Evaluation of the type a uncertainty caused by simultaneous influence of random noise and power line interference

The paper presents the type A evaluation of standard uncertainty when the result of measurement is determined by digital averaging of the input signal which is distorted by simultaneous influence of the random uncorrelated noise and power line interference. It was shown that the classical evaluation of uncertainty based on determining of the standard deviation of input observations is not sufficient, because it does not take into account the effect of suppression of the interference by averaging. To correctly evaluate uncertainty, both the amplitude of the interference component and the standard deviation of the random component should be estimated separately. Simple methods of separate estimation of these components are proposed and analysed in detail. The proposed solutions to the uncertainty evaluation were studied when uniform and triangle averaging were used and verified both by Monte Carlo simulations and by experimental tests. The simulation and test results obtained showed very good accordance with theoretical results.