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

The Totalize Method
6.C. Photo Totalize Method
An alternative measurement technique to the totalize method previously discussed
involves using a high speed camera (digital or film type). The equipment is set up
in the same manner as in Section 6.A. In this method, both the stopwatch being
calibrated and the universal counter are started in no particular order. When
both instruments are counting, a photo is taken of the two instruments. Under
appropriate shutter and lighting conditions, the resulting photo will clearly show
the time displayed on both the stopwatch and counter. Both readings are recorded
as the initial measurements in the calibration. After an appropriate amount of time
has elapsed, a second photo is taken and the displays are recorded as the closing
measurements. The difference in elapsed time for the stopwatch is compared to
the difference in elapsed time for the counter to determine the measured offset
of the stopwatch.
Figure 17 shows that the initial counter reading is 53.980 s and the stopwatch
is at 57.52 s. Figure 18 shows that the counter reading is 82.049 s and the
stopwatch is at 1 minute 26.18 s (86.18 s). The elapsed time on the counter is
82.049 – 53.980 = 28.069 s, and likewise the elapsed time on the stopwatch is
86.18 – 57.52 = 28.66 s. This would indicate that over the 28 s interval, the
stopwatch was in error by 0.59 s or approximately 1820 s per day.
Figure 17. Photo totalize start reading.
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