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Keithley 177 Microvolt DMM

1. Item Component Required Condition Check chopper amplifier operation per Table 5 7 steps 1 thru 10 Select 2kQ range Short input 0000 1 digit 1V Approximately Display TP9 INPUT HI to LO Remove short and connect ammeter from INPUT HI to LO Source current should be approximately 1mA HI terminal negative Remove ammeter and measure open circuit voltage Voltage must be 2 to bV Apply to INPUT 1 9000 12 digits INPUT HI to LO 1 9kQ resistor Display 19kQ resistor Display Apply to INPUT Select 20k2 range 19 000 12 digits 190kQ resistor Display Apply to INPUT Select 200k range 190 00 12 digits 1900k2 resistor Display 1900 0 12 digits 10M2 resistor Display Apply to INPUT Select 20M2 range 10 000 12 digits NOTE Reference loading by the ohms source does not affect 2 readout since A D converter is ratiometric Apply to INPUT Select 2000kQ range Remarks Inverted reference voltage plus calibrated offset of U107 If incorrect check R158 and switching to INPUT HI and chopper amplifier HI negative with respect to LO Display should be blink ing indicating overrange Calibrated resistance Subtract test lead resistance from reading Checks accuracy of R158 and feed back loop to U107 Calibrated resistance Source resistors R158 R154 8 975kQ R157 wiper Calibrated resistance Source resistors R158 R1
2. 20M 0 1 Rdg 1D ANALOG OUTPUT 2V full scale 5kQ output resistance Note 1 See manual for detailed information Note 2 Overrange is indicated by flashing 0000 Note 3 True root mean square crest factor 3 Note 4 Current fuse installed internally is 2A 3AG normal blow See Figure 5 4 for location 2000mA 0 05 Rdg 3D 20mV F S 0 05 Rdg 2D 200mV F S Yes Q Ohms Polarity Negative in indicated positive is implied when minus display is off Zero 177 MICROVOLT DMM 20 200 INNEN 2 20k 200 20004 20M 20n 200m 20 200 1000 M 2004 2m 20m 200m2000 REED N ONEN 1 SET POWER ON 2 SELECT FUNCTION 3 SELECT RANGE 4 CONNECT SOURCE Figure 2 3 Operating Controls NOTE Due to the long thermal time constant of the 20mV range zero a one hour warm up time may be necessary to adjust zero to the final 14V set ting Typically only a one to three microvolt zero shift can be expected during this warm up period if the ambient temperature is within the specified 18 to 28 C and the instrument has not been subjected to temperature outside of this range Thus since the expected zero shift is both small and slow normally zero can be ad justed and several measurements taken without having to achieve the final zero setting Make connections to the Model 177 as described above For the best performance connections should be made to the
3. 4 1 Range Switch Correlatioh ss ip ER aS SEERENEQECCES E VA GERE REA d ARENA ER 4 2 AC Converter Attenuation Amplification xe esu sec Jk oe e GRE RE A AAA 4 3 DC Signal Conditioning Attenuation and Gain LL 4 4 Ohms CONVERSION din ate ERIS Rp CR RUE USE Cre OI Ea 5 1 Recommended Test Equipment for Calibration mmn 5 2 Calibration Procedur 6 s katie e AUR ip RU Ra POR ER T E A ebd di UR RUP ot 5 3 Line Power Checks cac pd dead ee de C nae e tea ress 5 4 Battery Power Cheeke ocios iraniani PExqOS S Few FE Fi E ARA AAA E Y Ra arida 5 5 DISD BV intitola 5 6 Pe T siii ciente iride Speed bale tia tra 5 7 AC CONVENOR lierna ear 5 8 DC Attenuator and Chopper Amplifier co icine esas ees ve eee Rey Aaa ii 5 9 Ohms Source and BH68iSlOIB 1 ais cer aac KE Ron Rr EO e oboe VR A Rer POE OP SO RE E IG a CR det a 5 10 Cuit SONS cal ere xRPCLPLE repartida oes ER ETE X Se ERRAT pios xara see qd 5 11 Adjustment of Battery Charge Voltage eee ns 6 1 Model 177 Spare Parte Kit oou de Eros DR RT duroni nep dur Pops EIAS rivas habeis 6 3 6 2 Mother Board Parte iste coda versa CERA ad ERE VRAC hr ee ase KO DA Neh s 6 3 Model 1788 Battery Pack Parts List 4 6 lt 6i5 sees oi eee he aen yr has be sees eee ya RR ER Ex E nes 6 4 Display Board Parts List 2 sesi vinr Cete x ORO Ra ER acce hh A pud sce d bob kid e S Ron an a caca iii Figure 1 1 Model 177 Front Panel SECTION 1 GENERAL INFORMATION 1 1 INTRODUCTI
4. C108 Capacitor 1uF 100V 10 Polyester Film C 294 1 C109 Capacitor 1uF 100V 10 Polyester Film C 294 1 C110 NOT USED C111 Capacitor 2200pF 500V Ceramic Disc C 22 2200pF C112 Capacitor 100pF 1000V Ceramic Disc C 64 100p C113 NOT USED C114 NOT USED C115 Capacitor 14F 100V 1096 Polyester Film C 294 1 C116 Capacitor 4uF 100V 10 Polyester Film C 294 4 C117 Capacitor 224F 200VDC 10 Polyester Film C 269 22 C118 Capacitor 12uF 100V 10 Polyester Film C 294 12 C119 NOT USED C120 Capacitor 22004F 15V Aluminum Electrolytic C 290 2200 C121 Capacitor 4 7uF 25V Aluminum Electrolytic C 314 4 7 C122 Capacitor 4 7uF 25V Aluminum Electrolytic C 314 4 7 C123 Capacitor 4704F 35V Aluminum Electrolytic C 289 470 C124 Capacitor 4 7nF 25V Aluminum Electrolytic C 314 4 7 C125 Capacitor 470F 35V Aluminum Electrolytic C 289 470 C126 Capacitor 104F 25V Aluminum Electrolytic C 314 10 C127 NOT USED C128 NOT USED C129 NOT USED C130 Capacitor 100pF 1000V Ceramic Disc C 64 100p C131 Capacitor 100pF 630V 25 Polystyrene Film C 252 100p C132 Capacitor 100pF 630V 25 Polystyrene Film C 252 100p C133 Capacitor 00474F 100V Polystyrene C 301 0047 C134 Capacitor 124F 100V 10 Polyester Film C 294 12 C135 Capacitor 1000pF 500V Polystyrene C 138 1000p C136 NOT USED C137 NOT USED C138 Capacitor 1uF 100V 10 Polyester Film C 294 2 C139 Capacitor 14F 100V 10 Polyester Film C 294 1
5. half wave rectified DC signal at the input of the integrator stage that is inverted with respect to the chopper input signal 4 DC Amplifier Amplifier U109 is connected as an in tegrator with an offset adjustment U109 provides suffi cient gain to bring the total open loop DC gain to about one million U109 drives the feedback divider network and the A D converter and provides the low output im pedance necessary to drive the analog output Feedback capacitor C138 was selected to provide nominal settling time while meeting NMR requirements When the chop per is operating as a unity gain follower the DC signal pre sent at the output of U109 is the chopper feedback This is the condition for the 2VDC range and above On the 200mV and 20mV ranges where chopper gains of 10 and 100 are required the resistive divider feeds back a portion of the output of U109 to provide the required gain 5 Modulator Demodulator Drive Circuit CMOS inverters U111A and U111F provide opposite phase 0 to 15V square waves used to drive MOSFET modulator transistors Q104A and Q104B Inverter U111F also drives the 43 demodulator JFET 0105 Resistors R118 R119 and R142 and capacitors C131 and C132 affect the rise and fall times of drive signals R142 adjusts the rise and fall time of the drive signal to Q104A only so that the total charge both positive and negative transfered to the input can be minimized The frequency of the drive sig
6. refer to troubleshooting information in this section or contact your Keithley representative or the factory NOTE Calibration should be performed by qualified personnel using accurate and reliable test equip ment 5 2 RECOMMENDED TEST EQUIPMENT Recommended test equipment for calibration is listed in Table 5 1 Alternate test equipment may be used However the ac curacy of the alternate test equipment must be at least 10 times better than the Model 177 specifications or equal to Table 5 1 specifications 5 3 ENVIRONMENTAL CONDITIONS Calibration should be performed under laboratory conditions having an ambient temperature of 20 C to 26 C 68 F to 78 F and a relative humidity of less than 80 If the instru ment has been subjected to temperatures outside of this range or to higher humidity allow one hour minimum for the instrument to stabilize at the specified environmental condi tions before beginning the calibration procedure 5 4 CALIBRATION PROCEDURE Perform the following adjustments to calibrate the Model 177 and restore its operation to specified limits 5 4 1 Calibrating Shield Installation If the Model 1788 Battery Pack is installed in the instrument it must be removed and the calibration shield reinstalled before calibration If the calibration shield has been lost or mis placed order Keithley Part Number 29473 WARNING Disconnect the line cord before removing the case cover 1 Turn off the power
7. 0 1V 1V 10V 100V 1000V 0 00296 0 1V 1V 10V 100V 0 01 5000 1 9k2 190kQ 0 01 10 1 divider within 50 PPM See Figure 3 1 5 1 1 Refer to Table 5 2 and perform the listed adjustments in the sequence indicated on the calibration shield by boxed numerals The sequence must be followed exactly because the adjustments are interrelated and dependent on the preceding steps The step sequence box numerals is also shown on schematic diagram 29658E 2 If the indicated adjustment cannot be made to obtain the specified reading refer to troubleshooting information in this section 5 5 TROUBLESHOOTING The troubleshooting instructions contained in this section are intended for qualified personnel having a basic understanding of analog and digital electronic principles and components used in a precision electronic test instrument Instructions have been written to assist in isolating the defective circuit or subcircuit Isolation of the specified defective component has been left to the technician NOTE For instruments that are still under warranty less than 12 months since date of shipment if the instrument s performance is outside of specifica tions at any point contact your Keithley representative or the factory before attempting 5 6 TROUBLESHOOTING PROCEDURE This section contains tables listing step by step checks of the major Model 177 circuits described in Section 4 Theory of Operation The following st
8. 29658E and summarized in Table 4 2 Scaling is performed by using a relay and FET switches to switch feedback resistors in the attenuator U101 and the amplifier U102 The actual gains used in attenuator U101 are 0 99 0 0099 and 0 00099 Amplifier U102 gains are nominally 1 003 and 10 03 The combined gain of U101 and U102 is offset low to permit gain adjustment in the TRMS stage The only adjustments provided in the attenuator and amplifier stages are two high frequency compensation capacitors C102 and C103 AC coupling is used at the input and output of the attenuator and amplifier stages Input overload protection is provided by diodes CR106 and CR107 and resistors R107 1MQ 2W 4 3 2 AC Conversion AC to DC conversion is performed by a monolithic TRMS module U103 Output Voe VAvg Vin Averaging and output filtering are done before the internal output buffer to give a low impedance for the analog output Potentiometer R113 provides midband 10K count gain adjustment and R114 establishes output zero 1K count Capacitor C108 is used in the averaging circuit and C109 provides filtering as described above 4 3 3 AC Current Measurements For AC current measurements the appropriate shunt resistor is placed in front of the AC converter The 200mV range gain configuration is used for all current ranges 4 4 DC SIGNAL CONDITIONING For DC voltage measurements the input resistance is 10MQ which is established by ail of the
9. 49kQ 1 1 8W J1 A3 R 88 6 49k Resistor 3 65kQ 196 1 8W J1 A3 R 88 3 65k Resistor 8062 196 1 8W H1 A3 R 88 806 Resistor 2 15kQ 0 1 1 10W Metal Film H1 A3 R 263 2 15k Resistor 502 3 4W POT H1 A3 RP 64 50 Resistor 4020 0 1 1 10W H2 A3 R 263 402 Resistor 100kQ 1 1 8W H3 B2 R 88 100k Resistor Selected with VR104 H1 A3 27699A Resistor 33 2kQ 1 1 8W F5 C4 R 88 33 2k Resistor 50kQ 5 Cermet Trimmer D1 D3 RP 97 50k Resistor 47kQ 596 aW Composition A6 B3 R 76 47k Resistor 22M 10 4W A6 B3 R 76 22M Resistor 1kQ 1096 34 W Potentiometer B7 A3 RP 64 1k Resistor 100kQ 1096 2W Composition B5 D3 R 3 100k Resistor 22kQ 5 W Composition B5 D3 R 76 22k Resistor 9220 0 1 W Metal Film E5 C4 R 264 922 Resistor 10kQ 0 5W Potentiometer F5 C4 RP 97 10k Resistor 1000 0 5W Potentiometer E5 C4 RP 97 100 Resistor 8 95kQ 0 1 1 10W Metal Film F5 C4 R 263 8 95k Resistor 1002 1 1 10W Metal Film F6 C4 R 263 100 Resistor 998kQ 1 4 W Metal Film G1 D2 R 264 998k Resistor 998kQ 1 AW Metal Film G1 D2 R 264 998k Resistor 998kQ 1 4W Metal Film G1 D2 R 264 998k Resistor 994kQ 1 VW Metal Film G2 D2 R 264 994k Resistor Thick Film D1 D3 TF 78 Resistor 5kQ 10 Cermet Trimmer D1 D4 RP 97 5k Resistor 5002 10 Cermet Trimmer E1 D3 RP 97 500 Resistor 502 10 Cermet Trimmer E1 D4 RP 97 50 Resistor 1kQ 0 1 1 10W R 263 1 000k Res
10. A D CONVERTER The A D converter operates on the dual slope principle The timing is divided into three periods as described below 4 8 1 Auto Zero The auto zero period Figure 4 3 is 100mS in length which corresponds to 10 000 clock pulses During this period the reference voltage Vgep is stored on capacitor C116 Capacitor C115 stores Vage Vosi Vos 4 8 2 Signal Integrate The signal integrate period Figure 4 3 is also 100mS in length The A D input is buffered and integrated by U105 Positive signals generate a negative going ramp at the in tegrator ouput pin 14 while negative signals produce a positive going ramp The level of the integrated signal at the end of the signal integrate period is proportional to the average of the applied signal during this period Since signal integration continues for 100mS the A D converter exhibits high normal mode rejection for AC signals in multiples of 10Hz particularly the 50 and 60Hz line frequencies A AUTO ZERO 10k COUNTS VREF VREF Yos1 ene Vost 24 p PREF Vos1 M A136 QU te UU TO LOGIC BUFFER INTEGRATOR x AA E T 2115 COMPARATOR Vner Voss Vos2 VREF B SIGNAL INTEGRATE 10k COUNTS VREF i Vg VR x Ys cue Vos1 o i LE x mm o MR Vs VREF Vos1 Vaer Vosi Vos2 C115 4 8 3 Reference Integrate The reference integrate period for a full scale input Figure 4 3
11. Agg BATTERY Pate E instaumenrs ip se F Grameen foam 9 GA Figure 6 5 Model 1788 Battery Pack Schematic Diagram Dwg No 29659C 02 9 61 9 385962 ON Bmg wesbeig oneuieuos 18IBUINIDN HIA YP LLL IPPON 9 9 e1n514 coza 54183 3 Y S asi me mse mis a Poo bonos a gt PATA iso aa T X gt AAA TEN ESPOLI TO LELE Lai 9 v _ x U l ia Asi 10614 3 j DIA 4 on Mia Moria ENO NOLA NEMS Ng AAA s d e ca D e B AA Kar a Jui mete PEON LO 10 14Ud 199 I A Te 5 ap io 3 e i sE I DR D SLOVENO nous OA ON TTT E Nie i pe i i uit mor LOY See CAMINOS CIMA 3 53 331 deli ci a ai NT n g 2 5210830 5 71 E S ex a v id A S CG8 01 SUONTO gt t Gha SONK i COMNIS TINS nY OM SONIS s uti MOMO TALC RO A i i A i AN i ks ca n MAN TINEA 90041 SHLONIC i v i Sos Uno mi NCrnC IOWA 234103 amp etas 53 2800 X X 2 hae st A x aane DR N e Se oo a Ip K ta vios NOUS A SQwaviO A dA MAHO Olsuvm SS 5 wn 1 4 A A g Ew id T LANZ SJON Tar SOFS IOMA NI Int i 70 WOLDYqvO TT 2 z Adan meg lt gt yl sonno a ET Tee hO a a SIMAO A l Mo Mun S 110m30 SSD NO Seo NI JAY SOP YA CLS CCS gt S3LON a gr T JAC 2323905 PA 23 A pra p 4 L UU T 1 xi LI wad E ats xc e i ES E KA 2667 3 m f uri re gt D K AA ali E Che a r Q Q0 E biir n 1 A n F K AGE A A oo o 1 d T
12. C140 Capacitor 0474F 100V Polystyrene C 301 047 CR101 Bridge Rectifier 100V 1 5A RF 36 CR102 Silicon Rectifier 3A 50PIV 1N4139 RF 34 CR103 Bridge Rectifier 100V 1 5A RF 36 CR104 Bridge Rectifier 400V 1 5A RF 46 CR105 NOT USED CR106 Diode Silicon 1N4148 RF 28 CR107 Diode Silicon 1N4148 RF 28 CR108 NOT USED CR109 NOT USED CR110 Diode Silicon 1N4148 RF 28 Table 6 2 Model 177 Mother Board Parts List Cont Circuit Location Keithley Desig Description gt Part No Diode Silicon 1N4148 Diode Silicon 1N4148 Diode Silicon 1N4148 Diode Silicon 1N4148 NOT USED NOT USED Diode Silicon 1N4148 NOT USED NOT USED Rectifier 1A 800V 1N4006 Fuse 2A 250V 3AG Quick Fuse Slo Blo 1 8A 250V 3AG 115V Version Fuse Slo Blo 3 16A 250V 100V Version 8 Pin Connector 12 Pin Connector Female Connector Connector Housing Binding Post Black Binding Post Red NOT USED 14 Pin Connector Contact Relay 5V Reed Type 8 Pin Connector 12 Pin Connector Connector Male Connector Male NOT USED NOT USED Line Cord Transistor N Chan JFET 2N4392 Transistor N Chan JFET 2N4392 Transistor NPN Case TO 5 2N3439 Transistor N Chan JFET 2N4392 Transistor NPN 2N5139 Transistor NPN Silicon 2N3565 Transistor N Chan JFET Resistor 10 7 5W Wire Wound Resistor 0 8980 0 1 Wire Wound Resi
13. U106 input 6 Display 1 0000 2 digits If steps 4 and 6 are correct A D converter is functioning properly If not continue with step 7 7 TP4 O to 5V square wave at Clock input to U106 100kHz 100Hz 8 TP3 1 0 0 1V Stored autozero voltage 9 U105 pin 11 1 0 0 1V L node voltage to integrator in U105 10 U105 pin 14 1 2 0 2V U105 integrator output voltage 11 U105 pin 13 1V U105 buffer input 12 U105 pin 9 1V U105 buffer output 13 External Voltage Apply 1 9000V Calibration point Source 14 Display 1 9000 1 Digit if different check U106 input 15 TPi 1 9000V Input to U106 16 1U105 pin 14 Waveform per Figure 5 2 Integrator output 17 U105 pin 2 Waveform per Figure 5 2 Comparator output during ramping in integrator On main printed circuit board see Figure 5 1 Table 5 7 AC Converter Checks Step Item Component Required Condition Turn on power Select 2VAC range External voltage Apply 1V rms at 1kHz source TP10 99V rms nominal TP8 993V rms nominal U103 Pin 6 or 1V TP1 Select 20VAC range Apply 10V rms at 1kHz External voltage source TP10 099V rms nominal 993V rms nominal Select 1000VAC range Apply 10000V rms at 1kHz TP8 External voltage source TP10 99V rms nominal Select 200VAC range Apply 100V rms at 20kHz 100 00 nominal External voltage source Display Select 2VA
14. UIO5 giang CIZ L L ape Is 5 B He NJ Sols 9 I m re ED E rare tan Zi Bras ET PEDALA ILLE Seu d ear UI04 UNO S R T era l es MIRAR E ag sone it Sd Ta y e do I RA 7 X RI26 g SLI g p 109 e kt i Code E fo Front PANEL INPUT 7 RED Bintning Post _ RED UIO3 5 Rieg amp IT A RIO pon Da ni TEA 4 CIO L uoo 1 E Nue M a TS a t a E B 6 DUET SETE i T T F7 Y LT 9 7T 03 TI tet A A 294090 H PAGETOF2 A ipaa sns B c D E F G 23402 3194 A QbLvoz A FORM 209116 C D E F ITEM PART NO STREM ZONE ITEM PARTO hg E ITEM PART NO E ZONE E MEM PART NO trary ZONE 1 Tassa Pe Tel Di SI RF ZG CROG cS iQ R 1o 990K_ Rios cs AS 8 263 10K RISA DA 2 i i ORIO CS 102 R M6 9 97Kk RIOF cS 152 RP 89 10K_ 1S9 52 E y 1103 R 116 991 RIO cs AN IS a aaa ri 4 iC285 col CES 104 IR Ne 90 3K RUI 24 1159 R 76 3 9M Riol 24 Us lt 164 Coz ES RE 28 CRO az OS JR I76 IOK kie ca MSS RP 89 50K Rie c2 Y LOA CES i ERU 106 RP 97 500 R13 DA MEC RP 97 200 RIGS ca AL e Ca3e lIO0d cilOS CS i RD 108 E 158 B8 00 RIOS cz AN 9 1C 321 33 CIO c4 1
15. instru ments use a 3 16A fuse See Section 5 WARNING Ground the instrument through a properly earth grounded receptacie before opera tion Failure to ground the instrument can result in severe injury or death in the event of short circuit or malfunction 2 Plug the power cord into a properly grounded outlet Operate the Model 177 DMM as described in paragraph 2 7 2 5 OPERATION ON BATTERY PACK POWER The Model 177 DMM may also be operated from rechargeable sealed lead acid batteries contained in the optional Model 1788 Battery Pack The battery pack will operate the Model 177 DMM for up to six hours Circuits within the battery pack will automatically shut down the in strument when the battery charge is insufficient to maintain accurate readings To instali the Mode 1788 refer to Section 5 2 6 BATTERY CHARGING The Model 1788 Battery Pack contains an integral battery charger To charge the battery pack install the battery pack in the Model 177 DMM as described above and proceed as follows 1 Connect the instrument to line power as described in paragraph 2 4 2 1 These adjustments are used only for calibration They are not intended for adjustment during operation ANALOG OUTPUT INTERNAL FUSES CAUTION LNE TAA GAG Sit CANINA I ONIY I0 CURRENT 2A JAG NORMAL IICA TES LINI wat T AL 1 fi ile AV f Y VA MAX H LINE VOLTAGE 41009 SELECT SWITCH z LINE CORD S101 P1007 Figure 2 1 Rear View Of St
16. of your instrument may be directed to the applications engineer at any of these loca tions Check inside the front cover of this manual for ad dresses 1 4 MANUAL ADDENDA Information concerning improvements or changes to the instrument that occur after the printing of this manual will be covered in an addendum sheet packed with the instrument 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 may be found on the Model 177 The symbol AN on the instrument indicates that the user should refer to the operating instructions The symbol on the instrument denotes that a potential of 1000V or more may be found present on the terminals Standard safety practice should be observed when such dangerous voltages are encountered The WARNING heading used in this manual explains dangers that could result in personal injury or death if not handled properly Be sure to read the WARNING informa tion carefully before performing the associated procedure The CAUTION heading is used in this manual explains hazards that could damage the instrument 1 6 SAFETY PRECAUTIONS The following safety precautions should be observed before operating any digital multimeter 1 This instrument is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety precautions required to avoi
17. range resistors being con nected in series to signal ground On low voltage ranges the DC input is applied to the top of the resistive divider range resistor and to the buffer amplifier input without attenuation Also the chopper amplifier has appropriate gain to provide a 2V full scale output to the A D On high voltage ranges the DC signals are scaled down to 2V full scale by the resistive divider and the chopper is used in the unity gain follower mode as a buffer A summary of input attenuation and chopper amplifier gain is given in Table 4 3 Table 4 1 Range Switch Correlation Function Q 20 V 20m A 20u DC Only ACV 1000 DCV 1200 200 200m 2 2004 2m 20m 200m 2000m Table 4 2 Converter Attenuation and Amplification Attenuator Amplifier U101 U102 1 x 10 1 x 1 100 x 10 100 x1 1000 x 1 x 10 Q102 Off x 100 Q101 On F x 1000 K101 On Table 4 3 DC Signal Conditioning Attenuation and Gain Input Attenuation 4 4 1 Input Attenuation On the 20 200 and 1200V ranges the input signal is atten uated by the resistive divider to divide by 10 100 and 1000 respectively Depressing one of the above range push buttons interrupts the unattenuated signal from the volts switch pin 17 and connects the wiper of the appropriate range potentiometer to the input of the chopper Division by 10 100 and 1000 is ac
18. should be verified before troubleshooting the signal conditioning cir cuits Check the A D converter and display per Table 5 5 and 5 6 respectively 5 6 5 AC Converter Problems with AC voltage or AC current ranges may involve the AC converter Check this circuit per Table 5 7 If the pro blem is only on AC current ranges see below 5 6 6 Chopper Amplifier and Ohms Source Problems with DC voltage DC current or resistance ranges may involve the chopper amplifier Check this circuit per Table 5 8 After verifying chopper amplifier operation by completing steps 1 through 10 of Table 5 8 go to Table 5 9 if resistance measurements are erratic If problem is only on DC current ranges see below NOTE Dust flux or other contamination will degrade performance on resistance and DC voltage ranges 5 6 7 Current Shunts If problems occur with current readings check the current shunts and related circuitry per Table 5 10 It should be noted that since the current shunts are common to both AC and DC current problems should exist on the same AC and DC current ranges if there is a fault in the current shunt circuitry NOTE All measurements are referenced to analog com mon ground clip unless otherwise noted in the Tables If a gross failure exists that indicates a possible blown fuse line power battery pack or current fuse refer to paragraph 5 8 for fuse replacement instructions WARNING Some procedures in the following t
19. the bottom cover of the instru ment and contained in Table 2 1 These instructions should only be used after becoming completely familiar with the operation of the Model 177 through day to day use Until this familiarity has been achieved best performance and safest operation will be obtained by using the individual instructions provided in this section Refer to Figure 2 3 and operate the DMM as follows 1 Turn on the power by depressing the ON OFF pushbutton and allow a 10 minute warm up time Allow additional warm up for zero stability on lowest DMM and Q ranges 2 Select the function with the AC DC Q V or A push buttons 3 Select the range by depressing the appropriate push button 4 Connect the source to the INPUT terminals Accessories described in Section 1 should be used as required CAUTION Do not exceed the maximum input ratings shown below DCV 20mV 20mV 2V 450V rms continuous 1200V peak momentary for up to eight seconds per minute maximum 20 1200V 1200V peak ACV All Ranges 1000V rms 1400V peak 107VeHz DCA ACA All Ranges 2A 250V DC or rms fuse pro tected Q All Ranges 350V peak 2 8 ZERO ADJUSTMENT The front panel zero adjustment provides compensation for test lead resistance and thermal EMFs generated in the cir cuits connected to the DMM input terminals The zero adjust ment is operative on the 20mV and 200mV ranges of DCV 20 and 2000 ranges and all DCA ranges in gener
20. to remove any offset that was intr oduced by adjusting ZERO for a low DC voltage measure ment or a low 2 measurement This adjustment will also be necessary whenever the instrument is used outside of the temperature range of 18 to 28 C The specified accuracy for the DC current ranges assumes that ZERO was ad justed on the 204A range Adjust ZERO as follows A Disconnect all circuits from the Model 177 INPUT ter minals The INPUT terminals must have an open cir cuit B Turn on power and set the AC DC pushbutton to the out or DC position C Depress A and 204 pushbuttons D Adjust front panel ZERO knob for a display indication of 0 0004A 001 flashing 2 After adjusting ZERO use the Model 177 to measure DC current as follows CAUTIONS Do not install a larger capacity fuse than the one originally supplied 2A Current fuse F101 shown in Figure 5 4 protects the instrument against over current A Select the desired range from the six ranges available B Connect the circuit to be measured to the INPUT ter minals C Read the displayed polarity digits and decimal point Select the next higher range if overrange is indicated 2 13 AC CURRENT MEASUREMENT The Model 177 measures AC current from 10nA digit to 2A over five ranges The 204A and 20M ranges are not operative See note below The 2004A range is direct reading in microamperes The remaining AC current ranges are direct reading in milliamperes The maxi
21. voltage range is 0 25V to 15V rms Model 1685 Clamp On AC Current Probe The Model 1685 Clamp On Current Probe permits measurement of AC current by clamping around a single conductor eliminating the need to interrupt the current path The Model 1685 has a current conversion ratio of 0 1V A with three ranges 2A 20A 200A Accuracy is 4 at 60Hz 6 at 50Hz 1 10 4 Carrying Case and Rack Mounts Model 1684 Carrying Case The Model 1684 Carrying Case s a hard vinyl case with a fitted foam insert to help pro tect the Model 177 from damage There is also room in the case for the instruction manual and small accessories Models 1010 and 1017 Rack Mounting Kits The rack mounting kits permit mounting one 1010 or two 1017 Model 177 DMMs in a 19 inch rack for convenient viewing 1 10 5 Output Options Model 1792 Isolated BCD Output The Model 1792 con verts displayed reading to an electrically isolated latched and buffered parallel BCD format Output data includes sign overrange and busy It is compatible with Model 177 serial number 14 500 and above and can be either factory or field installed Installation of the 1792 precludes installation of Models 1788 or 1793 Model 1793 IEEE 488 Output The Model 1793 converts displayed readings to IEEE 488 bus compatible outputs to permit automatic gathering of measurement data Output in cludes 4 digit ASCII data sign an overrange It operates in either talk only or addre
22. 000V 9 915 to 10 085V 20kHz 10 000V 9 915 to 10 085V 3 4 5 Resistance 0 Accuracy Check 4A amp UD NN Select resistance function by depressing Q pushbuttons Select 2000 range Connect the decade resistor to the DMM Set the decade resistor to zero and compensate for lead resistance by adjusting front panel ZERO for a display in dication 00 10 010 flashing Set the decade resistor to 1902 Verify that the reading for the 2001 range is within the limits specified in Table 3 4 Select the 2kQ range Setthe decade resistor to zero and measure the resistance of the test leads Subtract this reading from the displayed reading in all of the following steps Set the decade resistor to 1 900kQ Verify that the reading is within the limits specified in Table 3 4 Continue by selecting the next range and measure the next resistance as specified in Table 3 4 Test each item in the table and verify that each reading is within specifications Table 3 4 Resistance Accuracy Check 2002 1900 2kQ 1 900kQ 20kQ 19 000kQ 200kQ 190 00k9 2000k12 1900 0kQ 20M2 10 000MQ Allowable Reading at 18 to 28 C 189 86 to 190 140 1 8989 to 1 9011kQ 18 989 to 19 011kQ 189 89 to 190 11kQ 1898 9 to 1901 1kQ 9 988 to 10 012MQ 2 digits 2 digits 2 digits 2 digits 2 digits 1 digit Manufacturer s specified uncertainty of the decade resistor in digits
23. 09 EAM 59 R 88 806K RIGG B3 i 7 wu cor ca A HO e e 27K Rh cg A 160 R B8 IOOK RIG7 B2 ii C234 oR cos OA IAA i 1 2 88 AER j 2 18 C Lie bw S1 uz i cos lt a AA CRH7 C3 UZ 2 88 4 99K RUS c2 16Z SW 397 102 a Ha OC mw 103 20034 IOS As jcgz egoogr ctra EE 18 RS RIZI At I LE RR MENE TN 15 lena ponjeti EINE eo 84 US R 16 K Rez A 16S TR 168 9 7001 AS lo __ E B Lie 166 ERES 5 La SEO i n Au NOM e ese lon eS Pia Flos jce8 e o8 Fu i FIOV 03 UB TE 39 BETEN CE 1e 9102 EA 19 C29a amp Clie EZ 09 Fu 20 XI FOZ 84 I Te B80 RP TAA i Ic 172 1 103 DS ZO 0209 22 CINI az 170 as Zo l o ic a2 04 A2 21 c 294 12 eng ca 351 s 356 4 7001 ESO iz E qe 27TK Ri28 DS pini ISTR 195 Az i IZ C 356 ei Tio Ei 22 d _ AN 72 ILSI Il EU c 23 e2a0 220010126 BS 133 5286 3 Pi003 1 123 R BB 6AeK RIGO AD 11713 1i 203 uo 42 AN 24 c 34 43 Cizi BS 1 7A_294G1A_IPI00A4_ 124 88 3 651 RIDI O AB AA 14 i30957A JOB CS 1 I r R 88 306 haa RP 6A 50 1 SZ LAs 1475 Ic 2023 Mog c3 126 R263 2 18K IT E E ne IC 197 QUO 82 rR134 Ta 1177 170 139 MEN cz 28 R 263 402 SIE O Mza IR B8 00K EJEA 32 Bo 1271699A q AS QXRIO 3s I3 R 88 33 2 2138 LA RISE aS 132 RP 97 50K_ RU 03 qVRIOS _ 85 38
24. 1 On optional line voltage units set to 90 110V or 180 220V as appropriate 5 6 Step Item Component Gn 0 Nn 5A 10 11 12 12A 13 14 15 S102 LINE BAT Switch P1007 Line Cord F301 BT301 Batteries Each battery cell voltage during charging 0301 Anode C304 0302 VR301 P1004 pin 8 or U301 pin 17 VR101 IN Q307 and Q308 Base Q307 Q308 Collector C304 C305 Table 5 4 Battery Power Checks Required Condition Remarks Check AC line power per Table 5 3 Turn off power Move to BAT Plugged into live receptacle Remove fuse and connect ammeter to fuse clip O to 500mA charging rate varies with line voltage and battery state of charge Full charge is 9 8V over 4 cells R301 adjusts charging rate float voltage 1 5 3V for any cell Full wave rectified voltage 15 VDC nominal 17 5V minimum Should saturate only when battery approaches full charge 8 2V zener Unplug line cord amp turn power on 100kHz 5V square wave 7V minimum Square wave 0 7V at 25kHz Must oscillate from saturation to twice battery voltage 19V at 25kHz 17 5V minimum 4 25V typical with fully charged bat Charge circuit checks No charge see step 5A Correct charging but short battery operating time see step 6 If voltage is low and adjust ment of R301 does not start charging see steps 7 and following If voltage is low and adjustment
25. 100V 0 01 1000V 9 0 04 1900 1 9kQ 19kQ 190kQ 1 9MQ 10M9 0 01 100A IMA 10mA 100mA 1A 0 025 10 1 divider within 50 PPM Table 3 2 DC Voltage Performance Check 2V to 1200V Range Allowable Readings at 18 to 28 C 0 9996 to 1 0004 9 996 to 10 004 99 96 to 100 04 999 5 to 1000 5 Applied Voltage 1 0000V 10 000V 100 00V 1000 0V 3 4 3 DC Voltage Accuracy Check 20mV and 200mV Ranges Select DCV and 20mV range Disconnect test leads at the DC calibrator and short them Adjust Model 177 front panel ZERO for a display indication of 0 000mV 0 001mV flashing Connect the DC calibrator and select 200mV range Set the DC calibrator to an output of 0 190000V Verify that the Model 177 reading is between 189 89 to 190 11mV Note that the allowable reading includes a t2 digit allowance for the uncertainty of the DC calibrator Repeat steps 4 and 5 with negative voltage Select 20mV range Connect the DC calibrator low thermal resistor and Model 177 as shown in Figure 3 1 Temporarily disconnect the leads from the DC calibrator and short them Adjust Model 177 front panel ZERO for a display indication of 0 000 0 001mV flashing Set the DC calibrator to an output of 0 190000V 11 Verify that the Model 177 reading is between 18 987 and 19 013mV Note that the allowable reading in cludes 2 digits for DC calibrator uncertainty and 1 di
26. 2187 S 2 E LITRO va 3_ Rose U A v bos al we T auto sted SZ nac mm MN 1013 4 Ose E iH l A lt aa 3 We 02 002 A0002 e SQQ 3 g y SS UA 954 15468 OS xsr amp g 005 760 35 X05 wmS26 8 i is 39m ET amea 7 29658E a COM AT COE TERRE ae a A TS ER H Ir anes A f H 9 4 3 0 9 g KEITHLEY SERVICE FORM Model No Serial No P O No Date Name Phone Company AER Address Li CitU ou oo A 1 gt 1 gt __ to ou _ ______ Zip i dae List all control settings and describe problem _ Attach additional sheets as necessary Show a block diagram of your measurement system including all instruments connected whether power is turned on or not Also describe signal source Where is the measurement being performed factory controlled laboratory out of doors etc What power line voltage is used Variation o Frequency 1 1 Ambient Temperature x HE Variation F Rel Humidity Other DE Any additional information If special modifications have been made by the user please describe below Be sure to include your name and phone number on this service form
27. 2V full scale for all ohms ranges Scaling of the ohms signal over the seven ranges is accomplished by using five constant current levels and the three gains of the chopper amplifier 4 2 2 A D Converter The A D converter is a large scale integration LSI ratiometric device Converter output is a multiplexed five digit number in binary coded decimal BCD form which is equal to the ratio of the input voltage to the reference voltage A separate clock circuit supplies a 100kHz timing input to the in tegrated circuit which also multiplexes the BCD output The full scale A D input for all ranges of the Model 177 is 2VDC with the polarity determined by the function as follows ACV and ACA 2V DCV and DCA 2V Resistance 0 2V 4 2 3 Range Switching It is important to note that the range switches on schematic 29658E are identified by the front panel marking for the U ranges The corresponding V and A ranges may either be determined from the instrument front panel or by using Table 4 1 4 3 AC CONVERTER When making AC voltage measurements the AC converter scales the input signal by appropriate attenuation or amplification performs TRMS conversion and provides the equivalent positive DC level to the A D for display Input resistance for AC volts is 1MQ R107 Shunt capacitance is less than 75pF Signal conditioning is as follows 4 3 1 Scaling Scaling is performed in the first two stages as shown on schematic drawing number
28. 33 TG 53 RP 97 20k R 76 330 R 76 1k R 268 3 9k R 76 4 7k R 76 3 3k R 76 82 R 76 82 R 76 10 R 76 10 R 76 100k R 76 100k R 76 100k R 76 6 8M R 88 576k R 88 100k IC 103 IC 177 DZ 61 Table 6 4 Display Board Parts List Circuit Desig Description Capacitor LED Display 1 LED Display 7 Segment LED Display 7 Segment LED Dsiplay 7 Segment LED Display 7 Segment Resistor Thick Film Resistor Thick Film Resistor Potentiometer 2W IC CMOS Quad 2 Input NAND Gate 4011 IC Digit Driver 75492 IC Segment Driver 4511 Location Sch Pcb Keithley Part No C 314 4 7 DD 31 DD 30 DD 30 DD 30 DD 30 TF 82 TF 102 3 RP 117 50k IC 102 IC 169 1C 168 6 9 6 10 arde R TEA 192 DuseC Cow ARES DETAIL A CHANGED ARTWORx To REV T 2401 39vd 8 E D E F T U AAA 34 Recensen A 08 S lsosz 94 12 18 5911 INTERCHANGED CRIA 9D CANS 4 26712 Arce CEG CRM LingpTet momo DA 2 GOV OLLETEG Nore Atour TALL NG 6 9 7978 24738 PC 476 Ase TIOS Aft WORK Wan Rav D m gym N Go n IS ajo e mls KJ To Front PANEL INPUT BL ALK BINDING Post K 6743 SEE SHEET amp ADDED RIGGERIC RE Lloras vi OX 107 I 26 CRIOGE M 0961 SEE SHEET B SHEET 2 um 7 80 N CHG D ARTWORK FROM REY GTO REV H REVISED 9 38 88 LA PER NEW ARTWORK EE PAGE 2 OF 2 CRI 7 i 4 JIOO9 A
29. 4 4 d oh 3 4d I Ww v v 4 d 3 4 3 4 3 v v 9 vom v m doc 8 4 P 3 P o3 9 9 Y 4 WoW e v 9 vos oc m oa coc s n n n SECTION 3 PERFORMANCE VERIFICATION Introduction aduidi S 3 3 3 9 oco 4d 4 F9 9 39 4 9 8 o3 F oFoOar a a 9 8 RR OR S9 4 4 4 dor 9o 3 9o oso D ov e mo os NONO 3 4 4 039 9 3 3 t t vov ot t ng n Recommended Test Equipment secs usce cos d pr EE REOR A EA A eR HE Mace e Environmental Conditions ed do morc or dee V ACA ED A AAA ADA a WR C ESO CR EUN Performance Verification Procedure hh RR RR RR RR ehh ehh hh s Initial Conditions ow 4 4 4 9 9 o o9 9 B 9 amp 9 4 9 C 9 v v 4 4 4d d 93 4 4 4 9 v vo vom 3 4 4 4 P P 9 4 rr o o9 3 n DC Voltage Accuracy Check 2V to 1200V Ranges cece mn DC Voltage Accuracy Check 20mV and 200mV Ranges K K K ett es AC Voltage Accuracy Check v exkex rr kia dna A PR Roda does Euros d VR VR dS Resistance D Accuracy Check oooooooomoromcrrcraracr cra arat edes eren DC Current Accuracy Check 45 es ducum x ente seco ACER RP eee eee dp d e RP Go dep Analysis 9 9 c 9 P SN U9 PF oG P P9 PF o9 4 9 9 89 o 9 c 39 4 4 3 4 4 4 9 v 9 E 4 3 4 4 4 4 ow 9 p c9 oc ov doc 9 8 9 t 35 3 9 t9 SECTION 4 THEORY OF OPERATION Introduction Overall Operation Signal Condit
30. 57 R156 wiper R154 89 75k 8 975kQ Calibrated resistance Source resistors R158 R157 R156 R155 wiper R154 all except 8 975MM Calibrated resistance Source resistors all 2 range resistors NOTE To con veniently measure the resis tance of all 2 range resistors turn power off set al function switches out and measure resistance INPUT HI to LO See Figure 5 1 Table 5 10 Currant Shunt Checks Item Component Required Condition Remarks F101 Continuity R101 R102 R103 Correct shunt value R104 R105 for specified range See schematic Turn power on Select BCA and 2004A range Apply a known Y scale current and measure voltage across shunt External voltage 0 to 3V source Clamping must occur at 2V 5 11 5 12 Table 5 11 Adjustment of Battery Charge Voltage Step Item Component Required Condition 1 Instrument off Turn full CCW maximum charge rate Monitor battery voltage for 7 9 8V Fully charged cells require several minutes to reach this level Dis charged cells require several hours CAUTION Charging to gt 10V for longer than 30 minutes will reduce battery life When cells reach 9 8V turn DMM on and adjust to maintain 9 8V across BT301 SECTION 6 REPLACEABLE PARTS 6 1 INTRODUCTION This section contains information for ordering r
31. 952 U i soe St gt N H ferie e 4 gt i o 3 5d e Few m I 5 TES 9 N el SL t e TO gt b zz nr ta paia FECE 1 1 ES 2 Med OS so Sy AMAN i Ola ot 3 ALL wwe Lll cl avo MORO Y Y Y 7 S Y OQI TULIIG 6 88 va 29 18 916 e2 pup A 50 go EPA DL FAS Ere 1 j va p re 4 AS 2218 28 yor nro Si Ig y gt gt e ov M LNd 1 2 ger Jung _ __ _ MMM MAm AT 1 SOUYNY HD S Zo Iw Id soon Spe aN i i sie 31072 yp Dp ny ie xa 5r E Pl Age Ong Ee Re 02 S b E gos oa di A mE n ve OK l gt m 92 vi ean gia S2L023ANOT JV gocir l SIMILVI i OBI f EP e SHILNNOI gr 9 9 51901 O0HiNO3 e 9 3920 I S 230 804 0837 i 3 lst AU i 1 BE de I ASi WO v Ra pn 2v o de OZ I i2 102 6t g Ol v NO t ome 34S v sort A 0002 Ls Se EN A 00 l ad see a NS EO 2 g uOO R ZL N e Tw ee m SINNHS WO E LATIN Gl d Ek S d gt EN 1N3uun HON a PA mt PES EE ONO e D l 006 0 Se AS my TT T SR STORIA t 7 c H A n N T 4 O0t vOu gorg 2013 fran c yw lt 0 Dee l sooir l x sua 002 0002 iai STA N gt l A Ria i LAdNI 2 10183 tela el COO o L da 3 0
32. AO um menm TE iun a gr rr PSEC A B C 4 E F G Figure 6 3 Display Board PC 475 Component Location Drawing Dwg No 29652C 9L 9 A ep ome BE oe a c 19 47 case za Da ea east EA 4 c 256 1 ca os es po caos r4 ccann ds 9 cs 287 8 31004 ns Lio Det va3ol tes ED 23 RAR R30S 03 24 r 268 3 3 Race ps ae RF crac Da g1 crzosle gt 29 X ET r4 RO pro GRAOA FA Bi T amp 41 laz cs az mA d 6229094444 E LLM ST RL iem 52 3 T a Stamens 475 as Aa si im CS NEXT ASSEMBLY USED On all DIMENSI RANCES ES p A Tl errar C G L L EN cs gt rios rr TS Bno C T in le 2OO 7 C E F KNAL TOLEI THER a Figure 6 4 Model 1778 Battery Pack PC 451 Component Location Drawing Dwg No 29007C 8L 9 L 9 F301 A 3AG Q arao L BY Li 2 5 AH E Lac cTcs R304 1 35 Q30 PR 1 ALL RESISTOR VALUES ARE IN OHMS UNLESS MARKED OTHERWISE K KILOHMS M MEGOHMS 2 ALL CAPACITOR VALUES ARE IN MICROFARADS 3 DENOTES INTERNAL ADJUST HIGHEST SCHEMATIC DESIGNATIONS USED BT301 c30s cr303 F3ol J1004 Q3IO R316 1301 ue vws TT COMMON SCHEMATIC DESIGNATIONS NOT USED JIOOI THRU J1003 PO AOT SCALE THIS DRA WO ep See a CA E UE SCHEMATIC e Ve me Toe poni a
33. C 50Hz and 60Hz RESISTANCE TEMPERATURE ACCURACY 12 mo COEFFICIENT NOMINAL MAXIMUM 18 28 C 0 18 C amp 28 55 C APPLIED RANGE READING ti rdg digits rdg digits C CURRENT 200 19 999 0 5 3d 0 004 0 6d 1mA 2000 199 99 0 5 2d 0 004 0 2d 1mA 20 1 9999 0 04 1d 0 004 0 2d 1mA 20k2 19 999 0 04 1d 0 004 0 2d 10024 200k 199 99 0 04 id 0 004 0 2d 104A 2000ktt 1999 9 0 0496 1d 0 005 0 2d UA 20M0 19 999 0 10 1d 0 02 0 2d 0 14A Front panel zero MAXIMUM ALLOWABLE INPUT 350V peak OPEN CIRCUIT VOLTAGE 5 volts Spec fications subject to change without notice DC amp TRMS AC CURRENT ACCURACY 12 mo 18 28 C rdg digits MAXIMUM MAXIMUM AC 45Hz 10kHz VOLTAGE RANGE READING ocr above 2006 counts BURDEN 204A 19 999 0 2 24 0 02V 2004 199 99 0 2 1d 0 8 15d 0 24 2mA 1 9999 0 2 Id 0 8 15d 0 24 20mA 19 999 0 2 ld 0 8 15d 0 2V 200mA 199 99 0 2 ld 0 8 15d 0 25V 2000mA 1999 9 0 2 ld 0 8 15d 0 6V Front panel zero MAXIMUM INPUT 2A 250V DC or rms fuse protected TEMPERATURE COEFFICIENT 0 18 C and 28 55 C DC 0 2 digits C except 0 01 0 6 digits C on 204A range AC 0 07 2 digits C CREST FACTOR 3 GENERAL DISPLAY Five 0 5 LED digits appropriate decimal point and polarity in dication CONVERSION PERIOD 400mS OVERRANGE INDICATION Display blinks all zeras above 19999 count
34. C range Apply 1V rms at 20kHz 1 0000 nominal External voltage source Display Select 1000VAC range Apply 1000V rms at 20kHz 1000 0 nominal External voltage source Display Select 2VAC range Apply 1V rms at 45Hz 1 0000V nominal External voltage source Display See Figure 5 1 NOTE Full scale input on all ranges should produce 2V rms output at TP8 Calibrated input Output of U101 and feed back components R108 and C103 nominal gain 99 Output of U102 Q102 on nominal gain 1 003 Output of U103 Gain of U103 adjusted to provide 1VDC output for IVAC scale input Gain check of U101 and U102 Nominally 0099 U101 and 10 03 U102 Output of U101 and feed back components R109 C104 and Q101 on Output of U102 Q102 off Calibrated input Check gain of U101 nominal 00099 Output of U101 and feed back components K101 R110 and C105 K101 Closed Calibrated input High frequency response compensation C102 C103 C104 Calibrated input High frequency response Compensation C102 C103 High frequency response Compensation C102 C103 C105 Low frequency response C101 C106 C107 C108 C109 5 9 5 10 Table 5 8 DC Attenuation and Chopper Amplifier Checks Required Condition Remarks Step Item Component 1 range Short input and adjust 7 5V DC on DMM External voltage source R143 yellow
35. Instruction Manual Model 177 Microvolt DMM and Model 1788 Battery Pack 1978 Keithley Instruments Inc Cleveland Ohio U S A Document Number 29683 Specifications DC VOLTAGE ACCURACY 12 mo MAXIMUM MAXIMUM 18 28 C ALLOWABLE RANGE READING rdg digits INPUT 20mv 19 999 0 04 2d 1200V momentary 200V 199 99 0 04 1d 1200V momentary 2V 1 9999 0 03 1d 1200V momentary 20V 19 999 0 03 1d 1200V 200V 199 99 0 03 1d 1200V 1200Y 1200 0 0 03596 1d 1200V Front panel zero TEMPERATURE COEFFICIENT 0 18 C and 28 55 C 0 005 0 1 digit C except 0 005 0 6 digit C on the 20mV range INPUT RESISTANCE 10M9 0 5 NMRR Greater than 80dB on the 20mV range at 50Hz and 60Hz greater than 60dB on ail other range CMRR 1k0 unbalance Greater than 120dB at DC 50Hz amp 60Hz AC VOLTAGE ACCURACY 12 mo above 2000 counts MAXIMUM 18 28 C 100Hz 10kHz RANGE READING 1 rdg digits 200mV 199 99 0 596 r 15d 2v 1 9999 0 5 15d 20V 19 999 0 5 15d 200V 199 99 0 5 15d 1000V 1000 0 0 5 16d EXTENDED FREQUENCY ACCURACY 45Hz 20kHz 0 7 15 digits TEMPERATURE COEFFICIENT 0 18 C amp 28 55 C 45Hz 20kHz 0 05 2 digits C RESPONSE True root mean square CREST FACTOR 3 INPUT IMPEDANCE 1MQ 1 shunted by less than 75pF MAXIMUM ALLOWABLE INPUT VOLTAGE 1000V rms 1400V peak 10 Hz maximum CMRR 1kO unbalance 60dB at D
36. ON The Keithley Model 177 Microvolt DMM is a versatile highly sensitive digital multimeter which is used for measurement of DC and AC voltages DC and AC currents as well as resistance For a complete summary of ranges for each of these five functions refer to the specifications at the front of this manual Ranges and functions are easily selected with front panel pushbuttons while connections for all functions are easily made with a single set of front panel input ter minals 1 2 MODEL 177 FEATURES 1 4 Digit LED Display An easy to read 4 digit display shows 20 000 counts of information with automatic polari ty indication 2 1uV 1m Q Resolution The Model 177 is capable of reading DC voltages as low as 14V and resistances down to IMI 3 Front Panel Zero The front panel zero control may be used to compensate for thermal offsets or lead resistance when making measurements 4 Analog Output An analog output of 1V 10 000 counts is available on the rear panel 1 3 WARRANTY INFORMATION Warranty information may be found inside the front cover of this manual Should it become necessary to use the warran ty contact your nearest Keithley representative or the factory to determine the correct course of action Keithley Instru ments maintains service facilities in the United States West Germany Great Britain France the Netherlands Switzerland and Austria Information concerning the appli cation operation or service
37. R TRMS AC ANALOG IEEE ATTENUATOR CONVERTER OUTPUT Lo NERY AC DISPLAY i RE El Q CURRENT OUTPUT DC INPUT g CURRENT Bea A D SHUNTS DC ATTENUATOR N 9 AC SOURCE RESISTORS i FUNCTION amp RANGE 5 LO SWITCHING a Q SENSE DC OUTPUT Z REFERENCE 100kHz CLOCK Li CHOPPER FEEDBACK ue BUFFER mM AMPLIFIER OPTIONAL BATTERY 390Hz CHOPPER DRIVE PACK CO Fimer OSCILATOR K AME ZERO DIVIDER AC MAINS ae POWER gt 5 SUPPLY 16 Figure 4 1 Model 177 Simplified Signal Flow Biock Diagram 4 1 2 In the ACV mode AC inputs for all ranges pass through the AC converter which consists of an amplifier attenuator and a TRMS converter as shown in Figure 4 2 The AC in put is scaled by the amplifier attenuator to 2V rms full scale for all ranges The TRMS converter provides a positive DC output signa which is proportional to the true root mean square AC signal This DC signal is the input to the A D converter In the ACA mode the shunt voltage is applied to the input of the AC converter The amplifier at tenuator provides a x 10 gain for all AC current ranges 3 Ohms conversion Resistance measurements are made by supplying a constant current from the ohms converter to the unknown resistor Ry The resulting voltage developed across the unknown resistor is proportional to its resistance and this voltage is applied to the input of the chopper amplifier used for DC volts The chopper amplifier output to the A D converter is scaled to
38. R oon Probes and Shunts Nom OR OON 4 4 odo 3 3 4 4 4 o 3 v v v ov o3 9 op PF o3 9 4 o3 4 4 3 3 3 9 or 9 4 9 o9 9 ON S3 03 3 tov o momo hos o go hot os om om m on n n ng on Carrying Case and Rack Mount 9 ad eges e dit todos dr a S e Output Options SECTION 2 OPERATION Introduction Safety Precautions for High Energy Circuits Preparation for Use 4 4 om om wo wow o 9 t9 9 mom osos mo OR OR SNO OR 9o oo a a ON torn omo on osos s n or n on H4 4 RR PF o4 4 4 8 3 W 4 Wee 3 a c s e 9 4 K P P P 39 4 9 v v 4 c o9 eK os oa mom mom o9 os om s s 9 mon mom ms m m 9 89 8 4 SN SON ros s o4 Operation on Dine ROWSE 22265224 saepe mE CER thes ie ha ssaa tr YR de Rn a Operation on Battery Pack Power 2 oka esc ak ede sca RETREAT A EE EA Re Battery Charging Operating Instructions Zero Adjustment ie e SS amp 4 9 9 8 Oo t ga toa rov mos mososos p mom 9 d os 9 s ot on DC Voltage Measurement uox Ad Ro ORDER FR ob d Cd AC Voltage Measurement striscio 9 9 9 0 Qe ERE RIP CERE T AAA qax dr tud Resistance Q Measurement ccc hahahaha rhe e hg 4h res DC Current Maagu remoerit sv cr a RA CAUDAE C Wed dol a d ol AC Current Mensuremont qs cac ae SCR CH RA CR ET iia dC eoe ROLES ia ES OR MU TS dan D ip a TRMS Measurements Analog Output Tilt Bail Adjustment AG DG Li D5uiod da a pedea V as dard tow ees EQ E Paca Se RC Pow 3
39. This uncertainty has been added to the specified accuracy of the Model 3 4 6 DC Current Accuracy Check Ts 2 Select the DC current function with the AC DC and A pushbuttons Select the 204A range With an open circuit at the INPUT terminals of the Model 177 adjust the front panel ZERO for a display indication of 0 000 0 0014A flashing Connect the DC current source to the DMM Select each range and apply the required current as specified in Table 3 b Verify that each reading is within specification Table 3 5 DC Current Accuracy Check Applied Allowable Reading at Current 18 to 28 C 100 004A 99 79 to 100 214 A 1 0000mA 0 9979 to 1 0021mA 10 000mA 9 979 to 10 021mA 100 00mA 99 79 to 100 21mA 1000 0mA 997 9 to 1002 1mA 177 to obtain the allowable reading 3 4 7 Analysis If the instrument is out of specified limits at any point in Table 3 2 through 3 5 calibrate the DMM as described in Section 5 If the unit is still under warranty refer to the note in paragraph 3 1 NOTE It is not necessary to specifically check the 200 or 204A ranges or any of the ACA ranges The circuit components that determine their accu racy have been checked elsewhere in the verification procedure 3 3 3 4 SECTION 4 THEORY OF OPERATION 4 1 INTRODUCTION This section contains circuit descriptions for the Model 177 DMM and the optional Model 1788 Battery Pack An overall block diagram of sig
40. ables re quire the use of high voltage Take care to prevent contact with live circuits which could cause electrical shock resulting in in jury or death 5 7 FRONT PANEL ZERO KNOB REMOVAL AND REPLACEMENT The front panel ZERO knob will have to be removed if either the front panel or display is to be removed To remove the knob proceed as follows 1 Carefully remove the end cap shown in Figure 5 3 using a thin biaded instrument 2 Loosen the slotted screw and remove the knob from the shaft 3 Take care not to damage or lose either the end cap or knob These items provide protection against electrical shock and must be installed when the instrument input is floating NOTE If the display board has to be removed for troubleshooting or repair the front panel ZERO knob will also have to be removed Integrator waveform for positive full scale input 100 mSEC i I t I 1 t a 1 100 200 msec I I AUTO SIGNAL REFERENCE I i i I AUTO ZERO OF ZERO INTEGRATE INTEGRATE NEXT CONVERSION Comparator waveform Logic 1 during ramping 5 0 Jo Figure 5 2 Integrator and Comparator Waveforms WARNING The ZERO potentiometer shaft is electrical ly connected to INPUT LO Maintain INPUT LO at ground potential while the ZERO knob or its cap is removed to prevent an electrical shock hazard 4 To replace the knob reverse the preceding steps Do not fuse proceed as follows substitut
41. ad Protection Two source calibration adjustments are required Poten tiometer R162 compensates primarily for the tolerance of Ry R158 while R159 compensates for ratio variations in the four gain resistors R150 through R153 The protection net work at the source output isolates the amplifier from positive voltage overloads Q103 and negative voltage overloads CR120 applied to INPUT HI Transistor Q107 clamps the source input during overload The ratio of the base to emitter resistors on Q103 sets the open circuit voltage 4 6 ANALOG OUTPUT The rear panel ANALOG OUTPUT provides a 2V full scale DC output signal 10K counts 1V The analog output signal is available on all instrument functions and ranges with a negative polarity on ohms Q and a positive polarity on AC The output is unbuffered supplied by either the chopper or the TRMS converter through 5kQ effective resistance with 1kQ placed in the LO leg to prevent ground loops through IN PUT LO 4 7 CLOCK A single chip CMOS oscillator 2N package is used to generate the 100kHz A D clock and the 390Hz chopper drive signals The 100kHz OV to 5V signal drives the A D and bat tery pack directly The 390Hz signal is level shifted to OV to 15V and split into two phases for driving the chopper FETs An RC adjustment R142 provides chopper input bias cur rent compensation Balancing and guarding is employed to keep the drive signal out of the chopper AC amp stage 4 8
42. al the zero must be readjusted whenever the function is changed and the measurement is to be made on a range where the zero adjust ment is operative The accuracy specifications assume that zero is adjusted on the lowest range of the function Where applicable a specific zero adjustment instruction is provided in the description of how to make the particular function measurement 2 9 DC VOLTAGE MEASUREMENT The Model 177 measures DC voltages from 1 V digit to 1200V The maximum displayed reading is 19999 Overrange is indicated by a flashing 0000 except on the 1200V range On the 1200V range the display can read beyond the maximum allowable input voltage Use the Model 177 to measure DC volts as follows CAUTION Do not exceed the maximum input voltage ratings or instrument damage may occur 1 Turn on power with ON OFF pushbutton and select DC with the AC DC pushbutton 2 Select the desired range from the six ranges available The decima point is positioned by the range pushbuttons The 1200V DC range is selected by the 1000 pushbutton NOTE The 20M pushbutton is inoperative for DC volts if this pushbutton is inadvertantly depressed the Model 177 will read zero regardless of the voltage applied and the eight second per minute overload rating will apply 3 Connect the signal to be measured between the INPUT HI and LO binding posts The binding posts accept wires spade lugs or banana plugs for ease of connecting the cir c
43. and disconnect the line cord Remove four screws from the bottom of the case and separate the top cover from the bottom cover 2 Push back the ground clip from the upper side of the bat tery pack and remove the battery pack from the spacers 3 Calibration may be performed on battery power as long as the battery pack is sufficiently charged Leave the battery pack plugged into the instrument but set the battery pack behind the Model 177 on the bench or table Ensure that LINE BAT switch S102 is in BAT position 4 Set the calibration shield in place on the spacers The shield should read correctly when viewed from the front of the instrument 5 Slide the ground clip over the top of the calibration shield so that it contacts the upper surface of the shield 6 If the battery power is not to be used plug in the line cord and position 102 to the LINE position if the battery pack has been disconnected 5 4 2 Warm Up Turn the Model 177 on and allow a one hour warm up time 4 3 Calibration Instructions 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 Use an in sulated tool when making adjustments Table 5 1 Recommended Test Equipment For Calibration Description DC Calibrator AC Calibrator Decade Resistor 1002 Per Step 4 Terminal Low Thermal Resistor Specification
44. andard Line Voltage Instrument These adjustments are used only for calibration They are not intended for adjustment during operation ANALOG OUTPUT INTERNAL FUSES CAUTION L t AURA RAG al Lay CASINI RIO OPI day CURRENT 2A BAG NORMAL INE VOLTAGE INDI ATE LI LINE SER AH CE o oov ee Bu AL DIN a 2204 JLN A MAX LINE VOLTAGE J1009 SELECT SWITCH Le UNE CORD 101 P1007 Figure 2 2 Rear View Of Optional Line Voltage Instrument 2 2 2 With the power switch off the battery charge circuitry is automatically energized to charge the battery at the maxi mum rate When the battery pack is first installed or if it has completely discharged allow it to charge for at least 14 hours in this condition NOTE For maximum battery life do not allow the bat tery pack to remain completely discharged Con stant charging will not harm either the battery pack or the instrument The Model 177 may be operated up to six hours from fully charged bat teries However since 10 charge discharge cycles may be required to reach full battery capacity less than six hours DMM operation can be expected when the battery pack is first in stalled 3 When the Model 177 DMM is in use on line power the bat tery charger maintains a trickle charge on the battery pack 2 7 OPERATING INSTRUCTIONS The basic operating instructions for the Model 177 DMM are outlined in the following steps and condensed operating in structions are provided on
45. are as follows Sine Wave CF 1 4 Square Wave CE lt 1 Triangular Wave CF 1 7 Positive pulse train CF 1 duty cycle duty cycle CF 3 is 0 11 5 The optional Model 1682A RF Probe can be used with the Model 177 to measure 0 25V to 15V rms AC signals with a frequency of 20kHz to 250MHz and above at reduced ac curacy 6 Refer to paragraph 2 14 for TRMS measurements of a signal with both AC and DC components 2 11 RESISTANCE 2 MEASUREMENT The Model 177 DMM measures resistance from 1mQ digit to 20MQ See Table 2 2 for ranges Nominal settling times to within one digit of final reading are three seconds on the 200 range two seconds on the 2000kQ and 20M ranges one se cond on the other four Q ranges Use the Model 177 to measure resistance as follows 7 Turn on power and depress the 2 pushbutton 2 6 CAUTION MAXIMUM ALLOWABLE INPUT VOLTAGE All ranges 350V peak Do not exceed maximum rating Instrument damage may occur 2 Connect the circuit to be measured to the INPUT binding posts and select the desired range from the seven available Table 2 2 Resistance Ranges Nominal Applied Current Full Scale Voltage Maximum Reading Range Setting 200 2000 2kQ 20kQ 200k2 2000kQ 20MQ Front Panel Zero All Ranges Maximum Allowable Input 350V Peak Open Circuit 5V max Overrange Flashing 0000 Hi binding post red is negative 3 Observe the displaye
46. binding posts rather than using banana plugs Set the Model 177 to the 20mV range Disconnect the leads at the circuit to be measured and short them Allow the thermal EMFs generated at the connections to stabilize Adjust the front panel ZERO knob for a display indica tion of 0 000mvV a flashing 0 001mV is permissible NOTE The ZERO control operates only on the 20mV and 200mV ranges It has no effect on the other DC voltage ranges Make the measurements by applying the signal and reading the mV on the display Nominal settling time for the 20mV range is three seconds to within one digit of final reading NOTE An overload input to the Model 177 may cause temporary zero shift due to thermal gradients The zero setting for the 20mV range will also be valid for the 200mV range Nominal setting time for the 200mV range is one second to within one digit of final reading 6 The optional Model 1600A High Voltage Probe can be used with the Model 177 to measure DC voltage up to 40kV at reduced accuracy 2 10 AC VOLTAGE MEASUREMENT The Model 177 measures AC voltages from 104V to 1000V The instrument measures the true root mean square TRMS of a signal within the frequency range of 45Hz to 20kHz The maximum reading is 19999 Overrange is indicated by a flashing 0000 except on the 1000V range On the 1000V range the display can read beyond the maximum allowable input voltage The maximum crest factor for rated accu
47. boez ae ITE e so TO Desa 72478 atze Tram Trem Fio was Ien udas TET Z rem STS msicnz fora esset TEM 36 wai C LE EP Ev METIA Pa TEAM ZR NAS CI T 7A Eee i ZA x Jess CHANGED TEM B FROM _ T 27 HO TO C 236 MO pas ADDED ITEMS 159 E CHANGED ITEM 74 FROM a LIESS 7b Ras Za 0 ITEMS 9 IO CIOG FROMC z28 3 p lind 1 33 ITEMS 242 M 6989 F27 Cizi 122 124 CH EE FROM C 4 7 TO CIN ITEM 2 M Boca Sie e T PAGE 8 27 G2 RTT MT R te sant mrt assem CE mm o VUONENT LAYOUT PC 416 DCI mence aan thr gt 29474 D m PAGE 2 OF Figure 6 2 Model 177 PC 476 Component Location Drawing Dwg No 29474D Sheet 2 of 2 6 13 6 14 GL 9 A B c E F G mom E 325962 liti a D le sese rene ws E 19 120 Ro 14 25 Lio le D ERA ATEN Kunnen aree ii IGO ARTWORK WAS REY E ia ese WED TEM S WAS E 178 Tea Hob Do 21 1o bp 3 CHG D DD 20 Q DD 30 CROV ARTUR FROM RES 2 8366 cuc EM 1S PROM TEA To TF 402 3 fz 6 85 Sig INTERNAL TooTH KOCKWASHER 2 Rea c a SEO 172 4 a Smau HEX Nor e grao DS201 z DS203 i DS205 R201 SCHEM i Cs ass a P1664 PART NO ITEM 5 Te po s9 Ds Oz 6A eszes tea RCN 682647 be a ps20s 4 EE uen ikka L NEXT ASSE v pare 3218 mace n rc mum serio Sme R a COMPONENT Layout PEATS S
48. cated at the front of this manual 1 1 1 8 UNPACKING AND INSPECTION The Model 177 was carefully inspected both mechanically and electrically before shipment Upon receiving the instru ment carefully unpack it from the shipping carton and check for any obvious signs of physical damage that might have oc curred during shipment Report any damage to the shipping agent at once Retain the original packing materials in case reshipment becomes necessary The following items are in cluded with every Model 177 shipment 1 Model 177 Microvnit DMM 2 Model 177 Instruction Manual 3 Additional accessories as ordered 1 9 SCOPE OF THE MODEL 177 INSTRUCTION MANUAL This manual contains information necessary to operate and service both the Model 177 and the optional Model 1788 Bat tery Pack and is divided into the following sections 1 Section 2 contains operating information 2 Information necessary to verify that instrument per formance is within specified accuracy is located in Section 3 3 Theory of operation is covered in Section 4 4 Servicing information including Model 1788 installation instructions may be found in Section 5 5 Replaceable parts information component layouts and schematic diagrams are located in Section 6 1 10 OPTIONAL ACCESSORIES 1 10 1 Power Options The Model 177 can be powered by line voltage 105 125V at 50 60Hz or 210 250V at 50 60Hz standard ranges or the optional Model 1788 Rechar
49. complished by connecting the wiper of R155 R156 or R157 respectively 4 4 2 Chopper The input signal to the chopper is filtered and applied to a modulator circuit The AC signal is then amplified and demodulated A fina high gain DC amplifier provides a DC signal to the A D converter and the analog output 1 Modular Circuit This circuit converts the input DC signal to an AC signal with a fundamental frequency component of approximately 390Hz This frequency was chosen because it reduces the amplitude of higher harmonics of the 50Hz and 60Hz line frequencies which minimizes beating The circuit utilizes a dual MOSFET Q104A and 0104B connected in a series shunt configuration to main tain the required high input impedance 2 AC Amplifier The AC amplifier uses a JFET input opera tional amplifier U108 The amplifier feedback network provides a gain of approximately 133 at the modulating fre quency of 390Hz while maintaining a gain of one for amplifier U108 DC offset voltages AC CONVERTER ATTENUATOR AMPLIFIER TAMS TO A D N F8 1 100 1000 CHOPPER R143 TO A D 2V FS VREFERENCE TO A D E s BUFFER GAIN Figure 4 2 Simplified Signal Conditioning 3 Demodulator Circuit The demodulator is sychronized with the input modulator A JFET Q105 with low on resistance is used to alternately attenuate and pass the signal present at the output of AC amplifier U108 This produces a
50. ct to the signal input and analog output the Model 177 acts as an amplifier for mV signals an attenuator for kV signals or a converter to DC volts for AC current or resistance signals Output accuracy is the same as the display except on ohms up to 0 05 error can be ex pected due to the ratio metric method used The analog out put floats at input LO For this reason do not connect a voltage source across INPUT LO and ANALOG LO This will result in a measurement error and may damage the Model 177 if the voltage is greater than 15V When the instrument is in an overrange condition up to 15V DC may be at the ANALOG OUTPUT dependent upon the function range and level of the input signal 2 16 TILT BAIL ADJUSTMENT The tilt bail of the Model 177 may be used to elevate the in strument to a convenient viewing height To adjust the bail pull the bail out from each side of the case and rotate it to the desired position Release the bail to allow it to lock into posi tion SECTION 3 PERFORMANCE VERIFICATION 3 1 INTRODUCTION Performance verification may be performed upon receipt of the instrument to ensure that no damage or misadjustment has occurred during transit Verification may also be per formed whenever ther is question of the instrument s ac curacy and following calibration if desired NOTE For instruments that are still under warranty less than 12 months since date of shipment if the instrument s performance fal
51. d 190 210V ranges 5 use a 3 16A 250V 3AG SLO BLO fuse Keithley part number FU 29 7 Replacement of current fuse F101 6 A Lift the calibration cover or battery pack off of the 7 spacers to gain access to the current fuse B Remove F101 shown in Figure 5 1 and replace it with a 2A 250V 3AG fuse Keithley part number FU 13 8 C Install calibration shield or battery pack on the spacers Be sure that the ground clip shown in Figure 5 1 is positioned on the top side of the shield or battery pack 8 Reinstall the top cover 5 9 MODEL 1788 BATTERY PACK INSTALLATION WARNING Disconnect the line cord before removing the case cover 9 1 Turn off the power and disconnect the line cord 2 Turn the Model 177 bottom side up and loosen the four screws in the bottom cover These screws are held cap tive by rubber O rings 10 Hold the top and bottom covers together to prevent their separation and turn the Model 177 over to normal posi tion Lift off the top cover and the calibration shield The four plastic spacers must remain in place on the upright studs projecting through the main printed circuit board Set the BAT LINE switch to the BAT position shown in Figure 5 4 Note that the battery pack will not operate properly if this switch is not in the BAT position Remove the fuse F301 on the battery pack Instali the battery pack in the instrument so that it rests on the plastic spacers The ground clip mu
52. d digits and decimal point to measure resistance using the 2k 20k 200k 2000k and 20MQ ranges The full scale voltage drop for these ranges is 2V which is sufficient to cause forward conduction of semiconductor junctions The HI Red terminal is negative To measure a resistance in parallel with a semiconductor junction without turning on the junction either reverse bias the junction or select the next higher Q range The latter method is possible because of the one decade reduction of applied test current but will result in a measurement with 3 digit accuracy It is suggested that the 2kQ range be used for diode testing This range has a nominal 1mA test current and the displayed reading is the forward voltage drop in volts NOTE The front panel ZERO control operates only on the 202 and 200 ranges It has no effect on the other resistance ranges 4 Before making measurements on the 200 or 2000 ranges adjust front panel ZERO on the 200 range to compensate for test lead resistance Best performance will be obtained on the low ohm ranges when test connections are made to the binding posts rather than using banana plugs Adjust ZERO and make resistance measurements as follows A Select 200 range B Disconnect the test leads at the circuit to be measured and short them If measurement is to be made right at the INPUT terminals no test leads used place a short such as a piece of copper wire across the binding posts C Adjus
53. d possible injury Read over the manual carefully before operating this instrument 2 Exercise extreme caution when a shock hazard is present at the instrument s input The American National Standards Institute ANSI states that a shock hazard ex ists when voltage levels greater than 30V rms or 42 4V peak are present A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring 3 Inspect the test leads for possible wear cracks or breaks before each use tf any defects are found replace with test leads that have the same measure of safety as those sup plied with the instrument 4 For optimum safety do not touch the test leads of 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 5 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 which is capable of withstanding the voltage being measured 6 Exercise extreme precaution when testing high energy power circuits AC line or mains etc Refer to the oper ation section of the manual 7 Do not exceed the instrument s maximum allowable input as defined in the specifications and operation section 1 7 SPECIFICATIONS Detailed Model 177 specifications are lo
54. e any other knob if the knob or its cap is lost or damaged order only Keithley part number KN 41 1 as a WARNING replacement Disconnect the line cord before removing the case cover 1 Turn off power and disconnect the line cord 2 Turn the Model 177 bottom side up and loosen the four screws in the bottom cover These screws are held captive by rubber O rings 3 Hold the top and bottom covers together to prevent their separation and turn the Model 177 over to normal position 4 Lift off the top cover CAUTION Do not install fuses with higher ratings than specified Instrument damage may occur 5 Replacement of battery pack fuse F301 Figure 5 3 Front Panel Zero Knob Removal A Leave the battery pack in place and connected B Remove F301 shown in Figure 5 4 and replace it with 5 8 FUSE REPLACEMENT a 2A 250V 3AG fuse Keithley part number FU 13 Ail fuses are located internally in the Model 177 To replace a BATTERY FUSE F301 1788 BATTERY PACK LINE BAT CONNECTOR P1004 PLASTIC SPACER 4 PLACES Figure 5 4 Battery Pack Installation 5 5 6 Replacement of line power fuse F102 3 A Once the top cover is removed F102 is accessible without removing any other components B Remove F102 shown in Figure 5 1 and replace it with 4 a 1 8A 250V 3AG SLO BLO fuse Keithley part number FU 20 for standard line voltage units Optional line voltage units with 90 110V an
55. ents of a signal with both AC and DC current components 2 14 TRMS MEASUREMENTS AC DC The Model 177 measures the AC component of a waveform and does not measure the DC component Use the Model 177 to measure TRMS of a signal which has both AC and DC components as follows 1 Measure and record the AC and DC components separate ly A Refer to paragraph 2 9 for DC voltage measurement B Refer to paragraph 2 10 for AC voltage measurement C Refer to paragraph 2 12 for DC current measurement D Refer to paragraph 2 13 for AC current measurement 2 Compute the TRMS value using the following equation Neca ee NIS 7135 ETRMS EpC2 Eac2 or ITRMS pc lAc 2 15 ANALOG OUTPUT The rear panel accessible ANALOG OUTPUT provides a 2V full scale DC signal 10k counts 1V The ANALOG OUTPUT is operable for all instrument ranges and functions The output polarity of the analog voltage is negative for the 2 8 ohms Q function positive for AC function and non inverting for DC functions The effective analog output resistance is 5k 4kQ in series with the HI output to protect the Model 177 against externally applied voltage and 1kQ between input LO and analog output LO to prevent a ground loop when con nection is made to a grounded load oscilloscope or recorder The analog output voltage is compatible with most modern analog recorders and may be used to determine signal changes with respect to time or other variables With respe
56. eplacement parts 6 2 PARTS LISTS Table 6 2 contains a list of parts for the Model 177 mother board Table 6 3 lists display board parts and Table 6 4 lists parts for the optional Model 1788 Battery Pack Each list is ar ranged in alphabetical order according to circuit designation Mechanical parts are listed on Figure 6 1 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 Modei Number 2 Instrument Serial Number 3 Part Description 4 Circuit Designation if applicable 5 Keithley Part Number 6 4 FACTORY SERVICE If the instrument is to be returned to the factory for service please complete the service form which follows this section and return it with the instrument 6 5 COMPONENT LOCATION DRAWINGS 1 Model 177 PC 476 Component Layout No 29474D 2 Display Board PC 475 Component Layout No 29652C 3 Model 1788 Battery Pack PC 451 Component Layout No 29007C 6 6 SCHEMATIC DIAGRAMS 1 Model 1788 Battery Pack Schematic No 29659C 2 Model 177 4 Digit Multimeter Schematic No 29658E 6 7 MAINTENANCE KIT A maintenance kit is available that contains a complement of spare parts that will maintain up to ten Model 177s Specify Model 1779 Spare Parts Kit when ordering A list of the kit parts is give
57. eps outline the use of these tables and provide instructions for preparing the Model 177 for troubleshooting Read all of these steps carefully before troubleshooting the instrument 5 6 1 Calibration Shield Battery Pack Removal If the Model 1788 Battery Pack or calibration shield is install ed it must be removed to gain access to test points and cir cuit components for troubleshooting WARNING Disconnect the line cord before removing the case cover 1 Turn off power and disconnect the line cord Remove the four screws from the bottom of the case and separate the top cover from the bottom cover 2 Push back the ground clip and remove either the calibra tion shield or battery pack from the spacers If operation on battery power is to be checked leave the battery pack plugged into the instrument but set the battery pack behind the Model 177 on the bench or table Table 5 2 Calibration Procedure troubleshooting or repair other than fuse replacement Step Function Range Input 1 DC V 2V Short 2 DC V 2V Open 3 DC V 2V Short 4 DC V 2V Open 5 DC V 2V 1 9V 6 DC V 20mV Short 7 DC V 200mV 190mV 8 DC V 20mV 19mV 9 Q 2kQ 5000 10 U 2kQ 1 9kQ 11 U 2kQ 5000 12 0 2kQ 1 9kQ 13 Q 200kQ 190kQ 14 DC V 200V 190V 15 DC V 20V 19V 16 DC V 1000V 1000V 17 AC V 2V AV 1kHz 18 AC V 2V 1V O 1kHz 19 AC V 2V AV O 1kHz 20 ACV 2V 1V 1kHz 21 AC V 200V 100V 20kHz 22 AC V 2V 1V 20kHz Adjustment Desired Test P
58. geable Battery Pack Optional line voltage ranges are described in Section 2 The Model 1788 is available factory installed or is field installable Instal lation and operating instructions are given in Section 2 1 10 2 Cables and Connectors Model 1681 Clip On Test Lead Set This set contains two 1 2m 48 in leads with banana plugs at one end and spring action clip on probes at the other end Model 1683 Universal Test Lead Kit This kit contains two 1m 40 in test leads and 14 screw in adapter tips The tips consist of two alligator tips with boots four banana plugs phone tips two spade lugs and four heavy duty tip plugs which permit connection of the Model 177 to virtually any source within its measurement range 1 10 3 Probes and Shunts Model 1600A High Voltage Probe The Model 1600A High Voltage Probe extends the measurable DC voltage range up to 40kV It has a 1000 1 division ratio so that a reading of 1V on the DMM corresponds to 1kV 1000V The Model 1600A has a basic accuracy of 25 and an input resistance of 1000MQ Model 1651 50 Ampere Shunt The Model 1651 50 Ampere Shunt permits current measurements of up to 50A AC or DC The shunt has a resistance of 0 0010 196 so that a 50A current will correspond to a reading of 50mV 0 0500V Model 1682A RF Probe The Model 1682A RF Probe per mits measurement of AC voltages at frequencies of 20kHz to 250MHz AC to DC transfer accuracy is 1dB at 1V and the input
59. git for low thermal resistor uncertainty 12 Repeat steps 10 and 11 with negative voltage DC CALIBRATOR 10 1 DIVIDER Figure 3 1 Test Circuit For 20mV DC Accuracy Check 3 4 4 AC Voltage Accuracy Check 1 Select AC voltage function with the AC DC and V pushbuttons 2 Connect the AC calibrator to the DMM Set the calibrator frequency to 1kHz 3 2 Set the DMM to the 200mV range and apply 100mV AC to the DMM The reading must be within the limits specified in Table 3 3 Select the 2 20 and 200mV ranges and apply the required voltages as specified in Table 3 3 Verify that the readings are within spcifications To check 1000V range connect the AC calibrator amplifier to the output of the AC calibrator per the manufacturer s instructions Connect the amplifier output to the Model 177 INPUT terminals Set the AC calibrator for amplifier output of 1000 000V at 1kHz Verify that the DMM reading is within the specified limits in Table 3 3 To check accuracy at 45kHz and 20kHz select the 20V range Apply the voltage specified in Table 3 3 at 45Hz then repeat at 20kHz Verify that the DMM readings are within the specified limits Table 3 3 AC Voltage Accuracy Check Applied Allowable Readings at Range Voltage 18 to 28 C 1kHz 100 00mV 99 35 to 100 65mV 1 0000V 0 9935 to 1 0065V 10 000V 9 935 to 10 065V 100 00V 99 35 to 100 65V 1000 0V 993 5 to 1006 5V 45Hz 10
60. he high impedance buffer amplifier for Q Refer to paragraph 4 4 for additioni chopper theory 4 5 1 Floatig Current Source The floating current source involves a differential arnplifier U107 driven by the A D reference voltage and the chopper feedback voltage This results in a constant valtage across the source resistance V reference which results in a con stant current in the unknown resistance One or more range resistors are always connected as the ohms source resistor R when ohms function is selected Five different constant current levels are supplied by changing the value of Rg with the range pushbuttons These levels are given in Table 4 4 For Q INPUT HI terminal is negative with respect to INPUT LO 4 5 2 Chopper For ohms the full scale chopper output is 2V Gain is employed on the 202 and 2000 ranges to give 2VFS out with the nominal IMA source current The front panel zero control functions on these two ranges allowing compensation for up 44 to 200m of lead resistance Settling time is determined primarily by chopper input T R C which results in two seconds to full scale on the 2000k2 and 20MQ ranges 047uF X 2MQ and 0047uF X 20MQ Table 4 4 Ohms Conversion R Sourc Chopper Nominal Range Resistance Gain Current 20 1k x 100 TIMA 200 1k x 10 1mA 2k 1k x 1 1mA 20k 10k x 1 1004 A 200k 100k x 1 2000k 1M x 1 20M 10M x 1 4 5 3 Adjustments and Input Overlo
61. ield installation aeaaea 5 4 2 A MEI haa A eR em ase eee 5 4 3 Calibration Instructions rn i ee ga parar 5 5 li ILICE 5 6 Troubleshooting Procedure i eus eere ah hh Rb hx dx EX RE aaa ARE rada bud 5 6 1 Calibration Shield Battery Pack Removal 0 0 0 0 0000 ccc cece eae an 5 6 2 LINE PEGWIR A a re ts gan a 5 6 3 A RI oon he RGA eee Oe Oh 5 6 4 Display and A D Converter td a 5 6 5 A NE E 5 6 6 Chopper Amplifier and Ohms Source issues lua 5 6 7 ET d E B oe sace Cane va Pa E Add des dr al oa ira 5 7 Front Panel ZERO Knob Removal and Replacement 5 8 Fuse Replacement Luu ir LIRA 5 9 Model 1788 Battery Pack Installation a nn 00 0 cece a ee SECTION 6 REPLACEABLE PARTS 6 1 A IA 6 2 Parts A ELE 6 3 Ordering ITO AON soe 1 crei ian saven da ice 6 4 E 6 ouu Sn n wa cen iT ey Ud RAT Led Rh a Fae Bde RA Dae oe oe are bed a Ew eke mada Gain 6 5 Component Location Drawings o 6 6 Schematic Diagrams cei iue si cra Pres d ee cata 6 7 Maintenance Kit 2 0 2 ccc ccc cer erence hahaha e ease eae ea Lille LIST OF FIGURES Figure Title 1 1 Model 177 Front Panel rabiar ERE EA ANNA ARE D 2 1 Model 177 Rear View of Standard Line Voltage Instrument 2 2 Model 177 Rear View of Optional Line Voltage Instrument LL 2 3 Operaio CONOS iara isur ict mine P pire reb CERAS S Ros dag Deke eee 3 1 Test Circuit for 20mVDC Accuracy Check esce cede eae cae i eb eee a enna eas 4 1 Model 177 Simplified S
62. ignal Flow Block Diagram Le 4 2 Simplified Signal Conditioning dci rd AAN ee betas a 4 3 A D Converter Function ria EA HE rc ee wee Ov A AAA ade cans 5 1 Test Point Locations 2o voe VERE oe REE Wee Rd OCC CREASE CED en dd we x RE dS QI ia 5 2 Integrator and Comparator Waveforms ee ees 5 3 Front Panel Zero Knob Removal voles rk P o3 mIF Prats EROR ds oi ar ein em d 5 4 Battery Pack Installation oid ese cba EA ee CREER Ra SER Seb eee Ney RR E AY a RP RE RE xr ERA 6 1 Model 177 Covers and Panels ss ias rhon A RCR ECC Coen rk E eo bee dass 6 2 Model 177 PC 476 Component Location Drawing Dwg No 294740 cc eee 6 3 Display Board PC 475 Component Location Drawing Dwg No 29652C eese 6 4 Model 1788 Battery Pack PC 451 Component Location Drawing Dwg No 29007C 6 5 Mode 1788 Battery Pack Schematic Diagram Dwg No 296590 6 6 Model 177 4 Digit Multimeter Schematic Diagram Dwg No 29658E LIST OF TABLES Table Title 2 1 Model 177 DMM Condensed Operating Instructions 2 2 Resistance Ranges casini iran ciae oa kde baad eRe ewan SHEA PSOne es GEESE He we 3 1 Recommended Test Equipment for Performance Verification lisse me 3 2 DC Voltage Performance Check 2V to 1200V Ranges cece tte nne 3 3 AC Voltage Accuracy CHECK oprimir K RR R RR che nea eden HEN ON SUR ARA AA R PR SCR ose ee 3 4 Resistance Accuracy Check aii eco iii AA ERA AA 3 5 DC Current Accuracy Check aussi diate weve inn ed da deere da
63. ioning RR CC E cc O TRI RR i KE KR 8 K OE wow E AA A e o o 4 2 2 LI lee rane ar a A dd LE RY A OE Ewe od 4 2 3 Manage SONG c srar a Tar 9 ar TE ferro atic R R Mende iii 4 3 A A apa dts 2392 Socr bu jae need eae BE V st a eee cosas de ou wees 4 3 1 CUR iii Aaa baie rrr 4 3 2 AG CONVESION AA iii rR REET RA A ORS ale a we vow Ga idee nao Oe oe Sa onan 4 3 3 AC Current Measurements liliis ars 4 4 DC Signal Conditioning scis iero a DEG UbGDE GGG Co de eet EE PRU a 4 4 1 Input ATSnuaOll sro rnt neen a a p eee Sea ee TAO e Ma Marais id 4 4 2 hip MEME PERPE C ERI IRPINO 4 5 Ohms Conversion coe se pensa rea ir AA ARA AAA Ow CREEL A 4 5 1 Floating Current Source picar dosis rare daa od sis rk 4 5 2 CRODBP essen er IRA pin EER 4 5 3 Adjustments and Input Overload Protection 4 6 Analog DUIPUl oreo ts A ad ed ae oh eat A a 4 7 E iid wake ts UE Ad Od oN anaes NR ek eho EE Laie Rasa eed 4 8 AD COMBO oa acordo RR aa ina rada 4 8 1 POON MEET 4 8 2 A ate eek LORO RT na 4 8 3 Reference Integrate ee 4 9 DSi ni id A a a 4 10 ACG OWE SUING nn ramets Dar A EUR drei ilaele 4 11 Model 1788 Battery Pack is sur eux Rx X ean a e UN ds 4 11 1 Battery Charging Circuit ooo o e e Oe os CREE RR a OE RO eu S 4 11 2 Battery Operation and Shutdown Circuit SECTION 5 MAINTENANCE 5 1 INCEOGNGHO Ni dai Rare inten 5 2 Recommended Test Equipment 5 3 Environmental Conditions LL 5 4 Calibration Procedure ii Ra E 5 4 1 Calibration Sh
64. ired Capacitor 4 74F 20V Capacitor 4 7uF 20V Capacitor 1 04F 250V Capacitor 1004F 35V Capacitor 1004F 35V Diode Silicon 1N4148 Diode Silicon 1N4148 Diode Silicon 1N4148 Diode Silicon 1N4148 Diode Silicon 1N4148 Fuse 2A 250V 3AG Quick blow Thyristor SCR 106F1 Transistor NPN 2N3904 Transistor PNP Silicon TO 92 Case 2N3905 Transistor NPN 2N3904 Transistor NPN 2N3904 Transistor PNP Silicon 2N3905 Transistor NPN 2N3725 Transistor NPN 2N3725 Transistor PNP Silicon MPS U95 Transistor PNP Silicon TO 92 Case 2N3905 Resistor 20kQ 10 Cermet Trimmer Resistor 3300 1096 4W Composition Resistor 1kQ 10 W Composition Resistor 3 9kQ 2096 3W Wire Wound Resistor 4 7kQ 10 4 W Composition Resistor 3 3kQ 1096 W Composition Resistor 820 10 aW Composition Resistor 820 1096 4W Composition Resistor 100 10 4 W Composition Resistor 100 1096 W Composition Resistor 100kQ 1 1 8W Composition Resistor 100kQ 1 1 8W Composition Resistor 100kQ 196 1 8W Composition Resistor 6 8M 10 W Composition Resistor 576kQ 1 1 8W Resistor 100k2 1 1 8W IC Dual D Type Flip Flop 4013 IC 1 1V Micro Power Detector ICL8211 Regulator 8 2V Zener 1N765A Keithley Part No BA 33 C 179 4 7 C 179 4 7 C 256 1 C 295 100 C 295 100 RF 28 RF 28 RF 28 RF 28 RF 28 FU 13 TG 132 TG 47 TG 53 TG 47 TG 47 TG 53 TG 131 TG 131 TG 1
65. is 200mS or 20 000 counts in length During this period the integrator is returned to baseline level by applying a reference voltage of a polarity opposite to that of the signal A positive going ramp is obtained by grounding the buffer in put while a negative going ramp is produced by the integra tion of 2x Voce that is Vg the voltage stored in C116 The time or number of clock pulses required for discharge is proportional to the signal input Digital output is from latches within U106 which store the number of clock pulses required for the integrator for the integrator to return to baseline level The maximum count during this period is 20 000 which cor responds to a discharge period of 200mS or full scale input For an input of less than full scale the A D automatically reverts to auto zero for that period of the 200mS remaining after return to baseline level Vagp is provided by a divider across a temperature compensated zener diode Operational amplifier U104 provides the zener with a self regulating bias C NEGATIVE REFERENCE INTEGRATE 20k COUNTS AT FULL SCALE POSITIVE INPUTS TO A D A VREF A da 4 a R Vos2 L lt a t ver Vost Vos I D POSITIVE REFERENCE INTEGRATE 20k COUNTS AT FULL SCALE VREF VREF R Figure 4 3 A D Converter Function 4 5 4 9 DISPLAY Five light emitting diodes LED are driven by U203 which is a CMOS BCD to seven segment decoder driver with bipolar current
66. istor 10kQ 10 Cermet Trimmer G2 D2 RP 89 10k NOT USED Resistor 4 3MQ W Composition R 76 4 3M Resistor 50kQ 10 Cermet Trimmer G2 C2 RP 89 50k Resistor 200k SW Potentiometer ES C4 RP 97 200k Resistor 200kQ 1 1 8W G2 D2 R 88 200k Resistor 1000 1 1 8W G2 C2 R 88 100 Circuit Desig Table 6 2 Model 177 Mother Board Parts List Cont Location Keithley Description Sch Pcb Part No Resistor 80 6kQ 1 1 8W Resistor 100kQ 1 1 8W Switch Line Selector Switch Line Battery Switch 12 Station Pushbutton Transformer Power 115 230V Transformer Power 100 200V IC 8 Pin Op Amp JFET TL081 IC BI FET Op Amp LF351 IC True RMS TO DC Converter AD536 TO 100 iC 8 Pin Op Amp 741 IC 4 Digit Analog Processor 8052 IC 4 Digit Logic Processor 7103 IC Linear Op Amp 8 Pin LM308 IC J FET Input Op Amp LF355 selected IC Linear Op Amp 8 Pin LM308 IC CMOS 14 Stage Binary Converter 4060 CMOS MOS Hex Converter 4069 Regulator 5V 3 Term TO 220 7805 Regulator 15V 500mA 78M15 Regulator 15V 500mA 79M15 Regulator Diode Selected with R137 Crystal Quartz 0 01 100kHz R 88 80 6k R 88 100k SW 318 SW 397 29434B TR 168 TR 169 IC 196 IC 176 IC 172 1 IC 42 LSI 12 LSI 11 IC 203 IC 205 IC 203 1C 197 1C 139 1C 93 IC 194 IC 195 27699A CR 8 6 7 Table 6 3 Model 1788 Battery Pack Parts List Location Description D Cells for BT301 4 requ
67. led connect disconnect device such as the circuit breaker main switch etc 2 Attach the test leads to the circuit under test Use ap propriate safety rated leads for this application 3 Set the DMM to the proper function and range 4 Energize the circuit using the installed connect disconnect device and make measurements without disconnecting the DMM 5 De energize the circuit using the installed connect disconnect device 6 Disconnect the test leads from the circuit under test 2 3 PREPARATION FOR USE The Model 177 is shipped ready to use on line power The instrument may also be powered from rechargeable batteries when the optional Model 1788 Rechargeable Battery Set is installed 2 4 OPERATION ON LINE POWER The Model 177 DMM has a three wire line cord which mates with third wire grounded receptacles Connect the instru ment to AC line power as follows CAUTION Connect only to the line voltage selected Application of incorrect voltage can damage the instrument 1 Set the LINE VOLTAGE switch on the back of the instru ment to correspond to the line voltage available Standard ranges are 105V to 125V and 210V to 250V AC as shown in Figure 2 1 Optional ranges of 90V to 110V and 180V to 220V AC are also available as shown in Figure 2 2 As in dicated on their respective rear panels the standard line voltage range instruments use an internal line fuse F102 of 1 8A rating and the optional line voltage range
68. ls outside specifica tions at any point contact your Keithley representative or the factory immediately 3 2 RECOMMENDED TEST EQUIPMENT Recommended test equipment for performance verification is listed in Table 3 1 Alternate test equipment may be used However if the accuracy of the alternate test equipment is not at least 10 times better than the instrument s specifica tions additional allowance must be made in the readings ob tained Some of the equipment listed in Table 3 1 is not 10 times better than the Model 177 specifications because such equipment is not readily available In these instances the verification procedures indicate the equipment manufacturer s specified uncertainty and include the uncer tainty in determining the allowable reading for the Model 177 3 3 ENVIRONMENTAL CONDITIONS All measurements should be made at an ambient temperature within the range of 18 to 28 C 65 to 82 F and a relative humidity of less than 80 3 4 PERFORMANCE VERIFICATION PROCEDURE Use the following procedures to verify the basic accuracy of the Modei 177 DMM for voltage resistance and current measurements If the instrument is out of specification at any point perform a complete calibration as described in Section 5 unless the instrument is still under warranty NOTE Performance verification should be performed by qualified personnel using accurate and reliable test equipment 3 4 1 Initial Conditions Before begi
69. mum reading is 19999 Overrange is indicated by a flashing 0000 Overload is protected by fuse F101 a 2A 3AG normal blow fuse The instrument measures the true root mean square TRMS of waveforms in the frequency range of 45 to 10kHz Use the Model 177 to measure AC current as follows 1 Turn on power and set the AC DC pushbuttons to in or AC position Depress the A pushbutton CAUTION Do not install a larger capacity fuse than the one supplied Current fuse F102 shown in Figure 5 4 protects the instrument against over current 2 Connect the circuit to be measured to the INPUT terminals and selact the desired range from the five ranges available NOTE The 204A and 20M ranges are not operative for AC current measurements If the 204A push button is inadvertently depressed an overrange will be indicated signalling the user to go to the next higher range if the 20M pushbutton is de pressed the instrument will read zero 3 Read the displayed digits and decimal point NOTE AC accuracy is specified for 2000 counts and above The method of calibrating the converter may yield an offset up to 80 digits with the Model 177 input shorted This does not affect in strument accuracy There will be some addi tional measurement error for signals with a crest 2 7 factor greater than 3 CF 3 Refer to paragraph 2 10 for information on how to determine the crest factor of a waveform 4 Refer to paragraph 2 14 for TRMS measurem
70. n in Table 6 1 6 1 TOP COVER 25728E OVERLAY 29464B SPACER 4 25762B LABEL MC 260 6 32 x mi BOTTOM SCREW 4 LABEL COVER MC 265 29435A HANDLE 25729D ALTERNATE PART MC 264 FOR OPTIONAL LINE VOLTAGE UNITS Figure 6 1 Model 177 Covers and Panels 6 2 Table 6 1 Model 1779 Spare Parts Kit Keithley Schematic Part No Number Description DS202 3 7 Segment Display 2 1 1 Display 5 Line Fuse 2 Current Fuse 1 BV Regulator 1 CMOS NAND Gate IC 1 CMOS Hex Inverter 1C 1 Segment Driver IC 1 Digit Driver IC 1 CMOS Binary Con verter IC U107 109 OP Amp IC U108 OP Amp IC Front Panel Knob Zero U106 Logic Processor IC U105 Analog Processor IC K101 Relay R126 Thick Film Resistor Q101 102 2N4392 JFET 105 Q103 2N3439 Transistor Q104 Dual MOSFET Anti Static Protection amp Handling Required Table 6 2 Model 177 Mother Board Parts List Circuit Location Keithley Desig Description Soh Part No C101 Capacitor 0 1nF 1000V Polyester Film C 285 1 C102 Capacitor 25 1 5pF 2000V Teflon Trimmer C 184 C103 Capacitor 25 1 5pF 2000V Teflon Trimmer C 184 C104 Capacitor 110pF 500VDC 1 Silver Mica C 278 110p C105 Capacitor 1100pF 500VDC 5 Mica C 236 1100pF C106 Capacitor 334F 16VDC 10 Aluminum Electrolytic C 321 33 C107 Capacitor 33uF 16VDC 10 Aluminum Electrolytic C 321 33
71. nal flow is provided in Figure 4 1 The schematic diagrams are contained in Section 6 of this manual The Model 177 schematic is drawing number 29658E and schematic drawing number 29659C is for the Model 1788 4 2 OVERALL OPERATION The Mode 177 uses a 2V 20 000 count full scale analog to digital A D converter with a 4 digit multiplexed display Signal conditioning permits the A D converter to ac comodate full scale DC voltage and current measurements over seven ranges 4 2 1 Signal Conditioning Signal conditioning icludes DC attenuation on the 20 200 and 1200V ranges modulation and demodulation of the OC signal by the chopper buffer amplifier with X100 and X10 gain on the 20 and 200mV ranges respectively AC atten uation on the 20 200 and 1000V ranges AC amplification on the 200mV and 20V ranges AC to DC conversion ohms source and conversion and current shunts as shown in Figure 4 1 1 In the DCV mode signal conditioning to the A D converter consists of range and function switching range resistors lattenuator and the chopper buffer amplifier For ail ranges the DC input signal is attenuated amplified to pro vide a 2V full scale output to the A D converter In the DCA mode the voltage developed across the shunt resistor is applied directly to the input of the chopper amplifier A chopper gain of X10 is used for all ranges ex cept 20A which uses X100 DIGITAL OUTPUT AC AMPLIFIE
72. nal is determined by the clock circuit Circuitry in U110 divides down a nominal clock frequency of 100kHz to produce 390Hz 6 Adjustments and Input Protection The front panel zero control R203 permits adjustment of the chopper feed back to compensate for input thermal EMFs It functions only on ranges where chopper gain is greater than one A span of 75V is considered adequate however it is typical for R203 to provide a greater than 400V change as it is turned end to end The span is skewed by R128 to give best resolution in both DCV and Q Potentiometer R146 provides a calibration adjustment to compensate 200mV range X10 gain configuration and R147 adjusts the X100 gain used on the 20mV range Chopper input resistor R143 limits the input current during momentary in put overloads to 12mA which is then absorbed by the chopper load resistance R145 and or R149 or the power supplies through CR116 and CR117 7 OC Current Measurements As previously described DC current measurements are made by placing the ap propriate buffer amplifier shunt resistor on the chopper in put A chopper gain of X10 is used for all current ranges except 20A which uses X100 The front panel zero control R203 is functional for all DC current ranges 4 5 OHMS CONVERSION The ohms converter contains two sections a floating current source and a high input impedance buffer amplifier The chopper employed as a buffer amplifier in DCV is also used as t
73. nning the verification procedure the instrument must meet the following conditions 1 If the instrument has been subjected to extremes of temperature allow internal temperatures to stabilize for one hour minimum at the environmental conditions specififed in paragraph 3 3 2 Turn on the Model 177 and allow it to warm up for one hour The instrument may be operated from either line power or from battery pack power as long as the battery pack has been fully charged as described in paragraph 2 6 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 3 4 2 DC Voltage Accuracy Check 2V to 1200V Ranges 1 Select DC voltage function with the AC DC V push buttons 2 Connect the DC calibrator to the instrument 3 Select the 2V range and apply positive 2VDC to the DMM The reading must be within the limits specified in Table 3 2 4 Select each remaining range and apply required voltage specified in Table 3 2 Verify that the reading is within specifications 5 Repeat all checks with negative voltage Table 3 1 Recommended Test Equipment For Perfomance Verification Description Specification Model DC Calibrator AC Calibrator AC Amplifier Decade Resistor Current Source 1000 Per Step 4 Terminal Low Thermal Resistor 0 19V 1V 10V 100V 1000V 0 00296 or 204V 0 1V 1V 10V
74. oca bor ci3O BA 2133 9 1e A1K RAO 33 __NRIOS AS C 39 lczse WOOF CUR cz BA TRT EM RIAL 83 AA ram 357 u BZ Az A 135 RP GA LK Risa AS ca QUES 3e lt 301 0097 1 CRS 2 c IBS R 3 100K R43 v8 Bel cr vio 85 FIERA de C34 0 0038 L8 76 5 9 0 gt l E Te ZK RA D rst s n O A 38 1 138 10009F 135 D3 B8 TRA Qda 02 138 TR 266 922 RIAS ca sa FH 12 AV y as rt 77 quos MERA 139 Re GI OK Rie 4 CIRS 12 90 a a 90 Tae Lo lo QU B az 14D RP 97 100 Ria CA 90 lcC 221 Pe gt 901 74 39 aie en Ii 1R 263 89Sk RAB c4 IAEA O O AA Te C Ajaz TG 139 GIOB DA staz e 203 100 RAS ca NE IPR L AA DE __ 93 i 43 RA 998K _RISO 2 193 2046502 ENS wM F3 ee aq R 292 RIO EZ EIS DZ Ma gSaesc 3 N ES ree AA ASS x 3 099 RIO EZ _ A ms ESS Be i i FS a A Ae REI CRIO R 96 E 1 2 9 O RIOS _ 22 Je Rizea aar RISI DI pS 4 RF 2 CRIO2 DI 31 TR 169 90 ROA pz C41 Tee CCE FA 48 7 36 CRIOS BS a 148 RP 97 5K RISS Da TOB 29468C 7 Wy KOK 74 0 RF Ae CROA 78 77 2979 ER 149 RP 97 300 R Si a SE 9 e IC aa NEUE YT 2s RRR sO 3091 DA 200 77 f ECKE NL i niv pa MA ev cw E EITHLEY I Mao INA TRUMENTO dle ne C D E F Te CANE SE sad E was FERMO JEL ZO Aner TRE NA TO Lt Manoni G CR TS ea 3 7 8 ROSE HEM Gl RE 28 h EREE E 4 BB RENE S S NM 3 eura
75. of R301 does start charging see Table 5 11 for adjust ment of battery charge voltage High voltage or zero indi cates damaged cell Output of CR103 Output of CR104 Triggers Q301 gate thru R306 and CR301 unless Q302 is on Discharge checks Clock input If no input see step 12A Battery voltage input to VR101 Output of U301 4 Inverter Inverter Output input to VR102 and VR103 5 7 5 8 Table 5 5 Display Checks Step Item Component Required Condition Remarks 1 Turn on power Any function or range except OHMS 2 5V Pad or 31001 5V 5 If low check per Table pin 7 5 3 3 U202 pins 2 6 7 Digit drive Low Enabled LED Cathode 9 and 13 4 U203 pins 1 2 6 HI Enabled BCD input to U203 seg and 7 ment decoder drive 5 U203 pin 2 Negative going signal lasting Leading digit suppres for 200 clock pulses sion 6 J1001 pin 2 Polarity Line sign Polarity output is dis Hi Off abled on AC an 2 LO 7 J1001 pin 4 Appropriate DP line high on Depress RANGE push 41002 pins 1 11 Er 12 buttons to check all DPs On main printed circuit board See Figure 5 1 Table 5 6 A D Converter Checks Step Item Component Required Condition Remarks 1 Turn power on Select 2VDC range 2 Display 0000 1 digit 3 TP1 0 0000V Input to U106 Chopper out put 4 TP2 1 00V Reference output 5 Short TP1 to TP2 Connects reference output to
76. oint Reading Equipment R163 0000 0000 None R142 0000 0000 None R163 0000 0000 None R142 0000 0000 None R134 1 9000 DC Calibrator R203 0000 0000 None R146 190 00 DC Calibrator R147 19 000 DC Calibrator and 10 1 Divider R162 4999 5000 Decade Resistor R159 1 9000 Decade Resistor R162 4999 5000 Decade Resistor R159 1 9000 Decade Resistor R156 190 00 Decade Resistor R139 190 00 DC Calibrator R155 19 000 DC Calibrator R157 1000 0 DC Calibrator R114 1000 AC Calibrator R113 1 0000 AC Calibrator R114 1000 AC Calibrator R113 1 0000 AC Calibrator C102 100 00 AC Calibrator C103 1 0000 AC Calibrator 5 2 F102 LINE FUSE 1 84 15V TPS TP3 15V TP4 BV C120 C125 1 C123 GROUND CLIP TP8 TP1 TP10 TP2 TP6 f R143 YELLOW LEAD TP9 CURRENT SHUNTS R101 THRU R105 TP7 F101 1 FRONT CURRENT PANEL FUSE 2A Figure 5 1 Test Point Locations 5 3 5 6 2 Line Power In general start troubleshooting with Table 5 3 line power checks to verify that the power supplies are providing the correct voltages to the electronic components 5 6 3 Battery Power If trouble occurs on battery power only or if battery operating time is substantially less than six hours after over night charging test the batteries and charging circuit per Table 5 4 5 6 4 Display and A D Converter Proper operation of the A D converter and display
77. racy is 3 AC accuracy is specified for 2000 counts and above Nominal settling time for all AC voltage ranges is 2 5 second to within 10 digits of final reading Use the Model 177 DMM to measure AC volts as follows 1 Turn on power and set the AC DC pushbutton to the in or AC position Depress the V pushbutton NOTE The 20 and 20M ranges are inoperative for AC volts If the 204 pushbutton is inadvertantly 2 5 depressed the display will read overrange signalling the user to go to the next higher range If 20M is depressed the display will read zero regardless of the voltage applied The method of calibrating the converter may yield an offset up to 125 digits with the Model 177 input shorted This does not affect instrument ac curacy 2 Select the desired range from the five ranges available CAUTION MAXIMUM ALLOWABLE INPUT VOLTAGE All ranges 1000V rms 1400V peak 107Ve Hz maximum Do not exceed the max imum rating Instrument damage may oc cur 3 Connect signal to be measured between INPUT HI and LO terminals Observe the displayed digits and decimal point location The 200mV range is direct reading in mV and the remaining four ACV ranges are direct reading in volts 4 The crest factor CF is the ratio of the peak voltage to the rms voltage as follows cf VPEAK VRMS NOTE There will be some additional measurement error for signals with a crest factor greater than 3 CF gt 3 Typical crest factors
78. s MAXIMUM COMMON MODE VOLTAGE 1400V peak ANALOG OUTPUT Output Voltage 1V 10 000 counts Output Resistance 50000 ENVIRONMENT Operating 0 C to 55 c 096 to 80 relative humidity up to 40 C Storage 25 C to 65 C CONNECTORS input Binding posts Output Banana jacks POWER 105 125 or 210 250 volts switch selected 90 110V available 50 60Hz 8 watts Optional 6 hour battery pack Model 1788 DIMENSIONS WEIGHT 85mm high x 235mm wide x 275mm deep 3 x 9 x 1034 Net weight 1 7kg 4 Ib ACCESSORIES AVAILABLE Model 1010 Single Rack Mounting Kit Model 1017 Dual Rack Mounting Kit Model 1301 Temperature Probe Model 16004 High Voltage Probe 40kV Model 1641 Kelvin Test Leads Model 1651 50 Ampere Current Shunt Model 1681 Clip On Test Lead Set Model 1682A RF Probe Model 1683 Universal Test Lead Kit Model 1684 Hard Shell Carrying Case Model 1685 Clamp On AC Probe Model 1691 General Purpose Test Lead Set Model 1779 Spare Parts Kit Model 1788 Rechargeable Battery Pack Model 1792 Isolated BCD Output Model 1793 Isolated IEEE 488 Output Paragraph h ni ed h I L ee dh _ gt AAA E SAN M A NN N oooooo OP GN 4 NN O NNNNN oon GB Gn 2 10 2 11 2 12 2 13 2 14 2 15 2 16 3 1 3 2 3 3 3 4 3 4 1 3 4 2 3 4 3 3 4 4 3 4 5 3 4 6 3 4 7 4 1 4 2 4 2 1 SECTION 1 GENERAL INFORMATION Introduction Model 177 Features Warrant
79. s installed battery charging proceeds as follows 1 Full wave rectified from CR103 is applied to the anode of 0301 which is an SCR which regulates charg ing voltage When Q301 is triggered on by a sufficient gate cathode voltage differential the batteries receive charge Charging continues as long as the bridge output voltage exceeds battery voltage by 1V or more Resistor R304 limits charging current when recharging a set of completely discharge cells a filtered positive output from CR104 or T301 provides the necessary gate turn on bias through R306 and diode CR301 Resistor R303 ensures proper high temperature operation of Q301 2 When the battery voltages reach the present float voltages of 9 8V zener VR301 conducts sufficient current to turn on Q302 and thus remove the gate trigger voltage from 0301 Float voltage is adjusted with R301 This is a factory adjustment which will normally not need field readjust ment 4 11 2 Battery Operation and Shutdown Circuit The Mode 177 operates as follows on battery power 1 When the power is turned on the batteries are connected to the input of VR101 to supply 5V for the logic display and the clock circuit The clock output is applied to the A D converter as described in paragraph 4 7 and U301 which is a divide by four binary counter The outputs of U301 drive a DC to DC inverter which is sychronized to the A D converter to filter out inverter noise The 25kHz operating frequency i
80. s optimal for the small transformer size and results in low switching losses Blocking capacitors C301 and C302 protect Q307 and Q308 from damage if the drive is lost Two half wave rectifiers CR304 and CR305 on the secondary of T301 provide rectified AC to filter capacitors C304 and C305 which provide power to 15 and 15V regulators VR102 and VR103 respectively 2 To prevent permanent loss of battery capacity caused by deep discharge a shutdown circuit stops operation on bat tery power when the battery voltage drops below approx imately 7 2V Shutdown is performed by micropower voltage detector U302 The open collector output U302 pin 4 saturates low and turns off pass transistor 0309 when the input voltage at U302 pin 3 drops below 1 15V typical Resistor R314 provides sufficient hysteresis to prevent discharge from resuming when the battery voltage rises following disconnection of the load SECTION 5 MAINTENANCE 5 1 INTRODUCTION This section contains information necessary to maintain the Model 177 and Model 1788 Battery Pack information con cerning adjustment calibration troubleshooting front panel zero knob removal and replacement and fuse replacement are contained in this section Calibration should be performed yearly every 12 months or whenever performance verifica tion see Section 3 indicates that the Model 177 is out of specifications If any step in the calibration procedure cannot be performed properly
81. sourcing outputs Segment currents are limited to ap proximately 20mA peak by resistor network R202 The LED readout is a multiplexed common cathode configuration with Darlington array U202 sequentially sinking current fram each digit Blanking of the overrange digit is accomplished by gates U104C and U104D U104A and U104B ensure that CMOS compatible levels are maintained on U104D regardless of the loading of U202 The minus polarity readout is blanked on AC voltage and resistance ranges by normally open contacts on the AC and 2 pushbuttons 4 10 AC POWER SUPPLY When the Model 177 is operated from AC line power the power supply furnishes 5 15 and 15V from regulators VR101 VR102 and VR103 respectively Full wave rectified AC from bridge rectifiers CR103 and CR104 is filtered by capacitors C120 C123 and C125 and is applied to the linear voltage regulators 4 11 MODEL 1788 BATTERY PACK When the Model 1788 Battery Pack is installed in the Model 177 S102 must be set to the BAT position to provide addi tional secondary voltage for battery charging S102 also swit ches the input to VR101 from bridge rectifier CR103 to bat teries BT301 Four 2V 2 5 ampere hour lead acid cells supply approximately 9 8V at full charge After six hours of use on battery power the battery pack should be recharged to en sure long battery life 4 11 1 Battery Charging Circuit While the Model 177 is plugged into line power and the bat tery pack i
82. ssable modes The Model 1793 is compatible with Model 177s serial number 16 500 and above and can be either factory or field installed Installation of the 1793 precludes installation of the Mode 1788 or 1792 SECTION 2 OPERATION 2 1 INTRODUCTION This section provides information needed for preparation for use and operation of the Model 177 and Model 1788 2 2 SAFETY PRECAUTIONS FOR HIGH ENERGY CIRCUITS To optimize safety when measuring voltage in high energy distribution circuits read and observe the directions in the following warning WARNING Dangerous arcs of an explosive nature in a high energy circuit can cause severe personal 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 to a voltage range if the minimum safety spac ing is reduced When making measurements in high energy circuits use test leads that meet the following requirements 1 Test leads should be fully insulated 2 Only use test leads that can be connected to the circuit e g alligator or spade lugs for a hands off measurement 3 Use test leads that do not reduce the arc protection by decreasing the voltage spacing between conductors or terminals Use the following sequence when testing power circuits 1 De energize the circuit using the regular instal
83. st make con tact with the upper side of the battery pack plate Carefully align the battery pack plug with connector P1004 on the circuit board Push the plug firmly onto the connec tor until the lip on the plug engages the lip of the connec tor to lock the plug in place CAUTION Make sure the connector is aligned so that all pins mate properly otherwise damage to the Model 177 and battery pack will result Install the fuse F301 Reinstall top cover and secure with four screws Charge the battery pack as described in paragraph 2 6 Table 5 3 Line Power Checks Item Component S101 Line Switch Step 1 470uF Required Condition Must be set to 105 125V or 210 250V as appropriate Must be set to BAT for use with 2 102 LINE BAT Switch battery pack 3 F102 Line Fuse Continuity 4 P1007 Line Cord Plugged into live receptacle 5 Turn on power 6 5V Pad 5V 5 7 VR101 IN C120 7V minimum 2200u4F 8 15V Pad 15V 10 9 VR102 IN C123 17 5V minimum 470uF 10 15V Pad 15V 10 11 VR103 IN C125 17 5V minimum Remarks Output of VR101 Output of CR103 input to VR101 Output of VR102 Output of CR104 input to VR102 Output of VR103 Output of CR104 input to VR103 NOTE Hot regulator may indicate shorted load On main printed circuit board see Figure 5
84. stor 90 196 5W Wire Wound Resistor 900 196 W Metal Film Resistor 9000 196 1 8W Metal Film NOT USED Resistor 1 005MQ 0 596 2W Metal Film Resistor 990kQ 196 1 8W Metal Film Resistor 9 97kQ 1 M 1 8W Metal Film Resistor 9912 196 1 8W Metal Film Resistor 90 3kQ 1 1 BW Resistor 10kQ 1 1 8W Resistor 5000 0 5W Potentiometer Transistor Dual P Channel MOSFET 8 Pin TO 77 RF 28 RF 28 RF 28 RF 28 RF 28 RF 38 FU 13 FU 20 FU 28 CS 356 4 CS 356 6 CS 288 3 CS 287 8 BP 11 0 BP 11 2 SO 70 29316A RL 56 CS 355 4 CS 355 6 CS 288 3 29467A CO 9 TG 77 TG 77 TG 93 TG 94 TG 77 TG 66 TG 39 TG 139 R 262 1 R 310 898 R 252 9 R 169 90 R 168 900 R 284 1 005M R 176 990k R 176 9 97k R 176 991 R 176 90 3k R 176 10k RP 97 500 6 5 Table 6 2 Modei 177 Mother Board Parts List Cont Circuit Location Keithiey Desig Description Sch Pcb Part No Resistor 50kQ2 10 Cermet Trimmer G2 D4 RP 97 50k NOT USED NOT USED Resistor 27kQ 5 W Composition A7 C2 R 76 27k Resistor 4 32kQ 196 1 8W B7 C3 R 88 4 32k Resistor 4 99kQ 196 1 8W B7 C2 R 88 4 99k NOT USED Resistor 3 9kQ 1096 1 2W Composition F5 Al R 1 3 9k Resistor 1kQ 5 4W Composition F6 A1 R 76 1k NOT USED NOT USED Resistor Thick Film SEV C3 TF 79 Resistor Thick Film SEV C3 TF 80 NOT USED Resistor 27kQ 5 W Composition G6 D5 R 76 27k NOT USED Resistor 6
85. t the front panel ZERO knob for a display indica tion of 0 000 0 0012 flashing The nominal ZERO adjustment span is 200mQ NOTE The specified accuracy for the 202 and 2000 ranges assumes that ZERO was adjusted on the 202 range Re adjust zero on the 200 range each time that a different set of leads is used or whenever measurements have been made on either the two lowest DC voltage ranges or any DC current range The zero setting for those measurements will be different than the zero set ting of ohms Also re adjust zero whenever the instrument is used outside the temperature range of 18 to 28 C D Reconnect the test leads to the circuit to be measured E Select either 200 range or 2000 range Read the displayed digits and decimal point NOTE An input overload to the Model 177 may cause a temporary zero shift due to thermal gradients 2 12 DC CURRENT MEASUREMENT The Model 177 measures DC current from 1nA digit to 2A over six ranges the 20M range is not operative and the instrument will read zero if 20M pushbutton is depressed The maximum reading is 19999 Overrange is indicated by a flashing 0000 Overload is protected by fuse F101 a 2A 3AG normal blow fuse Nominal settling time for DC current ranges is one second to within one digit of final reading ex cept three seconds on 204A range 1 Before making DC current measurements the front panel ZERO must be adjusted on the 20xA range This adjust ment is necessary
86. uit to be measured Low thermal cabling and connections are recommended for measurements on the 20mV and 200mV ranges 4 For the top four ranges merely observe the displayed digits polarity sign and decimal point locations The top four ranges are direct reading in volts Nominal settling time is located to within one digit of final reading 5 For the 20mV and 200mV ranges the front panel ZERO must be adjusted to obtain rated accuracy This adjust ment is necessary to compensate for thermal EMFs generated by the connections to the circuit to be measured These voltages may be only a few microvolts or several tens of microvolts The zero adjustment span is set up at the factory to allow at least 754V adjustment To adjust zero proceed as follows 2 3 2 4 Tabe 2 1 Model 177 DMM Condensed Operating Instructions Summary of Function Ranges and Other Information Accuracy Range 18 C 28 C Input Max Input Note 2 Note 1 Impedance Note 1 1200V Yes Momentary 10MQ 0 03 Rdg 1D 1200v 0 035 Rdg E 0 5 Rdg 15D 2V ACV 100Hz 10kHz Note 3 1MQ 1000V RMS 75pF 10 Ve Hz 200V 0 7 Rdg 15D 45Hz 20kHz 1000V 204A 0 2V Burden 2A 250V DCA PEN DC or rms Yes 20mA 0 2 Rdg 1D Note 4 0 2V Burden 2A 250V ACA Pena 0 8 Rdg 15D DC or rms Note 3 20mA 45Hz 10k Hz Note 4 Full Scale 5V Max Open Circuit Eu Eo 0 0496 Rdg 1D 200k
87. wire slide Apply 19mV 19mV TP1 t 1 9V External voltage source R143 4 190mV 190mV TP1 1 9V External voltage source R143 TP1 Select 2VDC range Apply 1 9V 1 9V External voltage source R143 Select 20VDC range Apply 19V 1 9V External voltage source R143 Select 200VDC range Apply 190V 1 9V Select 1000V 1200V DC range Apply 1000V 1V External voltage source R143 On main printed circuit board see Figure 5 1 Turn on power Select 20mVDC F P Zero for 0000 on display Select 200mVDC range Apply NOTE Insufficient zero adjustment may indicated leaky FET switches in Chopper Amplifier Circuit Chopper Drive Signals are actually 0 to 15 square waves at 390Hz A steady zero volt or 15V signal indicates a problem in the chopper drive or clock circuitry Calibrated input input to chopper amplifier 1 attenuation range resistors Input to U106 chopper output x 100 gain Calibrated input Input to chopper amplifier 1 attenuation Input to U106 chopper output x 10 gain Calibrated input 1 attenuation x 1 chop per gain Calibrated input 10 attenuation range resistors Calibrated input 100 attenuation range resistors Calibrated input 1000 attenuation range resistors Table 5 9 Ohms Source and Resistor Checks
88. y Information Manual Addenda TABLE OF CONTENTS 8o d 3 3 Foo 8s O82 o no o3 39 4 Nom 9 os EON 3 4 4 d 3 P 4d 4 4 P P 9 4 4d 4 Y 3 3 4 4 9 4 2 o9 or 9 4 39 4 9 9 9 99 E tov mor m t m n n a ROB OB O4 8 NOR O9 4 4 No 9 O9 3 3 3 O O vof 30 3 vos os 9 ovo os 8 dos mos SOR SFO 3 4 PON SO 09 9 P o3 o PON ON 3 3 3 4 o3 3 3 ros t o4 oa Fo wo 3 s 9o tot omo I 9 3 4 d 4 9 9 0 4 KKR 4 4 9 Oo so 8 os o s o mot o poa ortos m om meos m om o t n s m om m om t n on n Safety Symbols and TMS s xor AEREA Safety Precautions Specifications a 9 om m BON o ORO9 9 4 4 odo 3 3 4 3 4 93 93 9 3 33 4 4 4 vor mov ov ov E E a sa m o oA do OR om or 3 oS SO os FON 3o 9 3 o3 os Noa c s s o5 gr 6 RON SOROR o oO 9 o3 9 4 9 E toO 3 o3 vov ov ov don 4 4 o P NAT 4 Y V Y 4 M Vor 9 9 SS t9 tor hoe R mososos t m n on Unpacking and Inspection usi org REPE VR error ERE RC pi de Ee De dedic dE due d eto pe Scope of Model 177 Instruction Manual 54 RR ER ERR RR TREE RP RE ERE EAR SE een Optional Accessories Power Options 8o 9 o9 9 ORO 9 ow I 3 3 4 4 9 3 3 3 AAA kk amp os WoW Nos t os s o 3 3 3 4 vos os s t n5 n n 8r 4 d 39 3 BON 9 O3 3 3 3 3 4 2 o9 oco omo 9 O3 TO E o M o3 4 4 4 4 3 3 3 3 9 9 9 8 03 9 9 v NON ton tos mom ovy mos sos 9 9 os os 9 os t Cables and Connectors vuus irradia EE R

Keithley 177 Microvolt DMM

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