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 converter that digitizes the periodic input signal at each predetermined sampling timing and outputs a digital signal;
• a zero crossing specification means that detects a change in a sign of the digital signal;
• a count processor that counts and calculates a zero crossing detection count C through the zero crossing specification means 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 and immediately after the zero crossing specification means determines zero crossing and further calculates a fraction processing parameter Gj=Nj−Fj using a zero crossing detection number Nj (1≤Nj≤N) 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 C when the period ends and L fractions calculated by the fraction processor in a period of the sampling count N using Formula 1 and calculates a phase of the digital signal.
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