The Fluke Model 845 High Impedance Voltmeter-Null Detector allows measurement of dc voltages from one microvolt to 1000 volts dc inl9 ranges. When used as a null detector on the 100 millivolt range and below, the input impedance is 10 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. 1-3. The instrument consists of the line powered Model 845A, and the line-battery-powered Model 845AB. The instruments are half-rack in size, and are equipped with resilient feet and a tilt-up bail for field or bench use. A single instrument may be mounted in a standard 19 inch rack by means of metal handle rack adapter kit 881A-102. Two instruments may be mounted side-by-side in a standard 19 inch rack by means of metal handle rack adapter kit 881A-1Q3. 1-4. ELECTRICAL SPECIFICATIONS INPUT VOLTAGE RANGE 1 microvolt to 1000 volt dc end scale in nineteen ranges, using XI and X3 progression. INPUT RESISTANCE 100 megohms on 300 millivolt range and above. 10 megohms on 100 millivolt range and below. ACCURACY ±(2% end scale •+ 0.1 microvolt), MAXIMUM METER NOISE (Input Shorted) RANGE NOISE (peak-to-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