Electronic watthour meter

Abstract

An electronic watthour meter including a pulse width modulation circuit for converting a voltage signal proportional to the load voltage across the power supply lines to a pulse width duty cycle signal and a current-to-voltage converter for converting a current signal proportional to the load current across the power supply lines to a voltage signal. A multiplication circuit issues the product of the voltage signals under the control of the pulse width duty cycle signal as a pulse signal proportional to the instantaneous power consumption of the power supply lines. A filter circuit integrates the pulse signal of the multiplication circuit as an integrated voltage signal. A voltage-to-frequency converter converts the integrated voltage signal to a pulse signal proportional to the consumption power of the power supply lines. An automatic compensation circuit integrates the pulse signal of the voltage-to-frequency converter as a feedback signal to the input of the voltage-to-frequency converter thereby eliminating the inherent offset voltage caused by the pulse width modulation circuit, the current-to-voltage converter and the voltage-to-frequency converter.

Dependencies are inferred from the claim text.