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

More documents

Recommendations

Info

Stopwatch and Timer Calibrations 12 Figure 4. Interior of digital (Type I) stopwatch. 2.A.1.b. Mechanical (Type II) Stopwatches In a traditional mechanical stopwatch, the power source is a helical coil spring, which stores energy from the winding of the spring. The time base is usually a balance wheel that functions as a torsion pendulum. The rate at which the spring unwinds is governed by the balance wheel, which is designed to provide a consistent period of oscillation relatively independent of factors such as friction, operating temperature, and orientation. In most mechanical stopwatches, the balance wheel is designed to oscillate at 2.5 periods per second, which produces 5 “ticks” or beats per second. The balance wheel is connected to an escapement that meters the unwinding of the coil spring and provides impulses that keep the balance wheel moving. It is this metered unwinding of the coil spring that drives the counter indicator. In this type of device, the counter is composed of a gear train that divides the speed of rotation of the escapement wheel to the appropriate revolution speed for the second, minute, and hour hands. The time interval from the counter is displayed either on a face across which the second and minutes hands sweep, or on a series of numbered drums or discs that indicate the elapsed time (Figure 5) [6].
Description of Timing Devices Figure 5. Inner workings of a mechanical (Type II) stopwatch or timer. 13
Page 1: NIST Recommended Practice Guide Sto
Page 4 and 5: Certain equipment, instruments or m
Page 7: Acknowledgements ACKNOWLEDGEMENTS
Page 10 and 11: Stopwatch and Timer Calibrations Se
Page 12 and 13: Stopwatch and Timer Calibrations Li
Page 15 and 16: Section 1 Introduction to Stopwatch
Page 17 and 18: Introduction s or 42.13 s, but tha
Page 19 and 20: Introduction basic principles that
Page 21 and 22: Introduction and their traceabilit
Page 23 and 24: Description of Timing Devices Sect
Page 25: Description of Timing Devices Figu
Page 29: Description of Timing Devices One
Page 32 and 33: Stopwatch and Timer Calibrations
Page 34 and 35: Stopwatch and Timer Calibrations a
Page 36 and 37: Stopwatch and Timer Calibrations 3.
Page 38 and 39: Stopwatch and Timer Calibrations 3.
Page 41 and 42: The Direct Comparison Method Secti
Page 43 and 44: The Direct Comparison Method Pleas
Page 45 and 46: The Direct Comparison Method uncer
Page 47 and 48: The Direct Comparison Method the u
Page 49 and 50: The Direct Comparison Method path,
Page 51 and 52: The Direct Comparison Method When
Page 53: The Direct Comparison Method Table
Page 56 and 57: Stopwatch and Timer Calibrations To
Page 58 and 59: Stopwatch and Timer Calibrations Fi
Page 60 and 61: Stopwatch and Timer Calibrations di
Page 62 and 63: Stopwatch and Timer Calibrations Fi
Page 65 and 66: The Time Base Method Section 7 The
Page 67 and 68: The Time Base Method effectively t
Page 69 and 70: The Time Base Method 7.B.2. Using
Page 71 and 72: Required Uncertainty Section 8 How
Page 73 and 74: Other Topics Related to Measurement
Page 75 and 76: Other Topics Related to Measurement
Page 77:
Other Topics Related to Measurement
Page 80 and 81:
Stopwatch and Timer Calibrations Fi
Page 82:
Stopwatch and Timer Calibrations [1
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?