EFFECTIVE VALUE MEASURING INSTRUMENT

PROBLEM TO BE SOLVED: To provide an effective value measuring instrument capable of more accurately measuring an effective value with respect to a measurement object signal having an unknown frequency.SOLUTION: The effective value measuring instrument includes: a windowing processing unit 12 which subjects a prescribed number N of pieces of sampling data D1 (data D2) about a measurement object signal S1 to windowing processing to output window data D3; a squaring processing unit 13 which squares the window data D3 to output squared data D4; an averaging processing unit 15 which averages a prescribed number N of pieces of the squared data D4 to output average data D6; a square root calculation unit 16 which calculates a square root of the average data D6 to output square root data D7; and a correction unit 17 which corrects the square root data D7 by attenuation at the time of windowing processing to output an effective value Drms of the measurement object signal S1.