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

Specifications and Tolerances
3.A.3. Typical Performance
During the NIST centennial celebration of 2001, an exhibit at the NIST laboratories
in Boulder, Colorado, allowed visitors to measure the time base accuracy of their
quartz wristwatches. Over 300 wristwatches were tested. Nearly all quartz
wristwatches contain a 32 768 Hz time base oscillator, the same technology
employed by a Type I digital stopwatch. The results of these measurements,
showing the loss or gain in seconds per day for the watches, are summarized in
Figure 9, and give some idea of the typical performance of a quartz stopwatch
or timer. Roughly 70 % of the watches were able to keep time to within 1 s per
day or better, a relative accuracy of approximately 0.001 % (1 10 -5 ). About 12
% had a relative accuracy larger than 5 s per day, or larger than 0.005 %. It is
interesting to note that nearly all of the watches in this study gained time, rather
than lost time; and were presumably designed that way to help prevent people
from being late. This characteristic will not necessarily apply to stopwatches and
timers.
Quartz Wristwatch Performance
Figure 9. Typical performance of quartz wristwatches using 32 768 Hz time
base oscillators.
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