The Reproduction and Measurement of Very Short Intervals of Time
John Coulson · Physical Review · 1914
TT is often found desirable to have at one's disposal some means by -^ which two neighboring electric circuits can be broken in quick succession in such a way that the interval between these two operations is accurately predictable and under the control of the experimenter.This paper contains a brief description of a simple apparatus which can be made to give time intervals of very short duration.This work was suggested to the writer by Professor B. O. Peirce, to whom it was of much interest, since he required in his investigation of the dielectric constants of certain materials, a shorter time interval than was attainable, with accuracy, by any known apparatus.The many devices then in use either gave intervals much longer than would serve, or intervals which could not be repeated with a sufficient degree of accuracy.The measurement of very short intervals of time is a matter of but little difficulty.More than sixty years ago Helmholtz 1 used in his investigation " Sur la vitesse de propagation de P agent nerveux dans les nerfs rachidiens," a horizontal magnetic pendulum for determining the duration of an electric impulse.The apparatus was of the form of a Thompson galvanometer, and the angular deviation of the magnet from its position of rest was taken as a measure of the duration of the electric impulse sent through the galvanometer.The behavior of such swinging magnets had been studied by Gauss and W. Weber 2 while making their magnetic measurements at Gottingen.Of the many methods used by later investigators for measuring such intervals, perhaps the best is by determining either the partial discharge from a loaded condenser, 3 when short-circuited during the interval in question through a given non-inductive resistance, or the fractional part 1