An Approach for Improving the Accuracy of Measuring the Input Signal Frequency for the Measurement Method of Three Samples

The paper deals with the method of signal frequency measurement based on the analysis of three consecutive samples of the input signal. The main features of this method are considered, the analytical expression is given, the application of which makes it possible to obtain an estimate of the frequency value of the input signal by three sequentially taken samples. The advantages and disadvantages of the method are considered. The method of error reduction, based on the use of a lowpass filter, is proposed. The 4th order Butterworth infinite impulse response digital filter and a moving average filter are considered as a output filter. The moving average filter is realized by a recursive structure. The simulation model is performed by the application of Simulink package. The model proposed in the paper allows to estimate the methodological component of the error of signal frequency measurement by the method under study. It is shown that the main cause of the methodological error is associated with the uncertainty of the ratio of signal samples near the transition of the measured signal through zero. The scheme allowing to reduce this component of error is offered. An estimate of the error for the case of sinusoidal, polyharmonic and sinusoidal distorted by noise signals are obtained.