A simple technique is developed for measurement of power frequency deviation. It is based on multiplication of two signals having different frequencies and then filtering out the higher order frequency component. The lower order frequency component is converted into a square wave and modulated with a high frequency pulse train. The number of pulses corresponding to one time period of square wave is calibrated in terms of difference of frequency of the two signals. The results showed a linear relationship between frequency deviation and a pulse count. The technique is not sensitive to harmonic noise because of its ability to filter out all the higher order components.