Fluke 845AR Level Meter
High Impedence Voltmeter Null Detector


The Fluke Model 845AR High Impedance Voltmeter-Null Detector allows measurement of dc voltages from one microvolt to 1000 volts dc in 19 ranges. When used as a null detector on the 100 millivoltrange and below, the input impedance is an excellent l$s megohms A linear recorder output allows the instrument to be used for production testing, and also as a dc Amplifier with a maximum gain of 120 db. The instrument may be wired to 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 dc end scale in nineteen ranges, using XI and X3 progression. INPUT RESISTANCE 100 megohms on 300 millivolt range and above 10 megohms on 1OO-millivolt range and below. ACCURACY ±(3% end scale + 0.1 microvolt). MAXIMUM NOISE (input shorted) Range Noise (peak-peak) 1 microvolt 0.20 microvolt 3 microvolt 0. 25 microvolt 10 microvolt - 1000 volt 0.30 microvolt 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 10*2 ohms at less than 50% relative humidity and 25°C regardless of line, chassis, or recorder grounding. Better than 1010 ohms up to 80% relative humidity and 35°C. With driven guard, isolation improves by at least one order of magnitude up to 1013 ohms. Any input terminal may be floated 1100 volts off chassis ground. DC COMMON MODE REJECTION Better than 160 db, input short-circuited, 80% relative humidity; better than 140 db, open-circuited, 50% relative 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, whichever 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 exceed 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. Stability of zero Better than 0.15 microvolt/hr, better than 0. 3 microvolt/day. TEMPERATURE COEFFICIENT OF ZERO Less than 0.1 microvolt/0C from 15° C to 35° C. Less than 0. 2 microvolt/0 C from 0°C to 50° C. ZERO CONTROL RANGE ±5 microvolt minimum. OVERLOAD PROTECTION Up to 1100 volts dc may be applied on any range. Typical recovery time is 4 seconds. INPUT POWER 115/230 volts ac ±10%, 50 to 440 Hz, approximately 3 watts.

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User Manual
Manual type:
User Manual
1.57 Mbytes (1647780 Bytes)
Manual ID:
P/N 294181
01 April 1980
Scanned document, all readable.
Upload date:
10 August 2017


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