Stopwatch and Timer Calibrations - National Institute of Standards ...

Stopwatch and Timer Calibrations
To begin the measurement, start the stopwatch and manually open the gate of
the counter at the same time. One way to do this is by rapidly pressing the startstop
button of the stopwatch against the start button on the counter (Figure 14).
Another method is to press the start/stop button of the stopwatch with one hand
and simultaneously pressing the start/stop button of the counter. After a suitable
period of time (determined by the calibration requirements of the stopwatch or
timer being calibrated), use the same method to simultaneously stop the stopwatch
and close the gate of the counter.
Figure 14. Using the start-stop button of the stopwatch to start the counter.
Once the counter and stopwatch are stopped, compare the two readings. Use the
equation t/T to get the results, where t is the difference between the counter
and stopwatch displays, and T is the length of the measurement run. For example,
if t = 100 ms and T = 1 hour, the time uncertainty is 0.1 s / 3600 s or roughly
2.8 10 -5 (0.0028 %).
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