A wide-range fully-automatic digital voltmeter

The requirements which led to the development of a digital voltmeter are discussed and various possible systems are considered. The reasons for choosing the present system are given. The potentiometer network and reference supply, the transistorized comparator and difference amplifier, and the selector switch control circuitry are described. The voltmeter has an input impedance of 10M¿ and automatic polarity and range selection. It reads to 3 digits with an accuracy of ±1 digit over the range 10 mV to 1000 V.