Fluke 845AR User's Manual
Contents
1. SYNCHRONOUS DEMODULATOR 3 19 The synchronous demodulator detects the magni tude and phase of the amplified signal The 84 Hz drive signal is applied to the base of transistor Q106 which references the synchronous demodulator to the same phase as the photocell modulator The demodulated signal is filtered by R134 and C114 before being applied to the de amplifier 3 20 DC AMPLIFIER 3 21 The dc amplifier amplifies the detected de signal from the synchronous demodulator Transistors Q107 through Q112 comprise a two stage differential amplifier with a complementary emitter follower output Negative feedback through R149 and C116 is applied to the base of Q108 and controls the de amplifier gain The output from the common emitter of Q111 and Q112 is one volt de for a full range input on any range which drives the isolation converter Overall negative feedback through the resistive network of R138 through R142 and R114 is controlled by the position of the RANGE switch 8101C This negative feedback allows precise control of the overall gain of the Model 845AR amplifiers 3 22 ISOLATION CONVERTER 3 23 The isolation converter drives the recorder cut put and meter while providing isolation from the Model 845 amplifier circuitry The output signal from the am plifier is applied to the transistors Q113 and Q114 An 84 Hz reference drive signal is applied to the bases of transistors Q113 and Q114 which causes modulation of the de input signa2. the Model 845AR circuitry from overloads 3 11 The secondary voltage of T201 is rectified by bridge rectifier CR201 through CR204 The bridge rectifier output voltage is filtered by C201 and regu lated by zener CR207 This regulated output voltage is used as the operating voltage for the 84 Hz multivibrator 3 12 The 84 Hz multivibrator is used to provide syn chronous drive voltages and de operating voltages for the Model 845AR amplifier circuits free from any power line frequency variations and harmonics The multi vibrator is a transformer coupled free running multi vibrator composed of transistors Q201 and Q202 trans former T202 and frequency determining components C203 and R206 through R208 Variable resistor R206 is used to adjust the frequency of the multivibrator to 84 Hz The voltage at the secondary of T202 is recti fied by CR104 and CR105 to produce the positive and negative 15 volt dc operating voltages for the amplifier circuits The same winding furnishes the synchronous demodulator and isolation converter drive signals and is tapped at a higher voltage level to drive the neon lamps DS101 and DS102 These neon lamps provide the drive signal for the photocell modulators V101 and V102 3 2 D Aeg 3 13 INPUT DIVIDER 3 14 The basic full scale sensitivity of the Model 845AR is limited to a maximum of 1 millivolt There fore input signals above this value must be reduced The input divider consists of R101 throug
3. 5AR for maximum on scale deflection 2 11 OPERATION AS A NULL DETECTOR 2 12 The Model 845AR may be used to monitor small voltage differences in bridge circuits potentiometers and other measuring apparatus In most of these appli cations the circuits are adjusted for zero deflection or a null on the Model 845AR Equipment connections for 2 2 various types of null detector configurations are illus trated by Figure 2 2 through 2 4 To operate the Model 845AR as a Null Detector perform the preliminary operations according to paragraph 2 5 and proceed as follows a Select the desired equipment application as illus trated by Figure 2 2 through 2 4 and make the appropriate equipment connections b Place the Model 845AR controls as follows POWER ON OPR ZERO OPR RANGE as desired c Adjust the circuit being measured for zero or a null deflection on the Model 845AR meter Figure 2 2 BRIDGE DETECTOR FLOATING SUPPLY Figure 2 3 BRIDGE DETECTOR HIGH RESISTANCE Figure 2 4 BRIDGE DETECTOR FLOATING NULL DETECTOR 2 13 MEASURING VOLTAGES WITH A STANDARD CELL 2 14 The Model 845AR may be used with a voltage divider and a standard cell to calculate unknown volt ages with a high degree of accuracy Connect the equip ment as illustrated in Figure 2 5 Perform the pre liminary operation as outlined in paragraph 2 5 and proceed as follows a Place the Model 845AR controls as follows POWER ON OP
4. 845AR High Impedence Voltmeter Null Detector Instruction Manual WARRANTY Notwithstanding any provision of any agreement the following warranty is exclusive The JOHN FLUKE MFG CO INC warrants each instrument it manufactures to be free from defects in material and workmanship under normal use and service for the period of 1 year from date of purchase This warranty extends only to the origina purchaser This warranty shall not apply to fuses disposable batteries rechargeable type batteries are warranted for 90 days or any product or parts which have been subject to misuse neglect accident or abnormal conditions of operations In the event of failure of a product covered by this warranty John Fluke Mfg Co Inc will repair and calibrate an instrument returned to an authorized Service Facility within 1 year of the original purchase provided the warrantor s examination discloses to its satisfaction that the product was defective The warrantor may atits option replace the product in lieu of repair With regard to any instrument returned within 1 year of the original purchase said repairs or replacement will be made without charge If the failure has been caused by misuse neglect accident or abnormal conditions of operations repairs will be billed at a nominal cost In such case an estimate will be submitted before work is started if requested THE FOREGOING WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESS OR IMPLI
5. ED INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABILITY FITNESS OR ADEQUACY FOR ANY PARTICULAR PURPOSE OR USE JOHN FLUKE MFG CO INC SHALL NOT BE LIABLE FOR ANY SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES WHETHER IN CONTRACT TORT OR OTHERWISE li any failure occurs the foilowing steps should be taken 4 Notify the JOHN FLUKE MFG CO INC or nearest Service facility giving full details of the difficulty and include the model number type number and serial number On receipt of this information service data or shipping instructions will be forwarded to you 2 On receipt of the shipping instructions forward the instrument transportation prepaid Repairs will be made at the Service Facility and the instrument returned transportation prepaid SHIPPING TO MANUFACTURER FOR REPAIR OR ADJUSTMENT All shipments of JOHN FLUKE MFG CO INC instruments should be made via United Parcel Service or Best Way prepaid The instrument should be shipped in the original packing carton or if it is not available use any suitable container that is rigid and of adequate size If a substitute container is used the instrument should be wrapped in paper and surrounded with at least four inches of excelsior or similar shock absorbing material CLAIM FOR DAMAGE IN SHIPMENT TO ORIGINAL PURCHASER The instrument should be thoroughly inspected immediately upon original delivery to purchaser All material in the container shou
6. ORTING STRIPS ON EDGE CONNECTOR USUALLY PROVIDES COMPLETE PROTECTION TO INSTALLED SS DEVICES HANDL S DEVICES ONLY AT A STATIC FREE WORK STATION ONLY ANTI STATIC TYPE SOLDER SUCKERS SHOULD BE USED ONLY GROUNDED TIP SOLDERING IRONS SHOULD BE USED Anti static bags for storing S S devices or pcbs with these devices on them can be ordered from the John Fluke Mfg Co Ine See section 5in any Fluke technical manual for ordering instructions Use the following pari numbers when ordering these special bags John Fluke Part No Description 463622 6 X 8 Bag 453530 8 X 12 Bag 453548 16 X 24 Bag 454025 12 X 16 Bag Pink Poly Sheet Wrist Strap 30 x60 x60 Mii P N TL6 60 P N RC AS 1200 7 00 20 00 J0089B 07U781G0 SE EN Litho in U S A 845AR SECTION Ii OPERATING INSTRUCTIONS 2 1 RECEIVING INSPECTION 2 5 PRELIMINARY OPERATION 2 2 This instrument has been thoroughly tested and 2 6 Connect the Model 845AR line plug to a 115 volt inspected before being shipped from the factory Im ac power outlet or to 230 volts ac if the instrument is so mediately upon receiving the instrument carefully in wired spect for damage which may have occurred during ship ment If any damage is noted follow the instructions WARNING tlined in th he back of thi A outlined in the warranty page at the back of this manual The round pin on the polarized three prong 2 3 CONTROLS TERMINALS AND INDICATOR plu
7. R ZERO OPR RANGE as desired b Adjust the voltage divider for zero or null deflection on the Model 845AR meter while placing the RANGE switch to successively more sensitive ranges Figure 2 5 STANDARD CELL VOLTAGE MEASUREMENTS 845AR c Calculate the unknown voltage by dividing the standard cell voltage by the final division ratio of the divider 2 15 USE OF ISOLATED OUTPUT 2 16 DC ISOLATION AMPLIFIER 2 17 The Model 845AR may be used as a dc isolation amplifier having a voltage gain of up to 120 db de pending on the settings of the RANGE switch and the OUTPUT LEVEL control To compute the maximum voltage gain on any range of the Model 845AR use the following formula 1 volt maximum isolated output Voltage gain in db 20 log i Range in volts 2 18 RECORDER OUTPUT 2 19 The Model 845AR ISOLATED OUTPUT may be used to provide an output voltage adjustable from zero to one volt for a full scale meter deflection for use with a recorder Since the output is isolated from the input floating measurements can be made without the use of a floating recorder To use the adjustable recorder out put proceed as follows a Connect the recorder to the ISOLATED OUTPUT terminals Note The lower ISOLATED OUTPUT terminal is connected to chassis ground If a ground reference is undesirable remove the jumper wire above R202 on the power supply circuit board Refer to Figure 2 6 for jumper wire location b Turn th
8. RO ACCURACY mith voll anda avb Yeko 3 end scale 0 1 microvolt MAXIMUM NOISE input shorted Range Noise peak peak 0 20 microvolt 0 25 microvolt 0 30 microvolt 1 microvolt 3 microvolt 10 microvolt 1000 volt METER RESPONSE TIME to 90 of reading Range Time 1 microvolt 5 seconds 3 microvolt 3 seconds 10 microvolt 1000 volt 1 1 2 seconds INPUT ISOLATION Better than 1012 ohms at less than 50 relative humidity and 25 C regardless of line chassis or recorder Better than 0 15 microvolt hr better than 0 3 micro NOx hajg pYout day TEMPERATURE COEFFICIENT OF ZERO Less than 0 1 microvolt C from 15 C to 35 C Less than 0 2 microvolt C from 0 C to 50 C ZERO CONTROL RANGE 5 microvolt minimum OVERLOAD PROTECTION Up to 1100 volts de may be applied on any range Typical recovery time is 4 seconds INPUT POWER 115 230 volts ac 410 50 to 440 Hz approximately 3 watts 1 5 ENVIRONMENTAL SPECIFICATIONS OPERATING TEMPERATURE RANGE Within all specifications from 15 C to 35 C t I 845AR Within all specifications from 0 to 50 C except Derate by a factor of two Maximum Noise and Meter Response Time DC Common Mode Rejection Derate by 20 db STORAGE TEMPERATURE RANGE 40 C to 70 C RELATIVE HUMIDITY RANGE 0 to 80 SHOCK VIBRATION Meets 10 Hz to 55 Hz tests of MIL T 945A 1 6 MECHANICAL SPECIFICATIONS MOUNTING Standard EIA relay rack Resilie
9. S TERMINALS AND INDICATOR 2 1 845AR a Place the Model 845AR controls as follows POWER ON RANGE 10 MICROVOLTS OPR ZERO ZERO b Adjust thezero control for an initial zero meter deflection Place the RANGE switch to the 1 MICROVOLT RANGE and re zero with the zero control 2 7 MECHANICAL ZEROING 2 8 It may become nec ssary to adjust the mechani cal zero control of the Model 845AR at more frequent intervals than complete calibration To mechanically zero the instrument proceed as follows a Place the RANGE switch to 1000 VOLTS and the POWER switch to ON b Adjust the mechanical zero adjustment screw for zero meter deflection c Place the RANGE switch to 10 MICROVOLTS and electrically zero the instrument as outlined in paragraph 2 5 d Repeat steps a and b 2 9 OPERATION AS A HIGH IMPEDANCE VOLTMETER 2 10 To operate the Model 845AR as a High Impedance Voltmeter perform the preliminary operations according to paragraph 2 5 and proceed as follows a Place the controls as follows POWER ON OPR ZERO OPR RANGE 1000 VOLTS Mote When measuring voltages in the microvolt ranges use copper wire having low thermal EMF s b Connect the voltage to be measured to the Model 845AR INPUT terminal and connect the common point of the voltage being measured to the COMMON terminal c Deflection of the meter indicates the polarity and magnitude of the measured voltage Increase the sensitivity of the Model 84
10. ctions t Excellent results can be cbtaine twin lead or even lamp cord if sistance is not required Hf shiciding a length of flat braid over the cable For 2 25 HIGH SOURCE IMPEDANCE 2 26 Due to the very high input sensitive Thus a perso static voltage can caus input to the instrument and r flection as a hand app ches the input t Careful shielding will due to charges that may be nals when the OPR ZE appreciable transi to OPR if nothing is connected t t Turning the switch back and charge eliminating the prob impedances the response of the ably slow due to the low pass superimposed noise Howe pass filter is such that commo tremely high while the response t encountered low source impedance 2 4 Also input rI IRO an GROUND JUMPER R WIRE LOCATION OVERLOAD VOLTAGES The instrument is designed to withstand up to 1100 volts peak ac continuously applied the three ingut terminals or between gr ound and any of the three input terminals tting of the RANGE or OPR ZERO er repeated or continuous overloads nthe ranges below 3 millivolts will ion in protective low pass filter is will result in thermal voltages several minutes to subside after the oved ent hag an imer chassis connected inal on the front panel Ordinarily ninal is strapped to the COMMON termi nnected in this way the inner chassis id This greatly improves the lea
11. e recorder on c Proceed as outlined in paragraph 2 9 or 2 11 as desired d Adjust the ISOLATED OUTPUT LEVEL control for the desired output to the recorder This control has a log taper so that smooth control is possible at both high and low settings Note The ISOLATED OUTPUT current capability is 100 microamperes with a 5 kilohm source impedance 2 20 OPERATING NOTES 2 21 SPURIOUS VOLTAGES AND CURRENTS 2 22 Voltage measurements at the microvolt level involve the persistant problems of thermoelectric ef fects These effects may be compensated for by tempo rarily disconnecting the voltage from the circuit under measurement and noting the meter deflection of the 2 3 B45AR se tA eRe NARADA near Model 845AR on the desired r then be subtracted from all sub ments A thorough underst lead to reducing or eliminating 2 23 THERMOELECTRIC VOLTA 2 24 Wa circuit is composed of twa d a net voltage will result if iwo dissi are maintained at different temperaiur moelectric voltages also known couple voltages or Seebeck ve by using metals having iow thermoele and keeping all junctions af the same tem terminals of the Model 84548 are made of gold flashed to prevent tarnish voltages all connections te the Modsi made with pure copper wires Silver solder coated copper also produce sath Timed copper is less satisfactory than si copper coated copper Nickel and ni are not suitable for conne
12. g connects the instrument case to power system ground Use a three to two pin 2 4 The location and function of the front panel adapter when connecting to a two contact controls are described in Figure 2 1 Detailed oper outlet For personnel safety connect the ating descriptions are given in the following para short lead from the adapter to a high quality graphs earth ground METER PR ZERO CONTROLS Indicates the voltage applied ERO Opens input terminals ISOLATED OUTPUT i nd shorts amplifier input allow LEVEL CONTROL Sax ng zeroing of the instrument For full scale meter INPUT AND ith the lower zero control POWER LIGHT deflection this control COMMON TERMINALS PR Instrument is ready for Indicates line allows adjustment of th Provide connection to vol peration as a voltmeter or power is applied isolated output voltage tage being measured ull detector to the instrument from 0 to 1 volt de HH Saree CALAS GUARD TERMINAL S MECHANICAL ZERO This terminal is usually strapped to the common terminal Screwdriver adjustment used The terminal is connected directly to an inner chassis o set the meter to zero ovide connection to shield By removing the strap a guard potential equal an external recorder to the common terminal potential may be applied to the guard terminal shunting the leakage current from the ANGE CONTROL common terminal to ground Provides selection of the desired full scale sensitivity Figure 2 1 CONTROL
13. h R109 and RANGE switch S101A On ranges being a multiple of 1 input voltages above 1 millivolt are divided down to 1 millivolt or less upon selection of the proper range On ranges being a multiple of 3 input voltages above 1 millivolt are divided down to 300 microvolts or less upon selection of the proper range On ranges of 1 millivolt and below a 10 megohm resistor R104 is connected across the input to provide a fixed value of input impedance 3 15 AC AMPLIFIER 3 16 The input signal from the input divider is filtered by a three stage low pass filter composed of R110 C101 R111 C102 R112 and C103 This filter re duces any ac voltage having a frequency above 1 Hz The filtered dc voltage is then square wave modulated by photocell modulators V101 and V102 which are driven by DS101 and DS102 The resulting square wave signal is coupled through C104 and amplified by Q101 Q102 and Q103 which form a three stage amplifier having a high input impedance The gain of the ac am plifier is controlled by the common emitter resistance selected by the RANGE switch S101B Maximum gain is used on the 1 3 10 and 30 microvolt ranges and is gradually reduced by the selection of R124 through R126 as the range is increased The output of Q103 is ca patitively coupled to a two stage current amplifier composed of Q104 and Q105 The current amplifiers have a constant gain controlled by fixed negative feed back through R130 and C111 3 18
14. ignal 3 the isolation converter which produces th Ineter and iso lated recorder output The entire amplifier and the secondaries of both transformers are surrounded by a guard shield which permits the use of external guard voltages 3 6 The ac amplifier is a high impedance amplifier whose gain is controlled by the resistance selected by the RANGE control The amplified v signal is then detected by the synchronous demodulator 3 7 The synchronous demodulator is driven by the 84 Hz reference signal and detects the amplified dee signal The detected a Signal is then amplified by a de amplifier whose gain is controlled by fixed feed back The output signal of the dc amplifier is applied to the isolation converter which drives the isolated re corder output and the meter which indicate the polarity and magnitude of the measured voltage This same de 4c signal is also fed back to the input of the ac amplifier to control overall amplifier gain The feedback ratio is determined by the setting of the RANGE control and allows overall amplifier gain to be precisely controlled 3 8 CIRCUIT DESCRIPTION 3 9 POWER SUPPLY 3 10 Input power transformer T201 receives 115 volts ac or 230 volts ac if the instrument is so wired through the power switch S1 The primary winding of T201 is constructed in such a manner as to utilize either 115 volts ac input windings parallel or 230 volts ac wind ings in series Fuse F1 protects
15. kage ground and the common mode rejection the inner chassis is available at the t may be driven at the same voltage ION terminal This further increases the nce and common mode rejection by about he voltage used to drive the GUARD termi should be obtained from a separate source or by fa voltage divider connected directly across drops across impedances in the circuit under meagurement 2 31 INCREASING INPUT RESISTANCE 2 88 Inthe 1 microvolt to 1 millivolt ranges a 40 megohim resietor is connected directly across the input of the instrument The input resistance may Hin in creased oa these ranges by disconnecting the 46 meg ohm resistor where it attaches to the RANGE switch However the input resistance will no longer be well defined Typical input resistances with the 1 imegohm noved are as follows Input Resistance 300 megohms 1 000 megohms 3 000 megohms 10 000 megohms PAY Riles f j 7 j 845AR SECTION IH THEORY OF OPERATION 3 1 INTRODUCTION 3 2 The Model 845AR High Impedance Voltmeter Null Detector theory of operation is contained in this section of the manual A block diagram is illustrated in Figure 3 1 and a functional schematic diagram is located at the end of Section V The block diagram and functional schematic diagram are to be used as an aid in understanding circuit theory and in troubleshooting 3 3 BLOCK DIAGRAM ANALYSIS 3 4 The M
16. l to occur The resulting modulated 845AR signal is coupled to the secondary of T203 where tran sistors Q203 and Q204 demodulate secondary signals occuring at their 84 Hz base signal rate Capacitor C204 charges to the peak of the demodulated signal and discharges through the OUTPUT LEVEL control R1 R211 through R213 and the meter M1 The meter M1 indicates the polarity and magnitude of the input voltage Capacitor C3 and resistor R2 filter the resulting dc out put voltage for the recorder output 3 3
17. ld be checked against the enclosed packing list The manufacturer will not be responsible for shortages against the packing sheet unless notified immediately If the instrument is damaged in any way a claim should be filed with the carrier immediately To obtain a quotation to repair shipment damage contact the nearest Fiuke Technical Center Final claim and negotiations with the carrier must be completed by the customer The JOHN FLUKE MFG CO INC will be happy to answer all applications or use questions which will enhance your use of this instrument Please address your requests or correspondence to JOHN FLUKE MFG CO INC P O BOX 43210 MOUNTLAKE TERRACE WASHINGTON 98043 ATTN Sales Dept For European Customers Fluke Holland B V P O Box 5053 5004 EB Tilburg The Netherlands For European customers Air Freight prepaid John Fluke Mfg Co Inc P O Box 43210 Mountlake Terrace Washington 98043 Rev 4 80 845AR SECTION I INTRODUCTION AND SPECIFICATIONS 1 1 INTRODUCTION 1 2 The Fluke Model 845AR High Impedance Volt meter Null Detector allows measurement of de voltages from one microvolt to 1000 volts de in 19 ranges When used as a null detector on the 100 millivolt range and below the input impedance is an excellent 19 megohms A linear recorder output allows the instrument to be used for production testing and also as a de amplifier with a maximum gain of 120 db 1 3 The instrument may be wired to
18. nt feet provided for bench use WEIGHT 9 pounds Meets hammer blow requirements of MIL T 945A and SIZE MIL S 901B 3 47 inches high x 19 inches wide x 8 26 inches deep 19 00 14 875 Figure 1 1 MODEL 845AR OUTLINE DRAWING static awareness A Message From John Fluke Mig Co Inc Some semiconductors and custom IC s can be damaged by electrostatic discharge during handling This notice explains how you can minimize the chances of destroying such devices by 1 Knowing that there is a problem 2 Learning the guidelines for handling them 3 Using the procedures and packaging and bench techniques that are recommended The Static Sensitive S S devices are identifiedin the Fluke technical manual parts list with the symbol The following practices should be followed to minimize damage to S S devices 3 DISCHARGE PERSONAL STATIC BEFORE HANDLING DEVICES 1 MINIMIZE HANDLING 2 KEEP PARTS IN ORIGINAL CONTAINERS UNTIL READY FOR USE 4 HANDLE 5 5 DEVICES BY THE BODY Page 1 of 2 5 USE ANTI STATIC CONTAINERS FOR HANDLING AND TRANSPORT 7 AVOID PLASTIC VINYL AND STYROFOAM IN WORK AREA PORTIONS REPRINTED WITH PERMISSION FROM TEKTRONIX INC AND GENERAL DYNAMICS POMONA DIV Dow Chemical Page 2 of 2 WHEN REMOVING PLUG IN ASSEMBLIES HANDLE ONLY BY NON CONDUCTIVE EDGES AND NEVER TOUCH OPEN EDGE CONNECTOR EXCEPT AT STATIC FREE WORK STATION PLACING SH
19. odel 845AR is a photo chopper stabilized amplifier with the overall gain of the amplifier being RECTIFIER LINE POWER AND FILTER 84 HERTZ precisely controlled by negative feedback The instru ment s main circuits are an input range divider a photocell modulator an ac amplifier a synchronous demodulator a dc amplifier a meter an isolation converter a neon drive an 84 Hz multivibrator a supply rectifier and a rectifier filter 3 5 The input range divider provides a fixed input impedance to signals of less than 1 millivolt while al lowing reduction of input signals above i millivolt Photochoppers modulate the input signal to the ac am plifier at 84 Hz The drive signal for the photo modu lator is provided by the neon drive which is composed of neon lamps driven alternately at 84 Hz by the 84 Hz MULTIVIBRATOR 3 r NEON SUPPLY DRIVE RECTIFIERS SYNCHRONOUS DEMODULATOR afv sv INPUT RANGE DIVIDER NEGATIVE FEEDBACK RECORDER OUTPUT GUARD SHIELD Figure 3 1 MODEL 845AR BLOCK DIAGRAM 3 1 845AR a a multivibrator Eighty four Hz is used to provide the Model 845 with an operating frequency asynchronous with the power line frequency and its harmonics The 84 Hz multivibrator also drives the following circuits 1 the supply rectifiers which provide operating volt ages for the amplifiers 2 the synchronous demodu lator which demodulates the amplified d s
20. operate from a line power source of 115 volts ac or 230 volts ac as desired The instrument is designed to be mounted directly in a standard EIA 19 inch relay rack Resilient feet are also provided for bench top use 1 4 ELECTRICAL SPECIFICATIONS INPUT VOLTAGE RANGE 1 microvolt to 1000 volts de end scale in nineteen ranges using X1 and X3 progression INPUT RESISTANCE 100 megohms on 300 millivolt range and abovef 10 meg Wy grounding Better than 1010 ohms up to 80 relative humidity and 35 C With driven guard isolation im proves by at least one order of magnitude up to 1013 ohms Any input terminal may be floated 1100 volts off chassis ground iy DC COMMON MODE REJECTION Better than 160 db input short circuited 80 relative humidity better than 140 db open circuited 50 rela tive humidity better than 120 db open circuited 80 relative humidity AC COMMON MODE REJECTION below 100 kHz 100 volts rms or 120 db greater than end scale which ever is less will effect reading less than 2 of end scale Input open circuited AC NORMAL MODE REJECTION 60 Hz and above AC voltages 60 db above end scale will effect reading less than 2 of end scale Maximum voltage not to ex ceed 750 volts rms RECORDER OUTPUT 0 1 volt one side at chassis ground linear to 0 5 of end scale Source impedance 5k to 7 5k ohms on 100 millivolt raage and below Vesbuy RASE JOO WAKO Fame Mea ghwi ow VWeSTABILITY OF ZE
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