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Model 197A Autoranging Microvolt DMM User's Manual

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1. Figure 3 6 Connections for DC Current Verification 2000mA to 20A Figure 3 7 Connections for AC Current Verification 2004A to 2000MA Figure 3 8 Connections for AC Current Verification 2000mA to 10A SECTION 4 Maintenance Figure 4 1 Model 197A Miscellaneous Parts 60 0c ccc eee eee eee hehe Figure 4 2 Display Assembly Exploded View 0 cece e cence I Figure 4 3 DC Voltage Calibration Configuration 00 0 0 0 cece een een hh Figure 4 4 AC Voltage Calibration Configuration 2 0 0 0 0c cee cc cece ehe Figure 4 5 200 2k and 20k Four Wire Resistance Calibration 2 0 cece cere cence eevee eaae Figure 4 6 200k 2M and 20M Two Wire Resistance Calibration List of Tables SECTION 2 Bench Operation Table 2 1 Table 2 2 Table 2 3 Table 2 4 Table 2 5 Table 2 6 Table 2 7 Table 2 8 Error Messages sp s og om mmi 9 o q n Model 197A Maximum Allowable Inputs 8 cece eee Resistance Ranges dimmi momo RR Uh mos hose dh mom d sv d ov v oa ooh Pos Pom do o d oe dorem moss my ooo i dB Specifications for DC Volts 60002 Ref aan dB Specifications for A
2. KEITHLEY 197A AUTORANGING MICROVOLT DMM DC Voltage Calibration Configuration Hi Output DC Voltage Lo Output Calibrator Model 5440 Model 197A as shown in Figure 4 4 Steps 1 6 must be per formed in the exact sequence listed 1 2 3 B ON 4 6 6 Select the AC voltage function and the 200mV range Set the calibrator to output 190 000mV at 500Hz Adjust the display using the STO CLR and RCL but tons to read 190 000mV AC Press the dB button and verify that the dB annunciator is displayed Set the calibrator to output 19 000mV at 500Hz Adjust the displayed reading for 19 000mV Press the REL button and verify that the dB annunciator is off Repeat steps 2 and 3 for the remaining ranges using Table 4 4 as a guide Store the new cal constants before proceeding See para graph 4 6 8 Frequency Compensation The following section is to be used to determine if fre quency compensation should be performed on the Model 197A and to perform frequency compensation if necessary This procedure requires the Model 197A to be warmed up for at least one hour Note that this section is not to be used to verify that the Model 197A AC Voltage function is within specifications If desired refer to Section 3 Perfor mance Verification WARNING Steps 1 through 4 require the use of high volt age Take care not to come into contact with live circuits that could cause personal in
3. 4 If the IEEE interface was installed reinstall the interface as follows A Install the rear standoffs B Position the interface board above the rear stand offs WARNING Do not push down on J1008 The male connec tor pins will pass through J1008 and may cause personal injury C Guide the terminals of P1008 and firmly push down on that end of the board to mate the connectors D Push down on the other side of the interface board until it snaps onto the rear most standoff Make sure the board is properly seated on the other two standoffs E Reinstall the modified top cover 5 Reinstall the top cover as explained in paragraph 4 2 4 5 2 Current Fuse Replacement The current fuse protects the 2004A through 2000mA ranges from an input current greater than 2A To replace the current fuse perform the following steps 1 Turn off the power disconnect the power line and remove the test leads 2 Place the end of a flat blade screwdriver into the slot of the fuse holder on the front panel Carefully press in and rotate the fuse carrier one quarter turn counter clockwise Release pressure remove the fuse and the fuse carrier from the front panel 3 Remove the defective fuse and replace it with the fol lowing type 2A 250V 3AG normal blow Keithley Part Number FU 13 or equivalent CAUTION Use only the recommended fuse type If a fuse with a higher current rating is installed instru ment damage may occur upo
4. To save calibration constants after out appears on the display slide the calibration switch to ENABLED Press REL and dB simultaneously until CAL appears on the display Then simultaneously press REL and dB until Stor is displayed The calibration constants are now stored and the Model 197A is ready for normal operation KEITHLEY Service Form Model No Serial No Date Name and Telephone No Company List all control settings describe problem and check boxes that apply to problem Ql Intermittent A Analog output follows display Particular range or function bad specify IEEE failure 1 Obvious problem on power up Batteries and fuses are OK Front panel operational 0 All ranges or functions are bad LJ Checked all cables Display or output check one Drifts Unable to zero 21 Unstable Will not read applied input A Overload Calibration only Certificate of calibration required Data required attach any additional sheets as necessary Show a block diagram of your measurement system including all instruments connected whether power is turned on or not Also describe signa source Where is the measurement being performed factory controlled laboratory out of doors etc What power line voltage is used Ambient temperature E Relative humidity Other Any additional information If special modifications have been made by the user please describ
5. Bench Operation by the noise present The displayed noise of the Model 197A is 1 54V peak to peak This noise is inherent in the Model 197A and is the minimum amount present in all measurements The 1 5yV of noise is due to the instru ment voltage noise The noise at the Model 197A input in creases beyond this minimum when the noise current passes through a resistor thus generating a voltage noise The total noise becomes a function of the source resis tance and is given by the equation en iR e where n total noise input input voltage noise of the Model 197A in input current noise Rs parallel combination of source resistance and input impedance Johnson noise of the source resistance Even on the most sensitive range the noise due to the current is not applicable until Rs reaches approximately Thus for an of OQ to 1MQ the noise at the input is the inherent 1 54 V peak to peak Beyond 1MQ the noise due to Rs becomes a limiting factor in the measurement Therefore it is recommended that for sensitive measure ments R be kept relatively low if possible below 1MQ Asan example of determining er noise voltage generation due to Johnson noise of source resistance assume that the Model 197A is connected to a voltage source with an internal resistance of 1MQ At a room temperature of 20 C 293K the p p noise voltage generated over a bandwidth of 1Hz will be e 6 35 x 109 VR
6. For 4 terminal measurements rated accuracy can be obtained as long as the maximum lead resistance does not exceed the values listed in Table 2 3 For 2 terminal or 4 terminal measure ments on the 200Q range zero must be set by the REL function to obtain rated accuracy For best results on the 2000 2kQ and 20kQ ranges it is recommended that 4 terminal measurements be made to eliminate errors caused by the voltage drop across the test leads that oc curs when 2 terminal measurements are made To make resistance measurements proceed as follows 1 Connect the test leads to the HI and LO INPUT ter minals If four wire measurements are to be made connect an additional set of leads to the OHMS SENSE terminals NOTE The Model 1641 Kelvin test lead kit is ideal for low resistance 4 terminal measurements 2 Select the ohms function 3 Select a range consistent with the expected resis tance If desired use the autorange mode for auto matic range selection 4 If readings are to be made on the 200Q range zero the instrument to obtain rated accuracy To zero the instrument for resistance measurements Short the test leads together after disconnecting them from the measured circuit If 4 wire measurements are to be made short all four test leads as shown in Figure 2 5 allow the reading to settle then press the REL button 5 For 2 wire measurements connect the instrument as shown in Figure 2 6 For 4 wire measurements use the co
7. temperature range Environmental Conditions 2 6 2 Maximum Allowable Inputs Table 2 2 lists the maximum allowable inputs for the Model 197A Table 2 1 Error Messages RAM Error Calibration Error NVRAM Failure Overrange Invalid Q Function Model 197A locks up Model 197A locks up but operation can be restored by pressing any one of the four momentary pushbuttons If restored calibration is invalid as indicated by the flashing C annunciator Overrange input applied to the Model 197A Leading minus sign indicates that input signal has a negative value AC and Q annunciators flash Correct problem by releasing out AC DC pushbutton SECTION 2 Bench Operation Table 2 2 Model 197A Maximum Allowable Inputs 1000VDC or peak AC for less than 10sec per minute 300Vrms continuous 750Vrms 1000V peak for less than 10sec per minute 300Vrms continuous Function Ranges Maximum Allowable Inputs DCV 200mV 2V 20 1000V 1000VDC or peak AC ACV 200mV 2V 107 Hz maximum 20 750V 750Vrms 1000V peak 107 Hz maximum DCA ACA 200u 2000mA 2A 250VDC or rms fuse protected 10A 10A continuous 20A for 15sec unfused Q All 450V peak AC or DC 10 seconds per minute 350Vrms continuous 2 6 5 Warm Up The Model 197A requires one hour for warm up to achieve rated accuracy 2 7 BASIC BENCH MEASUREMENTS Basic measurement techniques
8. 2 22 SECTION 2 Bench Operation A 100Q not listed in Table 2 7 so the offset must be calculated as follows 10022 6000 Offset 10 log Offset 7 78dB B Subtract 7 78 from all subsequent displayed readings on the Model 197A dBm measurements referenced to another impedance can be read directly from the display of the Model 197A by utilizing the REL feature and an accurate voltage source The basic procedure is as follows 1 Calculate or look up the equivalent voltage level Table 2 7 for OdBm at the desired reference imped ance Input that voltage level to the Model 197A With the Model 197A in the dB mode press the REL button 4 dBm measurements referenced to the desired im pedance can now be read directly from the display of the Model 197A Wh dBW Measurements dBW is defined as decibels above or below one watt ref erence The procedure is the same as that found in para graph 2 7 9 step 2 The only difference is that the refer ence point is OdBW 1W rather than OdBm 1mW dBV Measurements dBV is defined as decibels above or below 1V 0dBV point This is a voltage relationship independent of im pedance The basic procedure is to simply subtract 2 22dB Table 2 7 from all subsequent displayed read ings on the Model 197A Relative dB Measurements Just about any voltage level within the measurement limit of the Model 197A can be established as the OdB point The ba
9. 22 24 C _ 18 28 C 30V peak Output LO to earth ground 200 Q 1 2mA 0 5V 0 01 2 0 018 3 IEEE OUTPUT See BUS IMPLEMENTATION 2 10mQ 2mA 40V 0 01 2 001842 20 100 400A 40V 0 01442 0 02642 IEEE BUS IMPLEMENTATION 200 1 2 40pA 40 0 014 2 0 026 2 1972 ANALOG IEEE amp 1973A OPTIONS 2 10 Q 40V 0 02 2 0 035 2 20 100 Q 400nA 40V 010 2 0 12 2 MULTILINE COMMANDS DCL SDC GET GTL UNT UNL SPE SPD bM inin mon el SONG UNILINE COMMANDS IFC REN EOI SRQ ATN INTERFACE FUNCTIONS 581 T5 TEO L4 LEO SR RLO PPO DC1 D11 CO El PROGRAMMABLE PARAMETERS Range REL dB EOI Trigger Calibration SRQ Status Output Format Terminator Data Logger Retrieval When properly zeroed Appropriate range selected automatically in CONFIGURATION Automatic 2 or 4 terminal MAXIMUM ALLOWABLE INPUT 450V DC or peak AC 10 seconds per minute 350V rms continuous OPEN CIRCUIT VOLTAGE 45V DIODE TEST Display reads junction voltage up to 2 2V Test Current 1 6mA nominal SETTLING TIME 2 seconds to within 3 counts of final reading on range GENERAL DISPLAY Backlit x220 000 count LCD 0 45 in height polarity function range and status indication RANGING Auto or manual an DC volts AC volts and ohms manual on AC amps and DC amps AUTORANGING TIME 300ms per range average RELATIVE Pushbutton allows zeroin
10. Current Fuse Replacement sosyo oire awaqpa hehehe Rear Panel Switches tbe us AAA ERROR MESSAGES es Sd aed bel ENE hey ice bcd esed dua eee ee OPERATING CONDITIONS u eee hn a hh hen Environmental Conditions re ehh mh he emen Maximum Allowable Inputs Warm UP sece 2 222 200 a ee ea ES BASIC BENCH MEASUREMENTS PowerUp C ee da u ange er Relative Mode ae DC Voltage Measurement ee eee oe HH e hne TRMS AC Voltage Measurements ehh heme Microvolt Measurement Considerations 0 cece ee hh Resistance Measurements iiem hh tenets Current Measurements DC or AC 0 0 hahet een AC Plus DC Measurements 2 0 0 ccc cece ee hehe ha Hh ehe dB Me surements u ees ea Shae eee E Sere a dB Measurement Considerations and eee MIN MAX and 100 Point Data Logger Operation isses nemen Diode Test un un dre Wr der Ree ee LE CP RAD URS aa 2 8 2 8 1 2 8 2 2 8 3 2 8 4 TRMS CONSIDERATIONS e a e haer He o eed anaq AC Voltage Offset u acct tes ten oe Ea Y ERES a TRMS Measurement Comparison Crest Factor Mm e Extended Frequency Response hash nhe nre SECTION 3 Performance Verification 3 1 3
11. Reinstall the top cover SECTION 4 Maintenance Table 4 4 AC Voltage Calibration 5 Set the calibrator to output L9kQ Adjust the display for a reading of 1 90000kO Calibrator Calibrator Model 197A 6 Press the REL button and note that the REL annunciator Range Voltage Frequency Reading turns off 200mV 190 000mV 500Hz 190 000mV 7 Select the 20kQ range and set the resistance calibrator 200mV 19 000mV 500Hz 19 000mV output zero ohms short Press REL REL annunciator 2 V 1 90000 V 500Hz 1 90000 V turns on 20 V 19 0000 V 500Hz 19 0000 V 8 Set the calibrator output to 19kQ Adjust the display for 200 V 190 000 V 500Hz 190 000 V a reading of 19 0000 Press REL REL annunciator turns off 4 6 7 Resistance Calibration 9 Repeat steps 7 and 8 for the 200k 2M and 20M ranges using Table 4 5 as a guide For these ranges use the con With the Model 197A in the calibration mode C annun figuration shown in Figure 4 6 ciator on select the ohms function and connect the calibra tor to the Model 197A as shown in Figure 4 5 Use the Table 4 5 Resistance Calibration following procedure and refer to Table 4 5 to calibrate the VES ohms function Model 1974 1 Select the 200 2 range and set the resistance calibrator to Range Ser bar Voltage Reading output zero ohms short 2000 190 Q 190 000 Q 2 Press the REL button on the Model 197A The REL 2kQ 1 9kQ 1 90000kQ annunciator appears on the display and the displ
12. 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 must 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 ap plied to the device under test Safe operation requires the use of a lid interlock Ifa D screw is present connect it to safety earth ground using the wire recommended in the user documentation The IN symbol on an instrument indicates that the user should re fer to the operating instructions located in the manual The symbol on an instrument shows that it can source mea sure 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 infor mation 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 warranty 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 main
13. for using the Model 197A to measure AC and DC volts resistance AC and DC current and dB are covered in the following paragraphs Also included is the operation of the minimum maximum and 100 point data logger WARNING Before operating the Model 197A observe all previously mentioned safety precautions When testing high energy power circuits fol low the instructions found in paragraph 2 2 Failure to observe these and other safety pre cautions mentioned in this manual could result in severe injury or death The LO terminal on the Model 197A is designed to float above earth ground to avoid ground loop problems WARNING Hazardous voltage may be applied to the LO terminal The maximum allowable voltage between the LO terminal and chassis ground is 500V Destruction of insulation which could present a shock hazard may occur if the 500V maximum is exceeded CAUTION Do not exceed the maximum input limits shown in Table 2 2 2 7 4 Power up NOTE The software revision level of the Model 197A can be displayed upon power up by running the diagnostic program Turn on the Model 197A by pressing in the ON OFF switch All zeroes are briefly displayed before going into the measurement mode 2 7 2 Relative Mode When the relative mode is selected with an on scale read ing on the display the following occurs 1 The REL annunciator is displayed 2 The next reading is stored 3 This reading is algebraically subtracted from al
14. ter minals for all volt ohm milliamp and dB measurements 10A and LO White and Black Use this pair of termi nals for measuring current up to 10A up to 20A for 15 seconds OHMS Sense HI and LO Use this pair of terminals along with HI and LO input for four wire resistance measurements 2 4 4 Current Fuse Replacement The current fuse protects the 2004A through 2000mA ranges from an input current greater than 2A To replace the current fuse perform the following steps NOTE The front panel current fuse F101 is rated at 2A With 220 000 count display the 2A range can momentarily approx one minute read 2 2A before the fuse will blow This 10 over range will not harm the instrument 1 Turn off the power and disconnect the power line and test leads 2 Place the end of a flat blade screwdriver into the slot in the fuse holder on the front panel Press in slightly SECTION 2 Bench Operation and rotate the fuse carrier on quarter turn counterclock wise Release pressure and remove the fuse carrier and the fuse 3 Remove the defective fuse and replace it with the fol lowing type 2A 250V 3AG normal blow Keithley part number FU 13 or equivalent CAUTION Use only the recommended fuse type If a fuse with a higher current rating is installed instru ment damage may occur 2 4 5 Rear Panel Switches The rear panel of the Model 197A is shown in Figure 2 2 Note that if an IEEE 488 interface modu
15. the AC DC button V is still selected The AC annun ciator turns off 5 Select the autoranging OHMS by pressing in the AUTO and Q buttons DC must still be selected The Q omega symbol is displayed Press the AC DC button in means select AC and note the Err message is displayed This indicates an invalid mode 6 Select AC or DC current by setting the AC DC button accordingly and pressing in the A button The annunciator that reflects the selected mode in displayed Note that current will not autorange The 10A and LO terminals must be used on the 10A range 7 Select dB by selecting AC or DC volts and press ing the dB button The dB annunciator will turn on and the default reference impedance 600 2 will be displayed momentarily Pressing dB a sec ond time disables the dB measurement mode To select an alternate dB reference impedance enable dB as previously described but hold in the dB button to scroll through the alternate imped ance selections Release the dB button when the desired dB reference impedance is displayed When finished again press dB to exit the dB mode 8 The REL relative feature can be used with any measurement function Volts Amps Ohms or dB For example select the ohms function and autorange The display reads approximately 000 140 which is the test lead resistance Press the REL button The REL annunciator is turned on and the display reads 000 0000 The relative level of 000 14Q wi
16. to exercise the warranty contact your Keithley representative or the factory to determine the proper course of action Keithley Instruments maintains service facilities in the United States United Kingdom and throughout Europe Information concerning the application operation or service of your instrument may be directed to the applications engineer at any of these locations Check the inside front cover for addresses 1 4 MANUAL ADDENDA Information concerning improvements or changes to this instrument which occur after the printing of this manual will be found on an addendum sheet included with this manual Be sure to review these changes before attempting to operate or service the instrument 1 5 SAFETY SYMBOLS AND TERMS The following safety symbols and terms are used in this manual or found on the Model 197A The symbol A on the instrument denotes the user shouid refer to the operating instructions in this manual The symbol AN on the instrument denotes that a poten tial of 1000V or more may be present on the terminal s Standard safety practices should be observed when such dangerous levels are encountered The WARNING heading used in this manual explains dan gers that could result in personal injury or death The CAUTION heading used in this manual explains haz ards that could damage the instrument 1 2 1 6 SPECIFICATIONS Detailed Model 197A specifications may be found preced ing the table of contents of this
17. with the addition of the Model 1973A or Model 1972A IEEE 488 interface IEEE operation is covered in the Model 1973 1972 Manual The optional battery pack Model 1978 is also covered in this section 2 2 HIGH ENERGY CIRCUIT SAFETY PRECAUTIONS To optimize safety when measuring voltage in high energy distribution circuits read and use the directions in the fol lowing warning WARNING Dangerous arcs of an explosive nature in a high energy circuit can cause severe personal injury or death If the meter is connected to a high energy circuit when set to a current range low resistance range or any other low impedance range the circuit is virtually shorted Dangerous arcing can result even when the meter is set to a voltage range if the minimum voltage spacing is reduced When making measurements in high energy circuits use test leads that meet the following requirements Test leads should be fully insulated Only use test leads that can be connected to the circuit e g alligator clips spade lugs etc for hands off measurements Do not use test leads that decrease voltage spacing This diminishes arc protection and creates a hazardous condition Use the following sequence when testing power circuits 1 De energize the circuit using the regular installed connect disconnect device such as the circuit breaker main switch etc 2 Attach the test leads to the circuit under test Use appro priate safety rated test lead
18. x f 6 35 x 107 x 109 1 0 635 Thus it is clear that optimum microvolt measurements with the Model 197A are possible with source resistance as high as 1MQ However this resolution will not be real ized unless shielding is employed Shielding The Model 197A is insensitive to AC volt ages superimposed upon a DC signal at the input termi nals However AC voltages which are extremely large compared with the DC signal may erroneously produce a DC output Therefore if there is AC interference the cir cuit should be shielded and the shield connected to the Model 197A ground particularly for low level sources Improper shielding can cause the Model 197A to behave in one or more of the following ways 1 Unexpected offset voltages 2 Inconsistent readings between ranges 3 Sudden shifts in reading To minimize pick up keep the voltage source and the Model 197A away from strong AC magnetic sources The voltage induced due to magnetic flux is proportional to the area of the loop formed by the input leads Therefore minimize the loop area of the input leads and connect each signal at only one point Thermal EMFs Thermal em s thermoelectric poten tials are generated by thermal differences between two junctions of dissimilar metals These can be large com pared to the signal which the Model 197A can measure Thermal emfs can cause the following problems 1 Instability or zero offset is much hi
19. 003 0 5u V 200mV 2V 20V 200V and 750V ranges 0 05 Fluke 5440 Fluke 5200A amp 5215A Fluke 5450A SECTION 4 Maintenance REL dB DATA LOGGER STOJCLH ACL POWER a Oz D Figure 4 3 The calibration mode is indicated by the C annuncia tor on the front panel display 2 Select the 200mV range short INPUT HI and LO and press the REL button REL annunciator is on 3 Set the calibrator to output 190 000mV 4 Adjust the display to read 190 000 with the use of the STO CLR and RCL buttons The STO CLR button increments the displayed reading The RCL button dec rements the displayed reading The longer either button is held in the faster the displayed reading is modified 5 Select the next range V and set the calibrator output to 1 90000V 6 Repeat step 4 to read 1 90000 7 Reverse the calibrator leads in order to output 1 90000V 8 Repeat step 4 to read 1 90000 9 Repeat steps 2 through 4 for the remaining DC voltage ranges listed in Table 4 3 Table 4 3 DC Voltage Calibration Range Calibrator Voltage Model 197A Reading 200mV B 190 000mV T 190 000mV 2 1 90000 V 190000 V 2 V 1 90000 V 1 90000 V 20 V 19 0000 V 19 0000 V 200 V 190 000 V 190 000 V 1000 V 1000 00 V 100000 V 4 6 5 AC Voltage Calibration With the Model 197A still in the calibration mode annunciator on connect the AC voltage calibrator to the
20. 1 1 2 1 3 14 1 5 1 6 1 7 1 8 1 9 1 10 SECTION 2 Bench Operation 2 1 22 23 2 3 1 2 3 2 2 3 3 24 2 4 1 242 2 4 3 2 4 4 2 4 5 2 5 2 6 2 6 1 2 6 2 2 6 3 2 7 2 7 1 2 7 2 2 7 3 2 7 4 2 7 5 2 7 6 2 7 7 2 7 8 2 7 9 2 7 10 2 7 11 2 7 12 INTRODUCTION u a Rie OU Woy eh FEATURES saa uir etude a dtes nu aci e sa e eite PU neue dS RP d WARRANTY INFORMATION 0 0 00 cee eee hase hem e erede MANUAL ADDENDA east ege rk de d ep ERE REESE GRE EOS Hawa E dee DAN PN EE SAFETY SYMBOLS AND TERMS 2 hme eme eee SPECIFICATIONS UNPACKING AND INSPECTION 0 Ih atn USING THE MODEL 197A MANUAL hh heh heh eee INITIAL OPERATION oia 4a ase nie m sedia ae aaa ati Sr ACCESSORIES ecarri ere es nee _________ ________ INTRODUCTION Ea ee en ih ann HIGH ENERGY CIRCUIT SAFETY PRECAUTIONS PREPARATION FOR USE 0 020 ee a aa ja Line Power nee een Battery Pack Power oo ommmmmmccronoro hash rr rr ee heh hehehe Battery Haren csi dE Febr ter iE pru editt drap e tace dex widest due eR dels FRONT AND REAR PANEL FAMILIARIZATION sese IIo Display wide des kem keep eu E php gt aid cor Front Panel Contiols Dies vlan aw Re Pelea b e Rp RR Input Terminals usan ss REA ds RANT AR Creed o rae
21. 1 For currents be tween 10A and 20A specified accuracy can only be obtained when measurements are limited to a maximum of 15 seconds 2 For current measurements up to 2000mA A Connect the test leads to the INPUT HI and LO terminals of the Model 197A B Select the ACA or DCA function C Select an appropriate range for the expected cur rent The current function does not autorange D Connect the test leads to the current source as shown in Figure 2 9 Ifan overrange indication is displayed select a higher range until a normal reading is shown Use the lowest possible range to obtain the best resolution REL dB DATA LOGGER STO CLR RCL POWER e 00008 oc Figure2 9 Current Measurements up to 2000mA 2 12 Q 00 20k 200k 20m 200m 2000m 10 197A AUTORANGING MICROVOLT MICROVOLT DMM 000000 000000 Caution Maximum Input 10A Current Measurement Between 2000mA and 20A E Take the reading from the display 2 7 8 AC Plus DC Measurements Use the Model 197A to measure TRMS on a signal which has both AC and DC components 1 Measure and record the TRMS AC component as de scribed in paragraph 2 7 4 2 Measure and record the DC component as described in paragraph 2 7 3 3 Computetherms value from the following equation Enns NE pc E24c Current Source 4 Caution Maximum Input 2A 000 AUTO AUTO SECTION 2 Bench Operation 2 7 9 dB Measuremen
22. 2 3 3 34 3 5 3 5 1 3 5 2 3 5 3 3 5 4 3 5 5 INTRODUCTION ee a AA Ca Sad hae ORO u ENVIRONMENTAL CONDITIONS RECOMMENDED TEST EQUIPMENT INITIAL CONDITIONS osui p ib VERIFICATION PROCEDURE ehh hh hera hh DC Voltage Accuracy Check esses heh He nennen AC Voltage Accuracy Check sn aaa sa A VE EY AAA Resistance Accuracy Che eier DC Current Accuracy Check rines SEE en AC Current Accutacy mea rare itteni a ae een SECTION 4 Maintenance 41 4 2 43 44 4 5 4 5 1 4 5 2 4 6 4 6 1 4 6 2 4 6 3 4 6 4 4 6 5 4 6 6 4 6 7 4 6 8 INTRODUCTION VU o RR KU ana Sue na DISASSEMBLY INSTRUCTIONS hehe ee sehn BATTERY PACK Model 1978 INSTALLATION LINE VOLTAGE SELECTION ahh FUSE REPLACEMENT iia rh an nenn ann ol Rl o a CIR A Line Fuse e coro eect nehme tnra Current Fuse Replacement 000 cece teen cette teen ehe hee nnn FRONT PANEL CALIBRATION Recommended Calibration Equipment Environmental Conditions hr Calibration SWC a ES a Qr PES EUER MI V ERU ER dd DC Voltage Calibration X di eed eR PO OG EREVRE Ea
23. 400 RANGE RESOLUTION RESISTANCE 22 24 C 18 28 C 2N 200V 1 00 100 0 35 100 0 6 200 1 5 250 3 400 200 mV 1 uv gt 1 GQ 0 607 2 0 016 3 750 V 1 25 100 0 5 4 100 1 0 200 1 8 250 3 400 zv 10 pV gt l GQ 0 005 2 0 011 2 Above 1800 counts Above 18000 counts 20 V 100 pV 0 006 2 0 015 3 MAXIMUM ALLOWABLE INPUT 750V rms 1000 peak 10 seconds per minute 200mV and 2V 200 V 10 0 006 2 0 015 2 ranges 300V rms continuous 107 maximum 1000 V 10mV 10 0 007 2 0 015 2 Relative to calibration accuracy When properly zeroed NMRR gt 60dB at 50Hz 60Hz 0 196 MAXIMUM ALLOWABLE INPUT 10007 DC or peak AC 10 seconds per 3dB BANDWIDTH 300kHz typical INPUT IMPEDANCE 1MQ paralleled by lt 75pF on 200V and 750V ranges 1 1MQ on 200mV 2V and 20V ranges Capacitively coupled SETTLING TIME second within 0 1 of final reading on range minute on 200mV and 2V ranges 300V rms continuous dB MODE ref 6000 SETTLING TIME 1 second to within 3 counts of final reading on range ACCURACY dBm dB MODE ref 6000 Accuracy 0 02dB count above 78dBm RANGE INPUT 20Hz 10kHz 10kHz 20kHz 20kHz S0kHz SOkHzlO0kHz RESOLUTION 0 01dB above 0 796 of range er 0 18 0 18 0 28 0 50 IMPEDANCE 50 75 93 135 300 or 600 ohms default 200mV 20 mV to 200 mV 0 18 018 028 085 panel selectable 32 to 12dBm DC AMPS MAXIMUM ACCURACY 1
24. 979 00 1983 00 1983 00 to to to 2021 00 2017 00 2017 00 5 0000 A 4 9150 4 9400 4 9400 to to to 5 0850 5 0600 5 0600 Not to exceed 1kHz SECTION 4 Maintenance 4 1 INTRODUCTION This section contains installation service and calibration information for the Model 197A and Model 1978 Fuse replacement line voltage selection and troubleshooting pro cedures are also included in this section WARNING The procedures described in this section are intended for use by qualified service personnel only Do not perform these procedures unless qualified to do so Many of the steps covered in this section expose the individual to potentially lethal voltages that could result in personal injury or death if normal safety precautions are not observed 42 DISASSEMBLY INSTRUCTIONS If it is necessary to troubleshoot the instrument replace a component or install an option use the following disassem bly procedure Disassembly should be done in order that it is presented since in general each step depends on a previ ously performed procedure Most parts referred to in the following steps are shown in Figure 4 1 WARNING Disconnect the line cord and any test leads from the instrument Top Cover Removal 1 Turn off the power disconnect the line cord and remove all test leads from the terminals of the Model 197A 2 Turn the unit over and remove the four screws from the bottom of the case 3 Turn the unit over again an
25. Be sure to connect the calibrator to the 10A and LO terminals Otherwise applying the5A as specified in Table 3 5 would blow the front panel current fuse Apply 0 50000VDC to the current calibrator to out put 5 0000A Verify that the reading is within the limits specified in Table 3 5 specified in Table 3 5 10 Repeat steps 1 through 10 with negative current REL d B Hi Output DATA LOGGER STO CLR RCL Os POWER la EE 200m jm 200m 2000m 10 10 DC Voltage Calibrator Current Calibrator Model 343A Model 2500E Figure 3 5 Connections for DC Current Verification 2001A to 2000mA REL dB DATA LOGGER STOCLA POWER L 200 2k 200 SECTION 3 Performance Verification Lo Output AUTO 20k 200K AUTO 2m 20m 200m 2000m 10 er 7 0005000000 PEAK PEAK DC Voltage Calibrator Model 343A Figure 3 6 Table 3 5 Limits for DC Current Verification 197A Applied Allowable Readings DC Range DC Current 18 C to 28 C 200 00uA 199 785 to 200 215 2 00000mA 1 99785 to 2 00215 20 0000mA 19 9785 to 20 0215 200 000mA 199 585 to 200 415 2000 00mA 1995 85 to 2004 15 5 0000 A 4 9735 to 5 0265 3 5 5 AC Current Accuracy Check AC current accuracy is checked by connecting a cali brated AC current source to the HI and LO INPUT termi nals for 200UA to 2000mA 10A and LO terminals for 2000mA to 20A and then verifying that the displayed reading is within the spec
26. C Volts 6000 Ref ciis Selectable Reference Impedances isses hee Levels for Other Reference Impedances csc ana Ha Ya Ras Comparison of Average and TRMS Meter Readings scene SECTION 3 Performance Verification Table 3 1 Table 3 2 Table 3 3 Table 3 4 Table 3 5 Table 3 6 Equipment Specifications csse ee een Ress L mits for DC Voltage Verification Limits for AC Voltage Verification Limits for Resistance Verification a ee ee een hh hat ras L mits for DC Current Verification Limits for AC Current Verification SECTION 4 Maintenance Table 4 1 Table 4 2 Table 4 3 Table 4 4 Table 4 5 Input Terminal Identification isses Henne Recommended Calibration Equipment DC Voltage Calibration AC Voltage Calibration Resistance Calibration Yo OR OR Oa oe OR ua S o os a mE a o m ao POR o P n gm dono ono n ror nn etos the i ats 9 iiti ro c s Pr o t c 9 n SECTION 1 General Information 14 INTRODUCTION The Model 1974 is a six function 5 1 2 digit resolution autoranging digital multimeter with a 220 000 count LCD Liquid Crystal Display This A D range is greater than the normal 199 999 count A D us
27. KEITHLEY Model 97A Autoranging Microvolt DMM Users Manual A GREATER MEASURE OF CONFIDENCE WARRANTY Keithley Instruments Inc warrants this product to be free from defects in material and workmanship for a period of 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 IMPLIED INCLUDING ANY IMPLIED WARRANTY OF MERCHA
28. LOGGER STO CLR RCL POWER Figure 2 4 TRMS AC Voltage Measurements 2 8 offset 22uV applied signal 20mV display reading 22uV V 0004 484x 107 _ 0200000121 This offset is seen as the last digit which is not displayed on the Model 197A Therefore the offset is negligible 5 Observe the display if the OL message is shown select a higher range until a normal reading is dis played Always use the lowest possible range to ob tain the best resolution 6 Take the reading from the display NOTE See paragraph 2 8 for TRMS considerations When measuring AC signals disconnect any test leads from the OHMS SENSE terminals 2 7 5 Microvolt Measurement Considerations Accuracy Considerations For sensitive measure ments other external considerations besides the Model 197A will affect the accuracy Effects not noticeable when working with higher voltages are significant in microvolt signals The Model 197A reads only the signal received at its input therefore it is important that this signal be properly transmitted from the source The following paragraphs indicate factors which affect accuracy noise source resistance thermal emfs and stray pick up Noise and Source Resistance The limit of resolution in measuring voltages with the Model 197A is determined AC Voltage Caution Maximum Input 750V RMS 1000V pk Input Impedance 1MQ Shunted by lt 75pF SECTION 2
29. NTABILITY OR FITNESS FOR A PARTICULAR USE THE REMEDIES PRO VIDED 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 DAMAGES SHALL INCLUDE BUT ARE NOT LIM ITED 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 OH 44139 440 248 0400 Fax 440 248 6168 http www keithley com BELGIUM Keithley Instruments B V Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 CHINA Keithley Instruments China Yuan Chen Xin Building Room 705 12 Yumin Road Dewai Madian Beijing 100029 8610 62022886 Fax 8610 62022892 FRANCE Keithley Instruments Sarl 3 all e des Garays 91127 Palaiseau Cedex 01 64 53 20 20 Fax 01 60 11 77 26 GERMANY Keithley Instruments GmbH Landsberger Strasse 65 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 GREAT BRITAIN Keithley Instruments Ltd The Minster 58 Portman Road Reading Berkshire RG30 IEA 0118 9 57 56 66 Fax 0118 9 59 64 69 INDIA Keithley Instruments GmbH Flat 2B WILOCRISSA 14 Res
30. SA 14 Rest House Crescent Bangalore 560 001 91 80 509 1320 21 Fax 91 80 509 1322 Viale San Gimignano 38 20146 Milano 02 48 39 16 01 Fax 02 48 30 22 74 2FL URI Building 2 14 Yangjae Dong Seocho Gu Seoul 137 130 82 2 574 7778 Fax 82 2 574 7838 Postbus 559 NL 4200 AN Gorinchem 0183 635333 Fax 0183 630821 Kriesbachstrasse 4 8600 D bendorf 01 821 94 44 Fax 01 820 30 81 IFL 85 Po Ai Street Hsinchu Taiwan R O C 886 3 572 9077 Fax 886 3 572 9031 No 2193 2 2000
31. Year mv to ey 0 85 110 290 VOLTAGE 18 28 C 52 to 32dBm RANGE RESOLUTION BURDEN rdg counts 1 mVto2 mV 2 00 3 00 200 pA 0 3 V 0 1 15 58 to 52dBm 2mA 10 03V 0 1 15 RESOLUTION 0 01dBm above 0 5 of range 20mA 100 03V 0 1 15 dB REPERENCE IMPEDANCE 50 75 93 135 300 600 ohms default front panel selectable 200mA LpA 03 02 15 2000 mA 10 pA 02 15 TRMS AMPS ACCURACY 1 Year 10 100 pA 03V 0 5 15 MAX VOLTAGE 18 28 C rdg counts Above derate 0 15 rdg per amp for self heating RANGE BURDEN 20Hz 50Hz 50H2 10kiiz 10kHz 30kHz OVERLOAD PROTECTION mA Input 2A fuse 250V externally acces 2000A 20mA 03V 1 0 100 0 8 100 2 250 sible 16A Input 20A for 15s unfused 200 mA 1 0 100 0 8 100 SETTLING TIME 1 second to within 3 counts of final reading 2000 mA 0 8V 1 0 100 0 8 100 1 03V 1 5 100 1 0 100 ANALOG IEEE OUTPUT Model 1972A Option Above 1800 counts ANALOG OUTPUT 1kHz max Above 5A derate 0 1596 rdg amp for self heating Accuracy 0 25 of displayed reading 2mV SETTLING TIME 1 second to within 0 1 of final reading Response Time Fotows display conversion rate Level 1V 100 000 counts on xl gain 1V 100 counts on x1000 gain OHMS OUTPUT ACCURACY Maximum output voltage 4V MAX V Yordg counts Output Resistance 10009 NOMINAL ACROSS 24 Hr 1 Year Isolation 500V peak Input LO to Output LO RANGE RESOLUTION I SHORT UNKNOWN
32. a logger cycle In the store mode STO annunciator on and when the buffer is full 100 readings stored the minimum and maximum readings are continuously updated When the store mode is turned off the minimum and maximum readings are not updated 3 Data Retrieval Data can be retrieved at any time but a flashing RCL annunciator indicates that the maximum number of readings 100 have been stored A Press and hold in the RCL button The display scrolls through the data points and MIN MAX LO HD The first data point displayed is the last stored reading The next two data points are the HI and LO readings made during that logging cycle Notice that the longer the RCL button is held in the faster the data points scroll on the dis play B Release the RCL button at the desired data point and note the reading data on the display The data pointer can be incremented by steps of one by momentarily holding in the RCL button 2 7 12 Diode Test The 2kQ and 200kQ ranges can be used for testing semi conductor junctions as follows 1 Select the ohms function 2 Press the 2k and 200k button diode symbols in si multaneously 3 Display reads forward V drop of a silicon diode at 1 6mA 1 1mA for an LED up to 2 2V Red terminal is positive Accuracy is typically better than 1 5 of reading SECTION 2 Bench Operation 2 8 TRMS CONSIDERATIONS Most DMMs actually measure the average value of an in put waveform but are ca
33. age to the card Before operating an instrument make sure the line cord is connect ed to a properly grounded power receptacle Inspect the connecting cables test 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 power dis connect device must be provided in close proximity to the equip ment 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 cables or jump ers 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 com mon side of the circuit under test or power line earth ground Always 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 equip ment may be impaired Do not exceed the maximum signal levels of the instruments and ac cessories as defined in the specifications and operating informa tion and as shown on the instrument or test
34. asurements between 1nA and 10A 20A for 15 sec onds If the expected current level is in question make the initial measurement on the 10A range This helps pre vent inadvertent blowing of the 2A current fuse which is located on the front panel NOTE For routine measurements above 10A it is rec ommended that the Model 1651 50A shunt be used 1 For current measurements between 2000mA and 20mA A Connect the test leads to the 10A and LO termi nals of the Model 197A Refex to Figure 2 8 Caution Maximum Input 450VDC or peak AC for 10sec min 350V RMS Continuous NOTE The test leads used must be rated to handle 20A Twist the wires as shown in Figure 2 8 to help in minimizing external fields which could affect the Model 197A or other equip ment Also keep the test leads as short as pos sible to minimize voltage drop Select the ACA or DCA function B C Select the 10A range The amps functions does not autorange D Connect the test leads to the current source as shown in Figure 2 8 and take the reading from the display NOTE Up to 5A may be applied continuously with out degradation of the measurement due to self heating effects Above 5A derate 0 15 rdg per amp for self heating refer to specifica 2 11 SECTION 2 Bench Operation REL dp KEITHLEY DATA LOGGER STO CLR RCL Os Figure 2 8 EET 20m o Lx x AER Md 2000 5505500000 tions that precede Section
35. available set the switch to 105V 125V CAUTION Connect only to the line voltage selected Application of incorrect voltage can damage the instrument 3 Plug the power cord into a properly grounded outlet SECTION 4 Maintenance WARNING Ground the instrument through a properly grounded receptacle before operation Failure to ground the instrument can result in severe injury or death in the event of a short circuit or malfunction 4 5 FUSE REPLACEMENT WARNING Disconnect the instrument from the power line and from other equipment before replacing fuses 4 5 1 Line Fuse Replacement The line fuse is located internally in the Model 197A For exact fuse location refer to Figure 4 1 To replace the fuse proceed as follows 1 Remove the top cover as explained in paragraph 4 2 2 If the Model 1973A or Model 1972A IEEE 488 interface is installed it must be removed to gain access to the fuse The IEEE board secured to the mother board by a support post at the rear and connector P1008 To remove lift the board up until it disengages from the connector and support post 3 Replace the blown fuse with the following type 1 8A 250V 3AG Slo Blo Keithley Part Number FU 20 CAUTION Do not use a fuse with a higher rating than specified or instrument damage may occur If the instrument persistently blows the fuse a problem may exist within the instrument If so the problem must be corrected before opera tion may continue
36. ay 20kQ 19kQ 19 0000kQ reads zero test lead compensation 200kQ 190kQ 190 000kQ 3 Set the calibrator to output 190Q Adjust the display P a MO using the STO CLR and RCL buttons for a reading of i 190 000 Press REL REL annunciator turns off 4 Select the 2kQ range and set the resistance calibrator to output zero ohms short Press REL REL annunciator Four terminal resistance measurements need turns on only be done when not using the REL feature Input Hi REL dp KEITHLEW 197A AUTORANGING MICROVOLT DMM UBHBBH _ 5450 wre Lo STOCLA RCL i Input Lo POWER 20m 200m Ter 10 LO Oz 0 0000000000 teak fem Figure 4 5 200 2k and 20k Four Wire Resistance Calibration SECTION 4 Maintenance REL dB DATA LOGGER STO CLR RCL POWER 20 X 20k 200k 197A AUTORANGING MICROVOLY DMM M Ou 2m _ 20m 00m 2000m 10 Os Di 10006 PEAK PEAK Figure 4 6 4 6 8 Calibration Storage To store the calibration constants simultaneously press the REL and dB buttons until the message Stor is displayed If instead the message out is displayed then calibration storage was not enabled and the calibration constants will only be valid until the Model 197A is turned off Temporary calibration is denoted by the flashing C annunciator 4 10 o ouat DODDOD 3000 200k 2M and 20M Two Wire Resistance Calibration
37. cked by connecting a cali brated DC current source to the HI and LO INPUT termi nals for up to 2000mA 10A and LO terminals for 2000mA through 10A The accuracy is then verified by referring to Table 3 5 which shows the exact number of counts al lowed in order to remain in the limit of the specifications CAUTION Do not exceed 2A to the HI and LO INPUT terminals or the front panel amps fuse will blow Refer to paragraph 2 4 4 Select the DC current function Select the 2000mA range Connect the instrument to the DC current calibrator as shown in Figure 3 5 The HI side of the AMPS ter minal should be connected to the HI terminal and the LO side of the calibrator output should be con nected to LO Set the calibrator to 00 000 and enable the relative REL mode Verify that the displayed reading is within the limits Switch the Model 197A to the 20mA range Set the calibrator to output 20 0000mA Verify that the dis played reading is within the limits specified in Table 3 5 Switch the Model 197A to the 200mA range Set the calibrator to output 200 000mA Verify that the dis played reading is within the limits specified in Table 3 5 Switch the Model 197A to the 2000mA range Set the calibrator output 2000 00mA Verify that the read ing is within the limits specified in Table 3 5 Set the Model 197A to the 10A range Connect the DC current to the 10A and LO terminal as shown in Figure 3 6 NOTE
38. ction 4 contains information on maintenance and cal ibration for the Model 197A NOTE The Models 1973A and 1972A IEEE 488 inter faces come supplied with their own manual SECTION 1 General Information 1 9 INITIAL OPERATION Perform the following steps in sequence to acquaint your self with the basic operation of the Model 197A Verify that the instrument was not damaged in transit see paragraph 1 7 Carefully read over all safety information see Section 2 Basic Operation Refer to paragraph 2 3 Line Power and set the line voltage switch Connect the female end of the power cord to the AC receptacle on the rear of the Model 197A Plug the other end of the line cord into a properly grounded receptacle If the Model 1978 is installed the charging circuit is activated Acquaint yourself with the front panel controls as follows 1 Turn on the instrument using the ON OFF button All of the zeroes are briefly displayed 2 Connect the supplied test leads to the HI and LO input terminals Connect the red test lead to the HI terminal and the black test lead to the LO ter minal Short the test leads together 3 Select AC volts and autoranging by pressing in the AC DC V and AUTO buttons The AC AUTO and mV annunciators are displayed Pressing in any of the other range buttons acti vates manual ranging This is indicated by the absence of the AUTO annunciator 4 Select DC volts by releasing out position
39. d during shipment The verification procedure may also be per formed whenever instrument accuracy is suspect or follow ing calibration If performance on any of the ranges or functions is inconsistent with specifications calibration should be performed as described in Section 4 NOTE If the instrument does not meet specifications and it is still under warranty less than 12 months since date of shipment contact your Keithley representative or the factory to determine the action to be taken 3 2 ENVIRONMENTAL CONDITIONS All measurements should be made at an ambient tempera ture between 18 C and 28 C 65 F to 82 F with a relative humidity less than 80 3 3 RECOMMENDED TEST EQUIPMENT Equipment for verifying the performance of the Model 197A is listed in Table 3 1 Alternate equipment may be used as long as equipment accuracy is at least equal to the specifica tions listed in Table 3 1 NOTE The verification limits in this section only reflect the specifications of the Model 197A They do not include test equipment tolerance 3 4 INITIAL CONDITIONS Before performing the verification procedures make sure the Model 197A meets the following conditions 1 If the instrument has been subjected to temperature below 18 C 65 F or above 28 C 82 F allow sufficient time for the instrument to reach temperatures within the range Generally it takes one hour to stabilize an instru ment that is 10 C 18 F outside of t
40. d p rds AC Voltage Calibration enseri ah rc obec ne e Frequency Compensation lesse enhn hh hne Resistance Calibration cee cece cece ete hehe hehe re mre Calibration Storage occa secs eek ocn nn ne dann aa ren aa List of Illustrations SECTION 2 Bench Operation Figure 2 1 Model 197A Front Panel 2 aen mes pha erri Ra PRE REEERE ee we Heese ed Figure 2 2 Model 197A Rear Panel ocio er Peace o at e ew ta e eec be bd Figure 2 3 DC Voltage Measurements 0 00 hehe hehe Figure 2 4 TRMS AC Voltage Measurements ema nen Figure 2 5 Four Terminal Zeroing u a A chines saa Ee eR E AL e n Figure 2 6 Two Terminal Resistance Measurement 0 cece eee hens Figure 2 7 Four Terminal Resistance Measurement cece eee ccc een Figure 2 8 Current Measurement Between 2000mA and 20 8 85 5 Figure 2 9 Current Measurements up to 2000MA n 0 6 0 cece hh e en Figure 2 10 Typical ACV Frequency Response 2 cece cee cnet een eee entree asia SECTION 3 Performance Verification Figure 3 1 Connections for DCV Verification 10 0 00 ccc hme Figure 3 2 Connections for ACV Verification ciis he heh Figure 3 3 Connections for 2000 2kQ and 20kQ Range Verification 4 terminal Figure 3 4 Connections for 200kQ through MQ Ranges Verification 2 terminal Figure 3 5 Connections for DC Current Verification 2004A to 2000mA
41. d separate the top cover from the rest of the unit NOTE When reinstalling the top cover make sure to properly position the tilt bail handle into the bot tom cover TEEE 488 Interface Removal If Installed The interface board is secured to the mother board by the 6 pin male connector P1008 and a rear standoff To remove the interface board gently lift it upward until it separates from the connector and the standoff SECTION 4 Maintenance TOP COVER 175A 313 LINE FUSE CURRENT FUSE HOLDER BODY FH 21 CURRENT FUSE CARRIER FH 25 SWITCH PAD tor 4 switches 175A 308 FRONT PANEL 197A 304 FRONT PANEL OVERLAY 197A 310 HANDLE 1754 326 PUSHBUTTONS ON OFF 29465 3 AC DC FUNCTION 29465 4 V FUNCTION 29465 5 FUNCTION 29465 7 A FUNCTION 29465 6 RANGE 7 29465 8 Figure 4 1 Model 197A Miscellaneous Parts LINE CORD CO 7 LINE VOLTAGE E SWITCH SWITCH GUARDS 2 175A 323 CALIBRATION SWITCH BOTTOM COVER 1754 314 FUSE HOLDER 2 FH 12 SPACER 4 175A 327 BOTTOM SHIELO 29691 MODEL 1978 BATTERY PACK FEET 4 FE 10 BANANA JACKS RED BJ 12 2 BLACK BJ 12 0 WHITE 12 9 SECTION 4 Maintenance Battery Pack Removal If Installed The Model 1978 battery pack is mounted on top of the mother board top shield Perform the following steps to remove the complete shield battery pack assembly 1 2 3 Disconnect the battery pack ribbon cable connecto
42. display gt ON dBm Measurements with Other Non Selectable Reference Impedances dBm measurements can be made with other reference impedances The most convenient method for using other reference impedances is to algebraically subtract the calculated dB offset for the desired reference imped ance from the reading on the display of the Model 197A Table 2 7 lists common reference impedances and the corresponding of set values The following equation can be used to calculate the offset forimpedances not listed in Table 2 7 2 14 New ref Z Offset for dBm 10 log 6000 To make dBm measurements referenced to a non selec table impedance proceed as follows 1 Choose the desired reference impedance 2 Calculate or look up the offset value in Table 2 7 for the desired reference impedance 3 Determine dBm at the desired reference impedance as follows dBm at ref Z 197A reading offset Example Make dBm measurements references to a 1000 reference impedance Table 2 7 Levels for Other Reference Impedances Reference Reference Voltage Offset impedance Level for 6002 Ref Q OdBm OdBW OdBm 0 0894 18 75 1125 0 2236 10 79 0 2739 9 03 0 3050 8 10 0 3674 6 49 0 3873 6 03 0 5477 3 01 0 7746 0 00 1 0000 Vie for OdBm VIO WeZrer Vie for OdBW VZaer ZREF Offset for dBm 10 log 6002 ZREF Offset for dBW 10 log 30dB 6002
43. e Be sure to include your name and phone number on this service form 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 KEITHLEY Keithley Instruments Inc BELGIUM CHINA FRANCE GERMANY GREAT BRITAIN INDIA ITALY KOREA NETHERLANDS SWITZERLAND TAIWAN Keithley Instruments B V Keithley Instruments China Keithley Instruments Sarl Keithley Instruments GmbH Keithley Instruments Ltd Keithley Instruments GmbH Keithley Instruments s r Keithley Instruments Korea Keithley Instruments B V Keithley Instruments SA Keithley Instruments Taiwan Copyright 2000 Keithley Instruments Inc Printed in the U S A 28775 Aurora Road Cleveland Ohio 44139 440 248 0400 Fax 440 248 6168 1 888 KEITHLEY 534 8453 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 Dewai Madian Beijing 100029 8610 6202 2886 Fax 8610 6202 2892 3 all e des Garays 91127 Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 Landsberger Strasse 65 D 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 The Minster 58 Portman Road Reading Berkshire RG30 JEA 0118 9 57 56 66 Fax 0118 9 59 64 69 Flat 2B WILLOCRIS
44. e Figure 4 2 Display Assembly Exploded View 6 Carefully place the shield with battery pack back into the Model 197A so that it seals properly on the two spacers Replace retaining screw in the shield NOTE The retaining screw on the rear of the shield also serves to connect the shield to circuit LO 7 Connect the ribbon cable from the battery board to P1009 on the mother board Make sure pin 1 on the cable connects to pin 1 of P1009 Refer to the detailed drawing of Figure 4 1 CAUTION Make a close visual inspection of the connec tions to ensure that they are properly con nected Otherwise damage to the instrument may result 8 Reinstall the top cover as explained in paragraph 4 2 NOTE The IEEE Interface options do not run off of bat tery power 4 4 Window Bezel 175A 305 Mask 175 306 LCD DD 50 Retainer 175A 307 Phosphor Layer for Backlight DD 48 Strip Connector 2 CS 460 2 4 4 LINE VOLTAGE SELECTION The Model 197A may be operated from either 105V 125V or 210V 250V 50 60Hz A special transformer may be installed for 90 110V or 195 235V operation The instru ment was shipped from the factory set for an operating voltage marked on the front panel To change the line volt age proceed as follows 1 Turn off the Model 197A and disconnect it from line power 2 Set the LINE VOLTAGE switch on the back of the instrument to correspond to line voltage available Example 110VAC is
45. e types of product users are Responsible body is the individual or group responsible for the use and maintenance of equipment for ensuring that the equipment is operated within its specifications and operating limits and for en suring 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 instru ment 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 for example setting the line voltage or replac ing consumable materials Maintenance procedures are described in the manual The procedures explicitly state if the operator may per form 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 ser vice personne may perform installation and service procedures Keithley products are designed for use with electrical signais that are rated Installation Category I and Installation Category II as de scribed in the International Electrotechnical Commission IEC Standard IEC 60664 Most measurement control and data I O sig nals are Installation Category I and must not be directly connected to mains voltage or to voltage sources with high transient over volt ages Ins
46. ed in many 5 1 2 digit DMMs The 5 1 2 digit resolution allows the Model 197A to measure DC voltage for 1uV count to 1000V AC voltage and current measurements are standard in the Model 197A TRMS ACV capability ranges from 1uV count to 750V The Model 197A measures resistance from 1mQ to 220 on seven resistance ranges The Model 197A has six current ranges that measure current from nA 10 A to 10A The dB function makes it possible to compress a large range of readings into a much smaller scope Model 197A dBm measurements can be referenced to 50 75 93 135 300 or 600Q default but can be modified with the use of the relative REL feature The Model 197A has two IEEE 488 interface options The Model 1972A and the Model 1973A These optional inter faces enhance the capabilities of the Model 197A by al lowing programmed control over the IEEE 488 bus The Model 19724 also includes an analog output The bus commands are the same for each interface and respond to IEEE 488 protocol 1 2 FEATURES The Model 197A includes the following features 2 Six Measurement Functions DCV ACV DCA ACA OHMS and dB all built in REL Relative Mode The relative mode allows offsets to be nulled out e g test lead resistance for low resistance measurements and selects a variety of reference impedances for dB measurements Digital Calibration A non volatile RAM stores calibration constants and can be performed from
47. einstalling the mother board make sure the two switch guards are installed on the rear panel CALIBRATION and LINE VOLTAGE slide switches These switch guards block openings in the rear panel preventing access to hazardous voltage 43 BATTERY PACK Model 1978 INSTALLATION Refer to Figure 4 1 and perform the following procedure to install the battery pack WARNING Disconnect the line cord and remove all test leads from the terminals of the Model 197A 1 Remove the top cover as explained in paragraph 4 2 2 Remove the shield A Remove the screw that secures the shield to the mother board The screw is located at the rear of the shield B Carefully pull up on either side of the shield C Liftthe shield out of the Model 197A Position the battery board as shown in Figure 4 1 and secure it to the shield using the two supplied screws The screws are positioned through the shield into the battery board fasteners Place the battery pack in the bracket and position on the shield as shown Route the two screws through the shield into the bracket and tighten CAUTION Do not allow the battery leads to short together or damage to the batteries may occur Connect the red battery lead to the RED terminal pin on the battery board Connect the black battery lead to the BLK terminal pin on the battery board CAUTION Be careful not to reverse the wires NOTE Reds to Red and Black to Black SECTION 4 Maintenanc
48. elati Kelative mV or V Millivolts or volts dB Decibel measurement mode Q kQ or Ohms kilohms or megohms STO Data being stored u mA or Microamps milliamps or amps RCL Data being recalled RCL flashes when buffer is full RMT Remote Model 197A being controlled over the during logging cycle IEEE 488 bus Model 1973A or Model 1972A installed 2 3 SECTION 2 Bench Operation 2 4 2 Front Panel Controls ON OFF Pressing this button turns on the Model 197A Releasing out this button turns the instrument off REL RELATIVE This button allows readings to be made with respect to any baseline value Also allows de tailed information on REL dB This button selects the dB function and is used along with the ACV or DCV function Measurements are made in dBm referenced to 50 75 93 135 300 or 6000 default REL can be used to make any voltage level the OdB reference point for dB measurements DATA LOGGER and MIN MAX 100 reading storage capacity records data at one of seven selectable rates from 3 reading second to 1 reading hour or by manual trigger r 6 Also detects and stores maximum and mini mum readings continuously while in the data logger mode 1 STO CLR Pressing this button initiates the log ging sequence Pressing this button a second time turns off the data logger For r 6 rate manual trig ger every time a reading is desired press t
49. g of on range read ings Allows readings to be made with respect to base line value Front panel annunciator indicates REL mode DATA LOGGER and MIN MAX 100 reading storage capaci ty records data at one of six selectable rates from 3 read ings second to 1 reading hour or by manual triggering Specifications are subject to change without notice Also detects and stores maximum and minimum read ings continuously while in data logger mode CONVERSION RATE 3 readings secand OVERRANGE INDICATION OL displayed CREST FACTOR ratio of peak value to rms value AC FUNCTIONS 3 MAXIMUM COMMON MODE VOLTAGE 500V peak COMMON MODE REJECTION RATIO 1kQ unbalance gt 120dB at DC 50Hz 60Hz 0 1 gt 60dB in AC volts TEMPERATURE COEFFICIENT 0 18 C 8 28 50 0 1 x applicable one year accuracy specification C ENVIRONMENT Operating 0 50 C lt 80 relative humidity up to 35 C linearly derate 3 RH C 35 50 C Storage 40 to 70 C WARM UP 1 hour to rated accuracy POWER 105 125V or 210 250V external switch sel ected 90 110V available 50 60Hz 12VA Removable power cord Optional 5 hour battery pack Model 1978 DIMENSIONS WEIGHT 89mm high x 235mm wide x 275mm 3 in x 9 in x 1034 in Net weight 1 8kg 3 Ib 14 oz ACCESSORIES SUPPLIED Model 1751 Safety Test Leads instruction manual Rev B 3 9 01 Table of Contents SECTION 1 General Information 1
50. gher than ex pected 2 The reading is sensitive to and responds to tem perature changes This can be demonstrated by touching the circuit by placing a heat source near the circuit or by a regular patten of instability corre sponding to heating and air conditioning systems or changes in sunlight 3 To minimize the drift caused by thermal emfs use copper leads to connect the circuit to the Model 197A A banana plug is generally sufficient and gen erates just a few microvolts A clean copper conduc tor such as 10 bus wire is about the best for the ap plication The leads to the mput may be shielded or unshielded as necessary Refer to Shielding 4 Widely varying temperatures within the circuit can also create thermal emfs Therefore maintain con stant temperatures to minimize these thermal emfs A cardboard box around the circuit under test also helps by minimizing air currents 5 The REL control can be used to null out constant off set voltages 2 7 6 Resistance Measurements The Model 197A can make resistance measurements be tween 1mQ and 220MQ The 2 20MQ and 200MQ ranges autorange when the MQ button is selected The Model 197A provides automatic selection of 2 terminal or 4 terminal resistance measurements This means that 2 9 SECTION 2 Bench Operation if the ohms sense leads are not connected the measure ment is done 2 terminal If the sense leads are connected the measurement is done 4 terminal
51. he HI and LO INPUT terminals of the Model 197A as shown in Figure 3 2 Setthe calibrator to output 2 00000V at a frequency of 50Hz Verify that the reading is within the limits specified in Table 3 3 Repeat the 2 00000V AC measurement at the other frequencies specified in Table 3 3 Check the 20V 200V and 750V ranges by applying the required voltage and frequencies specified in Table 3 3 and verifying that the readings are within the specified limits 200 000mV 2 00000V 20 0000V 200 000V 750 000V Exceeds the VeHz product Table3 3 Limits for AC Voltage Verification 197 900 199 200 198 600 196 750 to to to to 202 100 200 800 201 400 203 250 1 97900 199 200 1 98600 1 96750 to to to to 2 02100 2 00800 2 01400 2 03250 19 7900 19 9200 19 8600 19 6750 to to to to 20 2100 20 0800 20 1400 20 3250 197 900 199 200 198 600 196 750 to to to to 202 100 200 800 201 400 203 250 739 63 745 25 740 50 to to to 760 37 754 75 759 50 189 600 to 210 400 1 93600 to 2 06400 19 3600 to 20 6400 193 600 to 206 400 189 600 to 210 400 1 93600 to 2 06400 19 3600 3 3 SECTION 3 Performance Verification Figure 3 2 3 5 3 REL dB 000000 DATA LOGGER AC Calibrator Model 52004 and Model 5215A 0 20 0 AUTO 20k 200k MO AUTO 20m 200m 2000m 10 Mr 000 200 2k 2 A__ 200 Connections for ACV Verification Resistance Accuracy Check Resistance verificati
52. he STO CLR button 2 RCL Pressing and holding in this button scrolls the data pointer To read the data at a certain point simply release the button The logged readings are stored in buffer locations 01 to 102 They are depicted on the front panel as follows Buffer location 1 is represented by n 01 AC DC This button is used along with the volts V current A and dB functions Depressing in this button selects AC releasing out this button selects DC AC Q is invalid condition See Table 2 1 V Depressing this button selects the volts function Q Depressing this button selects the ohms function The AC DC button must be released out Depressing in this button selects the current func tion Up to2A on red and black input jacks and up to 10A 2 4 with the black and white input jacks Refer to paragraph 2 4 3 RANGE BUTTONS 1 Depressing AUTO button allows volts and ohms to autorange In current it selects the 10A range There is no autorange function for current 2 Manual ranging is accomplished by depressing the appropriate range button 2 4 3 Input Terminals The input terminals are intended to be used with safety shrouded test leads to help minimize the possibility of contact with live circuits Safety shrouded test leads Model 1751 are supplied with the Model 197A Always disconnect all unused test leads from the instrument HI and LO INPUT Red and Black Use this pair of
53. his range 2 Turn on the Model 197A and allow it to warm up for one hour The instrument may be operated from either line power or battery pack power as long as the battery pack has been fully charged as described in paragraph 2 3 3 SECTION 3 Performance Verification Table 3 1 Equipment Specifications motel Specifications DC Voltage Calibrator AC Voltage Calibrator AC DC Current Calibrator Resistance Calibrator Power Amplifier 200mV 2V 20V 200V 1000V ranges 0 005 200mV 2V 20V 100V 50Hz to 10kHz 0 05 200A 2mA 20mA 200mA 2000mA 10A ranges 0 03 DC 0 196 AC to 5kHz at full scale 1002 1kQ 10kQ 100kQ ranges 0 05 1mQ range 0 01 range 0 05 100MQ 0 5 1000V range 10Hz 30Hz 0 12 50kHz 100kHz 0 10 100V max O 100kHz 10 VHz 750V 3 5 VERIFICATION PROCEDURE Thefollowing paragraphs give the basic verification pro cedure for the following functions DC volts AC volts re sistance and current WARNING The maximum common mode voltage volt age between input low and chassis ground is 500V peak Exceeding this value may cause a shock hazard Some of the procedures in this section may expose the user to danger ous voltages Use standard safety precau tions when such dangerous voltages are en countered 3 5 1 DC Voltage Accuracy Check 1 Select the DC volt function and autorange REL dB DATA LOGGER STO CLR ACL POWER d 00 E 2 20 F
54. ified range CAUTION Donotexceed 2A between the HI and LO IN PUT terminals or instrument damage might occur Refer to paragraph 2 4 4 Current Calibrator Model 2500E Connections for DC Current Verification 2000mA to 20A 1 Select the AC current function on the Model 197A Place the instrument in the 2000mA range 2 Connect the AC calibrator to the Model 197A as shown in Figure 3 7 Set the calibrator frequency to 1kHz Do not use the relative mode to zero the offset in the AC mode 3 Set the calibrator to output 200 000 A and switch the Model 197A to the 200A range Verify that the dis played reading is within the limits specified in Table 3 6 4 Change the Model 197A to the 2mA range Set the calibrator to output 2 00000mA Verify that the dis played reading is within the limits specified in Table 3 6 5 Change the Model 197A to the 20mA range Set the calibrator to output 20 0000mA Verify that the dis played reading is within the limits specified in Table 3 6 6 Change the Model 197A to the 200mA range Set the calibrator to output 200 000mA Verify that the dis played reading is within the limits specified in Table 3 6 7 Changethe Model 197A to the 2000mA range Set the calibrator to output 2000 00mA Verify that the dis played reading is within the limits specified in Table 3 6 8 Connect the calibrator to the Model 197A 10A and LO terminals as shown in Figure 3 8 Change the Model 197A to the 10A
55. igure 3 1 Connections for DCV Verification max O 13kHz 10 VHz CAUTION Do not exceed 1000V between the input HI and LO terminals or damage to the instru ment may occur 2 Connect the calibrator to the instrument as shown in Figure 3 1 3 Setthe calibrator to OV and enable the relative mode Leave the relative mode enabled for all DCV meas urements Check to see that the reading is 000 000V 1 count 4 Apply a positive 200mV to the HI and LOINPUT ter minals The reading must be within the limits speci fied in Table 3 2 5 For each remaining range apply the required volt age as specified in Table 3 2 and verify that the read ing is within specifications 6 repeat all checks with negative voltage DC Calibrator Model 343A 00 000 A DOK 2m 20m 200m 2000m 10 Table 3 2 Limits for DC Voltage Verification 197A Applied Allowable Readings DCV Range DC Voltage 18 C to 28 C 200 000mV 199 965 to 200 035 2 00000 V 1 99976 to 2 00024 20 0000 V 19 9968 to 20 0032 200 000 V 199 968 to 200 032 1000 00 V 999 83 to 1000 17 3 5 2 AC Voltage Accuracy Check CAUTION Do not exceed 750V RMS 1000V peak SECTION 3 Performance Verification 10 VBzbetweenHlIandLO INPUT terminals or instrument damage may occur Select the AC volts function and autorange Do not use REL to zero the offset in this procedure Refer to paragraph 2 7 4 step 4 Connect the AC calibrator to t
56. ing is dis played Always use the lowest possible range for the best resolution 6 Take the reading from the display The term when properly zeroed means that the user must establish a proper baseline for subsequent measure DC Voltage Source Caution Maximum Input 1000V Input Resistance 10M except gt 1000M on 200mV and 2V Ranges 2 7 SECTION 2 Bench Operation ments on that range To zero the Model 197A use the fol lowing procedure 1 Short the INPUT HI and LO test leads together 2 Wait until the display reading settles Noise and thermal emfs may require a few moments to settle out 3 Press the REL button The 200mV DC range and the 2000 range require zero to be set in order to achieve rated accuracy 2 74 TRMS AC Voltage Measurements The Model 197A can make TRMS AC voltage measure ments between and 750V To measure AC proceed as follows 1 Connect the test leads to the HI and LO terminals of the Model 197A 2 Select the ACV function 3 Select a range consistent with the expected voltage For automatic range selection press in the AUTO button 4 Connect the test leads to the source as shown in Figure 2 4 NOTE There is a small amount of offset typically 50 counts or less present when using the AC function Do not REL this level out The rea son for this is that the offset is generally negli gible as compared to the input signal For ex ample REL DATA
57. itch must be moved to ENABLED to allow calibration constant storage The calibration switch is located in the middle of the rear panel Slide the switch to ENABLED Plug in the line cord and turn on the instrument Press in the REL and dB push buttons simultaneously until the message CAL is dis played Release the buttons The unit is now in calibration as indicated by the C annunciator WARNING Some procedures require the use of high volt age Take care to prevent contact with live cir cuits which could cause electrical shock resulting in injury or death NOTE Calibration may be stopped at any time and if desired only selected ranges may be calibrated 4 6 4 DC Voltage Calibration Select the DCV function Connect the DC calibrator to the Model 197A as shown in Figure 4 3 NOTE The following procedure must be performed in the exact sequence listed 1 Press the REL and dB buttons simultaneously until the message CAL is displayed Release the buttons The Model 197A is now in the calibration mode Table 4 2 Recommended Calibration Equipment Description DV Voltage Calibrator 2V 0 003796 0 5u V 20V 0 003 0 5u V 200V 0 003 0 5uV 1000V 0 003 0 5u V 90 day accuracy AC Voltage Calibrator Resistance Calibrator 19022 50ppm 19 50ppm 19kQ 50ppm 190kQ 50ppm 1 9 100ppm I9MQ 500ppm 90 day accuracy 4 6 Required Minimum Specifications 200 0
58. jury or death SECTION 4 Maintenance S 200000 DATA LOGGEA STO CLR ACL POWER 20 2t Hi Output 2k Asoc AUTO 200m 2000m 10 PEAK PEAK AC Voltage Calibrator Model 5200A Figure 4 4 AC Voltage Calibration Configuration Select the 1000VAC range and set the calibrator to out put 500 00V at 500Hz Press the REL button REL annunciator turns on Set the calibrator to output 500 00V at 20kHz Verify that the reading on the Model 197A is 000 00 150 counts Press REL REL annunciator turns off Set the calibrator to output 100 00V at 500Hz and select the 200VAC range Press the REL button REL annunci ator turns on Set the calibrator to output 100 000V at 20kHz Verify that the reading on the Model 197A is 000 000V 200 counts Press REL REL annunciator turns off Set the calibrator to output 10 0000V at 500Hz and select the 20VAC range Press REL REL annunciator turns on 6 Set the calibrator to output 10 0000V at 20kHz Verify that the reading on the Model 197A is 00 0000 200 counts Press REL REL annunciator turns off N C 4 m If any of the above verifications are not met by the Model 197A the top cover must be removed and three trimmer capacitors adjusted The adjustments must be per formed within 10 minutes after the top cover is removed so that the circuit components will be close to normal operat ing temperature The three trimmer capaci
59. l subse quent readings and displayed SECTION 2 Bench Operation A REL level can be established for any measurement function Volts Ohms Amps and dB and is effective only on that function Changing functions will not affect a REL level already established However if another REL level is set on any function the previous REL level is cancelled For example place the Model 197A in the ohms function and select the 200Q range Short the test leads and press the REL button Note that the REL an nunciator is on Select DCV and note that the REL annun ciator is off indicating that there is not a REL level estab lished for DCV Switch back to ohms and note that the REL level is still there Again go to DCV and set a REL level of 1V The REL annunciator turns on Switch back to ohms and note that the REL level for ohms is cancelled It is important to remember what the REL function does The REL function establishes a baseline That baseline is algebraically subtracted from all subsequent readings for that function Once a REL level is established for a measurement func tion that stored level will be the same regardless of what range the Model 197A is on For example if 1V is estab lished as the REL level on the 20VDC range 1V is also the REL level for other DCV ranges The dynamic range of the display is 400 000 counts This means that if a REL level of 2 00000V is established then applying 1 99999V to the input displa
60. le Mode 1972A or 1973A is installed a modified top cover provided with the interface will be installed The modified top cover has clearance holes in the rear panel to provide access to the interface connector s and switches Refer to the Model 1973 1972 IEEE 488 Interface Instruction Manual for details CALIBRATION This slide switch is used to enable or disable calibration of the Model 197A In the ENABLED position calibration constants can be stored In the DIS ABLED position newly entered calibration constants are lost when the instrument is turned off During normal operation keep this switch in the DISABLED position LINE VOLTAGE This slide switch is used to match the instrument to the available line power voltage 2 5 ERROR MESSAGES Table 2 1 lists the error messages associated with basic front panel operation Note that the instrument has a num ber of other messages that are discussed in the appropriate sections of the manual 2 6 OPERATING CONDITIONS 2 6 1 All measurements should be made at an ambient tempera ture within the range of 0 C to 50 C and with a relative humidity of less than 80 up to 35 C For ambient above 35 C derate humidity 3 per C up to 50 C If the instru ment has been subjected to extremes of temperatures allow sufficient time for internal temperature to reach envi ronmental conditions Typically it takes one hour to stabi lize a unit that is 10 C 18 F out of the specified
61. le decreases the crest factor increases The Model 197A has a crest factor of 3 which means the instrument gives accurate TRMS measurements of rectangular waveforms with duty cycles as low as 10 2 8 4 Extended Frequency Response Figure 2 10 illustrates the extended frequency response of the ACV ranges up to IMHz 2 17 SECTION 2 Bench Operation 0 ERROR Figure 2 10 2 18 Typical ACV Frequency Response f Hz 1 10 FULL SCALE FULL SCALE 2V 750V RANGES 200V AND 750V RANGES 1 100 FULL SCALE 200mV RANGE FULL SCALE 200mV RANGE SECTION 2 Bench Operation Table 2 8 Comparison of Average and TRMS Meter Readings Average AC Coupled AC Coupled Responding TRMS Averaging Peak Meter Meter Meter Waveform Value Reading Reading Percent Error Sine 10 77 Half Wave Rectified Sine 10 0 Full Wave Rectified Sine 410 0 Square q Rectified Square Wave 0 Rectangular Pulse 10VeYn 1 11V n D y 100 N DUTY CYCLE Triangular Sawtooth 410 2 19 SECTION 3 performance Ver 3 1 INTRODUCTION This section contains information necessary to verify that the Model 197A s performance is within specified accuracy Model 197A specifications may be found at the front of this manual Ideally performance verification should be per formed when the instrument is first received to ensure that no damage or change in calibration has occurre
62. librated to read its RMS equiva lent This poses no problems as long as the waveform be ing measured is a pure low distortion sine wave For complex nonsinusodial waveforms however measure ments made with an averaging type meter can be grossly inaccurate Because of its TRMS True Root Mean Square measuring capabilities the Model 197A provides accu rate AC measurement for a wide variety of AC input waveforms 2 8 41 Voltage Offset Typically the Model 197A displays 50 counts or less of offset on AC volts with the input shorted This offset is caused by amplifier noise and offset of the TRMS con verter This offset does not affect the reading accuracy and should not be zeroed out using the REL feature Refer to paragraph 2 7 4 step 4 2 8 2 TRMS Measurement Comparison The RMS value of a pure sine wave is equal to 0 707 times its peak value The average value of such a waveform is 0 637 times the peak value Thus for an average respond ing meter a correction factor must be designed in This correction factor K can be found by dividing the RMS value by the average value as follows By applying this correction factor to an averaged reading a typical meter can be designed to give the RMS equiva lent This works fine as long as the waveform is a pure sine wave but the ratios between RMS and average val ues of different waveforms are far from constant and can vary considerably Table2 8 shows a comparison of common
63. ll be subtracted from all subse quent measurements Press the REL button a sec ond time to cancel the REL level 9 To activate the 100 point DATA LOGGER with minimum maximum press and hold in the STO CLR button When the reading rate r 0 is displayed release the STO CLR button The STO annunciator turns on Press the RCL button and the last data point is briefly displayed followed by the reading data Other data points can be displayed by holding in the RCL button Turn off the DATA LOGGER by pressing the STO CLR button again 1 10 ACCESSORIES The following accessories can be used with the Model 197A MODEL 1010 SINGLE RACK MOUNTING KIT Used to mount one Model 197A in a standard 5 1 2 x 19 rack MODEL 1017 DUAL RACK MOUNTING KIT Used to mount two Model 197As in a standard 5 1 4 x 19 rack MODEL 1301 TEMPERATURE PROBE A rugged low cost temperature probe designed to allow precision tem perature measurements from 55 to 150 C MODEL 1600A HIGH VOLTAGE PROBE Extends DMM measurements to 40kV MODEL 1641 KELVIN TEST LEAD SET Special clip leads allow 4 terminal measurements to be made while making only two connections SECTION 1 General Information MODEL 1651 50 AMPERE CURRENT SHUNT The external 0 0010 1 4 terminal shunt permits current measurements from 0 to 50A AC or DC MODEL 1681 CLIP ON TEST LEAD SET Contains two leads 1 2m 48 long terminated with banana plugs and spri
64. manual 1 7 UNPACKING AND INSPECTION The Model 197A Autoranging Microvolt DMM was care fully inspected both electrically and mechanically before shipment Upon receiving the instrument carefully unpack all items from the shipping carton and check for any obvi ous signs of physical damage that may have occurred dur ing transit Report any damage to the shipping agent Retain and use the original packing material in case reship ment is necessary The following items are shipped with every Model 197A order Model 197A Autoranging DMM Model 197A User s Manual Model 1751 Safety Shrouded Test Leads Additional accessories as ordered If an additional instruction manual is required order the manual package Keithley Part Number 197A 901 00 The manual package includes an instruction manual and any applicable addenda 1 8 USING THE MODEL 197A MANUAL This manual contains information necessary for operating and servicing the Model 197A Autoranging Microvolt DMM and the 1978 Rechargeable Battery Pack This section of the manual contains general information and an initial operation procedure The rest of the manual is organized as follows Section 2 contains detailed bench operation information for the Model 197A Section 3 contains the information needed to verify the accuracy of the Model 197A Performance verification can be done upon receipt of the unit or whenever the basic accuracy of the instrument is in question Se
65. n overload 4 6 FRONT PANEL CALIBRATION Calibration should be performed every 12 months or if the performance verification procedures in Section 3 show that the Model 197A is out of specification If any of the calibra tion procedures in this section cannot be performed prop erly refer to the troubleshooting information in this section If the problem persists contact your Keithley rep resentative or the factory for further information NOTE ACA and DCA do not need to be calibrated These current ranges are calibrated when ACV is calibrated SECTION 4 Maintenance Recommended Calibration Equipment 4 6 1 Calibration may be performed using the equipment listed in Table 4 2 Alternate calibration equipment may be used as long as the equipment s accuracy is at least as good as the specifications listed in Table 4 2 4 6 2 Environmental Conditions Calibration should be performed in an ambient tempera ture of 23 C 3 C and a relative humidity of less than 7090 If the instrument has been subject to temperature outside of this range or to higher humidity allow at least one addi tional hour for the instrument to stabilize before beginning the calibration procedure 4 6 3 Calibration Switch The Model 197A is shipped from the factory with its exter nal calibration switch in the DISABLED position In this position calibration constants cannot be stored when entered from the front panel or over the IEEE 488 bus The sw
66. ng action clip probes MODEL 1682 RF PROBE Permits voltage measurements from 10kHz to 250MHz AC to DC transfer accuracy is 1dB from 100kHz to 250MHz at 1V peak responding cali brated in RMS of a sine wave MODEL 1684 HARD SHELL CARRYING CASE Hard vinyl case 100mm x 300mm x 350mm 4 13 x 14 has a fitted foam insert with room for the Model 197A an instruction manual and small accessories MODEL 1685 CLAMP ON AC PROBE Measure AC cur rent by clamping on to a single conductor Interruption of the circuit is unnecessary The Model 1685 detects currents by sensing the changing magnetic produced by the current flow MODEL 1751 SAFETY TEST LEADS This test lead set is supplied with every Model 197A Finger guards and shrouded banana plugs help minimize the chance of mak ing contact with live circuitry MODEL 1754 UNIVERSAL TEST LEAD KIT A 12 piece test lead kit with interchangeable plug in accessories Included in the kit is one set of test leads I red l black two spade lugs two standard banana plugs two phone tips 1 4 06 DIA two hooks and miniature alligator clips with boots MODEL 1972A ANALOG OUTPUT IEEE 488 INTER FACE The Model 1972A is an optional IEEE 488 interface that includes all of the logic necessary to interface the Model 197A to the IEEE 488 bus The Model 1972A is similar to the Model 1973A however it contains an analog output The analog output is a scaled output tha
67. nnections shown in Figure 2 7 Input Hi Input Lo Ohms Sense Lo Ohms Sense Hi Figure 2 5 Four Terminal Zeroing CAUTION The maximum input voltage between the HI and LO INPUT terminals is 450V DC or peak AC for 10 seconds per minute 350V RMS continuous Do not exceed these values orin strument damage may occur Table 2 3 shows the current output for various resis tance ranges CAUTION Incorrect readings will result if the resis tance being measured is part of a live circuit 6 Takethe reading from the display NOTE It is helpful to shield resistance greater than 100 if a stable reading is expected Place the resistance in a shielded enclosure and electrically connect the shield to the LO input terminal of the Model 197A Table 2 3 Resistance Ranges Resolution I Short Range 2 10 Maximum Test Lead Resistance for lt 1 Count Error Q SECTION 2 Bench Operation REL dB DATA LOGGER STO CLR RCL 20k Z00K POWEA 1 20m 200m 2000m 10 3 2A 2507 p Figure 2 6 Two Terminal Resistance Measurement DATA LOGGER Optional Shield Caution Maximum Input 450VDC or peak AC for 10sec min 350V RMS Continuous STOCLR RCL ALT 20k 200 AUTO POWER d 20m 200m 2000m 10 ec 5008500808 PEAK Figure 2 7 Four Terminal Resistance Measurement 2 7 7 Current Measurements DC TRMS AC The Model 197A can make DC or TRMS AC current me
68. nter to the load of the amplifier D Adjustthe frequency of the signal generator un til a peak AC voltage reading is measured on the Model 197A Pressthe dB button and then press the REL but ton The 0dB point is now established F Increase the frequency input until the Model 197A reads 3 00dB The frequency measured on the frequency counter is the high end limit of the bandwidth G Decrease the frequency input until the dB read ing again falls to 3dB The frequency measured on the signal generator is the low end limit of the bandwidth tri 4 Determining Q The Q of a tuned circuit can be determined as fol lows A Determine the center frequency and bandwidth as explained in paragraph 2 7 10 step 3 B Calculate Q by using the following formula Q Center Frequency Bandwidth 2 15 SECTION 2 Bench Operation 2 7 11 MIN MAX and 100 Point Data Log ger Operation The data logger can store up to 100 readings and store the minimum and maximum readings recorded during the period that the data logger is active The 100 points of data are stored at one of seven selectable rates from three persecond to one reading per hour Also manual trigger ing is available 6 In the r 6 mode one reading is stored every time the STO CLR button is pressed Read ings for minimum and maximum are sampled at the rate of three per second regardless of the selected rate The procedure for operating the data logger is as f
69. of electric shock 2 3 2 Battery Pack Power The Model 197A may be operated from rechargeable sealed nickel cadmium batteries contained in the optional Model 1978 Rechargeable Battery Pack The battery pack will operate the Model 197A for typically five hours The BAT annunciator turns on when the charge is insufficient to maintain accurate readings 2 3 3 Battery Charging After the Model 1978 is installed in the Model 197A it can be charged and recharged as follows 1 Connect the instrument to line power as described in paragraph 2 3 1 2 The battery charge circuit is energized automatically when the instrument is plugged into the AC line The rate at which the batteries charge is the same regardless 2 2 of the power switch state When the battery pack is first installed or if it is completely discharged allow it to charge for a minimum of 15 hours NOTE For maximum battery efficiency only charge the battery pack after it has become completely dis charged BAT annunciator on Do not make measurements with BAT annunciator on as the readings may be erroneous If the battery pack is not maintaining a charge BAT off for five hours after a full 15 hour charge cycle do the following A Disconnect the Model 197A from line power B Turn on the Model 197A and leave it on to com pletely discharge the battery pack C Connect the Model 197A to line power and charge the battery pack for 15 hours with power off D Re
70. ollows 1 Connect the desired measurement configuration to the Model 197A Make sure that the controls of the Model 197A are set appropriately 2 Logging Data A Pressand hold theSTO CLR button The follow ing reading rates will scroll on the display rate meaning r 0 every reading r 1 rdg sec r 2 1 rdg 10 sec 1 3 1 rdg min r 4 1 rdg 10 min r 5 1 rdg hour r 6 1 rdg every time STO CLR is pressed NOTE There is no need to select a rate if just mini mum maximum readings are desired Press the STO CLR button to start the logger B Release the STO CLR button when the desired reading rate is displayed The STO annunciator turns on and data is logged at the selected rate C In the manual trigger mode 6 a reading is stored every time the STO CLR button is pressed The following sequence takes place af ter the STO CLR button is pressed when in the manual trigger mode a The Model 197A stores the reading b The buffer location number is briefly dis played For example Buffer location 1 is represented by n 01 2 16 c The Model 197A displays the applied signal and waits for the next manual rigger NOTE The logging cycle can be terminated at any time by pressing the STO CLR button This shuts off the data logger However data is re tained and can be recalled at any time as long as the instrument remains on In the r 6 mode press the RCL and the STO CLR but ton to terminate the dat
71. on is performed by connecting known precise resistance values to the HI and LO input terminals and checking to see that the displayed reading is within the required limits Measurements on the 200Q 2kQ and 20kQ ranges will be done using the 4 terminal configuration to minimize errors due to the voltage drop across the test leads 3 4 CAUTION Do not exceed 450VDC or peak AC for 10 sec onds per minute 350V rms continuous be tweenthe HI and LOINPUT terminals orthe instrument might be damaged Select the ohms function AC DC button must be out and the 2002 range Use Kelvin test leads e g Keithley Model 1641 in the input HI and LO and then OHMS SENSE Hl and LO terminals Short the leads together Enable the relative REL mode Check to see that the display reads 000 000 Leave the relative mode enabled for the remaining resistance measurements Connect the 190Q calibration resistor as shown in Figure 3 3 Note that the 4 terminal configuration is used for this measurement Check to see that the displayed reading is within the limits specified in Table 3 4 Connect a 1 9kQ calibration resistor to the instru ment as shown in Figure 3 3 Switch the instrument to the 2kQ range Verify that the displayed reading is within the limits specified in Table 3 4 6 Connect a 19kQ calibration resistor to the instrument as shown in Figure 3 4 Switch the instrument to the 20kQ range Verify that the displayed reading is within the limi
72. ossible wear cracks or breaks before each use If any defects are found replace the test leads For optimum safety do not touch the test leads or the instrument while power is applied to the circuit under test Turn the power off and discharge all capacitors before connecting or disconnecting the instrument Do not touch any object which could provide a current path to the common side of the circuit under test or power line earth ground Always make measurements with dry hands while standing on a dry insulated surface capable of with standing the voltage being measured Exercise extreme safety when testing high energy power circuits AC line or mains etc Refer to High Energy Circuit Safety Precautions found in paragraph 2 2 Do not exceed the instrument s maximum allowable input as defined in the specifications and operation section Instrumentation and accessories should not be connected to humans Safety Precautions The following safely precautions should be observed before using this product and any associated instrumentation Although some in struments and accessories would normally be used with non haz ardous voltages there are situations where hazardous conditions may be present This product is intended for use by qualified personnel who recog nize shock hazards and are familiar with the safety precautions re quired to avoid possible injury Read the operating information carefully before using the product Th
73. peatsteps A through C three more times The battery pack should again be good for typically five hours 3 When the Model 197A is in use on line power the bat tery charger maintains a trickle charge on the battery pack NOTE The IEEE options Model 1972A and Model 1973A do not run off of battery power 2 4 FRONT AND REAR PANEL FAMILIARIZATION Figure 2 1 Figure 2 2 and the following paragraphs pro vide a brief description of the display front panel controls input terminals and rear panel switches 2 4 1 The Model 197A has a 5 1 2 digit liquid crystal display LCD Positive polarity is implied by the absence of the minus sign The following annunciators are displayed on the LCD Display SECTION 2 Bench Operation REL KEITHLEY 197A AUTORANGING MICROVOLT DMM 2200008 RMT i 0 200k MQ AUTO A 200 20m 200m 2000m LO 0 0000000000 O 450V PEAK PEAK Figure 2 1 Model 197A Front Panel WARNING REMOVE BATTERIES BEFORE SHIPMENT OR INACTIVE STORAGE Ol 30 DAYS OH MORE DISCONNECT UNE GORD BEFOHT SERVICING CALIBRATION UNE VOLTAGE LINE RATING 50 60 AC ONLY 12VA MAX EX ENABLED CE 105 125v KEITHLEN 7 210 250 Figure 2 2 Model 197A Rear Panel BAT Low battery indicator for the Model 1978 C Model 197A in calibration mode AC AC selected DC implied by the absence of the AC AUTO Autorange annunciator REL R
74. r from P1009 on the mother board Remove the one screw that secures the top shield to the mother board The screw is located at the rear of the shield Carefully remove the shield battery pack assembly from the unit Display Board Removal 1 N Disconnect the display board ribbon cable from the mother board at J P1006 Disconnect the input leads from the input jack termi nals Table 4 1 provides terminal identification for reas sembly Remove the front panel assembly from the unit The display board assembly is secured to the front panel with three screws Remove these three screws and separate the display board assembly from the front panel The LCD liquid crystal display assembly is secured to the display board by five tabs To remove gently push the tabs away from the display board and pull the LCD assembly away from the display board The phosphor layer of the electroluminescent backlight will remain intact with the display board An exploded view of the display assembly is shown in Figure 4 2 Table 4 1 Input Terminal Identification Conductor Input Terminal Insulator Color INPUT HI Red INPUT LO Black Q SENSE HI Orange Q SENSE LO Grey 10A INPUT White Mother Board Removal 1 2 Disconnect the AC power receptacle from the mother board at J P1007 Remove the four case spacers 3 Carefully lift the mother board out of the bottom case cover WARNING When r
75. r below a 1mW refer ence The default reference impedance on power up of the Model 197A is 600Q With this reference impedance the Model 197A is designed to read 0dBm when the volt age needed to dissipate 1mW through a 6000 impedance is applied That calculated voltage level is 0 7764V as de rived from the basic power equation Table 2 5 dB Specifications for AC Volts 6002 Ref dB Mode Ref 6000 200mV 1mV to 2mV 58 to 52dBm 2mV to 20mV 52 to 32dBm 20mV to 200mV 32 to 12dBm 200mV to 750V 12 to 59 8dBm Accuracy dBm 20Hz 10kHz 20kHz Range Input 10kHz 20kHz 50kHz 2 13 SECTION 2 Bench Operation E VPeR 410 We600Q E 0 77456V Thus with a 600Q reference impedance the Model 197A will read OdBm whenever 0 7746V is applied NOTE Do not confuse reference impedance with in put impedance The input impedance of the instrument is not modified in the dB mode To make dBm measurements referenced to one of the selectable impedances proceed as follows 1 Connect the test leads to the INPUT HI and LO ter minals of the Model 197A Select the ACV or DCV function Select autorange for optimum resolution Press and hold the dB button to scroll through the selectable reference impedances see Table 2 6 Re lease the button when the desired reference imped ance is displayed 5 Connect the test leads to the voltage source 6 Make the dBm reading from the
76. range 3 7 SECTION 3 Performance Verification ge KEITHLEY 197A AUTORANGING C c Hi Output 00000 is da 03T 0000000000 pc PEAK PEAK Hi Input AC Voltage Current Calibrator Calibrator Model 5200A Model 2500E Figure 3 7 Connections for AC Current Verification 200A to 2000mA REL KEITHLEY 197A AUTORANGING MICROVOLT DMM 3 DODDDD AAA O O L Output STOCLR RCL POWER L lo rx em wor um ES 2000m sm Os 3 0000000000 Ton PEAK PEAK Hi Input AC Voltage Current Calibrator Calibrator Model 343A Model 2500E Figure3 8 Connections for AC Current Verification 2000mA to 10A SECTION 3 Performance Verification NOTE 9 Set the calibrator to output 5 0000A Verify that the Be sure to connect the calibrator to the 10A displayed reading is within the limts specified in and LO terminals Otherwise applying the Table 3 6 5A as specified in Table 3 6 would blow the front panel current fuse Table 3 6 Limits for AC Current Verification 197A AC Applied Range AC Current 20Hz 50Hz 10kHz 30kHz 200 0001 197 900 198 300 198 300 195 750 to to to to 202 100 201 700 201 700 204 250 2 00000mA 1 97900 1 98300 1 98300 1 95750 to to to to 2 02100 2 01700 2 01700 2 04250 20 0000mA 19 7900 19 8300 19 8300 19 5750 to to to to 20 2100 20 1700 20 1700 20 4250 200 000mA 197 900 198 300 198 300 to to to 202 100 201 700 201 700 2000mA 2000mA 1
77. s circuits including the power transformer test leads and input jacks must be purchased from Keithley Instru ments Standard fuses with applicable national safety approvals may be used if the rating 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 se lected 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 according to in structions If the board becomes contaminated and operation is af fected the board should be returned to the factory for proper cleaning servicing 2 01 197A 5 Digit Multimeter Specifications DC VOLTS TRMS AC VOLTS ACCURACY 1 Year ACCURACY 18 28 C rdg counts rdg counts RANGE 20Hz 50Hz 50Hz 10kH2 10kHz 20kHz 20kHz 50kHz 50kHz 100kHz INPUT 24Hr 1Year 200mV 1 00 100 0 35 100 0 6 200 1 5 250 5
78. s for this application 3 Set the DMM to the proper function and range 4 Energize the circuit using the installed connect disconnect device and make measurements without disconnecting the DMM 5 De energize the circuit using the installed connect disconnect device Disconnect the test leads from the circuit under test o CAUTION The maximum common mode input voltage the voltage between input LO and chassis ground is 500V peak Exceeding this value may damage the instrument SECTION 2 Bench Operation 2 3 PREPARATION FOR USE 2 3 1 Line Power The Model 197A has a three wire line cord which mates with third wire grounded receptacles Connect the instru ment to AC line power as follows 1 Set the LINE VOLTAGE switch on the back of the instrument to correspond to line voltage available Ranges are 105V 125V or 210V 250V 50 60Hz AC CAUTION Be sure that the power line voltage agrees with the indicated range on the panel of the instru ment Failure to observe this precaution may result in instrument damage 2 Connect the female end of the power cord to the AC receptacle on the rear panel of the Model 197A Plug in the other end of the power cord into a properly grounded receptacle WARNING The Model 197A is equipped with a 3 wire power cord that contains a separate ground wire and is designed to be used with grounded outlets Failure to use a grounded outlet may result in personal injury or death because
79. sic procedure is to establish the level as the OdB point by using REL and making the desired dB meas urement 2 7 10 dB Measurement Considerations and Applications 1 Typical Instrument Performance Typically the Model 197A will perform better than its published dB specification The following exam ple will illustrate this point A Using the Model 197A in the dB mode 6002 ref measure a ImV RMS 1kHz source common ap plication in the communications field Typi cally the Model 197A will read 57 7dBm B The calculated dBm level for that source is 57 8dBm C The0 1dBm error is considerably better than the 2dBm specification The specifications are in tended to cover worst measurement conditions 2 Measuring Circuit Gain Loss Any point in a circuit can be established as the OdB point Measurements in that circuit are then refer enced to that point expressed in terms of gain dB or loss dB To set the OdB point A PlacetheModel 197A in volts autorange and dB B Connect the Model 197A to the desired location in the circuit C Press the REL button The display will read OdB D Gain Loss measurements can now be made ref erenced to the OdB point 3 Measuring Bandwidth The Model 197A can be used to determine the bandwidth of an amplifier as follows A Connect a signal generator to the input of the amplifier B Setthe Model 197A to ACV and autorange C Connect the DMM and a frequency cou
80. t House Crescent Bangalore 560 001 91 80 509 1320 21 Fax 91 80 509 1322 ITALY Keithley Instruments s r l Viale S Gimignano 38 20146 Milano 02 48 39 16 O1 Fax 02 48 30 22 74 NETHERLANDS Keithley Instruments B V Postbus 559 4200 AN Gorinchem 0183 635333 0183 630821 SWITZERLAND Keithley Instruments SA Kriesbachstrasse 4 8600 D bendorf 01 821 94 44 Fax 01 820 30 81 TAIWAN Keithley Instruments Taiwan Fl 85 Po Ai Street Hsinchu Taiwan R O C 886 3572 9077 Fax 886 3572 903 9 00 Model 197A Autoranging Microvolt DMM User s Manual 1990 Keithley Instruments Inc All rights reserved Cleveland Ohio U S A Third Printing February 2001 Document Number 197A 901 01 Rev C SAFETY PRECAUTIONS The following safety precautions should be observed before operating the Model 197A This instrument is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury Read over the manual carefully before operating this instrument Exercise extreme caution when a shock hazard is present at the instrument s input The American National Standards Institute ANSI states that a shock hazard exists when voltage levels greater than 30V rms or 42 4V peak are present A good safety practice is to expect that a hazardous voltage is present in any unknown circuit before measuring Inspect the test leads for p
81. t follows the display of the Model 197A The Model 19724 is field installable MODEL 1973A IEEE 488 INTERFACE The Model 1973A is an optional IEEE 488 interface for the Model 197A This interface adds extra versatility to the Model 197A by allowing the transmission of data and commands over the IEEE 488 bus The interface provides all the logic necessary to interface the Model 197A to the bus using standard IEEE 488 1978 protocol The Model 1973A is field installable MODEL 1978 RECHARGEABLE BATTERY PACK The rechargeable battery pack allows off line or in the field operation of the Model 197A The pack typically provides five hours operation from full charge The battery pack contains its own charging circuit and can be recharged within 15 hours The battery pack is field installable MODEL 7008 IEEE 488 DIGITAL CABLE Useful for con necting the 1973 to the IEEE 488 bus The Model 7008 3 is 0 9m 3 ft in length and has a standard IEEE 488 connec tor at each end The Model 7008 6 is 1 8m 6 ft in length and has a standard IEEE 488 connector at each end SECTION 2 Bench Operation 2 1 INTRODUCTION This section contains the information needed to prepare and operate the Model 197A as a bench DMM Bench operation consists of using the Model 197A to perform basic voltage current resistance and dB measurements Also the opera tion of the data logger is covered The capabilities of the Model 197A can be enhanced
82. tallation Category II connections require protection for high transient over voltages often associated with local AC mains connections The user should assume all measurement control and data I O connections are for connection to Category I sources un less 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 Users of this product must be protected from electric shock at all times The responsible body must ensure that users are prevented access and or insulated from every connection point In some cases connections must be exposed to potential human contact Product users 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 sources NEVER connect switching cards directly to AC mains When con necting sources to switching cards install protective devices to lim it fault current and volt
83. the front panel or over the IEEE 488 bus Data Logger A data storage buffer is included to allow up to 100 readings and minimum maximum readings beinternally stored at a user selectable rate The buffer may be read and controlled from the front panel or over the IEEE 488 bus In the talk only mode the output rate can also be programmed Autoranging The Model 197A includes a fast autoranging feature for easier measurements 9 1 2 Digit Resolution The Model 197A has a 220 000 count A D that surpasses the more com mon 199 999 count A D Four Terminal Ohms These terminals are used to eliminate the voltage from across the current carry ing leads Sensitivity The Model 197A has 11 and InA sensitivity The 11 of sensitivity allows minute levels of offset temperature etc A 1nA sensitivity al lows low current measurements without special equipment Measure leakage bias and offset cur 1 1 SECTION 1 General Information rent A 1mQ sensitivity allows easy low resistance measurements 9 Electroluminescent Display Backlight electroluminescent display backlight is used to enhance the liquid crystal display under low light or dark conditions 10 dB Reference Impedances Selectable dB reference impedances of 500 750 930 1350 3009 and 6000 default 1 3 WARRANTY INFORMATION Warranty information may be found on the inside front cover of this manual Should it become necessary
84. tors C103 C105 and C107 are accessible through the shield The shield and PC board must be secured to the bottom cover in order to prevent movement This assembly can be secured with two screws and nuts not supplied Route the screws through the bottom cover through the two brown spacers to the shield Secure the screws with the nuts High Valtage Amplifier Model 5215 Also use a flat blade insulated calibration tool for all the adjustments Perform the following steps in the exact sequence listed WARNING Steps 1 through 4 require the use of high volt age Take care not to come into contact with live circuits that could cause personal injury or death 1 Select the 1000VAC range and set the calibrator to out put 500 00V at 500Hz Press the REL button REL annunciator turns on 2 Set the calibrator to output 500 00V at 20kHz Adjust C103 for a reading of 000 00 50 counts Press REL REL annunciator turns off 3 Set the calibrator to output 100 00V at 500Hz and select the 200VAC range Press REL REL annunciator turns on 4 Set the calibrator to output 100 00V at 20kHz Adjust C105 for a reading on the Model 197A of 000 000V 50 counts Press REL REL annunciator turns off 5 Set the calibrator to output 10 0000V at 500Hz and select the 20VAC range Press REL REL annunciator turns on 6 Set the calibrator to output 10 0000V at 20kHz Adjust C107 for a reading on the Model 197A of 00 0000V 50 counts 7
85. ts The dB function makes it possible to compress a large range of readings into a much smaller scope The rela tionship between dB and voltage can be expressed by the following equation Vin dB 20 log Tables 2 4 and 2 5 list the dB specifications for DC volts and AC volts Table 2 4 dB Specifications for DC Volts 6000 Ref Linear Counts Resolution Accuracy 10 99 1dBm 2dBm typical 100 999 0 1dBm 1dBm 1000 9999 0 01dBm 0 1dBm 10000 220 000 0 01dBm 0 02dBm The Model 197A can make dB measurements referenced to one of six selectable impedances The selectable refer ence impedances are listed in Table 2 6 dB measure ments referenced to other non selectable impedances can also be done One method is to use the relative REL feature REL can also be used to make dB measurements independent of impedance Table 2 6 Selectable Reference Impedances Reference Impedances Power up default impedance The basic procedure for placing the instrument in the dB mode is to first select AC or DC volts and then press the dB button The currently selected dB reference imped ance will then be displayed briefly and the dB annuncia tor will turn on Note that on power up the reference im pedance will default to 600Q To exit from the dB mode again press dB or press the Q or A function button dBm Measurements with Selectable Reference Impedances dBm is defined as decibels above o
86. ts specified in Table 3 4 7 Connect a 190kQ calibration resistor to the instru ment as shown in Figure 3 4 Switch the instrument to the 200kQ range Verify that the displayed reading is within the limits specified in Table 3 4 Note that the 2 terminal configuration may be used on the 200kQ and higher ranges 8 Continue with each of the calibration resistance val ues listed in Table 3 4 Be sure to place the Model 197A on the correct range for each measurement The remaining readings may be done using 2 termi nal configuration Table 3 4 Limits for Resistance Verification 197A Applied Allowable Readings Range Resistance 18 C to 28 C 190 000 189 963 to 190 037 1 90000 kQ 1 89964 to 1 90036 19 0000 kQ 18 9949 to 19 0051 190 000 kQ 189 949 to 190 051 1 90000MQ 1 89931 to 1 90069 19 0000 18 9770 to 19 0230 190 000M02 186 199 to 193 801 SECTION 3 Performance Verification REL dB L librati DATA LOGGER OL Calibration Resistance EJE Model 54504 it 10 80 AUTO POWER I 20m 200m 2000m 10 o 30 Ug Figure 3 3 Connections for 200Q 2kQ and 20kQ Range Verification 4 terminal dB Calibration Resistance Model 5450A DATA LOGGER STO CLR RCL San a POWER L 20m 200m 2000m 10 Oz 0 Figure 3 4 Connections for 200kQ through MQ Ranges Verification 2 terminal SECTION 3 Performance Verification 3 5 4 DC Current Accuracy Check DC current accuracy is che
87. types of waveforms For reference the first waveform is an ordi nary sine wave with peak amplitude of 10V The average value of this voltage is 6 37V while its RMS value is 7 07V If weapply the 1 11 correction factor to the average reading it can be seen that both meters will give the same reading resulting in no error in the average type meter reading The situation changes with the half wave rectified sine wave As before the peak value of the waveform is 10V but the average value drops to 3 18V The RMS value of this waveform is 3 86V but the average responding me ter will give 3 53V 3 18 x 1 11 creating an error of 11 A similar situation exists for the rectified square wave which has an average value of 5V and an RMS value of 7 07V Here the average responding meter gives a read ing of 5 55V 95 x 1 11 while the Model 197A gives a TRMS reading of 5V Other waveform comparisons can be found in Table 2 8 28 3 Crest Factor The crest factor of a waveform is the ratio of its peak value to its RMS value Thus the crest factor specifies the dy namic range of a TRMS instrument For sinusodial waveforms the crest factor is 1 414 For a symmetrical square wave the crest factor is unity The crest factor of other waveforms will of course de pend on the waveform in question because the ratio of peak to RMS value varies For example the crest factor of a rectangular pulse is related to its duty cycle as the duty cyc
88. ys 3 99999V Once the REL level is established that level is algebrai cally subtracted from the input signal For example if a 1 00000V REL level is established then applying a 2 00000V level displays a 1 00000V level REL DATA LOGGER STO CLR RCL POWER uH 7 00050005000 PEAK PEAK Figure 2 3 Voltage Measurements The instrument accepts a 220 000 count input before go ing into the overrange condition OL For example 1 00000V REL level is established and 1 50000V is ap plied The instrument displays 2 500000V If the input is 2 20000V the instrument overranges 2 7 3 DC Voltage Measurement The Model 197A can make DC voltage measurements be tween and 10005 The basic procedure is as follows 1 Connect the test leads to the HI and LO INPUT ter minals of the Model 197A 2 Select the DCV function 3 Select a range consistent with the expected voltage For automatic range selection press in the AUTO button NOTE To prolong instrument life manual ranging is recommended for routine measurements above 200V 4 Connect the test leads to the source as shown in Figure 2 3 If the positive source terminal is con nected to the LO terminal of the instrument the dis play shows a negative value If the negative source terminalis connected to the LO terminal the display shows a positive value 5 Observe the display If the OL message is shown select a higher range until a normal read

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