Calibration of the Plants for Verification of Stopwatchs

The method of calibration of plants for verification of stopwatches with the help of the electronic-counting CNT-90 frequency meter is presented. The measurement circuits for verification (calibration) of reference plants for verification (calibration) of stopwatches are given. The device for synchronous start, which is based on the transformation of the motion signal of the moving part of the plant into an electrical signal of direct current using optical sensors, is used in the measuring circuit for calibration plants of mechanical stopwatches, and, the device for synchronous start, which is based on the transformation of the audio signal of an electronic stopwatch into an electrical signal of direct current using microphone, is used in the measuring circuit for calibration plants of electronic stopwatches. An example of the applying of the CNT-90 electronic frequency counter software is provided, which allows you to calculate the verification and calibration results (rejections the measurements of time and instability indexes) in the automatic mode. The calibration model and uncertainty budget for calibration of stopwatches are presented. The components of Type A and B, in accordance with calibration model are recorded when calculating the combined standard uncertainty in the form of standard uncertainties. The components of Type B: standard uncertainty due to the electronic counting frequency meter readings from the nominal value is taken from the calibration certificate of the frequency meter; standard uncertainty due to the drift of an electron-counting frequency meter since its last calibration; standard uncertainty due to the discreteness of indications of the plant indicator; standard uncertainty due to the effect of the device for synchronous start. The method of verification and calibration of installations for verification (calibration) of stopwatches, which are describe in the article, can be used in scientific metrological institutions, state enterprises, metrological services of state bodies, by enterprises and organizations, conformity assessment bodies of measuring instruments and in any other laboratories which have appropriate equipment and required standards.