematics This chapter presents a brief description of the SIM928 circuit design A complete parts list and circuit schematics are included In This Chapter 3 1 Circuit Description css 3 2 3 1 1 Microcontroller 3 2 3 1 2 Battery charger 24 a da Oe e 3 2 3 1 3 Battery pack lt a ab ca aa eae ee 3 5 3 1 4 Isolated voltage regulator stage 3 5 3 1 5 Display and buttons 3 6 32 Parts Listen edi eres ma He ek ES a 3 7 3 3 Schematic Diagrams 3 7 Circuitry 3 1 3 1 1 Circuit Description The SIM928 isolated voltage source contains five distinct circuit blocks 1 a microcontroller 2 a battery charger circuit 3 the battery pack 4 an isolated voltage regulator circuit and 5 a front panel display Microcontroller The single chip microcontroller U103 controls the battery charger the isolated voltage regulator the display and responds to remote serial commands 3 1 2 Battery charger The SIM928 battery pack cont
28. ipation like the SIM928 evenly over the mainframe slots In any case the effects on actual lifetime should be small 3 1 2 3 Battery voltage monitoring While the battery is connected to the charger circuit its cathode is referenced to 15 V A battery voltage monitor made of R216 R217 U203 and QN204 level shifts the battery anode voltage to comply with the microcontrollers internal ADC input range of 0 V to 5V The circuit is essentially a precision current mirror built with a 2 5 V voltage reference The mirrored current creates a voltage drop across sense resistor R119 which is referenced to the microcontroller ADC s voltage reference generated by U105 The circuit has a battery voltage range of approx 20 V 35 V and is factory calibrated to have millivolt offset voltage and drift The microcontroller s 10 bit internal ADC achieves a resolution of approx 15mV LSB which is further increased by averaging The effective voltage resolution per NiMH cell is better than 100 uV allowing it to follow battery charging very precisely 3 1 2 4 Switches and voltage regulators The batteries are connected to the charger and the isolated voltage regulator through relays K201 K204 The microcontroller algorithm makes sure that only combinations of switches can be activated which isolate the charger from the isolated output stage Coupling between input and output is therefore purely capacitive albeit the capacitance of approx 40pF changes by
29. iving the Device Clear the interface is reset to 9600 baud and CONS mode is turned OFF Note that this only resets the communi cation interface the basic function of the SIM928 is left unchanged to reset the instrument see RST ASRS SIM928 Isolated Voltage Source 2 4 Commands 2 4 Commands 2 4 1 Command syntax tokens This section provides syntax and operational descriptions for remote commands The four letter mnemonic shown in CAPS in each command se quence specifies the command The rest of the sequence consists of parameters Commands may take either set or query form depending on whether the character follows the mnemonic Set only commands are listed without the query only commands show the after the mnemonic and optionally query commands are marked with a Parameters shown in and are not always required Parameters in are required to set a value and are omitted for queries Parameters in are optional in both set and query commands Parameters listed without any surrounding characters are always required Do not send or or as part of the command Multiple parameters are separated by commas Multiple commands may be sent on one command line by separating them with semi colons so long as the input buffer does not overflow Commands are terminated by either CR or LF characters Null commands and whitespace are ignored Execution of c
30. mination SIM928 Isolated Voltage Source 4 SRS 2 4 Remote Operation 2 2 Alphabetic List of Commands CLS 2 11 Clear Status ESE 1 1 j 2 12 Standard Event Status Enable ESR 1 2 12 Standard Event Status IDN 2 14 Identify OPC 2 14 Operation Complete RST 2 13 Reset SRE i j 2 12 Service Request Enable STB 1 2 12 Status Byte B BATS 2 10 Battery State BAUD i 2 11 Baud Rate BCOR 2 9 Battery charger override BIDN z 2 10 Battery Identification C CESE LIU 2 12 Communication Error Status Enable CESR i 2 12 Communication Error Status CONS z 2 14 Console Mode E EXON z 2 9 Excitation On Off F FLOW z 2 11 Flow Control L LBTN 2 15 Button LCME 2 15 Device Error LEXE 2 14 Execution Error O OPOF 2 9 Output Off OPON 2 9 Output On OVCR i 2 13 Overload Condition OVSE LIU 2 13 Overload Status Enable OVSR i 2 13 Overload Status P PARI z 2 11 Parity ASRS SIM928 Isolated Voltage Source 2 2 Alphabetic List of Commands PSTA z 2 13 Pulse STATUS Mode T TERM z TOKN z 2 16 Response Termination 2 16 Token Mode V VOLT f 2 9 Voltage SIM928 Isolated Voltage Source ASRS 2 6 Remote Operation 2 3 Introduction Remote operation of the SIM928 is through a simple command lan guage documented in this chapter Both set and query forms of most commands are
31. n the PC TXD directly to TD and similarly RTS RTS and CTS CTS In other words a null modem style cable is not needed Although the serial interface lines on the DB 15 do not satisfy the minimum voltage levels of the RS 232 standard they are typically compatible with desktop SIM928 Isolated Voltage Source personal computers SRS Getting Started 1 3 2 2 Serial settings To interface directly to the DB 9 male DTE RS 232 port typically found on contemporary personal computers a cable must be made with a female DB 15 socket to mate with the SIM928 and a female DB 9 socket to mate with the PC s serial port Separate leads from the DB 15 need to go to the power supply making what is sometimes know as a hydra cable The pin connections are given in Table 1 2 DB 15 F to SIM928 Name DB 9 F 3 7 RTS 4 8 CTS 10 3 TxD 11 2 RxD 5 Computer Ground to P S 7 gt 15VDC 13 lt 4 5VDC 15 24VDC 8 9 Ground P S return current 1 lt Signal Ground separate wire to Ground Table 1 2 SIM928 Direct Interface Cable Pin Assignments The initial serial port settings at power on are 9600 Baud 8 bits no parity 1 stop bit and RTS CTS flow control These may be changed with the BAUD FLOW or PARI commands The maximum standard baud rate that the SIM928 supports is 38400 The minimum baud rate is 110 Above 38400 the SIM928 can be set to the following non RS 232 standard b
32. ndition still exists the output will again trip off The primary connection to the SIM928 Isolated Voltage Source is the rear panel DB 15 SIM interface connector Typically the SIM928 is mated to a SIM900 Mainframe via this connection either through one of the internal Mainframe slots or the remote cable interface It is also possible to operate the SIM928 directly without using the SIM900 Mainframe This section provides details on the interface The SIM928 has no internal protection against reverse polarity missing supply or overvoltage on the power supply pins Misapplication of power may cause circuit damage SRS recommends using the SIM928 together with the SIM900 Mainframe for most applications SIM interface connector The DB 15 SIM interface connector carries all the power and commu nications lines to the instrument The connector signals are specified in Table 1 1 ASRS SIM928 Isolated Voltage Source 1 3 SIM Interface Direction Pin Signal Src gt Dest Description 1 SIGNAL GND ME SIM Ground reference for signal 2 STATUS SIM gt ME Status service request GND asserted 5 V idle 3 RTS MF SIM HW handshake 5 V talk GND stop 4 CTS SIM MF HW handshake 5 V talk GND stop 5 REF_1OMHZ MF gt SIM 10 MHz reference optional connection 6 5V MF SIM Power supply no connection in SIM928 7 15V MF gt SIM Power supply battery charger 8 Pa KTN MF gt SIM
33. nergized by internal storage batteries the control circuitry is powered externally typically by the SIM900 Mainframe Absent any external power the SIM928 will be off The SIM928 stores its operation state programmed voltage and on off configuration in non volatile memory At power on the SIM928 will return to its previous configuration after a brief system check and initialization The power on system check includes a brief test of both internal bat teries If either battery appears fully discharged it will be switched onto the internal charger circuit if both batteries appear discharged as can occur after an extended storage period the SIM928 will not be able to turn on the output stage In this case you should allow about 5 6 hours of powered operation to bring the first battery up to full charge at which time it will switch to the On state and begin charging the second battery This period can be shortened by power cycling the SIM900 Mainframe which will cause the SIM928 to re initiate it s power on checks Note that at least 1 2 hours should be allowed to provide a sufficient partial charge for reasonable operation 1 2 Front Panel Operation The front panel of the SIM928 see Figure 1 1 provides a simple op erator interface ASRS SIM928 Isolated Voltage Source 1 2 Front Panel Operation 1 3 SRS SIM928 Isolated Voltage Source Figure 1 1 The SIM928 front and rear panels 1 2 1 Adjust Routine op
34. nsiderations Batteries are chemical storage devices with finite efficiency They have temperature dependent efficiencies and life times NiMH bat teries are best operated at temperatures close to room temperature The SIM928 power dissipation and the thermal environment of the SIM900 Mainframe will lead to a temperature rise of the batteries which is slightly above room temperature Two particular heat sources will influence the battery temperature most 1 During battery discharge the module dissipates an additional 1 2W of heat and temperatures may rise somewhat This is perfectly normal and the effect can not thermally damage either electronics or batteries if the external temperature is kept within the range guaranteed by the data sheet 2 During charging NiMH batteries will heat up slightly espe cially towards the end of the charge cycle This heating is usually longer than that associated with discharge and will last several hours The maximum temperature rise is always safe and the charger algorithm will cut off the charging current before damage to the battery can occur SIM928 Isolated Voltage Source 4 SRS Circuitry Battery lifetime is temperature dependent especially at the higher end of the useful temperature range Users concerned with maximiz ing the battery lifetime who are operating several SIM928 modules in the same SIM900 mainframe can reduce maximum temperatures by spreading out modules with higher power diss
35. ommand s does not begin until the command terminator is received Token parameters generically shown as Z in the command de scriptions can be specified either as a keyword or integer value Command descriptions list the valid keyword options with each keyword followed by its corresponding integer value For example to set the response termination sequence to CR LF the following two commands are equivalent TERM CRLF or TERM 3 For queries that return token values the return format keyword or integer is specified with the TOKN command SIM928 Isolated Voltage Source 4 SRS 2 8 Remote Operation 2 4 2 Notation 2 4 3 Examples The following table summarizes the notation used in the command descriptions symbol definition ij Integers f Floating point values Z Literal token Required for queries illegal for set commands var Parameter always required var Required parameter for set commands illegal for queries var Optional parameter for both set and query forms Each command is provided with a simple example illustrating its usage In these examples all data sent by the host computer to the SIM928 are set as straight teletype font while responses received the host computer from the SIM928 are set as slanted teletype font The usage examples vary with respect to set query optional param eters and token formats These examples are not exhaustive but are intended to provide a conv
36. pen spade lugs for 8 studs 0 165 minimum opening The lower green terminal is tied to the SIM928 chassis and is avail able for user grounding Either output terminal may be tied to chassis ground if desired SIM928 Isolated Voltage Source 4 SRS 1 6 Getting Started 1 2 3 1 1 2 3 2 Overvoltage TRIP Output Overload 1 3 SIM Interface 1 3 1 CAUTION The SIM928 is specified to maintain its programmed voltage dif ference between the output terminals for load currents smaller than 10 mA If an low impedance load causes the output current to reach around 15 mA the output will go into current limit mode and the red OVLD indicator will turn on The SIM928 can remain in over load indefinitely and will return to its programmed output voltage as soon as the load current is reduced In addition to its current limiting circuitry the SIM928 has an over voltage sensing circuit that detects excessive voltage across the out put terminals If the voltage across the outputs exceeds 30 V this protection circuitry disconnects the output driver from the output terminals and the red Trip indicator will turn on Typically an over voltage TRIP is generated by some external voltage applied to the SIM928 across its output terminals To clear an overvoltage TRIP press On Off This will return the SIM928 to the Off state a second press of On Off will attempt to switch the instrument back on If the overvoltage co
37. r bit to j OVSE 3 PSTA 2 Example Pulse STATUS Mode Set query the Pulse STATUS Mode to Z OFF 0 ON 1 When PSTA ON is set any new service request will only pulse the STATUS signal low for a minimum of 1 us The default behavior is to latch STATUS low until a STB query is received At power on PSTA is set to OFF PSTA OFF 2 4 8 Interface commands RST Example Reset Reset the SIM928 to default configuration The following commands are internally executed upon RST e VOLT 0 e EXON OFF RST SIM928 Isolated Voltage Source 4 SRS Remote Operation Example Console Mode Set query the Console mode to Z OFF 0 ON 1 CONS causes each character received at the Input Buffer to be copied to the Output Queue At power on and Device Clear CONS is set to OFF CONS 0 IDN Example Identify Read the device identification string The identification string is formatted as Stanford_Research_Systems SIM928 s n ver where is the 6 digit serial number and is the firmware revision level IDN Stanford Research _Systems SIM928 s n003075 ver1 1 OPC Example Operation Complete Operation Complete Sets the OPC flag in the ESR register The query form OPC writes a 1 in the output queue when complete but does not affect the ESR register OPC LEXE Example Execution Error Query the last execution
38. supported allowing the user complete control of the voltage source from a remote computer either through the SIM900 Mainframe or directly via RS 232 see Section 1 3 2 1 See Table 1 1 for specification of the DB 15 SIM interface connector 2 3 1 Power on configuration 2 3 2 Buffers 2 3 3 Device Clear The settings for the remote interface are 9600 baud with no parity and hardware flow control and local echo disabled CONS OFF Most of the SIM928 instrument settings are stored in non volatile memory and at power on the instrument returns to the state it was last in when power was removed Exceptions are noted in the com mand descriptions Reset values of parameters are shown in boldface Incoming data from the host interface is stored in a 32 byte input buffer Characters accumulate in the input buffer until a command terminator either CR or LF is received at which point the mes sage is parsed and executed Query responses from the SIM928 are buffered in a 128 byte output queue If the input buffer overflows then all data in both the input buffer and the output queue are discarded and an error is recorded in the CESR and ESR status registers The SIM928 host interface can be asynchronously reset to its power on configuration by sending an RS 232 style break signal From the SIM900 Mainframe this is accomplished with the SRST command if directly interfacing via RS 232 then use a serial break signal After rece
39. tus Bit Indicates whether one or more of the enabled events in the Standard Event Status Register is true Master Summary Status Indicates whether one or more of the enabled status messages in the Status Byte register is true Note that while STATUS is released by the STB query MSS is only cleared when the underlying enabled bit message s are cleared Communication Error Summary Bit Indicates whether one or more of the enabled flags in the Communication Error Status Register has become true Bits in the Status Byte are not cleared by the STB query These bits are only cleared by reading the underlying event registers or by clearing the corresponding enable registers 1 but see the PSTA command ASRS SIM928 Isolated Voltage Source 2 5 Status Model 2 5 2 Service Request Enable SRE Each bit in the SRE corresponds one to one with a bit in the SB register and acts as a bitwise AND of the SB flags to generate the MSS bit in the SB and the STATUS signal Bit 6 of the SRE is undefined setting it has no effect and reading it always returns 0 This register is set and queried with the SRE command This register is cleared at power on 2 5 3 Standard Event Status ESR The Standard Event Status register consists of 8 event flags These event flags are all sticky bits that are set by the corresponding event and cleared only by reading or with the CLS command Reading a single bit with the ESR i q
40. uery clears only bit i Weight Bit Flag 1 0 OPC 2 1 INP 4 2 OYE 8 3 DDE 16 4 EXE 32 5 CME 64 6 URO 128 7 PON OPC INP OYE DDE EXE CME URQ PON Operation Complete Set by the OPC command Input Buffer Error Indicates data has been discarded from the Input Buffer Query Error Indicates data in the Output Queue has been lost Device Dependent Error Indicates a SIM928 had a delayed execution error due to an illegal mode state The error code can be queried with LDDE Execution Error Indicates an error in a command that was successfully parsed Out of range parameters are an example The error code can be queried with LEXE Command Error Indicates a parser detected error The error code can be queried with LCME User Request Indicates a front panel button was pressed Power On Indicates that an off to on transition has occurred SIM928 Isolated Voltage Source ASRS 2 20 Remote Operation 2 5 4 Standard Event Status Enable ESE The ESE acts as a bitwise AND with the ESR register to produce the single bit ESB message in the Status Byte Register SB It can be set and queried with the ESE command This register is cleared at power on 2 5 5 Communication Error Status CESR The Communication Error Status register consists of 8 event flags each of which is set by the corresponding event and cleared only by reading or with the CLS
41. uses the STATUS signal to be deasserted Note that STB i will not clear STATUS even if bit i is the only bit presently causing the STATUS signal STB 16 SRE i i Example Service Request Enable Set query the Service Request Enable register bit i to j SRE 0 1 ESR i Example Standard Event Status Reads the Standard Event Status Register bit Upon executing ESR the returned bit s of the ESR register are cleared ESR 64 ESE 11 4 Example Standard Event Status Enable Set query the Standard Event Status Enable Register bit i to j ESE 6 1 ESE 64 CESR i Example Communication Error Status Query Communication Error Status Register for bit Upon executing a CESR query the returned bit s of the CESR register are cleared CESR 0 CESE 1 101 Example Communication Error Status Enable Set query Communication Error Status Enable Register bit i to j CESE 0 ASRS SIM928 Isolated Voltage Source 2 4 Commands OVCR 1 Example Overload Condition Query Overload Condition Register for bit i OVCR 1 OVSR 1 Example Overload Status Query Overload Status Register for bit Upon executing a OVSR query the returned bit s of the OVSR register are cleared OVSR 1 OVSE i Example Overload Status Enable Set query Overload Status Enable Registe
42. vent register If any bit position is set in an event register while the same bit position is also set in the enable register then the corresponding summary bit message is set Enable register names end with SE Communication Error Status DCAS Device Clear Beb CTSH CTS Halted og Status Byte Overload Status Figure 2 1 Status Register Model for the SIM928 SIM928 Isolated Voltage Source ASRS 2 18 Remote Operation 2 5 1 Status Byte SB The Status Byte is the top level summary of the SIM928 status model When masked by the Service Request Enable register a bit set in the Status Byte causes the STATUS signal to be asserted on the rear panel SIM interface connector Typically STATUS remains asserted low until a STB query is received at which time STATUS is deasserted raised After clear ing the STATUS signal it will only be re asserted in response to a new status generating condition Weight Bit Flag 1 0 OVSB 2 1 undef 0 4 2 undef 0 8 3 undef 0 16 4 IDLE 32 5 ESB 64 6 MSS 128 7 CESB OVSB IDLE ESB MSS CESB Overload Status Summary Bit Indicates whether one or more of the enabled flags in the Overload Status Register has become true Indicates that the Input Buffer is empty and the command parser is idle Can be used to help synchronize SIM928 query responses Event Sta
43. xt few seconds the standby battery will be switched in and the previously On battery will be switched to the standby Ready state not to the charger where it will remain 1 2 2 3 Service batteries The nickel metal hydride battery packs used in the SIM928 have a finite lifetime After around 1000 charge discharge cycles the re maining battery capacity is significantly reduced to restore the in strument to full performance the battery pack must be replaced The yellow service batteries indicator turns on when the battery pack has reached this limit The SIM928 will continue to operate properly with reduced capacity batteries the only effect will be the battery switch over will occur more frequently It is also possible if a SIM928 is left in storage for several years with out operation that the batteries will have lost a significant fraction of their capacity due to aging In this case the yellow service batteries indicator will not turn on but the user may notice a shorter period between battery charge cycles The manufacture date of the battery pack can be determined with the remote BIDN query Replacement battery packs can be ordered from Stanford Research Systems 1 2 3 Output The SIM928 output voltage is available at the front panel between the red and black banana jack binding posts These connectors accept standard 0 175 in Banana plugs The binding post accomo dates wire leads up to 12 AWG as well as o
44. zed modifications to this instrument The SIM928 is a single wide module designed to be used inside the SIM900 Mainframe Do not turn on the power until the module is completely inserted into the mainframe and locked in place 111 iv General Information Symbols you may Find on SRS Products Alternating current Caution risk of electric shock Frame or chassis terminal Caution refer to accompanying documents Earth ground terminal SRS SIM928 Isolated Voltage Source General Information Notation A WARNING A CAUTION The following notation will be used throughout this manual A warning means that injury or death is possible if the instructions are not obeyed A caution means that damage to the instrument or other equipment is possible Typesetting conventions used in this manual are e Front panel buttons are set as Button Adjust AY is shorthand for Adjust 4 amp Adjust 1 e Front panel indicators are set as Overload e Remote command names are set as IDN e Literal text other than command names is set as OFF Remote command examples will all be set in monospaced font In these examples data sent by the host computer to the SIM928 are set as straight teletype font while responses received by the host computer from the SIM928 are set as slanted teletype font SIM928 Isolated Voltage Source 4 SRS vi General Information Specifications Performance Characteristics
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