Practical Physics is a free textbook on basic laboratory physics. See the editorial for more information.... 
Home Measurement of the More Simple Quantities Time Rating a Watch by means of a SecondsClock  
Search the VIAS Library  Index  
Rating a Watch by means of a SecondsClock
The problem consists in determining, within a fraction of a second, the time indicated by the watch at the two instants denoted by two beats of the clock with a known interval between them. It will be noticed that the secondsfinger of the clock remains stationary during the greater part of each second, and then rather suddenly moves on to the next point of its dial. Our object is to determine to a fraction of a second the time at which it just completes one of its journeys.
We can thus compare to within ^{1}/_{4} sec. the time as indicated by the clock and the watch, and if this process be repeated after the lapse of half an hour, the time indicated by the watch can be again compared, and the amount gained or lost during the halfhour determined. It will require a little practice to be able to count along with the watch. During the interval we may find the number of ticks per second of the watch. To do this we must count the number of beats during a minute as indicated on the clock. There being 4 or 5 ticks per second, this will be a difficult operation if we simply count along the whole way; it is therefore better to count along in groups of either two or four, which can generally be recognised, and mark down a stroke on a sheet of paper for every group completed; then at the end of the minute count up the number of strokes; we can thus by multiplying, by 2 or 4 as the case may be, obtain the number of watchticks in the minute, and hence arrive at the number per second. Experiment  Determine the number of beats per second made by the watch, and the rate at which it is losing or gaining. Enter results thus:  No. of watchticks per minute: 100 groups of 3 each No. of ticks per second: 5 hr. m. s. Clockreading: 11 38 3 Estimated watchreading, 11 hr. 34 m. and 10 ticks: 11 34 2 Difference: 4 1 Clockreading: 12 8 3 Estimated watchreading, 12 hr. 4m. and 6 ticks: 12 4 1.2 Difference: 4 1.8 Losing rate of watch, 1.6 sec. per hour.


Home Measurement of the More Simple Quantities Time Rating a Watch by means of a SecondsClock 