A digital peak voltmeter is described which determines the unknown voltage by comparing it with each of 100 known constant voltages in turn. Each constant voltage exceeds its predecessor by a fixed amount. Despite the large number of reference voltages employed, only ten comparators are used. The reading of the voltmeter is displayed until the instrument is reset. The voltmeter's accuracy is 1%. The reading is available in simple decimal form or in binary coded decimal form, which facilitates the preparation of computer paper tape. The instrument can also be used to measure time intervals. However, there is a lower limit of 13 mu s which is determined by the time required to make the necessary comparisons and an upper limit of 1s which results from finite leakage associated with certain components. With the addition of a simple oscillator the voltmeter could be used to monitor a continuous direct voltage or the peak value of an alternating voltage. The oscillator would serve to reset the instrument and to operate a relay connecting the unknown signal to the voltmeter's input. The measurement could be carried out with sampling rates in the order of 100 kHz.