| 摘要 |
PURPOSE: To reduce an error generated by excitation energy for exciting a current transformer in a wattmeter for measuring electric energy by using the current transformer for converting a negative current signal to a voltage signal and digitizing, multiplying, and integrating an electric circuit voltage signal and a negative current signal. CONSTITUTION: A rectifier 105 outputs a signal obtained by superposing a voltage signal corresponding to a load current on a voltage signal corresponding to a signal with a frequency which is not correlated to an electric circuit frequency. The signal passes through an amplification circuit 102, a filter 103, and an A/D converter 104 and is converted into a digital signal. Then, the signal is multiplied by a digitized voltage signal by a multiplication circuit 109, is integrated by an accumulation adder/subtractor 109b, is converted into pulses by a pulse conversion circuit 110a and is counted by a processing circuit 110b, and at the same time, is multiplied by an arbitrary coefficient, and is outputted to a display 111. |
