Phase measurement device and instrument in which phase measurement device is applied

A phase measurement device that measures a phase of a periodic input signal varying periodically through a digital circuit, comprising:

• an AD (analog to digital) converter that digitizes the periodic input signal at each predetermined sampling timing and outputs a digital signal;
• a count processor that controls a zero crossing specifying detecting a change in a sign of the digital signal and counts and calculates a zero crossing detection count C through the zero crossing specifying at each sampling timing;
• a fraction processor that calculates a fraction Fj (j=1 to L) of the zero crossing detection count on the basis of the digital signals at sampling timings immediately before the zero crossing specifying and when the zero crossing specifying and further calculates a fraction processing parameter Gj=Nj−Fj using a zero crossing detection number Nj (0≤Nj≤N−1) in a period of a predetermined sampling count N (the number of data to be averaged) necessary for averaging;
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• an averaging processor that averages the count processor calculation value that is the zero crossing detection count C when the period ends and L fractions calculated by the fraction processor in a period of the sampling count N using Formula 1 (L indicates the number of Gj included between the averaging counts N) and calculates a phase of the digital signal.
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