ELECTRONIC ELECTRICITY METERS

摘要

Apparatus whose measurement means consists solely of electronic components, measures the power taken by an electrical load connected to an alternating source of electricity supply in such a manner that the power sensed or energy accumulated is in agreement with the same measurements as performed by a conventional rotating disc electromechanical meter. Fundamental frequency filtering means when applied to either one or both supply voltage and load current ensure that the electronic circuitry performs the appropriate measurements in determining power consumption. A single sample per mains cycle applied to load current and supply voltage is sufficient to measure power consumption, energy consumption accumulation, and produce accumulated energy pulses appropriate to measurement of real power, true power and volt-ampere power consumed by the load. Similar multiphase meters apply the fundamental frequency filtering means to each load current and optionally to each supply voltage to extend the method used in single-phase meters. To improve accuracy of the measurements where an analogue to digital converter is used the current signal, and optionally the supply voltage signal, is perturbed by a Quantisation Error Dispersion (Q.E.D.) signal. Various circuits are described to generate the Q.E.D. signal and the essential properties of the signal are defined.