Stopwatch and Timer Calibrations - National Institute of Standards ...
Stopwatch and Timer Calibrations - National Institute of Standards ...
Stopwatch and Timer Calibrations - National Institute of Standards ...
- No tags were found...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Description <strong>of</strong> Timing Devices <br />
Section 2<br />
Description <strong>of</strong> Timing Devices that Require Calibration<br />
This section describes the various types <strong>of</strong> stopwatches (Section 2.A. <strong>Stopwatch</strong>es)<br />
<strong>and</strong> timers (Section 2.B. <strong>Timer</strong>s) that are calibrated in the laboratory. These<br />
types <strong>of</strong> stopwatches <strong>and</strong> timers are <strong>of</strong>ten used as transfer st<strong>and</strong>ards to perform<br />
field calibrations <strong>of</strong> the commercial timing devices described in Section 2.C.<br />
2.A. <strong>Stopwatch</strong>es<br />
<strong>Stopwatch</strong>es can be classified into two categories, Type I <strong>and</strong> Type II [5]. Type<br />
I stopwatches have a digital design employing quartz oscillators <strong>and</strong> electronic<br />
circuitry to measure time intervals (Figure 2). Type II stopwatches have an<br />
analog design <strong>and</strong> use mechanical mechanisms to measure time intervals (Figure<br />
3). The key elements <strong>of</strong> Type I <strong>and</strong> Type II stopwatches are summarized in<br />
Table 3.<br />
Table 3 - Type I <strong>and</strong> Type II stopwatch characteristics.<br />
Description<br />
Operating principle<br />
Time base<br />
Case<br />
Crystal<br />
Minimum time interval<br />
Type I <strong>Stopwatch</strong><br />
(digital)<br />
Time measured by division<br />
<strong>of</strong> time base oscillator<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
Quartz oscillator<br />
Corrosion resistant metal<br />
Impact resistant plastic<br />
Protects display<br />
Allows for proper<br />
viewing<br />
May be tinted<br />
May employ<br />
magnification<br />
48 hours without<br />
replacement <strong>of</strong><br />
battery<br />
Type II <strong>Stopwatch</strong><br />
(analog)<br />
Time measured by<br />
mechanical movement<br />
Mechanical<br />
mainspring<br />
Synchronous<br />
motor, electrically<br />
driven<br />
<br />
<br />
<br />
<br />
Protects dial/h<strong>and</strong>s<br />
Allows for proper<br />
viewing<br />
Must be clear <strong>and</strong><br />
untinted<br />
3 hours without<br />
rewinding<br />
9