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

Description of Timing Devices
One type of timer used extensively in industry is the process control timer. As
their name implies, process control timers measure or control the duration of a
specific process. For example, when a product is made, it may need to be heat
treated for a specific length of time. In an automated manufacturing system, the
process control timer determines the length of time that the item is heated. In
some applications, such as integrated circuit manufacturing, the timing process
can be critical for proper operation.
Process control timers are also used in many different types of laboratory
environments. Calibration laboratories use timers to calibrate devices such as
radiation detectors, by regulating the amount of time that the device is exposed to
the radiation source. The uncertainty in the time of exposure directly influences
the overall measurement uncertainty assigned to the detector calibration.
Timers are also used in the medical field. For example, medical laboratories use
process control timers when specimen cultures are grown. Hospitals use timers to
regulate the amount of medication given to patients intravenously.
2.C. Commercial Timing Devices
Many types of timing devices are used every day in commercial applications.
Parking meters, automatic car wash facilities, taxicab meters, and commercial
parking lots are examples of entities that either charge a certain amount for a
specified period, or provide a certain period of service for a specified amount of
money.
The calibration requirements and allowable tolerances for these devices are
usually determined on a state-by-state basis by state law, or locally by city or
municipality ordinances. The allowable uncertainties are often 1 % or larger.
Generic guidance is provided in Section 3.
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