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1. 3 2 Limits for AC Voltage Verification 3 3 Limits for Resistance Verification 3 3 Limits for DC Current Verification 3 4 Limits for AC Current Verification 3 6 Recommended Calibration 5 4 DC Voltage Calibration 5 5 AC Voltage Calibration 5 6 Resistance Pes eee PAENG pea ee parva 5 7 Recommended Troubleshooting 5 8 Model 197 Troubleshooting Mode 5 10 Power Supply and Battery Pack Model 1978 Checks 5 12 Display Board Checks euer pepe Y eb 5 12 A D Converter Checks RE vga wa e a pies Pa esses 5 13 Model 197 Static Sensitive Devices 5 13 Model 197 Pars ecce Ee er kr beide ad 6 3 Display Board Parts List eccere reri ter rire ope d eel
2. i TO PIN PAGE 2 ZONE TT 11098 777 em QIK IK lt 793 L EEA DELETED C141 220pF ADDED 1398 2 v na WAS tik 8144 pan 11 86 ADDED 222 wo 7782 la 2 1 2 113 82 3 286 zone eco care 7717 7 62224 He An EVA d CHED HIGHEST Sr 28 To 220 Pin i 3 ie 112389 e PAGE 2 ge 12560 1 SEE ZA ADDED CAT ES 5 27 28 044018 244 d a TERI02 ov WER 113 aka sl 1 1104 CRIO3 EET 77 p Pou j 125 46 cue 12 9 917 VRIOI NY _ OTO 0114 PIN 10 ZON PAO 114 PBI 014 PIN LI 2820 TO 0114 PIN 12 UlI4 PIN 13 PAI PALO TO 0114 PIN 3 0114 PIN 4 0114 PIN 5 S30 TO 0114 PIN 8 O TO PIN 14 UII4 PIN 15 2 20 PAS a meam ett ami ore arat poe a 5 RI25C Baon xut M yo na ue W 2 230 71 11 R d 4 Ng VAIO5 Y 2 D
3. 1 1 4 1 Analog Circuitry lees sec 4 1 Mu ltpl xet 4 1 Input Buffer Amplifier kw at RO ERE bete BAGA ERU 4 1 2V Reference Source he ee 4 1 Input Signal Conditioning 1 4 1 A D Converters a ae e 4 4 E Res i Boemie gs 4 5 Digital Circuitry Deae DL DA ddr d HUS he Pana diae ated wile te 4 5 25522295 cle pee _________ 4 5 Address Decoding ere ______________ 4 6 AA AP 4 6 Display BOALA _ _ 4 6 Digital Calibration 4 6 Power SUPPI E edat ____ BEH bonos 4 6 Model 1978 Battery Option derer eet End Ps 4 7 SECTION 5 MAINTENANCE IntroducHOon ee RU Neh ode qe 5 1 Top Cover Removal Installation 2 4 2 5 1 Battery Pack Model 1978 5 Line Voltage S lection fur Saee 5 2 Fuse Replacement oo dae end 5 2 Line Fuse Replacement cs hes 5 2 Current Fuse Replacement b sospes
4. EIU ERR CE nn 5 9 SECTION 6 REPLACEABLE PARTS naa 6 1 Replaceable Paris ___________________ 6 1 Ordering Information cie eet ease ME edle a de 6 1 Factory Service uo Ye go ous Dio torpor cua ma LAN qp eee 6 1 Schematic Diagrams and Component Location Drawings 6 1 iii Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 2 1 2 2 2 4 2 5 2 7 3 1 3 2 3 3 3 5 3 6 5 1 5 2 5 3 5 4 5 5 5 7 5 8 5 10 6 1 6 2 6 3 LIST OF TABLES Error Messages ens daa ed ter e _ 2 4 Model 197 Maximum Allowable Inputs 2 5 Resistance Range Output 5 2 8 dB Specification for DC Volts 6000 Ref 2 10 dB Specification for AC Volts 6000 Ref 2 11 Levels for Other Reference Impedances 2 12 Comparison of Average and TRMS Meter 2 15 Recommended Test 3 Limits for DC Voltage Verification
5. PA Eee 11 ss Jalan PETERET TI 1 1 Warranty Information 1 1 Manual Addenda 4 i e ere e Sale bees OE EEG ha Oe 11 Safety Symbols and Terms odore NG eR Nea BA e i eddie 11 Specifications REL ct 1 2 Unpacking and Inspection ees 1 2 Using the Model 197 1 2 Initial 24 secus oe CER ARE RA e KG a o tim La 1 2 Accessories 2 27 ke oe Qik KON 125 Ee 1 m SECTION 2 BENCH OPERATION Introduction ss di PALAPA a ILL 2 1 High Energy Circuit Safety Precautions 2 1 Prepatation For Use eos eie nb haba on cued Aged d bd 2 1 Line POW r 31522 2m 9 VERG RO ERU ERR RE d ver 21 Battery Pack Power wei is ALE yeri uc e Re ER W bet e PIT 2 2 Battery Charging ede kane is 2 2 Front Panel Familiarization 2 2 2 2 2 Display 22244 bue Lets 2 2 Front Panel Controls sas ecer ocen pte Seay oP ng edo at P tek SCR UK Poche 2 3 Input Terminals eem beg 2 3 Current Fuse Replacement
6. 2 3 Error Messages scu eeu SSS ees PY a C4 Sde i pe ew a npa dd Pha es lapa a 2 4 Operating 2222 2 2 2 2 2 4 Environmental 4 5 2 4 Maximum Allowable Inputs 2 4 ubi 2 4 Basic Bench Measurements 4 2 4 Power Bea 2 5 Relative Mode eS P de ee NG NO RED mE CREE 2 5 DC Voltage Measurement 2 6 TRMS AC Voltage Measurements 2 6 Microvolt Measurement Considerations 2 7 Resistance Measurements he ees 2 8 Current Measurements DC or TRMS AC 2 9 AC Plus DC Measurements w kw a Ka me Ga en on dur Re Rar E ER 2 10 dB 2 10 dB Measurements Considerations and Applications 2 12 MIN MAX and 100 Point Data Logger Operation 2 13 E es 2 13 TRMS Considerations npn 2 13 AC
7. ace e rer i 5 2 Front Panel Calibration es 5 4 Recommended Calibration 5 4 Environmental hes 5 4 Calibration Jumper bak BENG e aee baee 5 4 DC Voltage Calibration ia 800444004 rm epe b Re Ra 5 5 AC Voltage Calibration re t ea d ea 5 5 Frequency 2 2 2 4 2 77 5 5 Resistance Calibration correron e pe BG NG Eee aee eue 5 7 Calibration Storage viw ___ __ _____ 5 7 Troubleshooting irrena karenna dA Rida e RACER UR eds 5 8 Power Up Sequence de Pad eed 5 8 Self Diagnostic edes i ilv _________ 5 8 Power Supply and Battery Pack Model 1978 Checks eee 5 9 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 5 7 4 5 7 5 5 8 6 1 6 2 6 3 6 4 6 5 A D Converter and Display w se sh e ebbe erm ye es 5 9 Signal Conditioning ss sse UU __ _____ 5 9 Special Handling of Static Sensitive Devices
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9. ciator appears on the display and the display reads zero test lead compensation Set the calibrator to output 1900 Adjust the display using the STO CLR and RCL buttons for a reading of 190 0002 Press REL REL annunciator turns off Select the 2kQ range and set the resistance calibrator to output zero ohms short Press REL REL annunciator turns on Set the calibrator to output 1 9kQ Adjust the display for a reading of 1 90000kQ Press the REL button and note that the REL annunciator turns off Select the 20kQ range and set the resistance calibrator out put zero ohms short Press REL REL annunciator turns on Set the calibrator to output 19kQ Adjust the display for a reading of 19 0000 Press REL REL annunciator turns off Repeat steps 7 and 8 for the 200k 2M and 20M ranges using Table 5 4 as a guide For these ranges use the con figuration shown in Figure 5 6 SENSE HI MODEL 197 Figure 5 5 200 2k and 20k Four Wire Resistance Calibration NOTE Four terminal resistance measurements need on ly be done when not using the REL feature 5 6 8 Calibration Storage To store the calibration constants simultaneously press the REL and dB buttons until the message Stor is dis plaved 1f instead the message out is displaved then calibration storage was not enabled and the calibration constants will only be valid until the Model 197 is turned off To save cali
10. A rtisan tisan Technology Group is your source for quality Tecmoboycrow new and certified used pre owned equipment FAST SHIPPING AND SERVICE CENTER REPAIRS WE BUY USED EQUIPMENT DELIVERY Experienced engineers and technicians on staff Sell your excess underutilized and idle used equipment TENS OF THOUSANDS OF at our full service in house repair center We also offer credit for buy backs and trade ins IN STOCK ITEMS www artisantg com WeBuyEquipment 7 EQUIPMENT DEMOS HUNDREDS OF Instra REMOTE INSPECTION LOOKING FOR MORE INFORMATION MANUFACTURERS Remotely inspect equipment before purchasing with Visit us on the web at www artisantg com 7 for more our interactive website at www instraview com 7 information on price quotations drivers technical LEASING MONTHLY specifications manuals and documentation RENTALS ITAR CERTIFIED Contact us 888 88 SOURCE sales artisantg com www artisantg com Instruction Manual Model 197 Autoranging Microvolt DMM Keithley Instruments Inc Cleveland Ohio U S A Document Number 197 901 01 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com SPECIFICATIONS DC VOLTS OHMS ACCURACY ACCURACY OUTPUT rdg counts MAX V rdg counts RESO INPUT 24 Hr 1 RESO NOMINAL ACROSS 24 Hr 1 Yr RANGE LUTION RESISTANCE 22 24 C 18 28 LUTION 1 5
11. CE INSTRUMENTS Instruments Division Keithley Instruments Inc 28775 Aurora Road Cleveland Ohio 44139 216 248 0400 Fax 248 6168 WEST GERMANY Keithley Instruments GmbH Heiglhofstr 5 e Munchen 70 089 71002 0 Telex 52 12160 Fax 089 7100259 GREAT BRITAIN Keithley Instruments Ltd The Minster 58 Portman Road Reading Berkshire RG 3 1EA 011 44 734 575 666 Fax 011 H 734 596 469 FRANCE Keithley Instruments SARL 3 Allee des Garays e B P 60 91124 Palaiseau Z I 1 6 0115 155 e Telex 600 933 Fax 1 6 0117726 NETHERLANDS Keithley Instruments BV Avelingen West 49 4202 MS Gorinchem P O Box 559 4200 AN Gorinchem 01830 35333 Telex 24 684 Fax 01830 30821 SWITZERLAND Keithley Instruments SA e Kriesbachstr 4 e 8600 Dubendorf e 01 821 9444 Telex 828 472 e Fax 0222 315366 AUSTRIA Keithley Instruments GesmbH e Rosenhugelstrasse 12 e A 1120 Vienna e 0222 84 65 48 Telex 131677 Fax 0222 8403597 ITALY Keithley Instruments SRL e Viale S Gimignano 4 A e 20146 Milano 02 4120360 or 02 4156540 Fax 02 4121249 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com A rtisan tisan Technology Group is your source for quality Tecmoboycrow new and certified used pre owned equipment FAST SHIPPING AND SERVICE CENTER REPAIRS WE BUY USED EQUIPMENT DELIVERY Experienced engineers and technic
12. dBV is defined as decibels above or below 1V OdBV point This is a voltage relationship independent of impedance The basic procedure is to simply subtract 2 22 dB Table 2 6 from all subsequent displayed readings on the Model 197 Relative dB Measurements Just about any voltage level within the measurement limit of the Model 197 can be established as the OdB point The basic procedure is to establish the level as the OdB point by using REL and make the desired dB measurements 2 7 10 dB Measurement Considerations and Applications 1 Typical Instrument Performance Typically the Model 197 will perform better that its published dB specification The following example will il lustrate this point A Using the Model 197 in the dB mode 600Q ref measure a 1mV RMS 1kHz source common application in the communications field Typically the Model 197 will read 57 7dBm B The calculated dBm level for that source is 57 8dBm C The 0 1dBm error is considerably better than the 2dBm specification The specifications are intended to cover worst measurement conditions 2 12 Table 2 6 Levels for Other Reference Impedances Reference Reference Voltage Offset Impedance Level for 6002 Ref 0 048 __ OdBW _ 0dBm OdBW 8 0 0894 2 828 18 75 11 25 50 0 2236 10 79 75 0 2739 9 03 150 0 3873 6 02 300 0 5477 3 01 600 0 7746 0 00 1000 1 0000 222 Viet for OdBm
13. 1 6 2 e1nBi4 Awo0z 31 25 Vins AWOOZ 3799 1103 01 1 AWOO S 11014 001 1 de SIONVY 3 1995 ki A00Z 1 31925 In i SIDNVY AOGL AZ 3199 VINA 0121 t 4 4 DE van 1M 100K 10K 1K 100 10 08 08 oz OL YOUYI Yo 0 oz Guaranteed 888 88 SOURCE www artisantg com Artisan Technology Group Quality Instrumentation Table 2 7 Comparison of Average and TRMS Meter Readings Ac Coupled Ac Coupled Average TRMS Averaging Peak Responding Meter Meter Waveform Value Meter Reading Reading Percent Error Sine 10 Half Wave Rectified Sine 10 e WE Full Wave Rectified Sine 10 ANN Square 10 H Rectified Square Wave 10 Rectangular Pulse ed 1 11 1 x 100 TI DUTY CYCLE Triangular Sawtooth 10 0 2 16 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com SECTION 3 PERFORMANCE VERIFICATION 3 1 INTRODUCTION This section contains information necessary to verify that the Model 197 s performance is within specified accuracy Model 197 specifications may be found at the front of this
14. 107eHz maximum 20 750V 750Vrms 1000V peak 107eHz maximum ACA 200 2000 10A Q 450V peak AC or DC 10 seconds per minute 350Vrms continuous 2A 250VDC or rms fuse protected 10A continuous 20A for 15sec unfused ty precautions mentioned in this manual could result in severe injury or death The LO terminal on the Model 197 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 vol tage 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 1 Power Up NOTE The software revision level of the Model 197 can be displayed upon power up by running the diagnostic program See Section 5 Mainten ance for more information Turn on the Model 197 by pressing in the ON OFF switch All zeroes are briefly displayed before going into the measure ment mode NOTE If the Model 197 does not enter the measurement mode refer to section 5 7 1 2 7 2 Relative Mode When the relative mode is selected with an on scale reading 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 all subse quent readings and displaye
15. 20 200 1000 AUTO 20k 200k AUTO 20m 200m 2000m Figure 2 1 Model 197 Front Panel 2 2 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com BAT Low battery indicator for the Model 1978 selected DC implied by the absence of the AC an nunciator mV or V Millivolts or volts 0 or MQ Ohms kilohms or megohms mA or A Microamps milliamps or amps RMT REMOTE Model 197 being controlled over the 488 bus Model 1973 or Model 1972 installed C Model 197 in calibration mode AUTO Autorange REL Relative dB Decibel measurement mode STO Data being stored RCL Data being recalled RCL flashes when buffer is full during logging cycle 2 4 2 Front Panel Controls ON OFF Pressing this button turns on the Model 197 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 zeroing of on range readings See paragraph 2 7 2 for more detailed infor mation 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 6000 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 s
16. MODEL 1681 CLIP ON TEST LEAD SET Contains two leads 1 2m 48 long terminated with banana plugs and spring action clip probes MODEL 1682A RF Permits voltage measurements from 100kHz to 250MHz AC to DC transfer accuracy is 1dB from 100kHz to 250MHz at 1V peak responding calibrated in RMS of a sine wave MODEL 1684 HARD SHELL CARRYING CASE Hard vinyl case 100mm X 300mm X 350mm 4 x 13 X 14 has a fitted foam insert with room for the Model 197 an in struction manual and small accessories MODEL 1685 CLAMP ON AC PROBE Measures 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 field produced by the current flow Artisan Technology Group Quality Instrumentation MODEL 1751 SAFETY TEST LEADS This test lead set is supplied with every Model 197 Finger guards and shrouded banana plugs help minimize the chance of making contact with live circuitry MODEL 1754 UNIVERSAL TEST LEAD KIT A 12 piece test lead kit with interchangeable plug in accessories Includ ed in the kit is one set of test leads 1 red 1 black two spade lugs two standard banana plugs two phone tips 06 DIA two hooks and miniature alligator clips with boots MODEL 1972 ANALOG OUTPUT IEEE 488 INTERFACE The Model 1972 is an optional IEEE 488 interface that in cludes all of the logic necessary to interface the Model 197 to
17. UNKNOWN 225 24 C 18 28 200mV 14V 1690 0 007 4 2 0 0163 200 Q 1mQ 2mA 0 5V 0 01 2 0 02 3 2 10 pV PIGA 0 005 2 0 011 2 2 10m2 2mA 4 0 V 0 01 2 0 018 2 20 V 100 11MQ 0 006 2 0 015 2 20 100mQ 400 pA 4 0V 0 00442 0 0262 200 V ImV 10MQ 0 006 2 0 015 2 200 kQ gt 1 2 40 pA 4 0V 0 014 2 0 02642 1000 V 10mV 10MQ 0 007 2 0 015 2 2MQ 10 0 4 pA 4 0V 0 02 2 0 03542 Relative to calibration accuracy When properly zeroed 0 100 0 400 4 0 0 10 2 012 2 NMRR Greater than 6088 at 50Hz 60Hz 0 1 kB 20051 240 TE MAXIMUM ALLOWABLE INPUT 1000V dc or peak ac less than 10 seconds per minute on the 200mV and 2V ranges 300V rms continuous SETTLING TIME 1 second to within 3 counts of final reading on range dB MODE ref 6000 Accuracy 0 02dB 1 count above 78dBm Resolution 0 014 above 0 546 of range VOLTS ACCURACY 1 Yr 18 28 rdg counts 20Hz 50Hz 10kHz 20kHz 50kHz RANGE 50Hz 10kHz 20kHz 50kHz 100kHz 200mV 1 00 100 0 35 100 0 6 200 1 54250 5 400 2V 200V 1 00 100 0 35 100 0 6 200 1 54250 34 400 750V 1 25 100 0 75 100 1 0 F 200 1 8 250 3 400 Above 1800 counts Above 18000 counts MAXIMUM ALLOWABLE INPUT 750V rms 1000V peak less than 10 seconds per minute on 200mV and 2V ranges 300V rms continuous 107 2 maximum 348 BANDWIDTH 300kHz typical INPUT IMPEDANCE 1 paralleled
18. applying 1 99999V to the input displays 4 3 99999V Once the REL level is established that level is algebraically subtracted from the input signal For example it a 1 00000V REL level is established then applying a 2 00000V level displays 1 00000V level The instrument accepts 220 000 count input before going into the overrange condition OL For example 1 00000V REL level is established and 1 50000V is applied The instru ment displays 2 500000V If the input is 2 20000V the in strument overranges 2 7 3 DC Voltage Measurement The Model 197 can make DC voltage measurements between 14 and 1000V The basic procedure is as follows 1 Connect the test leads to the HI and LO INPUT terminals of the Model 197 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 2 If the positive source terminal is connected to the LO ter minal of the instrument the display shows a negative value If the negative source terminal is 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 reading is displayed Always use the lowest possible range for the best resolution 6 Ta
19. 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 In the manual trigger mode r 6 a reading is stored every time the STO CLR button is pressed The follow ing sequence takes place after the STO CLR button is pressed when in the manual trigger mode a The Model 197 stores the reading b The buffer location number is briefly displayed For example Buffer location 1 is represented by n 01 c The Model 197 displays the applied signal and waits for the next manual trigger Artisan Technology Group Quality Instrumentation 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 retained and can be recalled at any time as long as the instru ment remains on In the r 6 mode press the RCL and the STO CLR button to terminate the data 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 up dated 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 po
20. waveform Refer to schematic 197 106 for detailed compo nent location The charge balance phase begins when the input enable disable line is set high This occurs at the end of a software generated delay period that allows the signal to set tle after the appropriate multiplexer FET is turned on Once this occurs an offset is added to the signal from the buf fer to convert it to a negative unipolar input to the integrator The signal from the buffer has a range of 2 2V to 2 2V on the volts and amps functions and to 4V on the ohms function Therefore it is necessary to have a larger offset on the ohms function This is done by switching in R117B The integrator comprised of Q121 U110 and C123 ramps up until it just passes the charge balance comparator threshold voltage When the rising edge of Q3 U119 occur Q1 of U117A goes high forcing into the integrator input The time Q1 of U117A remains high depends upon the state of comparator U108B when Q3 U119 goes high Thus the amount of fed back to the integrator input will be propor tional to the input voltage Each time the output U117A goes high it is gated inside the microprocessor with the microprocessor s internal clock and pulses are counted Once U117A goes low the process repeats itself The charge balance phase continues for 100msec At the end of the charge balance phase the output of the integrator is resting at some positive voltage Since the
21. 6 12 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com G 13247 e CA Telz 0 36 L A6 02S 2 213282 MS Ask RN Ng eS dd 9 vel 19 9 q ng Ng N NG wy V O 3 k vu NG Pi O c KO ki Lee Os ak 5 We f 5 NE x lt Sg lt sa N NN hw A JO Nal o lt SVI Sx Q mu aux ls 3 WIN A 9 5 lt 51953 lt MG KU IPIN 17 89 Sho 7 NS S c D S 6 24 70222 ELETED ITEM 4S 295 100 143 lw 13403 DELETED tTEM 8 C 367 1 5p C106 C2 ON OO 4 6 52 05 ro on eoo 3 oa ka S PER EV 1 5P TO l 2451 I 50 HD 5400P TO lt RI3B p 28 2es5 __ 22221 422454 _ gt 2251 E 76 21 ANB Fico LTEM WASC 9 220 HG D 2 Br 1 Lp je 9 Nb eer t E E HH 1141 171 72 Bee 0O Z 267 be ITEM 203 WAS 3 VELIT Y 92311519 944500 91111 lt 191815514 l ANN Ol 2 ISIN S SN SS 8 wi LIE S
22. 750V ranges 0 05 5200A 8 5215A 5450A Resistance Calibrator 19022 50ppm 1 9 50ppm 19k 62 50ppm 190k 50ppm 1 9MQ 100ppm 19M 500ppm 90 day accuracy Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com NOTE Calibration may be stopped at any time and if desired only selected ranges may be calibrated FIGURE 5 2 WAS DELETED ON REVISION C OF THIS MANUAL Figure 5 2 5 6 4 DC Voltage Calibration Select the DCV function Connect the DC calibrator to the Model 197 as shown in Figure 5 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 197 is now in the calibration mode The calibration mode is indicated by the C annunciator 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 in crements the displayed reading The RCL button decrements the displayed reading The longer either button is held in the faster the displayed reading is modified 5 Select the next range 2V and set the calibrator output to 1 90000V 6 Repeat step 4 to read 1 90000 7 Reverse the calibrat
23. 901 00 The manual package includes an instruction manual and all perti nent addenda 6 4 FACTORY SERVICE If the instrument is to be returned to the factory for service photo copy and complete the service form which follows this section and return it with the instrument 6 5 SCHEMATIC DIAGRAMS AND COMPONENT LOCATION DRAWINGS The component location drawings and schematic diagrams are presented as follows Figure 6 2 Model 1978 Battery Pack Component Location Drawing Dwg No 1978 100 Figure 6 3 Mother Board Component Location Drawing Dwg No 197 100 Figure 6 4 Display Board Component Location Drawing Dwg No 197 110 Figure 6 5 Mother Board Schematic Diagram Dwg No 197 106 Figure 6 6 Display Board Schematic Diagrm Dwg No 197 116 Figure 6 7 Model 1978 Battery Pack Schematic Diagram Dwg No 1978 106 6 1 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com WINDOW BEZEL si 175 305 MASK 175 306 wou kib DD 36 ___ RETAINER 175 307 STRIP CONNECTOR 2 CS 460 2 Figure 6 1 Display Assembly Exploded View Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 6 6 Table 6 2 Display Board Parts List Schematic Location Keithley Desig Description Sch Pcb Part No DS 201 5 1 2 Digit Li
24. Guaranteed 888 88 SOURCE www artisantg com T101 the power transformer has two secondary windings one for the Model 197 and the other for the Model 1972 Analog Output IEEE option or the Model 1973 IEEE option The bridge rectifier CR107 functions as a fullwave rectifier for both the plus and minus supplies R131 limits current to the 15V zener VR104 and to the batteries if installed for charging VR104 acts as a pre regulator to the 4 10V supply R132 limits current to the 15V zener VR105 105 acts as a pre regulator to the 9V supply 4 7 MODEL 1978 BATTERY OPTION Maximum battery charging rate is achieved when the instru ment is connected to line power and the on off switch is off Fullwave rectified voltage from CR107 is applied to R102 and BT101 to charge the batteries 0101 acts as a current sink if the charging current rises above 150mA The batteries are of the quick recharge type and will charge in 8 to 10 hours With the instrument turned on the batteries will trickle charge at approximately 40mA With the battery pack installed the negative supply is generated using a CMOS voltage inverter U101 The output of the inverter is applied to CR101 and C101 for filtering Low battery detection is accomplished by the comparator U102 and the microprocessor A voltage level of 11 6V across BT101 signals and end of useful battery life The trip level for the comparator is set by R103 and R104 4 7 4 8 Artisa
25. Input Buffer Amplifier Protection for the AC and DC voltage functions is provided by 0103 Q127 114 Q115 CR102 CR104 R106 R107 and R113 R106 and R107 are used exclusively on the 200mV and 2V ranges of DCV to limit current to Q114 and 115 R113 is used exclusively on the 200mV and 2V ranges of ACV to limit current to CR102 and CR104 Signal conditioning for current is performed by R112 R118 and R123 current shunts For DC current measurements the shunt voltage drop 220mV full range is applied directly to the input signal FET for conversion In AC current the shunt voltage drop is treated as a 220mV AC signal and is switch ed to the AC converter section Overload clamping occurs at 3 diode drops which is a level high enough to permit high crest factor current waveforms In DCV the properly scaled signal is applied directly to Q111 through R106 R107 and C109 In ACV the scaled signal is ap plied to the AC converter for transformation to a DC signal that is applied to Q111 Resistance measurements are made using the ratiometric technique see Figure 4 4 When the resistance function is selected a series circuit is formed between the ohms source a reference resistor and the external unknown resistance ohms source of 4 3V is obtained by placing a protection diode CR101 in series with a 5V supply and the ratiometric net work current then flows through the reference resistor and the unknown resistance Sin
26. Logic Levels On U Range Mode U102 U104 FET On Transistor On PAO PA1 PA2 2kQ 002 X1 0113 0104 0105 0 0 0 1 102 X1 0112 0104 0105 0 0 0 0 202 Q111 0104 0105 0 0 1 0 2 Q110 Q104 Q105 1 0 0 0 20 0 003 X1 Q113 Q104 0105 0108 0109 O 0 0 1 103 X1 0112 0104 0105 0108 0109 0 0 0 0 203 X1 Q111 0104 0105 0108 0109 0 0 1 0 3 X1 0110 0104 0105 0108 0109 1 0 0 0 200kQ 004 X1 Q113 0104 0105 0108 0109 0 0 0 1 104 X1 Q112 0104 0105 0108 0109 0 0 0 0 204 X1 Q111 0104 0105 0108 0109 0 0 1 0 304 X1 0110 0104 0105 0108 0109 1 0 0 2MQ 005 X1 Q113 Q104 Q105 i 0 0 0 1 105 X1 Q112 0104 0105 0 0 0 0 205 X1 Q111 0104 0105 0 0 1 0 12 305 X1 Q110 0104 0105 1 0 0 20M amp 006 X1 Q113 0 0 0 1 200M 106 X1 Q112 0 0 0 0 Auto 206 xj 0111 9 10 17120 306 XI 0113 01070 1 0 1 0 6 X1 Xb Q111 0 0 110 All 1A1 1A6 XI X5 0112 0 0 0 0 Ranges 2 1 2 6 X1 X5 0113 0 0 0 1 3A1 3A6 X1 X5 0112 0 0 0 0 5 8 SPECIAL HANDLING OF STATIC SENSITIVE DEVICES CMOS devices are designed to operate at very high im pedance levels for low power consumption a result any normal static charge that builds up on your person or clothing may be sufficient to destroy these devices if they are not handled properly Table 5 10 lists all the static sensitive devices in the Model 197 When handling these devices use the following precautions to avoid damaging them 1 The devices l
27. Model 197 is 1 54 V peak to peak This noise is inherent in the Model 197 and is the minimum amount present in all measurements The 1 54 V of noise is due to the instrument voltage noise The noise at the Model 197 input increases 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 resistance and is given by the equation n2 2 i R 2 e where n total noise input e input voltage noise of the Model 197 i input current noise R parallel combination of source resistance and input im pedance e Johnson noise of the source resistance Even on most sensitive range the noise due to the current is not appreciable until reaches approximately 1 0 Thus for an of 00 to 1 the noise at the input is the inherent 1 54V peak to peak Beyond 1MQ the noise due to R becomes a limiting factor in the measurement Therefore it is recommended that for sensitive measure ments be kept relatively low if possible below 1MQ As an example of determining e noise voltage generation due to Johnson noise of the source resistance assume that the Model 197 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 10 10lR x f e 6 35 x 10 19 1 x 105 1 e 0 6354V Thus i
28. N10 3WeZpep Viet for OdBW VZREF 2 Offset for dBm 10 log 7 6000 ZREF Offset for dBW 10 log 6002 3048 2 Measuring Circuit Gain Loss Any point in a circuit can be established as the OdB point Measurements in that circuit are then referenced to that point expressed in terms of or loss dB To set the OdB point A Place the Model 197 in volts autorange and dB B Connect the Model 197 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 referenced to the OdB point Measuring Bandwidth Model 197 can be used to determine the bandwidth of an amplifier as follows A Connect a signal generator to the input of the amplifier B Set the Model 197 to ACV and autorange C Connect the DMM and a frequency counter to the load of the amplifier D Adjust the frequency of the signal generator until a peak AC voltage reading is measured on the Model 197 E Press the dB button and then press the REL button The OdB point is now established F Increase the frequency input until the Model 197 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 reading again falls to 3dB The frequency measured on the signal generator is the low end limit of the bandwidth Artisan Technology Grou
29. SEE 197 106 OR 580 106 mE LS m RE ADDED KEFEBENLE gt 586 VIA 2 2210 220 L pook ti 5 fo 5 _ t MATES WITH JI009 5330 DELETED 1PI TP2 4 24 lt 24 92 NC NC NC a W W E 1 12 0 3 NG ES 3 SEE TABLE 7 T 9 3 3 5 V n e 4 cio2 p s E CIOI i mE A 5 CRIOI 4 NOTES 1 ALL RESISTOR VALUES ARE IN OHMS UNLESS OTHERWISE MARKED K KILOHMS M MEGOHMS 2 ALL CAPACITOR VALUES IN MICROFARADS UNLESS OTHERWISE MARKED pF PICOFARADS 3 Y DENOTES ANALOG COMMON 4 _0 DENOTES TEST POINT 4 103 K 88 40 2K a x 88 44 2 d HIGHEST SCHEMATIC SCHEMATIC DESIGNATIONS 1 6 DESIGNATIONS USED NOT USED ion NG 6 MODEL NEXT ASSEMBLY QTY nG USEDON 5 3 scateNONE ME SCHEMATIC Dx ros ANS ren PRA Ze een mA BATTERY OPTION __ SURFACE MAX 463 C 1978 106 2 20 se NE 7 Keithley Instruments Inc KEITH LEY Cleveland Ohio 44139 88 SOURCE www artisanta com m ON NEN NGA CPP ENS REE m Artisan Technology Group Quality Instrumentatidp 4 Guaranteed 888 ENAR 720956970 Dh
30. Voltage Offset ero e d a oben Na ers E 2 14 TRMS Measurement 2 14 Crest Pacto as ioo ath us aed Deos ad dada Deest a GRAIN deseri 2 14 Extended Frequency Response 2 14 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com SECTION 3 PERFORMANCE VERIFICATION Introduction Dette 3 1 Environmental 2 3 1 Recommended Test 2 3 1 Initial Conditions ex aca g _________________ VY Eee s 3 1 Verification Proced te esos a gu ap BER kad 3 1 DC Voltage Accuracy 3 2 AC Voltage Accuracy Check iiis sheen a XH et Eventi NAG 3 2 Resistance Accuracy Check 3 3 DC Current Accuracy 2 3 4 AC Current Accuracy 2 3 5 SECTION 4 THEORY OF OPERATION 809 AA AA 4 1 Overall Functional Description
31. as well as standard troubleshooting procedures The informa tion presented here has been written to assist in isolating a defective circuit or circuit section isolation of the specific component is left to the technician The success or failure in troubleshooting an instrument such as the Model 197 depends not only the skill of the technician but also relies on accurate reliable test equipment Table 5 5 lists the required test equipment and specifications recom mended for troubleshooting the Model 197 Other equipment such as logic analyzers capacitance meters etc could also be helpful in difficult situations 5 7 1 Power Up Sequence The software revision level of the Model 197 may be displayed upon power up by running the diagnostic program The diagnostic program is explained in paragraph 5 7 2 When the Model 197 is turned on it goes through a power up sequence that is outlined as follows 1 Reset All zeroes are briefly displayed before going into the measurement mode During this display the Model 197 goes through a check of the RAM circuitry and a check of the NVRAM circuitry 2 If the RAM circuitry has a problem the Model 197 locks up with all zeroes Refer to Table 2 1 3 If the NVRAM test fails the following message is displayed cErr 5 8 4 If no problem is found by the RAM and NVRAM checks the Model 197 goes into the measurement mode If the RAM check reveals a problem check U121 If the NVRAM che
32. calibrator to the HI and LO INPUT ter minals of the Model 197 as shown in Figure 3 2 3 Set the calibrator to output 2 00000V at a frequency of 50Hz Verify that the reading is within the limits specified in Table 3 3 4 Repeat the 2 00000V AC measurement at the other fre quencies specified in Table 3 3 5 Check the 20V 200V and 750V ranges by applying the re quired voltage and frequencies specified in Table 3 3 and verifying that the readings are within the specified limits AC CALIBRATOR MODEL 5200A and MODEL 5215A MODEL 197 Figure 3 2 Connections for ACV Verification Guaranteed 888 88 SOURCE www artisantg com Table 3 3 Limits for AC Voltage Verification 197 AC Applied Range AC Voltage 20Hz 50Hz 10k Hz 20kHz 50kHz 100kHz 200mV 200 000mV 197 900 199 200 198 600 196 750 189 600 189 600 to to to to to to 202 100 200 800 201 400 203 250 210 400 210 400 2 2 00000V 1 97900 1 99200 1 98600 1 96750 1 93600 1 93600 to to to to to to 2 02100 2 00800 2 01400 2 03250 2 06400 2 06400 20 V 20 0000V 19 7900 19 9200 19 98600 19 6750 19 3600 19 3600 to to to to to to 20 2100 20 0800 20 1400 20 3250 20 6400 20 6400 200 V 200 000V 197 900 199 200 199 860 196 750 193 600 to to to to to 202 100 200 800 201 400 203 250 206 400 750 V 750 000V 739 63 743 37 740 50 to to to 760 37 755 62 759 50
33. checked by connecting a calibrated DC current source to the HI and LO INPUT terminals 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 allowable 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 3 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 terminal should be connected to the HI terminal and the LO side of the calibrator output should be connected to LO 3 Set the calibrator to 00 000 and enable the realtive REL mode 4 Verify that the displayed reading is within the limits specified in Table 3 5 5 Switch the Model 197 to the 20mA range Set the calibrator to output 20 0000mA Verify that the displayed reading is within the limits specified in Table 3 5 6 Switch the Model 197 to the 200mA range Set the calibrator to output 200 000mA Verify that the displayed reading is within the limits specified in Table 3 5 7 Switch the Model 197 to the 2000mA range Set the calibrator output 2000 00mA Verify that the reading is within the limits specified in Table 3 5 8 Set the Model 197 to the 10A range Connect the DC cur rent to the 10A and LO terminal as show
34. if frequency compensation should be performed on the Model 197 and to perform frequency compensation if necessary This procedure requires the Model 197 to be warmed up for at least one hour Note that this section is not to be used to verify that the 5 5 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Model 197 AC Voltage function is within specifications If desired refer to Section 3 Performance Verification WARNING Steps 1 through 4 require the use of high voltage Take care not to come into contact with live circuits that could cause personal injury or death 1 Select the 750VAC range and set the calibrator to output 500 00V at 500Hz Press the REL button REL annunciator turns on 2 Set the calibrator to output 500 00V at 20kHz Verify that the reading on the Model 197 is 000 00 150 counts Press REL REL annunciator turns off 3 Set the calibrator to output 100 00V at 500Hz and select the 200VAC range Press the REL button REL annunciator turns on 4 Set the calibrator to output 100 000V at 20kHz Verify that the reading on the Model 197 is 000 000V 200 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 Verify that the reading on the Model 197 is 00 0000 200 counts Press REL REL annunciator
35. manual Ideally performance verification should be performed when the instrument is first received to ensure that no damage or change in calibration has occurred during shipment The verification procedure may also be performed whenever in strument accuracy is suspect or following calibration If per formance on any of the ranges or functions is inconsistent with specifications calibration should be performed as described in Section 5 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 deter mine the action to be taken 3 2 ENVIRONMENTAL CONDITIONS measurements should be made at an ambient temperature 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 197 is listed in Table 3 1 Alternate equipment may be used as long as equipment accuracy is at least equal to the specifications listed in Table 3 1 3 4 INITIAL CONDITIONS Before performing the verification procedures make sure the Model 197 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 instrument that is 10 C 18 F outs
36. maximum and 100 point data logger WARNING Before operating the Model 197 observe all previously mentioned safety precautions When testing high energy power circuits follow the instructions found in paragraph 2 2 Failure to observe these and other safe Table 2 1 Error Messages Display Message Comments 00000 RAM Error Calibration Error NVRAM Failure Overrange Model 197 locks up See Section 5 for troubleshooting information Model 197 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 annunciator See Section 5 for troubleshooting information Overrange input applied to the Model 197 Leading minus sign indicates that input signal has a negative value lac Err a Invalid 0 Function AC and 0 annunciators flash Correct problem by releasing Ha out AC DC pushbutton 2 4 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 2 3 Table 2 2 Model 197 Maximum Allowable Inputs Function Ranges Maximum Allowable Inputs DCV 200mV 2V 1000VDC or peak AC for less than 105 per minute 300Vrms continuous 20 1000V _ 1000VDC or peak AC ACV 200mV 2V 750Vrms 1000V peak for less than 10sec per 300Vrms continuous
37. on the other two standoffs E Reinstall the modified top cover 5 Reinstall the top cover as explained in paragraph 5 2 5 5 2 Current Fuse Replacement The current fuse protects the 2004A through 2000mA ranges from an input current greater than 2 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 Carfeully press in and rotate the fuse carrier one quarter turn counterclockwise Release pressure remove the fuse and the fuse carrier from the front panel 3 Remove the defective fuse and replace it with the following type 2A 250V 3AG normal blow Keithley Part Number FU 13 or equivalent CAUTION Use only the recommended fuse type fuse with a higher current rating is install ed instrument damage may occur upon overload Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com TOP COVER 175 313 REAR PANEL LABEL MC 372 4 Es FUSE HOLDER 12 ma FH 12 BOTTOM COVER 175 314 o D LINE CORD ES an 9 CURRENT FUSE HOLDER BODY FH 21 i CURRENT FUSE CARRIER FH 25 BOTTOM SHIELO SPACER 14 25762 FEET 141 FE 10 TOP SHIELD 197 312 HANDLE SWITCH PAD FOR 4 SWITCHES 175 308 FRONT PANEL 197 304 FRONT PANEL OVERLAY 197 310
38. protection of the ohms source by limiting current The Model 197 is equipped to make 2 or 4 terminal resistance measurements Generally 4 terminal measurements should be made on the 2000 range because the relatively large output current can develop a significant voltage across the test leads affecting instrument accuracy Figure 4 4 shows the equivalent circuit of the input circuit Ry is the unknown measured resistance and R1 R2 R3 and R4 represent the test lead resistance R2 and R3 are connected on ly during 4 terminal measurements When using a 2 terminal configuration all the current flows through the test leads R1 and R4 If has a low value the amount of voltage developed across the test leads can be significant Since the voltage is sensed across the combined resistance of Rx and R4 considerable error can be introduced into the reading To use a 4 terminal connection a second set of leads R2 and R3 are connected to the unknown resistance The amount of 44 current through R2 and R3 is much smaller than the current through R1 and Thus the voltage seen by the instrument is much closer to the actual value across the measured resistance minimizing the error 4 3 5 A D Converter The Model 197 uses a combination constant frequency variable pulse width charge balance single slope analog to digital converter A simplified schematic of the A D used in the Model 197 is shown in Figure 4 4 with an associated
39. the IEEE 488 bus The Model 1972 is similar to the Model 1973 however it contains an analog output The analog out put is a scaled output that follows the display of the Model 197 The Model 1972 is field installable MODEL 1973 IEEE 488 INTERFACE The Model 1973 is optional IEEE 488 interface for the Model 197 This interface adds extra versatility to the Model 197 by allowing the transmission of data and commands over the IEEE 488 bus The interface provides all the logic necessary to interface the Model 197 to the bus using standard IEEE 488 1978 protocol The Model 1973 is field installable MODEL 1978 RECHARGEABLE BATTERY rechargeable battery pack allows off line or in the field opera tion of the Model 197 The pack provides typically five hours operation from full charge The battery pack contains its own charging circuit and can be recharged within 10 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 connector at each end The Model 7008 6 is 1 8m 6 ft in length and has a standard IEEE 488 connector at each end MODEL 8573 IEEE 488 INTERFACE The Model 8573 is an IEEE 488 standard interface designed to interface the IBM PC or XT computers to Keithley instrumentation over the IEEE 488 bus The interface system contains two distinct parts an interf
40. to charge for a minimum of 10 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 10 hour charge cycle do the following A Disconnect the Model 197 from line power B Turn on the Model 197 and leave it on to completely discharge the battery pack Connect the Model 197 to line power and charge the battery pack for 10 hours with power off Repeat steps through C three more times The bat tery pack should again be good for typically five hours 3 When the Model 197 is in use on line power the battery charger maintains a trickle charge on the battery pack C D NOTE The IEEE options Model 1972 and Model 1973 do not run off of battery power 2 4 FRONT PANEL FAMILIARIZATION Figure 2 1 and the following paragraphs provide a brief description of the display front panel controls and input ter minals 2 4 1 Display The Model 197 has a 54 digit liquid crystal display LCD The minus sign is displayed The plus sign is implied by the absence of the minus sign The following annunciators are displayed on the LCD KEITHLEY 197 AUTORANGING MICROVOLT DMM BAT REL d8 STO mVC rrr Li Kt Lt RQ uma RMT
41. 0200000121 This offset is seen as the last digit which is not displayed on the Model 197 Therefore the off set is negligible 5 Observe the display if the OL message is shown select a higher range until a normal reading is displayed Always use the lowest possible range to obtain the best resolution Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 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 AC VOLTAGE SOURCE CAUTION MAX INPUT 750V RMS 1000V pk INPUT IMPEDANCE 1MQ SHUNTED lt 75pF MODEL 197 Figure 2 3 TRMS AC Voltage Measurements 2 7 5 Microvolt Measurement Considerations Accuracy Considerations For sensitive measurements other external considerations besides the Model 197 will affect the accuracy Effects not noticeable when working with higher voltages are significant in microvolt signals The Model 197 reads only the signal received at its input therefore it is im portant that this signal be properly transmitted from the source The following paragraphs indicate factors which af fect accuracy noise source resistance thermal emfs and stray pick up Noise and Source Resistance The limit of resolution in measuring voltages with the Model 197 is determined by the noise present The displayed noise of the
42. 101 Base Battery option 1978 checks tacle power on 13V to 16 5 6 4 596 6 4 5 10V 41096 15V 10 6 4V 10 6 4V 1096 9 0V 5 5V 5 5V 5 5 0 4596 5 0V 1096 0 6V while charging Power switch off 17 U101 pin 8 gt 10 8V Line cord disconnected battery pack charged and power on 18 U102 pin 7 5V with batteries charged V power for regulator circuitry Virtual Reference Reference Zener 10V Supply V power for regulator circuitry Inverting input for U107 Low noise negative supply reference 9V Supply 5V supply reference Inverting input for U116 5V analog supply 45V digital supply Current Sink Voltage Inverter Voltage Comparator f Q123 is replaced be sure that the device is properly seated on the mother board so that it will not touch the IEEE board if installed Table 5 8 Display Board Checks Step Item Component Required Condition Remarks 1 Turn on power select the 2V range 2 P1006 pin 5 3 3V Vicd1 3 P1006 pin 6 1 66V Vicd2 4 P1006 pin 7 5V 5 Power to Display 5 P1006 pin 2 81 92kHz Clock 6 P1006 pin 1 OV to 5V Pulses Data From 7 P1006 pin 12 OV to 5V Pulses Data From 8 P1006 pin 13 OV to 5V Pulses Data From yp 9 1006 pin 14 5V to Pulses Data From yp 10 LCD Verify that thet LCD is properly posi tioned 11 Connector P1006 Check that connector is not r
43. 4 Q107 0118 0 0 110 1u1 X1 X5 Q112 0104 0107 0118 0 o 0 0 2u1 X1 X5 0113 0104 0107 0118 01 3u1 X1 X5 0112 0104 0107 0118 0 0 0 0 a 2VAC 0 2 X1 X1 0111 0104 0107 O118 0 0 110 102 X1 X1 Q112 0104 0107 0118 0 0 2u2 X1 X1 0113 0104 0107 0118 0 0 0 1 3u3 X1 X1 Q112 Q104 0107 0118 0 0 O 0 20VAC 003 X1 X1 0111 0104 0105 0106 0107 0 0 110 143 X1 X1 0112 0104 0105 0106 0107 0 0 0 0 2u3 X1 X1 0113 0104 0105 0106 0107 0 0 0 1 3u3 X1 X1 0112 0104 0105 0106 0107 0 0 0 0 200 044 X1 X1 0111 0104 0105 0108 0109 0 0 1 0 1u4 X1 X1 0112 0104 0105 0108 0109 0 0 010 244 X1 X1 0113 0104 0105 0108 0109 0 0 0 1 3u4 x1 X1 0112 0104 0105 0108 0109 010 010 750 045 X1 X1 Q111 Q104 Q105 0 0 1 0 1u5 X1 X1 Q112 Q104 Q105 0 0 0 0 245 X1 X1 0113 0104 0105 0 0 0 1 3u5 X1 X1 0112 0104 0105 0 0 0 0 DCA 0 6 10 0111 0 1 1 0 1A1 1A6 X10 Q112 0 1 0 0 Ranges 2A1 2A6 X1 Q113 0 0 0 1 3A1 3A6 X1 Q112 0 0 0 0 2000 001 X10 Q113 0104 0105 0 1 0 1 101 X10 Q112 0104 0105 0 1 0 0 201 X1 Q111 Q104 Q105 0 0 1 0 301 X1 Q110 Q104 Q105 1 0 0 0 5 10 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Table 5 6 Model 197 Troubleshooting Mode Cont Function DC Amp AU Range Control and Test Gain Multiplexer Range
44. ACT DESCRIPTION gt _ _ em _ 1 AUTO REL STO 1 2 3 4 dB f 5 6 7 8 9 O 69 54 6b 6c 3 Sdp 3 18 5a 5g 54 11 5b 5 12 4 4e 44 4 MATES WITH JIOO6 3f OF MOTHER BOARD 3s SEE 197 106 3b 3e 4 4 da 4 ib te m M NOTES E ALL PUSHBUTTON SWITCHES ARE SHOWN IN THE PUSHBUTTON OUT POSITION CUM 8 DENOTES DIGITAL COMMON 5 15 Ep SCHEMATIC DESIGNATIONS NOT USED 1 a 197 774 NEXT ASSEMBLY a 020 21006 PIOOI THRU PIOO T Mone Next a 0520 me SCHEMATIC NES WL wm AA DISPLAY BOARD KEITHLEY ka mee 2 Cj 197 16 FORM 30152C REV D p t A a B Artisan Te amp hnology Group Quality w GNG gom rmm dm F Figure 6 7 Model 1978 Battery Pack Schematic Diagram Dwg No 1978 106 6 21 6 22 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com m 2 9 282 M A 3 5 MI 901 8261 _______ _______ ON RELEASED X OF MOTHER BOARD A 2542 4 19 27 LEASED PAP 1p
45. C Current 9 Set the calibrator to output 5 0000A Verify that the Verification 2000mA to 20A displayed reading is within the limits specified in Table 3 6 3 5 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Table 3 6 Limits for AC Current Verification Applied 197 AC Range AC Current 20Hz 50Hz 5kHz 200 pA 200 000 197 900 198 300 195 750 to to to 202 100 201 700 204 250 2mA 2 00000mA 1 97900 1 98300 1 95750 to to to 2 02100 2 01700 2 04250 20mA 20 0000mA 19 7900 19 8300 19 5750 to to to 20 2100 20 1700 20 4250 200mA 200 000mA 197 900 198 300 198 270 to to to 202 100 201 700 201 730 2000mA 2000mA 1979 00 1983 00 1982 70 to to to 2021 00 2017 00 2017 30 10 A 5 0000 A 4 9150 4 9400 4 9400 to to to 5 0850 5 0600 5 0600 Not to exceed 1kHz HI OUTPUT LO OUTPUT MODEL 197 AC VOLTAGE CURRENT AC VOLTAGE CURRENT CALIBRATOR CALIBRATOR CALIBRATOR CALIBRATOR MODEL 5200A MODEL 2500E MODEL 343A MODEL 2500E Figure 3 7 Connections for AC Current Figure 3 8 Connections for AC Current Verification 2005 to 2000mA Verification 2000mA to 10A 3 6 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com SECTION 4 THEORY OF OPERATION 4 1 INTRODUCTION This section contains an overall functional descr
46. Current Verification 2000mA to 20 Connections for AC Current Verification 200 to 2000mA Connections for AC Current Verification 2000mA to 10 Simplified Block Diagram JFET 2 2 2 2 2 2 Simplified Schematic of the Input Buffer Amplifier Input Configuration During 2 and 4 Terminal Resistance Measurements Resistance Measurement Simplified Circuit A D Converter icis EE E CR a de ERGO ERE OUR CGU ROO Model 197 Miscellaneous Parts DELETED ON REVISION G oe com dle EAR KH a dp zi eo ORE agen RR DC Voltage Calibration Configuration AC Voltage Calibration Configuration ee 200 2k and 20k Four Wire Resistance Calibration 200k 2M and 20M Two Wire Resistance Calibration Segment Identification Display Assembly Exploded Waka ham Dee ivan eats Model 1978 Battery Pack Component Location Drawing Dwg No 1978 100 Mother Board Component Location Drawing Dwg No 197 100 Display Board Component Location Drawing Dwg No 197 110 Mother Board Schematic Diagram
47. Dwg No 197 106 eee ee nen er ea veve va eee ven Display Board Schematic Diagram Dwg No 197 116 Model 1978 Battery Pack Schematic Diagram Dwg No 1978 106 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com v vi SAFETY PRECAUTIONS The following safety precautions should be observed before operating the Model 197 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 instru ment Exercise extreme caution when a shock hazard is present at the instrument s input The American National Stan dards Institue ANSI states that a shock hazard exists when voltage levels greater than 30V rms or 42 4V peak are present good safety practice is to expect that a hazardous voltage is present in any unknown circuit before measuring Inspect the test leads for possible wear cracks or breaks before each use If any defects are found replace with test leads that have the same measure of safety as those supplied with the instrument 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 Always disconnect all unused test leads from t
48. FIED 02156 5 AA SCALES 015 ANG 005 16109 161 59 SAT 2 M 3 H G E D Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com REV FORM 285110 A Figure 6 4 Display Board Component Location Drawing Dwg No 197 110 6 13 6 14 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Pea Ue ILLU St ey o E s mE ae Taas REVISION ENG DATE j 2 2 55 YA ee DI Z6 Z Z eo DAE REV FROM D TOE 27 2 Era r 197 112 01 MADE IN USA a 4 E DISPLAY Plooc CS Rer S Dec c4 Rer R ZEBRA 3 MASK LCD STRIP S EN 3 5 5 7 3 4 Ny SE RETAINER EAE a DISPLAY LCD Cl Ul 197 2 2 MODEL NEXT ASSEMBLY 6 T COMPONENT LAYOUT mm 5219 DRN7 e APPR INA DISPLAY BOA jw Keithley Instruments Inc FRAC 1 64 NO KEITHLEY Cleveland Ohio 44139 9 a E FORM 30152 Rx C m n E F G _ B Artisan Techhology Group Quality Instru tation Guaranteed 888 88 SOURCE www artisantg Z m Figure 6 5 Mother Board Schematic Diagram Dwg No 197 106 s
49. I W 4 1 1 gt a MATES WITH PIOO9 OF BATTERY OPTION BOARD E 1978 106 Ter SCHEMATIO A 015 ANG 19 ngg rs MOTHER BOARD HLE Y Keithley Instruments Cleveland Ohio M SHE 9E e a A EXE di HE EM 4 E AZ we IDE Lese she TING Duces av EHE DEOR LY See ree Ta C SURFACE MAX 57 Figure 6 5 Mother Board Schematic Diagram Dwg No 197 106 sheet 2 of 2 6 17 6 18 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com BRUNING 44 131 60137 PAGE ZONE H4 r PAGE ZONE H3 1A RELEASEO Pad 445 Jon C VOO 26 110 WAN lDpeso seeP4 amp i W 23 85 At 22 PIE as ue 2 7 O 7669 SEE CGI MN 2266 12058 SEE PAGE 14 ME 68 pace 1 27 SEE L A B C D 1 Zu RJ 5 7709 0 4 13247 REMOVED 145 2245 10 49 89 13403 SEE PAGE 2 72 14 12 89 CHG D FROM 65C21 63821 4 TEEN Q117 ULIZA PIN 9 O 01128 PIN 5 UII2C PIN 7 6 9120 PI
50. I and LO terminals or damage to the instru ment may occur Connect the calibrator to the instrument as shown in Figure 3 1 Set the calibrator to and enable the relative mode Leave the relative mode enabled for all DCV measurements Check to see that the reading is 000 000V t count Apply a positive 200mV to the HI and LO INPUT ter minals The reading must be within the limits specified in Table 3 2 For each remaining range apply the required voltage as specified in Table 3 2 and verify that the reading is within specifications Repeat all checks with negative voltage DC CALIBRATOR MODEL 343A MODEL 197 Figure 3 1 Connections for DCV Verification 3 2 Artisan Technology Group Quality Instrumentation Table 3 2 Limits for DC Voltage Verification 197 Applied T Allowable Readings DCV Range DC Voltage 18 to 28 200 200 000 199 965 to 200 035 2 2 00000 V 1 99976 to 2 00024 20 V 20 0000 V 19 9968 to 20 0032 200 V 200 000 V 199 968 to 200 032 1000 V 1000 00 V 999 68 to 1000 32 The limits shown do not include test equipment tolerances 3 5 2 AC Voltage Accuracy Check CAUTION Do not exceed 750V RMS 1000V peak 107VHz between HI and LO INPUT ter minals or instrument damage may occur 1 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 2 Connect the AC
51. INISE VS NI F FIFA Fx 10 a vi d 9 A a S z Y iQ KAN ANA dah tae 0009 out sx T al f 11 39 19 13132019 2 is law 3 03 83 55 SAN c NG AY NIA 50116499 9 5 NAINA A Q 0 9 MG emm e vila 8 N 94 94 4 919 QR 46 M Ng din ARO po c 3 4 220 CHG O ARTWORK FROM REV T ADDED ITEM 45 C 295 100 C443 TO i3 4448 IN M iv YIN Y N 111 ke mimm im Iw m v 16 ka ka e SIG 9 919 N d a S TN Nes 3 J m 9190 l 5 NISI WO 39 595559 Sea 95200111 bi LI P ALYY A OS Ng A M i 4 Sg gt Si 8 NIN NSISE f l gt NDN gr RA O s ng BON b IN ng ONS FY ng lo A 9 KO N4 91 3 E EE EET RARE m v 3 00 fy PN d e Sf a Se RR RR Nnm SSRIS SISIEN 9999 Ng 27 74 14 75 2 ISSN SIX NN
52. L PINS TO BE CUT TO A MAX OF FROM SIDENE 5 nG L KWA 230 MUST POSITIONED BETWEEN THE RC BOARD AND GROUND CLIP 191 3514 201 2 SEE DETAIL stb e 2 H PRIM e E 148 E 5 f 7 EE E f Ps 222 a 4 A A A 211 TO INPUT HIGH RED ON FRONT PANEL 5 5 7 4 0128 ENG WALA 4 TO OHMS SENSE HI RED KA Se ON FRONT PANEL CZ 5 E 3 TEN O IOA WHT ON fi em pe FRONT PANEL INPUTLOW Yo l a NT ET PANEL 208 zd L 6 EE 4 Llc E W NS 4 m ag MODEL 1 NEXT ASSEMBLY 2 T W 2 uL T USED ON HA RU SENE EI 22221 775 COMPONENT LAYOUT 3 BLK ON FRONT PANEL TENT TET mo o MOTHER BOARD aL E THLEY Ne 1 E ee 97 100 ul 6 m EE i TLS A FORM 285110 MEN sa B PU CAM _ Artisan Instrumentation Guaranteed 888 88 SOURCE www artisantg com E Ll F G r H Figure 6 3 Mother Board Component Location Drawing Dwg No 197 100 sheet 2 of 2 6 11
53. Lo 3 5 3 Resistance Accuracy Check Resistance verification 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 re quired limits Measurements on the 2000 2kQ and 20kQ ranges will be done using the 4 terminal configuration to minimize errors due to the voltage drop across the test leads CAUTION Do not exceed 450VDC or peak AC for 10 seconds per minute 350V rms continuous between the HI and LO INPUT terminals or the instrument might be damaged 1 Select the ohms function AC DC button must be out and the 2000 range 2 Use Kelvin test leads e g Keithley Model 1641 in the in put HI and LO and then OHMS SENSE HI and LO ter minals 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 3 Connect a 190Q calibration resistor as shown in Figure 3 3 Note that the 4 terminal configuration is used for this measurement 4 Check to see that the displayed reading is within the limits specified in Table 3 4 5 Connect a 1 9kQ calibration resistor to the instrument 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
54. MODEL 197 MANUAL This manual contains information necessary for operating and servicing the Model 197 Autoranging Microvolt DMM and the Model 1978 Rechargeable Battery Pack The informa tion is divided into the following sections 1 Section 2 contains detailed bench operation information for the Model 197 2 Section 3 contains the information needed to verify the ac curacy of the Model 197 Performance verification can be done upon receipt of the unit or whenever the basic ac curacy of the instrument is in question 3 Information concerning theory of operation maintenance and servicing is contained in Sections 4 through 6 12 NOTE The Models 1973 and 1972 IEEE 488 interfaces come supplied with their own instruction manual 1 9 INITIAL OPERATION Perform the following steps in sequence to acquaint yourself with the basic operation of the Model 197 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 Plug the power 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 of the zeroes are briefly displayed 2 Connect the supplied test leads to the HI and LO input ter minals Co
55. MODEL 1978 BATTERY PACK HANDLE OVERLAY BANANA JACK Red BJ 12 2 NOT SHOWN 197 318 BANANA JACK Black BJ 120 BANANA JACK White BJ 129 Figure 5 1 Model 197 Miscellaneous Parts Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 5 6 FRONT PANEL CALIBRATION Calibration should be performed every 12 months or if the performance verification procedures in Section 3 show that the Model 197 is out of specification If any of the calibration procedures in this section cannot be per formed properly refer to the troubleshooting informa tion in this section If the problem persists contact your Keithley representative or the factory for further infor mation If vou have revision C level software in vour Model 197 a rear panel external calibration switch has been added to vour instrument When this switch is in ENABLED it al lows you to permanently store calibration constants in NVRAM NOTE For Revision A or Revision B software contact the factory for calibration information Refer to paragraph 5 7 2 to determine software revi sion level 5 6 1 Recommended Calibration Equipment Calibration may be performed using the equipment listed in Table 5 1 Alternate calibration equipment may be used aslong as the equipment s accuracy is at least as good as the specifications listed in Table 5 1 5 6 2 Environmental Conditions Calibration should be performed in an ambient t
56. N 9 01038 PIN 5 0103 PIN7O UIO3D PIN IIC 0125 01200 PINS O lt tc a aie o ama od A A AG ees 6 02 By Vua ANA ib uc MATES WITH PIOOG gt OF DISPLAY BOARD SEE 197 116 mE 3 2 22K Fo s vi vas ar 5V 4 Darn AW AE ho dai tede ta s POE NIS UL TAREA n RIVE Q4 TN ayi SIERE POOT ae ai an ATAN Ma an ak vain TT DIMENSIONAL TOU NLESS OTHERWI XX 015 005 FRAC 1 64 e 207 PWEN CR p SHT FORM 285110 REV D Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com M P ANG BANA ma a E N DEE TR mai GB 5 KE PAKO TAGA LANE PAGA PAP KAG Figure 6 6 Display Board Schematic Diagram Dwg No 197 116 6 19 6 20 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com TTA o o 1 1 ee 1 1 2 O 5V 2 CONT
57. Pack Component Location Drawing Dwg No 1978 100 6 7 6 8 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 44 131 58425 BRUNING A B 1 432 CI BE 1 758 0 a MARE NA a 8 12 398 02 DS GG ECCE GENERE AA 77070 oh s 2153 12 11 ann 17 A R 88 402K OS R 88 324K 104 D3 IE NERONE AKIAN men 25 27 28 975 28 43 peo 1 sou REV D B D E F Du WAS lt 2 7 ENKA DREV LI TO PF WE TEM 3 FROM 2 9 25 017 2058 ro c s 4 220 423 REkLACED RI IO wit RT IS 7 a f 25408 NAG KA N NI N 107 SIS dy N N W N N B LO 1 9 0 SN REIN UE NOMINE EET KRAN ed MODEL NEXT ASSEMBLY QTY TOLERANCES an mue COMPONENT LAYOUT BATTERY OPTION _ Instruments 005 FRAC 1 64 MATERIAL ms NG 14 44 1 534 22133 LXXX 5 005 i972 Artisan Group Quality instru tation Guaranteed sls www artisantgicom F 4 m Figure 6 3 Mothe
58. TION The maximum input voltage between the and LO INPUT terminals is 450V DC or peak AC for 10 seconds per minute 350V RMS continuous Do not exceed these values or instrument damage may occur Table 2 3 shows the current output for various resistance ranges CAUTION Incorrect readings will result if the resistance being measured is part of a live circuit 6 Take the reading from the display Table 2 3 Resistance Ranges Max V Maximum Test Lead Across Resistance for Range Resolution l Short Unknown 1 Count Error Q 200 1mQ 05 10 2k 10 0 2 4 0V 32 20k 100mQ 4004A 4 0V 100 200 10 40 40V 320 2M 10 Q 40V 1k 20M 100 2 400nA 4 0V 3 2k 200M 10 kQ 400 nA 5 0V 10k 2 8 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com NOTE It is helpful to shield resistance greater than 106Q 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 197 OPTIONAL SHIELD RESISTANCE UNDER TEST CAUTION MAX INPUT 450VDC or PEAK AC for 10sec min 350V RMS CONTINUOUS OPTIONAL SHIELD i 1 l CAUTION INPUT 450VDC or pk AC for 10sec min 350V RMS CONTINUOUS MODEL 197 Figure 2 5 Four Terminal Resistance Measure
59. URE COEFFICIENT 0 18 amp 287 50 C 0 1 applicable one year accuracy specification ENVIRONMENT Operating 0 50 C less than 80 relative humidity up to 35 linearily derate 3 RH C 35 50 Storage 25 to 60 C WARMUP 1 hour to rated accuracy POWER 105 125V or 210 250V external switch selected 90 110V available 50 60Hz 12V A Optional 5 hour battery pack Model 1978 DIMENSIONS WEIGHT 89mm high X 235mm wide X 275mm deep 31 in X 914 X 1034 in Net weight 1 8kg 3 lbs 14 2 ACCESSORIES SUPPLIED Model 1751 safety test leads instruction manual ACCESSORIES AVAILABLE Model 1010 Single Rack Mounting Kit Model 1017 Dual Rack Mounting Kit Model 1301 Temperature Probe Model 1600A High Voltage Probe Model 1641 Kelvin Test Lead Set Model 1651 50 Ampere Current Shunt Model 1681 Clip On Test Lead Set Model 1682A RF Probe Model 1684 Hard Shell Carrying Case Model 1685 Clamp On Ac Probe Model 1751 Safety Test Leads Model 1754 Universal Test Lead Kit Model 1972 IEEE 488 with Analog Output Model 1973 IEEE 488 Interface Model 1978 Rechargeable Battery Pack Model 7008 3 IEEE 488 Digital Cable 3 ft Model 7008 6 IEEE 488 Digital Cable 6 ft Model 8573 IEEE 488 Interface for IBM use with 1972 3 Guaranteed 888 88 SOURCE www artisantg com TABLE OF CONTENTS SECTION 1 GENERAL INFORMATION Introduction see eg
60. 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 measurements on the 2000 range zero must be set by the REL function to obtain rated accuracy For best results on the 2000 2kQ and 20 ranges it is recommended that 4 terminal measurements be made to eliminate errors caused by the voltage drop across the test leads that occurs when 2 terminal measurements are made To make resistance measurements proceed as follows 1 Connect the test leads to the HI and LO INPUT terminals If four wire measurements are to be made connect an ad ditional 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 resistance If desired use the autorange mode for automatic range selec tion 4 If readings to be made on the 2000 range zero the in strument 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 6 allow the reading to settle then press the REL button 5 For 2 wire measurements connect the instrument as shown in Figure 2 4 For 4 wire measurements use the connec tions shown in Figure 2 5 CAU
61. ace board containing logic to perform the necessary hardware functions and the handler software supplied on disk to perform the required control functions These two important facets of the Model 8573 join together to give the IBM advanced capabilities over IEEE 488 inter faceable instrumentation 1 3 1 4 Guaranteed 888 88 SOURCE www artisantg com SECTION 2 BENCH OPERATION 2 1 INTRODUCTION This section contains the information needed to prepare and operate the Model 197 as a bench DMM Bench operation consists of using the Model 197 to perform basic voltage cur rent resistance and dB measurements Also the operation of the data logger is covered The capabilities of the Model 197 can be enhanced with the addition of the Model 1973 or Model 1972 IEEE 488 interface IEEE operation is covered in the Model 1973 Instruction 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 follow ing warning WARNING Dangerous arcs of an explosive nature in a high energy circuit can cause severe per sonal injury or death If the meter is con nected 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 t
62. bration 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 dP until Stor is displayed The calibration constants are now stored and the Model 197 is ready for normal operation MODEL 5450A MODEL 197 Figure 5 6 200k 2M and 20M Two Wire Resistance Calibration Table 5 4 Resistance Calibration Calibration Model 197 Range Resistance Reading 200 2 190 Q 190 000 Q 2 1 9 1 90000 20 19 19 0000 200 190 190 000 2MQ 1 9 MQ 1 90000 kQ 20MQ 19 M 19 0000 0 5 7 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Table 5 5 Recommended Troubleshooting Equipment Equipment Use Five function DMM with 0 196 basic DCV accuracy 10M input impedance Dual trace triggered sweep oscilloscope DC to 50MHz Digital Frequency Counter Power supply and DC voltage checks analog signal tracing continuity logic levels Digital and analog waveform checks Checking clock frequencies 5 7 TROUBLESHOOTING The troubleshooting instructions contained in this section are intended for use by qualified personnel having a basic understanding of analog and digital circuitry The individual should also be experienced at using electronic test equipment
63. by less than 75pF on 200V and 750V ranges 1 1MQ paralleled by 75pF on 200mV 2V and 20V ranges Capacitively coupled SETTLING TIME 1 second to within 0 196 of final reading on range dB MODE ref 6000 ACCURACY dBm 20Hz 10 20kHz 50kHz RANGE INPUT 10kHz 20kHz 50kHz 100kHz 2V 750V 200mV to 750 V 0 18 0 18 0 28 0 50 12 to 59 8dBm 200mV 20mV to 200mV 0 18 0 18 0 28 0 65 32to 12dBm 2mV to 20mV 0 85 1 10 2 00 52 to 32dBm lmV to 2mV 2 00 3 00 58 to 52dBm RESOLUTION 0 01dB above 0 5 of range DC AMPS MAXIMUM ACCURACY 1 Yr VOLTAGE 18 28 C RANGE RESOLUTION BURDEN rdg counts 200 LA nA 0 3V 0 1 15 2mA 10nA 0 3V 0 1 15 20mA 100nA 0 3V 0 1 15 200mA 14A 0 3V 0 2 15 2000mA 10 pA 0 8V 0 2 15 10 A 100 pA 0 3V 0 75 15 Above 5A derate 0 15 rdg per amp for self heating When properly zereod OVERLOAD PROTECTION mA Input 2A fuse 250V externally accessible 10A Input 20A for 15s unfused SETTLING TIME 1 second to within 3 counts of final reading TRMS AC AMPS ACCURACY 1 Yr MAXIMUM VOLTAGE 18 28 4 Jordg counts RANGE BURDEN 20Hz 50Hz 50Hz 10kHz 10kHz 30kHz 2004A 20mA 0 3V 1 0 100 0 8 100 2 250 200mA 0 3V 1 0 100 0 8 100 2000mA 0 8V 1 0 100 0 8 100 10 A 0 3V 1 5 100 1 0 100 Above 1800 counts 1kHz max Above 5A derate 0 15 rdg amp for self heating SETTLING TIME 1 second to
64. ce this current is common to both resistances the value of the unknown resistance can be calculated by measuring the voltage across the reference resistor and the voltage across the unknown resistance The following ohms reference resistors are used see Figure 4 5 R103l R105AI R105B on 2000 and 2kQ ranges R105DIl R105AIIR105B on 20kQ range R105CI R105AIIR105B 100kQ on 200 range R105AI R105B on 2MQ range R105A 10MQ on 20 9 and 200 ranges By measuring the four inputs to the A D converter the unknown resistance can be computed by the microprocessor using this equation Rx RREF SENSE HI VQ SENSE LO VQ REF HI VQ REF LO For the 2000 range VQ SENSE HI and VQ SENSE LO are ac tually multiplied by a factor of 10 in the buffer circuit Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com FRONT PANEL CONN yo REF HI SENSE HI SENSE LO 4 RREF SENSE HI VA SENSE LO VQ REF HI VQ REF LO Rx Figure 4 4 Input Configuration During 2 and 4 Terminal Resistance Measurements Protection on the ohms ranges is accomplished by RT101 Q101 and Q102 For an input voltage applied to the Q input terminals Q101 and Q102 clamp the voltage to the reference resistors to a safe limit RT101 limits the current to Q101 and Q102 R105A provides
65. ck reveals a problem check U113 and refer to 5 7 2 NVRAM test 5 7 2 Self Diagnostic Program The self diagnostic program is designed to aid the technician in troubleshooting the Model 197 There are several tests that may be performed using the self diagnostic program These tests display software revision level and sequential display test are run automatically After this sequence the Model 197 goes into the troubleshooting mode To use the self diagnostic program press and hold in the dB button while turning on the Model 197 The following se quence occurs 1 AII LCD digits and annunciators turn on 2 The software revision level is then displayed e g A1 3 The sequential display test runs 4 The Model 197 goes into the troubleshooting mode If the dB button is released the instrument flags either RAM or NVRAM self test failures should they occur If neither RAM nor NVRAM fails the instrument defaults to the troubleshooting test mode RAM Test If the RAM test fails the Model 197 locks up with all zeroes displayed Replacing U112 may correct the problem Non Volatile RAM Test If the NVRAM test fails the following message is displayed cErr Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com This is a message indicating that the instrument is not calibrated properly since calibration constants are stored in NVRAM The Model 197 remains at this point
66. d 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 exam ple place the Model 197 in the ohms function and select the 2000 range Short the test leads and press the REL button Note that the REL annunciator is on Select DCV and note that the REL annunciator is off indicating that there is not a REL level established 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 can celled It is important to remember what the REL function does The REL function establishes a baseline That baseline is alge braically subtracted from all subsequent readings for that function Once a REL level is established for a measurement function that stored level will be the same regardless of what range the Model 197 is on For example if HIV is established as the REL level on the 20VDC range 1V is also the REL level for other DCV ranges 2 5 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com The dynamic range of the display is 400 000 counts This means that if a REL level of 2 00000V is established then
67. d k annunciators are displayed 8 The decimal points most significant digit and the STO and A annunciators are displayed Figure 5 7 Segment Identification Troubleshooting Test Modes The troubleshooting mode is designed to switch on various switching FETs transistors relays and logic levels to allow signal tracing through the in strument The first displayed mode reflects the selected func tion and range For example assume that Ou1 is displayed In this case 0 is the test number u corresponds to the volts function 1 corresponds to the 200mV range The test number can be changed by pressing in the dB button Table 5 6 lists test modes for all functions and ranges Troubleshooting consists of selecting the desired test mode and using the data found in Table 5 6 to signal trace the cir cuit NOTES 1 When a different function or range is selected the dB but ton must be pressed and held in to update the display with the corresponding test mode 2 Do not use AUTO when in AC or DC volts 3 Use AUTO when checking circuitry on the 20M and 200M2 range 006 106 206 306 and 406 5 7 3 Power Supply and Battery Pack Model 1978 Checks Table 5 7 shows the various checks that can be made to the power supplies of the Model 197 and 1978 In addition to the normal voltage checks it is a good idea to check the various supplies with an oscilloscope for signs of noise or oscillations 5 7 4 A D Converter a
68. econd to 1 reading hour or by manual trigger Also detects and stores maximum and minimum readings continuously while in the data logger mode 1 STO CLR Pressing this button initiates the logging se quence Pressing this button a second time turns off the data logger For r 6 rate manual trigger every time a reading is desired press the 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 loca tions 01 to 102 They are depicted on the front panel as follows Buffer location 1 is represented by 01 _ AC DC This button is used along with the volts V cur rent and dB functions Depressing in this button selects AC releasing out this button selects DC AC 0 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 A Depressing in this button selects the current function Up to 2A on red and black input jacks and up to 10A 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 ap propriate range button 2 4 3 Inp
69. empera ture of 23 3 and a relative humidity of less than 70 If the instrument has been subject to temperature outside of this range or to higher humidity allow at least one additional hour for the instrument to stabilize betore beginning the calibration procedure 5 6 3 Calibration Switch The Model 197 is shipped from the factory with ils exter nal calibration switch in the DISABLED position In this position calibration constants cannot be stored when en tered from the front panel or over the ILEL 455 bus The switch 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 Plugin the line cord and turn on the instrument Press in the RET and db pushbuttons simultaneously until the message CAL is displayed Release the buttons The unit is now in calibra tion as indicated by the C annunciator WARNING Some procedures require the use of high voltage Take care to prevent contact with live circuits which could cause electrical shock resulting in injury or death 5 4 Table 5 1 Recommended Calibration Equipment Required Minimum Specifications Model No 200mV 0 003 Yo 0 5uV 2V 0 003 0 5 20V 0 003 0 5uV 200V 0 003 Yo 0 5u V 10000 0 003 0 5 80 5440 DC Voltage Calibrator AC Voltage Calibrator 200mV 2V 20V 200V and
70. eversed 12 Strip Connector Verify that they are positioned properly 5 12 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Table 5 9 A D Converter Microcomputer Checks Step Item Component Required Condition Remarks 10 11 12 13 14 U124 pin 38 U119 pin 10 U119 pin 6 U119 pin 5 U119 pin 7 U119 pin 12 U118 pin 6 U110 pin 6 U108B pin 7 U117 pin 6 U105A pin 15 U105A pin 10 U117B pin 9 Short the input 3 276800MHz Clock 655 36kHz Clock 81 92kHz Clock 40 96kHz Clock 163 84 kHz Clock 1 28kHz Clock Integrator Waveform positive going Turn on power select 2VDC range 5V to OV pulse train 3usec duration every 22 Set signal to end charge balance pulse Variable waveform to 5V Variable pulse train to 5 Variable pulse train OV to 5V 4msec pulses approximately every 150msec to 5V 50msec and 100msec pulses Crystal Frequency Y101 A D timebase and address strobe Clocks for U117A Minimum pulse generator signal Generates set for U117A proper phase of Q4 and O3 required Timebase for real time uP interrupt S1 input of U118B Comparator Output Charge Balance Charge Balance Current Control U124 Timer Input Single Slope Control Line Integrator charge Balance Control Table 5 10 Model 197 Static Sensitive De
71. f 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 197 of 00 0000V 50 counts 7 Reinstall the top cover HI OUTPUT MODEL 197 HIGH VOLTAGE AMPLIFIER AC VOLTAGE CALIBRATOR MODEL 5200A MODEL 5215 Figure 5 4 AC Voltage Calibration Configuration Table 5 3 AC Voltage Calibration Calibrator Calibrator Model 197 Voltage Frequency Reading 200mV 190 000mV 500Hz 190 000mV 200mv 19 000mV 500Hz 19 000mV 2 V 1 90000 V 500Hz 1 90000 V 20 V 19 0000 V 500Hz 19 0000 V 200 V 190 000 V 500Hz 190 000 V dB annunciator must be on indicates two point calibration Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 5 6 7 Resistance Calibration With the Model 197 in the calibration mode C annun ciator on select the ohms function and connect the calibra tor to the Model 197 as shown in Figure 5 5 Four wire re sistance measurements need only be done when not using the REL feature Use the following procedure and refer to Table 5 4 to calibrate the ohms function 1 Select the 2000 range and set the resistance calibrator to output zero ohms short Press the REL button on the Model 197 The REL annun
72. formed by K101 K102 K103 Q105 Q106 and 0109 0107 and 0108 are used to sense zero in a manner that eliminates the errors due to the on resistances of Q106 and Q109 The FETs are driven by U112 The following attenuation is provided 1 is used on the 200mV and 2V ranges 10 is used on the 20V range 100 is used on the 200V range 1000 is used on the 1000V 750V range 4 1 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com a AV ldSIQ SIHILIMS 3YNLW34 3DNVY NOILONNS 4ILNdWOD OHIIN SX LX TOYLNOD 104100 q v U31H3ANOO IV payidwis 71 39NVH A 1081NOD A6 AOL Alddns HIMOd S OL 1NNHS VOL SINNHS INFYYNI LAdNI O13SN3S 0 IH 3SN3S 6 SYOLSISAY 3oNa3uad3H MOLVNNALLV IH LAdNI JA IV 42 Guaranteed 888 88 SOURCE www artisantg com Artisan Technology Group Quality Instrumentation Q111 VSIGNAL Q REF FROM FET DRIVER VZERO ON 20VDC 200VDC and 1000VDC RANGES FROM FET DRIVER OUTPUT TO BUFFER AMPLIFIER VREF 2 SENSE HI 0113 FROM FET DRIVER 2 0 SENSELO 0112 FROM FET DRIVER Figure 4 2 JFET Multiplexer OUTPUT TO A D INPUT FROM 200 0 CONVERTER MULTIPLEXER GAIN SELECT Figure 4 3 Simplified Schematic of the
73. ge current of U102 Ordinarily FET switching creates transients which could be seen in the final measurement These effects are minimized in the Model 197 through the use of software generated delays 4 3 2 Input Buffer Amplifier The input buffer amplifier provides the necessary isolation between the input signal and the A D converter The amplifier is a noninverting low noise high impedance circuit with X1 or X10 gain The amplifier gain is controlled by the microprocessor and is range and function dependent Figure 4 3 shows the simplified schematic of the input buffer amplifier The gain is X10 when Q116 is ON and X1 when Q116 is OFF 4 3 3 2V Reference Source The Model 197 voltage and current measurements are based on comparing the unknown signal with an internal 2V reference voltage During each measurement cycle the unknown is sampled along with a zero measurement and a 2V reference measurement to compute the unknown voltage The 2V reference is made up of a highly stable zener diode VR103 an op amp and a resistive divider U109 and R125C D and E act as a constant current source to minimize the zener voltage variations R121D E and F is then used to divide down the 6 4V zener voltage to 2V The output of U109 is buffered by Q122 to form a 10V sup ply 4 3 4 Input Signal Conditioning For and the signal conditioning is performed by R103 R104 R105 and their shunt capacitors Range switch ing is per
74. he various sections of the microcomputer and associated digital circuitry For more complete circuit details refer to schematic diagram number 197 106 at the end of this manual 4 4 1 Microcomputer The microcomputer centers around the 146805E2 CMOS microprocessor It is an 8 bit microprocessor with direct ad dressing of up to 8k bytes on a shared address and data bus Timing of the microprocessor is accomplished by the use of Y101 a 3 2768MHz crystal Internally this frequency is divid ed down by 5 to obtain a bus operating frequency of 655 36kHz This is present on the address strobe of U124 pin 6 and supplies timing to all other parts of the instrument through the binary divider U119 The software for the MPU is stored in 0122 PROM Tem porary storage is provided by U121 U121 is used to share the calibration constants on power up and as RAM for the microprocessor s in house functions It also stores readings for the data logger U113 is the NVRAM and is used to store the calibration constants 4 5 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com SINGLE SLOPE ENABLE DISABLE SINGLE SLOPE COMPARATOR CHARGE BALANCE COMPARATOR ENABLE DISABLE UNA PS CLOCK GENERATOR U119 Figure 4 6 A D Converter 4 4 2 Address Decoding U123 is used to latch in the address that is on the bus when the address strobe of U124 goes high and presents it to t
75. he PROM U122 during data strobe 4 4 3 PIA U114 provides for most of the control of the instrument It controls all ranging hardware A D converter and data out put and input for the IEFE option 4 4 4 Display Board The LCD display is driven by a flat pack LCD controller chip U201 and it communicates to the microprocessor through 4 control lines During power up the microprocessor configures U201 to drive the triplexed display In order to drive the display correctly four voltages are ob tained from R134 The clock required by U201 is obtained from U119 4 6 The display board also houses the special function keys dB REL STO CLR and RCL 4 5 DIGITAL CALIBRATION The Model 197 uses digital calibration to eliminate all poten tiometers in the instrument to facilitate calibration The con stants that the Model 197 uses are stored in a nonvolatile elec trically alterable read only memory U113 and are read on power up of the instrument There is one constant for each range on DCV ACV and 0 except for the 750VAC range which uses the constant from the 2V range On the DCA and ACA functions the 200mV DC and 200mV AC constants are used respectively 4 6 POWER SUPPLY Fuse F102 is the LINE FUSE which is internally accessible 101 is the power on off switch and S102 selects 115V or 230V operations by placing the transformer primary win dings in parallel or series Artisan Technology Group Quality Instrumentation
76. he 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 withstanding the voltage being measured Exercise extreme safety when testing high energy power circuits AC line or mains etc Refer to the operation sec tion Do not exceed the instrument s maximum allowable input as defined in the specifications and operation section Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com SECTION 1 GENERAL INFORMATION 1 1 INTRODUCTION The Model 197 is a six function 5 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 used in many 572 digit DMMs The 57 digit resolution allows the Model 197 to measure DC voltage from 14 V count to 1000V AC voltage and current measurements are standard in the Model 197 TRMS ACV capability ranges from 1pV count to 750V The Model 197 measures resistance from 1mQ to 220 0 on seven resistance ranges The Model 197 has six current ranges that measure current from 1nA 10 9 to 10A The dB function makes it possible to compress a large range of readings into a much smaller scope The Model 197 dBm measurements are referenced to the standard 6000 impedance but ca
77. heet 1 of 2 6 15 6 16 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com BRUNING 44 131 60137 NOTES 2 a ALL CAPACITOR VALUES ARE IN MICROFARADS a 4 a V mapisa ba SIGNAL COMMON 225 DENOTES NTERNAL ADJUSTMENT EE NEN e ul Qeon CE B Na 41001 a SEL ALL RESISTOR VALUES ARE IN OHMS UNLESS OTHERWISE ARKED K KILOHMS M MEGOHMS UNLESS OTHER WISE MARKED pF 05 ALL PUSHBUTTON SWITCHES ARE pipi IN DENOTES DIGITAL COMMON 22 TA Jones as ANAN M d NG SAGA PNIS RN Paa mn ha he Amen akan aapaw ti un 3 ids ACTORY SELECTED DENOTES RONT PANEL CONTROL e REAR PANEL MOUNTING 222 XX WARNINGIRIO IS FUSIBLE RESISTOR EXACT IREPLACEMENT ONLY DESIGNATIONS USED RIAI a REV D 23 B FORM 28510 HIGHEST SCHEMATIC 21006 FUSIBLE Ax dn 3 43 bha Ka to 105 Lcio4 Way seQH095K A AURA tome pa ome a GT do A Du Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com
78. hield to circuit LO Connect the ribbon cable from the battery board to P1009 on the mother board Make sure pin 1 on the cable con nects to pin 1 of P1009 Refer to the detailed drawing of Figure 5 1 5 1 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com CAUTION Make a close visual inspection of the con nections to ensure that they are properly connected Otherwise damage to the instrument may result 8 Reinstall the top cover as explained in paragraph 5 2 NOTE The IEEE Interface options do not run off of bat tery power 5 4 LINE VOLTAGE SELECTION The Model 197 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 instrument was ship ped from the factory set for an operating voltage marked on the rear panel To change the line voltage proceed as follows 1 Turn off the Model 197 and disconnect it from line power 2 Set the LINE VOLTAGE switch on the back of the instru ment to correspond to line voltage available Example 110VAC is 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 WARNING Ground the instrument through a properly grounded receptacle before operation Failure to ground the instrument can result i
79. ians on staff Sell your excess underutilized and idle used equipment TENS OF THOUSANDS OF at our full service in house repair center We also offer credit for buy backs and trade ins IN STOCK ITEMS www artisantg com WeBuyEquipment 7 EQUIPMENT DEMOS HUNDREDS OF Instra REMOTE INSPECTION LOOKING FOR MORE INFORMATION MANUFACTURERS Remotely inspect equipment before purchasing with Visit us on the web at www artisantg com 7 for more our interactive website at www instraview com 7 information on price quotations drivers technical LEASING MONTHLY specifications manuals and documentation RENTALS ITAR CERTIFIED Contact us 888 88 SOURCE sales artisantg com www artisantg com
80. ide of this range 2 Turn on the Model 197 and allow it to warm up for one hour The instrument may be operated from either line power of battery pack power as long as the battery pack has been fully charged as described in paragraph 2 3 3 3 5 VERIFICATION PROCEDURE The following paragraphs give the basic verification pro cedure for the following functions DC volts AC volts resistance and current Table 3 1 Equipment Specifications Fluke Fluke Valhalla DC Voltage Calibrator AC Voltage Calibrator AC DC Current Calibrator Fluke Resistance Calibrator Fluke Power Amplifier Artisan Technology Group Quality Instrumentation 200mV 2V 20V 200V 1000V ranges 0 005 200mV 2V 20V 100V 50Hz to 10kHz 0 05 200uA 2mA 20mA 200mA 2000mA 10A ranges 0 03 DC 0 1 AC to 5kHz at full scale 1000 1 10 100 ranges 0 005 1MQ range 0 01 10M9 range 0 05 100MQ 0 5 1000V range 10Hz 30Hz 0 12 50kHz 100kHz 0 10 100V 100kHz 107 2 750V max 13kHz 10 VHz 3 1 Guaranteed 888 88 SOURCE www artisantg com WARNING The following procedures require that high voltages may be applied to the input ter minals of the Model 197 Use normal safety precautions to avoid possible electrical shock which could result in personal injury or death 3 5 1 DC Voltage Accuracy Check Select the DC volt function and autorange CAUTION Do not exceed 1000V between the input H
81. if the test fails but operation may be restored for troubleshooting by press ing either the REL dB or DATA Logger buttons The flashing C annunciator indicates that the unit failed the NVRAM test At this point try calibrating the instrument with the constants already entered by simultaneously pressing REL and dB until the CAL message is displayed Then release the REL and dB buttons Simultaneously press the REL and dB buttons again until the STOR message is displayed If the error is corrected indicating that the NVRAM is probably good a full calibra tion is required If the error persists try replacing the NVRAM chip U113 Again the Model 197 must be completely recalibrated after the problem is corrected Sequential Display Test Segments and annunciators are sequentially displayed in eight steps Use Figure 57 for seg ment identification The steps are as follows 1 The a segments of the digits the dB and V annunciators are displayed 2 The b segments of the digits are displayed 3 The c segments of the digits are displayed 4 The d segments of the digits are displayed Also the m mA RCL and RMT annunciators are displayed 5 The e segments of the digits are displayed Also the minus sign REL M and annunciators are displayed 6 The f segments of the digits are displayed Also the AUTO BAT m mV and c annunciators are displayed 7 The g segments of the digits are displayed Also the AC an
82. igned to read OdBm when the voltage needed to dissipate 1mW through a 6009 impedance is applied to the Model 197 That calculated voltage level is 0 7746V as derived from the basic power equation E N R T 0 3 weeooQ E 0 77456V Thus with 6000 reference impedance the Model 197 will read OdBm whenever 0 7746V is applied NOTE Do not confuse reference impedance with input impedance The input impedance of the instru ment is not modified in the dB mode To make dBm measurements referenced to 6000 proceed as follows 1 Connect the test leads to the INPUT HI and LO terminals of the Model 197 Select the ACV or DCV function Select autorange for optimum resolution Press the dB button Connect the test leads to the voltage source Make the dBm reading from the display Artisan Technology Group Quality Instrumentation dBm Measurements with Other Reference Impedances dBm measurements can be made with other reference im pedances The most convenient method for using other reference impedances is to algebraically subtract the calculated dB offset for the desired reference impedance from the reading on the display of the Model 197 Table 2 6 lists common reference impedances and the corresponding offset values The following equation can be used to calculate the offset the offset for impedances not listed in Table 2 6 New ref Z 6000 Offset for dBm 10 log To
83. in Figure 3 3 Switch the instrument to the 20kQ range Verify that the displayed reading is within the limits specified in Table 3 4 Connect a 190kQ calibration resistor to the instrument 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 configura tion may be used on the 200kQ and higher ranges 8 Continue with each of the calibration resistance values listed in Table 3 4 Be sure to place the Model 197 on the correct range for each measurement The remaining readings may be done using 2 terminal configuration N Table 3 4 Limits for Resistance Verification Applied Allowable Readings 197 Range Resistance 18 to 28 200 190 000 Q 189 959 to 190 041 2k 1 90000 kQ 1 89964 to 1 90036 20k 19 0000 kQ 18 9949 to 19 0051 200k 190 000 kQ 189 949 to 190 051 2M 1 90000 0 1 89931 to 1 90069 20M 19 0000MQ 18 9770 to 19 0230 190 000MQ 200M 186 199 to 193 801 3 3 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com RESISTANCE MODEL 5450A MODEL 197 Figure 3 3 Connections for 200 2k and 20k Range Verification 4 terminal CALIBRATION RESISTANCE MODEL 5450A MODEL 197 Figure 3 4 Connections for 200k through Ranges Verification 2 Terminal 3 5 4 DC Current Accuracy Check DC current accuracy is
84. integrator output is connected to the noninverting input of the U108A its output will stay high until the intergrator ramps negative During single slope Q120 is turned off and R129 is connected to 5V The single slope comparator is then gated with the microprocessor s internal clock and counted Once the com parator output goes low the microprocessor stops counting and can compute the reading Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 4 3V OHMS SOURCE REFERENCE RESISTORS INPUT HI TO Q111 OF MULTIPLEXER gt Q SENSE gt TO 0110 OF MULTIPLEXER Q REF LO 3 TO 0113 OF MULTIPLEXER 0 SENSE LO INPUT LO TO 0112 MULTIPLEXER Figure 4 5 Resistance Measurement Simplified Circuit 4 3 6 AC Converter On the 200mV AC range the input is routed through U104 for a X5 voltage amplification The gain stage is used to permit accurate voltage measurements at higher frequencies and lower input levels On all other ranges U104 is configured for a gain of X1 The gain of U104 is controlled by the micro processor The output of U104 is applied to the TRMS con verter chip U106 which converts the AC input signal to the corresponding DC level The DC output is then applied to the signal FET 4 4 DIGITAL CIRCUITRY Model 197 operation is controlled by the internal microcom puter This section briefly describes the operation of t
85. ints 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 display 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 semicon ductor junctions as follows 1 Select the ohms function 2 Press the 2k and 200k button diode symbols in simultaneously 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 2 8 TRMS CONSIDERATIONS Most DMMs actually measure the average value of an input waveform but are calibrated to read its RMS equivalent This poses no problems as long as the waveform being measured is a pure low distortion sine wave For complex nonsinusodial waveforms however measurements made with an averaging type meter can be grossly inaccurate Because of its TRMS True Root Mean Square measuring capabilities the Model 197 provides accurate AC measurement for a wide variety of AC input waveforms 2 13 Guaranteed 888 88 SOURCE www artisantg com 2 8 1 AC Voltage Offset Typically the Model 197 displa
86. iption of the Model 197 Information pertaining to the Model 1978 Battery Pack option is also included Detailed schematics and compo nent layout drawings are located at the end of this instruction manual 4 2 OVERALL FUNCTIONAL DESCRIPTION The Model 197 is a 572 digit DMM with five AC and DC voltage ranges seven resistance ranges and six AC and DC current ranges simplified block diagram of the Model 197 is shown in Figure 4 1 The heart of the Model 197 is the A D converter that translates the conditioned analog input signal into a form usable by the microcomputer 4 3 ANALOG CIRCUITRY The following paragraphs contain a description of the input multiplexer buffer amplifier 2V reference and A D verter circuits These circuits may be found on schematic diagram number 197 106 located at the end of this manual 4 3 1 Multiplexer The multiplexer connects one of four signals to the buffer amplifier signal zero reference and ohms reference The multiplexer shown in Figure 4 2 is made up of 4 JFETs which are controlled by the microprocessor through U114 The FETs are driven by drivers U103 and U112 The drivers convert the digital signals of the microprocessor to signals usable by the FETs Note that the particular FET used to sense zero on DCV is range dependent This is done so that zero may be sensed in a manner that eliminates the errors due to the ON resistances of Q106 and Q109 It also reduces errors due to leaka
87. isplay reads 000 0000 The relative level of 000 142 will be subtracted from all subsequent measurements Press the REL button a second time to cancel the REL level Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 9 activate the 100 point DATA LOGGER with minimum maximum press and hold in the STO CLR but ton When the reading rate 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 197 MODEL 1010 SINGLE RACK MOUNTING KIT Used to mount one Model 197 in a standard 5 X 19 rack MODEL 1017 DUAL RACK MOUNTING KIT Use to mount two Model 197s in a standard 514 X 19 rack MODEL 1301 TEMPERATURE rugged low cost temperature probe designed to allow precision temperature 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 MODEL 1651 50 AMPERE CURRENT SHUNT The exter nal 0 0010 1 4 terminal shunt permits current measurements from 0 to 50A AC or DC
88. isted in Table 5 10 should be transported and handled only in containers specially designed to prevent static build up Typically these devices will be received in static protected containers The parts should remain there until ready for installation Remove the devices from their protective containers only at a properly grounded work station Always ground yourself with a suitable wriststrap Handle the devices only by the body Do not touch the pins Any printed circuit board into which the device is to be in serted must also be grounded to the bench or work station Use only grounded type solder suckers Use only a grounded type soldering iron Once the device is installed on the PC board the device is adequately protected and normal handling may resume 5 11 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Table 5 7 Power Supply and Battery Pack Model 1978 Checks Step Item Component Required Condition Remarks 1 16102 Set to 115V or 230V as required 5102 is externally accessible from rear panel 2 F102 Line Fuse Continuity 3 Line Cord Plugged into proper line recep 4 Power ON OFF switch pin 6 5 U109 pin 2 6 10109 pin 3 7 Q126 collector or U116 pin 7 8 Power ON OFF switch pin 12 9 0107 pin 2 10 U107 pin 3 11 0128 Emmitter 12 U116 pin 3 13 U116 pin 2 14 0126 Emitter Q123 Emitter or J1009 pin 7 Q
89. ke the reading from the display The term when properly zeroed means that the user must establish a proper baseline for subsequent measurements on that range To zero the Model 197 use the following pro cedure 1 Short the INPUT HI and LO test leads together 2 Wait until the displayed reading settles Noise and thermal emfs may require a few moments to settle out 3 Press the REL button 2 6 DC VOLTAGE SOURCE CAUTION 1000V MAXIMUM INPUT INPUT RESISTANCE 10M EXCEPT 7 1000M on 200mV and 2V RANGES MODEL 197 Figure 2 2 DC Voltage Measurements The 200mV DC range and the 2000 range require zero to be set in order to achieve rated accuracy 2 7 4 TRMS AC Voltage Measurements The Model 197 can make TRMS AC voltage measurements between 14 V and 750V To measure AC proceed as follows 1 Connect the test leads to the HI and LO terminals of the Model 197 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 3 NOTE There is a small amount of offset typically 50 counts or less present when using the AC func tion Do not REL this level out The reason for this is that the offset is generally negligible as compared to the input signal For example offset 22uV applied signal 20mV displayed reading W20mV 2 224V 10004 484 x 10 12
90. make dBm measurements referenced to another im pedance proceed as follows 1 Choose the desired reference impedance 2 Calculate or look up the offset value in Table 2 6 for the desired reference impedance 3 Determine dBm at the desired reference impedance as follows dBm at ref Z 197 reading offset Example Make dBm measurements references to a 1000 reference impedance A 1000 not listed in Table 2 6 so the offset must be calculated as follows 1000 Offset 10 log 6009 Offset 7 78dB B Subtract 7 78 from all subsequent displayed readings on the Model 197 Guaranteed 888 88 SOURCE www artisantg com dBm measurements referenced to another impedance can be read directly from the display of the Model 197 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 6 for OdBm at the desired reference impedance 2 Input that voltage level to the Model 197 3 With the Model 197 in the dB mode press the REL button 4 dBm measurements referenced to the desired impedance can now be read directly from the display of the Model 197 dBW Measurements dBW is defined as decibels above or below a one watt reference The procedure is the same as that found in paragraph 2 7 9 step 2 The only difference is that the reference point is OdBW 1W rather than OdBm 1mW dBV Measurements
91. ment INPUT HI INPUT LO OHMS SENSE LO OHMS SENSE HI Figure 2 6 Four Terminal Zeroing 2 7 7 Current Measurements DC or TRMS AC The Model 197 can make DC or TRMS AC current measurements between 1nA and 10A 20A for 15 seconds If the expected current level is in question make the initial measurement on the 10A range This helps prevent inadver tent blowing of the 2A current fuse which is located on the front panel NOTE For routine measurements above 10A it is recommended that the Model 1651 50A shunt be used 1 For current measurements between 2000mA and 20A Connect the test leads to the 10A and LO terminals of the Model 197 Refer to Figure 2 7 NOTE The test leads used must be rated to handle 20A Twist the wires as shown in Figure 2 7 to help in minimizing external fields which could affect the Model 197 or other equipment Also keep the test leads as short as possible to minimize voltage drop B Select the ACA or DCA function C Select the 10A range The amps function does not autorange D Connect the test leads to the current source as shown in Figure 2 7 and take the reading from the display NOTE Up to 5A may be applied continuously without degradation of the measurement due to self heating effects Above 5A derate 0 15 rdg per amp for self heating refer to specifications that precede Section 1 For currents between 10A and 20A specified accuracy can only be obtained when measurement
92. my 4164 RA i Rm Ki 1 N 9 Ma NISUS WO Ix j j 4 AS JER ANA ONA A KANN NE KRE NEN EI SE REN pi RE ka P k l kt 19 9 5 19 fo a 05 419515 l Ki ki GIGS AYI KI Ka RAY AY V Volo AN KWEN KAY KA ANJ V VO 0 4 5 E RE OOF OO ZO A3 7 G 7 AB PART NO 2 2 220 10142 G 97 GO 77 97 60 7G SJ ITEM Ea A OUE CL gt 2 82 4 c o Q Cv Cle 7 SO 3S yon re 228 2 9g 2 C eG4 2 2 3IGO IS 2 24 5 E 3iolo 34p 22 7 22 69 O S F 12 C 306 BA N oa 197 101 M 9 e cC3ems eodc o Ls 2 724 z C 3s amp 8 WENN 727 NEXT ASSEMBLY QTY TITLE COMPONENT LAYOUT SIOTHER C i NO Om 244 64 MATERIAL SURFACE MAX 4327 FINISH O ENG 1 2 APPR Keithley Instruments Inc T H LEY Cleveland Ohio 44139 DIMENSIONAL TOLERANCES DO NOT SCALE THIS DRAWING UNLESS OTHERWISE SCECI
93. n Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com SECTION 5 MAINTENANCE 5 1 INTRODUCTION This section contains installation service and calibration in formation for the Model 197 and Model 1978 Fuse replace ment line voltage selection and troubleshooting procedures 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 pro cedures 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 ob served 5 2 TOP COVER REMOVAL INSTALLATION The top cover of the Model 197 must be removed in order to service the unit or install the Model 1978 battery pack and or the Model 1973 or Model 1972 IEEE 488 interface Proceed as follows WARNING Disconnect the line cord and all other equipment from the Model 197 before removing the top cover Turn off the power disconnect the line cord and remove all test leads from the terminals of the Model 197 Turn the unit over and remove the four screws from the bottom of the case Turn the unit over again and separate the top cover from the rest of the unit To reinstall the top cover position the tilt bail properly in to the bottom cover replace top cover and sc
94. n be modified with the use of relative REL feature The Model 197 has two IEEE 488 interface options The Model 1972 and the Model 1973 These optional interfaces enhance the capabilties of the Model 197 by allowing pro grammed control over the IEEE 488 bus The Model 1972 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 197 includes the following features 1 Six Measurement Functions DCV ACV ACA OHMS and dB all built in 2 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 im pedances for dB measurements 3 Digital Calibration A non volatile RAM stores calibra tion constants and can be performed from the front panel or over the 488 bus 4 Data Logger A data storage buffer is included to allow up to 100 readings and minimum maximum readings be internally 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 5 Autoranging The Model 197 includes a fast autoranging feature for easier measurements 6 572 Digit Resolution The Model 197 has 220 000 count A D that surpasses the more common 199 999 count A D 7 Four Terminal Ohms These terminals are used to elimi
95. n in Figure 3 6 N NOTE Be sure to connect the calibrator to the 10A and LO terminals Otherwise applying the 5A as specified in Table 3 5 would blow the front panel current fuse NO Apply 4 0 50000VDC to the current calibrator to output 5 0000A Verify that the reading is within the limits specified in Table 3 5 10 Repeat steps 1 through 10 with negative current Table 3 5 Limits for DC Current Verification Applied Allowable Readings 197 DC Range DC Current 1 18 to 29 200 pA 200 0004A 199 785 to 200 215 2mA 2 00000mA 1 99785 to 2 00215 20mA 20 0000mA 19 9785 to 20 0215 200mA 200 000mA 199 585 to 200 415 2000mA 2000 00mA 1995 85 to 2004 15 10 A 5 0000 A 4 9610 to 5 0390 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 3 5 5 AC Current Accuracy Check HI OUTPUT AC current accuracy is checked by connecting a calibrated AC current source to the HI and LO INPUT terminals for 2002 to 2000mA 10A and LO terminals for 2000mA to 20A and then verifying that the displayed reading is within the specified range CAUTION MODEL 197 Do not exceed 2A between the HI and LO INPUT terminals or instrument damage might occur Refer to paragraph 2 4 4 DC VOLTAGE CURRENT CALIBRATOR CALIBRATOR 1 Select the AC current function on the Model 197 Place the instrument in the 2000mA range 2 Connect the AC calibrator to the Model 197 a
96. n severe injury or death in the event of a short circuit or malfunction 5 5 FUSE REPLACEMENT 5 5 1 Line Fuse Replacement The line fuse is located internally in the Model 197 For exact fuse location refer to Figure 5 1 To replace the fuse proceed as follows 1 Remove the top cover as explained in paragraph 5 2 2 If the Model 1973 or Model 1972 IEEE 488 interface is in 5 2 IEEE board is 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 sup port post 3 Replace the blown fuse with the following type 1 8A 250V 3AC 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 instru ment If so the problem must be corrected before operation may continue 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 standoffs WARNING Do not push down on J1008 The male con nector 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
97. nate the voltage drop across the current carrying leads 8 Sensitivity The Model 197 has 14V 1m and 1nA sen sitivity The 14V of sensitivity allows minute levels of off set temperature etc 1nA sensitivity allows low current measurements without special equipment Measure leakage bias and offset current A 1mf sensitivity allows easy low resistance measurements 1 3 WARRANTY INFORMATION Warranty information may be found on the inside front cover of this manual Should it become necesary to exercise the warranty contact your Keithley representative or the factory to determine the proper course of action Keithley In struments maintains service facilities in the United States United Kingdom and throughout Europe Information con cerning the application operation or service of your instru ment 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 in strument 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 197 The symbol A on the instrument denotes the user should refer to the operating instructions in this manual The symb
98. nd Display Make sure the A D converter and display are operating pro perly BEFORE attempting to troubleshoot the signal condi tioning circuits Check these circuits using the information in Table 5 8 and 5 9 5 7 5 Signal Conditioning These circuits can be checked by using the diagnostic pro gram troubleshooting modes See paragraph 5 7 2 Also refer to Table 5 6 5 9 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Table 5 6 Model 197 Troubleshooting Mode Function DC Amp Range Control and Test Gain Gain Multiplexer Range ogic Levels On U Range Mode U102 U104 FET On Transistor On PAO 2 200mVDC 0 1 10 0111 0 1 1 0 141 10 0112 0 1 0 0 241 X1 0113 0 0 0 1 3u1 X1 Q112 0 0 0 0 2VDC 0u2 X1 Q111 0 0 1 0 1u2 X1 0112 0 0 0 0 0113 0 0 0 1 0112 0 0 0 0 0104 0105 0 0 1 0 143 0110 0104 105 1 0 0 0 203 0113 0104 0105 0 0 0 1 3u3 Q112 Q104 Q105 0 0 0 0 200VDC 0 4 0111 0104 0105 0106 0107 0 0 1 0 1 4 0110 0104 0105 0106 0107 1 0 0 0 244 0113 0104 0105 0106 0107 0 0 0 1 3u4 Q112 0104 0105 0106 0107 0 0 0 0 1kVDC Ou5 Q111 Q104 Q105 Q109 Q108 0 0 1 0 145 0110 0104 105 Q109 Q108 1 0 0 205 0113 0104 0105 0109 0108 0 0 0 1 345 Q112 0104 0105 0109 0108 0 000 200mVAC 041 X1 X5 0111 Q10
99. nnect the red test lead to the HI terminal and the black test lead to the LO terminal 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 activates manual ranging This is indicated by the absence of the AUTO annunciator 4 Select DC volts by releasing out position the AC DC button V is still selected The AC annunciator turns off 5 Select the autoranging OHMS by pressing in the AUTO and Q buttons DC must still be selected The 0 omega symbol is displayed Press the AC DC button in means select AC and note that the Err message is displayed This indicates an invalid mode 6 Select AC or DC current by setting the AC DC button ac cordingly and pressing in the A button The annunciator that reflects the selected mode is displayed Note that cur rent 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 pressing the dB button The dB annunciator is now displayed Press the dB button to take the instrument out of the dB mode 8 The REL relative feature can be used with any measure ment function Volts Amps Ohms or dB For example select the ohms function and autorange The display reads approximately 000 1400 which is the test lead resistance Press the REL button The REL annunciator is turned on and the d
100. o 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 condi tion 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 N Attach the test leads to the circuit under test Use ap propriate safety rated test leads for this application 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 disconnect device 6 Disconnect the test leads from the circuit under test using the installed connect 2 3 PREPARATION FOR USE 2 3 1 Line Power The Model 197 has a three wire line cord which mates with third wire grounded receptacles Connect the instrument to AC line power as follows 1 Set the LINE VOLTAGE switch on the back of the instru ment to correspond to line voltage available Ranges are 105V 125V or 210V 250V 50 60Hz AC CAUTION Connect only to the line
101. ol on the instrument denotes that a potential of 1000V or more may be present on the terminal s Stand ard safety practices should be observed when such dangerous levels are encountered 1 1 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com The WARNING heading used in this manual explain dangers that could result in personal injury or death The CAUTION heading used in this manual explain hazards that could damage the instrument 1 6 SPECIFICATIONS Detailed Model 197 specifications may be found preceding the table of contents of this manual 1 7 UNPACKING AND INSPECTION The Model 197 Autoranging Microvolt DMM was carefully inspected both electrically and mechanically before ship ment Upon receiving the instrument carefully unpack all items from the shipping carton and check for any obvious signs of physical damage that may have occurred during tran sit Report any damage to the shipping agent Retain and use the original packing materials in case reshipment is necessary The following items are shipped with every Model 197 order Model 197 Autoranging DMM Model 197 Instruction 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 197 901 00 The manual package includes an instruction manual and any ap plicable addenda 1 8 USING THE
102. or 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 5 2 5 6 5 AC Voltage Calibration With the Model 197 still in the calibration mode C annun ciator on connect the AC voltage calibrator to the Model DC VOLTAGE CALIBRATOR MODEL 5440 MODEL 197 Figure 5 3 DC Voltage Calibration Configuration Table 5 2 DC Voltage Calibration Calibrator Model 197 Voltage Reading 200mV 190 000 190 000mV 2 1 90000 V 1 90000 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 1000 00 V 197 as shown in Figure 5 4 Steps 1 6 must be performed in the exact sequence listed 1 Select the AC voltage function and the 200mV range 2 Set the calibrator to output 190 000mV at 500Hz 3 Adjust the display using the STO CLR and RCL buttons to read 190 000mV AC 4 Press the dB button and verify that the dB annunciator is displayed 5 Set the calibrator to output 19 000mV at 500Hz 6 Adjust the displayed reading for 19 000mV 7 Press the REL button and verify that the dB annunciator is off 8 Repeat steps 2 and 3 for the remaining ranges using Table 5 3 as a guide 9 Store the new cal constants before proceeding See paragraph 5 6 8 5 6 6 Frequency Compensation The following section is to be used to determine
103. p Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 4 Determining Q The Q of a tuned circuit can be determined as follows A Determine the center frequency and bandwidth as ex plained in paragraph 2 7 10 step 3 B Calculate Q by using the following formuala Center Frequency Bandwidth 2 7 11 MIN MAX and 100 Point Data Logger 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 per second to one reading per hour Also manual triggering is available r 6 In the r 6 mode one reading is stored every time the STO CLR button is pressed Readings 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 follows 1 Connect the desired measurement configuration to the Model 197 Make sure that the controls of the Model 197 are set appropriately 2 Logging Data A Press and hold the STO CLR button The following reading rates will scroll on the display rate meaning every reading 1 rdg sec 1 rdg 10 sec 1 rdg min 1 rdg 10 min 1 rdg hour gt 2 3 4 5 6 Irdg every time STO CLR is pressed r r r r NOTE There is no need to select a rate if just minimum maximum readings are desired Press
104. quid Crystal Display LCD D2 D3 DD 36 P1006 Cable Assembly 14 Conductor B4 C4 30 2 U201 LCD Controller Driver D3 C4 LSI 59 Retainer Strip Connector 175 307 Strip Connector 2 required CS 460 2 LCD Mask 175 306 Window Bezel 175 305 Switch Pad Conductive Touch 175 308 Table 6 3 Model 1978 Battery Pack Parts List Schematic Location Keithley Desig Description Sch Pcb Part No BT101 Battery Assembly 12 0V Sealed Rechargeable NiCad Mou B3 BA 40 C101 Capacitor 2504F 25V Aluminum Electrolytic 02 E4 C 314 220 C102 Capacitor 10uF 25V Aluminum Electrolytic C4 C 314 10 CR101 Rectifier Schottky Barrier 1N5820 D2 D4 RF 53 P1009 Cable Assembly 10 Conductor 102 B1 CA 274 101 Resistor 4 70 10 1W Fixed Wound E2 33447 R102 Resistor 4 70 596 1 4W Composition E1 C2 R 76 4 7 R103 Resistor 44 2k 196 1 8W Metal Film R 88 44 2k R104 Resistor 37 4k 196 1 8W Metal Film E3 E4 R 88 37 4k 105 Resistor 1 2M 596 1 4W Composition 76 12 0101 Transistor NPN High Voltage TIP 49 D3 C2 TG 137 U101 Voltage Converter SI7661CJ 03 D4 340 U102 Voltage Comparator LM393 03 IC 343 Heat Sink used 0101 D3 HS 28 Standoff Battery Board to Shield 03 Static Sensitive Device Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Figure 6 2 Model 1978 Battery
105. r Board Component Location Drawing Dwg No 197 100 sheet 1 of 2 6 9 6 10 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com D KI E F G Hi 00 2610 mn Te one CON LA 2747 RELEASED t DETAIL A Von awto 70s Mab M6tE 73 ADDEDADIE Jo ono Danes CHG DAKTU ORK lt p pun SEE DETAIL AND NOTE 5 ee cr H Ak E 82085 E x y TO Je OCHTE D E 6108 CRIOL RIZZS C2 ES LAGD AkTworr 1 7 7o ADDED 6 43 6 7072 2 J 1098 d A BEA Sw 46 57 MA 2 AER L2 D 56 1 779 220 WAS CALLED Dir 2 8 2 2 NOW ADDED PARTS LIST WJ SEE PAGE 2 KRZA E H 12781 566 FACE 2 PAA DT THESE PINS Flas Lii AL OTHER PALS 20 CHOCO ITEM 29 FROM 2 9 250 72 AN 5161 R 2058 ro c 314 220 22 35 __ 5 DO ee pr uses AJE 12979 Henke was l v LAB TIN 5297 eemoven crys LHI HABI Pw 13403 REMOVED 1 ia NOTES L C 24 MUST BE POSITIONED O 15 MINIMUM AWAY FROM 7 13 2 25 MUST BE POSTIONED 0 15 MINIMUM AWAY FROM 704 QIZ MUST IM 22 A 9 2 MUST MAINTAIN 02 LLEAKANCE FLOM Plor A4 AL
106. rements in dB independent of impedance The basic procedure for placing the instrument in the dB CURRENT mode is to first select AC or DC volts and then press the dB SOURCE button Note that once dB is selected dB annunciator on pressing in the Q or A function pushbuttons will turn dB off CAUTION MAX INPUT Table 2 4 dB Specifications for DC Volts 6000 Ref MODEL 197 Linear Counts Resolution Accuracy Figure 2 8 Current Measurements up to 2000mA 10 99 1dBm 2d8m typical 100 999 0 1dBm 1dBm 1000 9999 0 01dBm 0 1dBm 10000 220 000 0 01dBm 0 02dBm 2 7 8 AC Plus DC Measurements Use the Model 197 to measure TRMS on a signal which has both AC and DC components 2 10 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com Table 2 5 dB Specifications for AC Volts 6000 Ref dB Mode Ref 6000 Accuracy dBm 20Hz 10kHz 20kHz 50kHz 52 to 32dBm 20mV to 200mV 32 to 12dBm 2V 750V 200mV to 750V 12 to 59 8dBm Range Input 10kHz 20kHz 50kHz 100kHz 200 1mV to 2mV 2 00 3 00 58 to 52dBm 2mV to 20mV 0 85 1 10 2 00 0 18 0 18 0 28 0 65 0 18 0 18 0 28 0 50 dBm Measurements with 6000 Reference Impedance dBm is defined as decibels above or below a 1mW reference The standard reference impedance of the Model 197 is 6000 What that means is that the Model 197 is des
107. rews 5 3 BATTERY PACK Model 1978 INSTALLATION Refer to Figure 5 1 and perform the following procedure to in stall the battery pack WARNING Disconnect the line cord and remove all test leads from the terminals of the Model 197 1 Remove the top cover as explained in paragraph 5 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 Lift the shield out of the Model 197 3 Position the battery board as shown in Figure 5 1 and secure it to the shield using the two supplied screws The screws are positioned through the shield into the battery board fasteners 4 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 Red to Red and Black to Black Carefully place the shield with battery pack back into the Model 197 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 s
108. s 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 ter minals of the Model 197 B Select the ACA or DCA function C Select an appropriate range for the expected current The current function does not autorange Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com D Connect the test leads to the current source as shown in 1 Measure and record the TRMS AC component as des Figure 2 8 If an overrange indication is displayed cribed in paragraph 2 7 4 select a higher range until a normal reading is shown 2 Measure and record the DC component as described in Use the lowest possible range to obtain the best resolu paragraph 2 7 3 uon 3 Compute the rms value from the following equation E Take the reading from the display Ems 2 E2ac 2 7 9 dB Measurements The dB function makes it possible to compress a large range of readings into a much smaller scope The relationship bet ween dB and voltage can be expressed by the following equa tion VIN dB 20 log VREF CAUTION MAX INPUT 10A MODEL 197 Tables 2 4 and 2 5 list the dB specifications for DC volts and AC volts Figure 2 7 Current Measurements Between 2000mA and 20A The Model 197 can make dB measurements referenced to the standard 6000 impedance to other impedances The relative feature allows measu
109. s 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 0004A and switch the Figure 3 5 Connections for DC Current Model 197 to the 2004A range Verify that the displayed Verification 200 A to 2000mA reading is within the limits specified in Table 3 6 4 Change the Model 197 to the 2mA range Set the calibrator to output 2 00000mA Verify that the displayed reading is within the limits specified in Table 3 6 5 Change the Model 197 to the 20mA range Set the O calibrator to output 20 0000mA Verify that the displayed reading is within the limits specified in Table 3 6 f INPUT 6 Change the Model 197 to the 200mA range Set the LO OUTPUT calibrator to output 200 000mA Verify that the displayed reading is within the limits specified in Table 3 6 7 Change the Model 197 to the 2000mA range Set the calibrator to output 2000 00mA Verify that the displayed reading is within the limits specified in Table 3 6 8 Connect the calibrator to the Model 197 10A and LO ter minals as shown in Figure 3 8 Change the Model 197 to the 10A range MODEL 343A MODEL 2500E DC VOLTAGE CURRENT CALIBRATOR CALIBRATOR NOTE Be sure to connect the calibrator to the 10A and LO terminals Otherwise applying the 5A as MODEL 343A MODEL 2500E specified in Table 3 6 would blow the front panel current fuse Figure 3 6 Connections for D
110. se 3 Remove the defective fuse and replace it with the following type 2A 250V 3AG normal blow Keithley part number FU 13 or equivalent CAUTION Use only the recommended fuse type fuse with a higher current rating is in stalled instrument damage may occur 2 5 ERROR MESSAGES Table 2 1 lists the error messages associated with basic front panel operation Note that the instrument has a number of other messages that are discussed in the appropirate sections of the manual 2 6 OPERATING CONDITIONS 2 6 1 Environmental Conditions All measurements should be made at an ambient temperature within the range of O C to 50 and with a relative humidity of less than 8090 up to 35 For ambient above 35 derate humidity 3 per up to 50 If the instrument has been subjected to extremes of temperature allow sufficient time for internal temperature to reach environmental conditions Typically it takes one hour to stabilize a unit that is 10 18 F out of the specified temperature range 2 6 2 Maximum Allowable Inputs Table 2 2 lists the maximum allowable inputs for the Model 197 2 6 3 Warm Up The Model 197 requires one hour for warm up to achieve rated accuracy 2 7 BASIC BENCH MEASUREMENTS Basic measurement techniques for using the Model 197 to measure AC and DC volts resistance AC and DC current and dB are covered in the following paragraphs Also includ ed is the operation of the minimum
111. seb Tex Y 6 6 Model 1978 Battery Pack Parts 1168 2 6 6 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 2 1 2 2 2 4 2 5 2 7 2 8 2 9 3 1 3 3 3 4 3 6 3 7 3 8 LIST OF ILLUSTRATIONS Model 197 Front ea e DC Voltage Measurements TRMS AC Voltage Measurements Two Terminal Resistance Four Terminal Resistance Measurement Four Terminal 2 2 222 Current Measurements Between 2000mA and 20A Current Measurements up to 2000mA Typical ACV Frequency Response Connections for DCV Verification Connections for ACV Verification Connections for 200 2k and 20k Range Verification 4 Connections for 200k through MQ Ranges Verification 2 Terminal Connections for DC Current Verification 200x to 2000 Connections for DC
112. t is clear that optimum microvolt measurements with the Model 197 are possible with source resistances as high as 1MQ However this resolution will not be realized unless shielding is employed Shielding The Model 197 is insensitive to AC voltages superimposed upon a DC signal at the input terminals 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 circuit should be shielded and the shield connected to the Model 197 ground particularly for low level sources Improper shielding can cause the Model 197 to behave in one or more of the follow ing 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 197 away from strong AC magnetic sources The voltage in duced 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 emfs thermoelectric potentials are generated by thermal differences between two junction of dissimilar metals These can be large compared to the signal which the Model 197 can measure Thermal emfs can cause the following problems Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 1 Instability or
113. turns off If any of the above verifications are not met by the Model 197 the top cover must be removed and three trimmer capacitors adjusted The adjustments must be performed within 10 minutes after the top cover is removed so that the circuit components will be close to normal operating temperature The three trimmer capacitors C103 C105 and C107 are accessible through the shield The shield and PC board must be secured to the bottom cover in order to pre vent movement This asssembly 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 Also use a flat blade in sulated 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 voltage Take care not to come into contact with live circuits that could cause personal injury or detah 1 Select the 750VAC range and set the calibrator to output 500 00V at 500Hz Press the REL button REL annunciator turns on 5 6 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 197 o
114. ut 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 tests leads Model 1751 are supplied with the Model 197 Always disconnect all un used test leads from the instrument HI and LO INPUT Red and Black Use this pair of ter minals for all volt ohm milliamp and dB measurements 10A and LO White and Black Use this pair of terminals 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 a 220 000 count display the 2A range Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com can momentarily approx one minute read 2 2A before the fuse will blow This 1096 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 and rotate the fuse carrier one quarter turn counterclockwise Release pressure and remove the fuse carrier and the fu
115. value of the waveform is 10V but the average value drops to 3 18V The RMS value of this waveform is 5V but the average responding meter will give 3 53V 3 18 x 1 11 creating an error of 29 4 A similar situation exists for the rectified square wave which has an average value of 5V and an RMS value of 5V Here theaverage responding meter givesareading of 5 55V 5 x 1 11 while the Model 197 gives a TRMS reading of 5V Other waveform comparisons can be found in Table 2 7 2 8 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 dynamic 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 depend on the waveform in question because the ratio of peak to RMS value varies For example the crest factor of a rec tangular pulse is related to its duty cycle as the duty cycle decreases the crest factor increases The Model 197 has a crest factor of 3 which means the instrument gives accurate TRMS measurements of rectangular waveforms with duty cycles as low as 1090 2 8 4 Extended Frequency Response Figure 2 9 illustrates the extended frequency response of the ACV ranges up to 1 2 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com asuodsay Aduanbas4 AJY
116. vices Circuit Designation Keithley Part No 0104 0107 0108 0110 0111 0112 0113 0101 0105 0107 U113 U114 U115 U117 U118 U119 U120 U121 U122 U123 U124 TG 139 TG 139 TG 139 TG 139 415 283 347 353 LSI 61 1C 143 1 337 341 348 351 LSI 62 197 800 1C 338 LSI 60 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 5 13 5 14 SECTION 6 REPLACEABLE PARTS 6 1 INTRODUCTION This section contains replacement parts information compo nent location drawings and schematic diagrams for the Model 197 and Model 1978 6 2 REPLACEABLE PARTS Parts are listed alpha numerically in order of the schematic designation Table 6 1 contains parts list information for the mother board Table 6 2 contains parts list information for the display board Parts list information for the Model 1978 Battery Pack is contained in Table 6 3 6 3 ORDERING INFORMATION To place an order or to obtain information concerning replacement parts contact your Keithley representative or the factory See the inside front cover for addresses When ordering include the following information 1 Instrument Model Number 2 Instrument Serial Number 3 Part Description 4 Circuit Designation if applicable 5 Keithley Part Number If an additional instruction manual is required order the manual package Keithley Part Number 197
117. voltage selected Application of incorrect voltage can damage the instrument 2 Plug the power cord into a properly grounded outlet WARNING Ground the instrument through a properly grounded receptacle before operation Failure to ground the instrument can result in severe injury or death in event of a short circuit or malfunction NOTE Although the Model 197 is specified at 50 and 60Hz the instrument may be operated at 400Hz and 440Hz 21 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 2 3 2 Battery Pack Power The Model 197 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 197 for typically five hours NOTE The Model 197 uses the most power on the amps function and also in the 2000 2kQ or 750VAC ranges The BAT annunciator turns on when the charge is insufficient to maintain accurate readings Refer to paragraph 5 3 for installation procedures 2 3 3 Battery Charging After the Model 1978 is installed in the Model 197 it can be charged and recharged as follows 1 Connect the instrument to line power as described in paragraph 2 3 1 2 With the power switch off the battery charge circuitry is automatically energized to charge the battery at the max imum rate When the battery pack is first installed or if it is completely discharged allow it
118. within 0 1 of final reading Specifications subject to change without notice Artisan Technology Group Quality Instrumentation When properly zeroed Appropriate range selected automatically in MQ CONFIGURATION Automatic 2 or 4 terminal MAXIMUM ALLOWABLE INPUT 450V dc or peak ac 10 seconds per minute 350V rms continuous OPEN CIRCUIT VOLTAGE 5V 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 220 000 count LCD 0 45 in height polarity function range and status indication RANGING Auto or manual on dc volts ac volts and ohms manual on ac amps and dc amps RELATIVE Pushbutton allows zeroing of on range readings Allows readings to be made with respect to baseline value Front panel annunciator indicates REL mode DATA LOGGER and MIN MAX 100 reading storage capacity records data at one of six selectable rates from 3 readings second to 1 reading hour or by manual trigger ing Also detects and stores maximum and minimum readings continuously while in data logger mode CONVERSION RATE 3 readings second 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 1 unbalance Greater than 120dB at dc 50Hz 60Hz 0 1 Greater than 60dB in ac volts TEMPERAT
119. ys 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 converter 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 responding meter a correction factor must be designed in This correction fac tor K can be found by dividing the RMS value by the average value as follows 0 707 1 11 0 637 By applying this correction factor to an averaged reading a typical meter can be designed to give the RMS equivalent This works fine as long as the waveform is a pure sine wave but the ratios between the RMS and average values of dif ferent waveforms is far from constant and can vary con siderably Table 2 7 shows a comparison of common types of waveforms For reference the first waveform is an ordinary sine wave with a peak amplitude of 10V The average value of this voltage is 6 37V while its RMS value is 7 07V If we apply 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 2 14 The situation changes with the half wave rectified sine wave As before the peak
120. zero offset is much higher than expected 2 The reading is sensitive to and responds to temperature changes This can be demonstrated by touching the circuit by placing a heat source near the circuit or by a regular pattern of instability corresponding 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 197 A banana plug is generally sufficient and generates just a few microvolts A clean copper conductor such as 10 bus wire is about the best for the application The leads to the input may be shielded or unshielded as necessary Refer to Shielding 4 Widely varying temperatures within the circuit can also create thermal emfs Therefore maintain constant tem peratures 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 offset voltages 2 7 6 Resistance Measurements The Model 197 can make resistance measurements between ImQ and 220MQ The 2 0 20 0 and 200 ranges autorange when the button is selected The Model 197 provides automatic selection of 2 terminal or 4 terminal resistance measurements This means that if the ohms sense leads are not connected the measurement is done 2 terminal If the sense leads are connected the measurement is done 4 terminal For 4 terminal measurements rated

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