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

Stopwatch and Timer Calibrations
a stopwatch that is accurate to 0.0003 % (although not stated, it is assumed that
this percentage has been stated as a percent of reading or relative accuracy).
To compute the time accuracy for a 24 h measurement, we simply multiply the
relative accuracy by the measurement period:
0.0003 % 24 h 0.000 072 h 0.2592 s .
This computation shows that this stopwatch is capable of measuring a 24-hour
interval with an accuracy of about 0.26 s. However, it is again important to
note that when measuring small time intervals, the resolution uncertainty of the
stopwatch must be considered. For example, if the stopwatch in Figure 8 is used
to measure a time interval of 5 s, the computed accuracy is much smaller than the
resolution of the stopwatch:
Timer: 9 hours, 59 minutes, 59 seconds,
99 hundredths.
Stopwatch: Single-action timing: timein/time-out;
continuous timing; cumulative
split, interval split and eight
memories. Triple display shows cumulative
splits, interval splits and running
time simultaneously.
Features: Captures and stores up to
eight separate times. After timed event is
complete, stopwatch displays information
in its memory. Counter box show
number of split times taken. Solid-state
design with an accuracy of 0.0003 %.
Durable, water-resistant construction
makes stopwatch suitable for field use
(operates in temperature from 1° to 59° C
[33° to 138° F]). With triple line LDC: top
two lines are each 1/8 in. high (3.2 mm);
third line is ¼ in. high (6 mm).
0.0003 % 5 s 0.000 015 s .
20
Figure 8. Sample specifi cations for a digital stopwatch (Example 2).