PURPOSE: To perform accurate measurement with high accuracy even when a waveform to be measured has strain by generating respective reference waveforms almost the same as a pair of AC waveforms to be measured in frequency and delayed from said waveforms by π/2 in phase.
CONSTITUTION: A sine wave generating circuit 1 as the first reference waveform generating circuit generates a sine waveform Vp(t) almost the same as AC waveforms X(t), Y(t) to be detected in frequency. A cosine wave generating circuit 2 as the second reference waveform generating circuit generates the same cosine waveform VQ(t) as the waveform V(t) and delayed from said waveform by π/2 in phase. The waveforms Vp(t), VQ(t) are respectively multiplied by the waveforms X(t), Y(t) by multipliers 3 - 6 and the results are respectively integrated with respect to one cycle by integrators 7 - 10. These integrated values are inputted to an operation circuit 12 through an analogue/digital converting circuit 11 and operation is performed on the basis of a predetermined formula to make it possible to obtain the phase difference between a pair of the waveforms X(t), Y(t).
SHIRAISHI KIMINOBU
KAGAWA EIJI
| JPS4942076A | 1974-04-20 |