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High Impedance Voltmeter and Null Detector
Manufacturer: Fluke
Model: 845AB
Description
A sensitive high impedance DC voltmeter and null detector.
Specifications
Input Range | 1 µV-1000V DC |
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Accuracy | ± (2%end scale + 1 µV) |
Input Resistance |
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300 mV range and above: | 100 M Ohms |
100 mV range and below: | 10 M Ohms |
Maximum meter noise |
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1 µV range: | 0.20 µV |
3 µV range: | 0.25 µV |
Other ranges: | 0.20 µV |
Meter response time (to 90% of reading) |
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1 µV range: | 5 seconds |
3 µV range: | 3 seconds |
Other ranges: | 1-1/2 seconds |
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Operating Instructions
Preliminary
- Turn Power to LINE OPR
- Turn RANGE to 1000V
- Adjust the mechnical zero adjustment screw for zero deflection.
- Turn RANGE to 10 MICROVOLTS
- Turn the OPR switch so the line on the knob points towards ZERO.
- Adjust the ZERO control for an initial zero meter deflection.
- Place the RANGE switch to 1 MICROVOLT.
- Re-zero with the ZERO control.
- Repeat steps 2 through 8 until the instrument is zeroed.
Operation as a voltmeter
- Turn POWER to LINE OPR>
- Turn OPR to OPR.
- Turn RANGE to 1000 Volts.
- Connect voltage to be measured to the INPUT terminal, and the common point of the voltage to the COMMON terminal.
- Increase the sensitivity for maximum on-scale deflection.
Operation as a null detector: Consult the manufacturer's manual.
Note:
When measuring voltages in the microvolt range, use copper wire having low thermal emf's.
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keywords: voltmeter, voltage measurement device, voltage measurement device, electrical measurement device.
Document created June, 1996. Original author: David Harrison.