Determination of very small changes in rate over intervals of several days in mechanical timepieces

Abstract

A device for automatically plotting the isochronism of a clock or watch is described. It was developed to assist in precision tests on marine chronometers and watches, but it may be altered without difficulty to plot the curves for any timepiece. Its accuracy is 0.01 second, which is sufficient for ordinary timepieces, but by a few simple changes this accuracy may be increased. Some of the curves plotted by this instrument are shown. The sensitivity of this instrument, as well as its graphic scale, may be varied depending upon the quality of the timepiece being tested.