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

Table of Contents
Contents
Section 1:Introduction to Stopwatch and Timer Calibrations.......................1
1.A. The Units of Time Interval and Frequency..............................1
1.B. A Brief Overview of Calibrations............................................4
1.C. Traceability and Coordinated Universal Time (UTC).............5
Section 2: Description of Timing Devices that Require Calibration............9
2.A. Stopwatches............................................................................9
2.B. Timers....................................................................................14
2.C. Commercial Timing Devices.................................................15
Section 3: Specifications and Tolerances ....................................................17
3.A. Interpreting Manufacturer’s Specifications............................17
3.B. Tolerances Required for Legal Metrology..............................22
Section 4: Introduction to Calibration Methods..........................................25
Section 5: The Direct Comparison Method.................................................27
5.A. References for the Direct Comparison Method......................27
5.B. Calibration Procedure for Direct Comparison Method...........31
5.C. Uncertainties of Direct Comparison Method.........................33
Section 6: The Totalize Method...................................................................41
6.A. Calibration Procedure for the Totalize Method......................41
6.B. Uncertainties of Totalize Method...........................................43
6.C. Photo Totalize Method...........................................................47
Section 7: The Time Base Method...............................................................51
7.A. References for the Time Base Method....................................51
7.B. Calibration Procedure for the Time Base Method...................51
7.C. Uncertainties of Time Base Method .......................................56
Section 8: How to Determine if the Calibration Method Meets the Required
Uncertainty..................................................................................57
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