MEASURING DEVICE FOR EFFECTIVE VALUE OF FUNDAMENTAL WAVE OF DISTORTED WAVE

PURPOSE:To obtain an inexpensive measuring device which can be handled easily, by deriving the product of a sine wave signal generated by a sine wave generating part, and an input signal being an object to be measured, and deriving its time average value. CONSTITUTION:A sine wave signal generator 1 for generating a sine wave signal iA of a prescribed amplitude having a frequency being equal to a fundamental frequency of an input signal (i) being an object to be measured is constituted of comparators 11, 12, an RS-FF 13, JK-FFs 14, 17, a phase shifter 15, etc. The comparators 11, 12 compare the input signal (i) with a zero level and a set level, respectively. The FF 13 is set or reset by output signals of the comparators 11, 12. Output signals of the FF 13 and the phase shifter 15 are brought to a frequency division by the FF 14 and 17, respectively. In this way, when the sine wave signal iA of a prescribed amplitude is outputted from the generator 1, multiplication of the signal iA and the signal (i) is executed by a multiplier 2, and an output signal Iout is outputted from an average value generating part 3. When this output signal Iout and the signal iA are multiplied by a multiplier 4, a signal i1 corresponding to an instantaneous value of a fundamental value of the signal (i) can be obtained.