ELECTRONIC WATT-HOUR METER.

摘要

In a method for digitizing the voltage signal and current signal of an electronic watt-hour meter to calculate electric power by digital multiplication, the circuit has a small analog scale, signals are mainly digitally processed in the circuit, and the circuit can be composed of ICs, thus enhancing the accuracy of calculating the power. A voltage signal (v) and a current signal (i) are respectively inputted into analog-digital converting means comprising sigma-delta modulation circuits (10 and 11) and others. The outputs are averaged by running by the running-averaging means (12, 13, 14 and 15) which are low-pass filters. Then the voltage is multiplied (18) by the current. The analog scale in the sigma-delta modulation is small. Also, the scale of circuit is small by the adoption of low-pass filters provided for the running average. Further, the power calculation can be made at a high accuracy. <IMAGE>