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.

Abstract: An electronic watthour meter comprising: a pulse width modulation circuit for subjecting a voltage signal, proportional to the load voltage of a power supply line, to pulse width modulation to obtain a pulse width duty cycle signal; a multiplication circuit in which a plurality of analog switches are selectively operated, with the aid of the pulse width duty cycle signal, so that positive and negative DC voltages equal in absolute value are obtained from the product of a voltage signal, proportional to the consumption current of the power supply line, and the pulse width duty cycle signal attributing to the voltage signal proportional to the load voltage; and a dual-slope type frequency conversion circuit for converting the positive and negative DC voltages into a frequency signal.