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.

Wearable microfluidics: fabric-based digital droplet flowmetry for perspiration analysis

Here we show for the first time a wearable microfluidic platform, named as digital droplet flowmetry (DDF), implemented on all-textile materials for real-time measurement of perspiration rates, via converting continuous flow into discrete droplets with identical volumes and assessing the flow rates by an electronic counting circuitry.

A Fringe Signal Processing Method With Multi-Sample Zero-Crossing Detection Based on DSP and its Application in Absolute Gravimeters

The absolute gravitation acceleration (g) is generally measured by observation of a free-falling test mass in a vacuum chamber based on laser interference. Usually the free-falling object trajectory is obtained by timing the zero-crossings of the interference fringe signal. A traditional way to time the zero-crossings is electronic counting method, of which the resolution is limited in principle. In this paper, a fringe signal processing method with multi-sample zero-crossing detection based on Digital Signal Processor (DSP) is proposed and realized for the application in absolute gravimeters. The principle and design of the fringe signal processing method are introduced. The measuring precision is evaluated both theoretically and from numerical software simulations with MATLAB®, and verified by hardware simulated free-falling experiments. The results show that the absolute error of the gravity acceleration measurement introduced by the fringe signal processing method is less than 0.5 μGal (1 μGal = 1×10−8 m/s2), and the impact on the standard deviation is about 2 μGal. This method can effectively reduce the systematic error of the traditional electronic counting method, and satisfy the requirements for precision and portability, especially for field ready absolute gravimeters.