| 摘要 |
PURPOSE:To attain to enhance operational accuracy, by regarding such a case that the instantaneous multiplication value of quantity of AC electricity is not zero as an error to cancel the same by a signal in a reverse direction. CONSTITUTION:Inputted AC voltage and current are supplied to an instantaneous value multiplier circuit 1 and zero-cross detection circuits 3, 4. An OR circuit 5 takes the logical sum of the rectangular wave outputs of the circuits 3, 4 and, when one of the inputted voltage and current crosses a zero point, rectangular wave output is led out. The error output of the circuit 1 is stored and held in a sample hold circuit 6. The output of the circuit 6 is substracted from that of the circuit 1 in a circuit 7 in the next timing. The AC component of this subtraction output is removed through LPF 2 and the DC output corresponding to the effective power values of the input voltage and current is obtained.
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