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Abstract

An electronic watt-hour meter includes a multiplier/integrator circuit which performs 'pulse height-pulse width' multiplication of current and voltage and simultaneously integrates the product of this multiplication to generate packets of electrical charge representative of the electrical energy consumed. A first set of switches alternately, at one-half the frequency of a pulse width modulated (PWM) signal having a duty cycle proportional to the current, connects one of a pair of capacitors to be charged by the voltage signal, and the other capacitor to dump charge into an accumulator. When charge in the accumulator reaches a preset value, a pulse is generated representing a predetermined unit of energy. When the first capacitor is connected to the voltage signal by the first set of switches, a second set of switches applies the voltage to the first capacitor in one sense when the PWM signal has one value and in the opposite sense when the PWM signal has a second value. Similarly, a third set of switches alternates the polarity in which the voltage signal is applied to the second capacitor as a function of the value of the PWM signal. The second and third sets of switches also determine the polarity of charge transferred to the accumulator from the first and second capacitors respectively in response to a polarity signal which indicates the direction of integration of charge by the accumulator.

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