Spiral Chronograph for Measurement of Single Millisecond Time Intervals with Microsecond Accuracy

Abstract

A chronograph is described which measures time intervals up to 2000 microseconds with an error not exceeding one microsecond. The chronograph traces a spiral on a cathode-ray tube at a known constant angular velocity; the spiral trace starts with the reception of an electrical pulse marking the beginning of the time interval and stops with the reception of a second pulse marking the ending of the interval so that the number of revolutions in the spiral is a direct measure of the time interval. The cathode-ray tube screen is of long persistence so that an immediate measurement of the time interval, as well as a photographic record, is obtained. Measurements may be made as rapidly as one every 30 seconds. A circuit used in conjunction with the chronograph selects the beginning of a slowly rising pulse, sharpens the pulse to one rising in about 0.2 microsecond, and blocks all subsequent pulses from the chronograph until reset manually.