REACTIVE POWER MEASURING INSTRUMENT

PURPOSE:To eliminate the need to use an analog integrator by storing digitized data temporarily, and generating a difference in read timing among respective signals and delaying either of a current signal and a voltage signal by an electric angle of pi/2. CONSTITUTION:Analog signals which show the AC voltage and AC current at a terminal to be measured are inputted through a voltage signal input circuit 11 and a current signal input circuit 21. A period measuring means 4 measures the periods of the analog signals. The two inputted analog signals are converted into two digital data, which are written in a 1st storage circuit 31 and a 2nd storage circuit 32 with clock signals synchronized with the sampling periods of 1st and 2nd A/D converters 12 and 22. Then an arithmetic circuit 3 reads data corresponding to the voltage and data corresponding to a current which is delayed in phase by the electric angle pi/2 out of the digital data stored in the storage circuits 31 and 32 and calculates the means value of the time integration of their product.