Electronic active-energy meter

摘要

The invention relates to an electronic watt hour meter or active-energy meter with a pulse-width modulation circuit (14) which converts a voltage signal proportional to the load voltage across feed voltage lines into a pulse-width keying signal. In addition, a current/voltage converter (25) is provided which converts a current signal proportional to the load current on or in the feed voltage lines into a voltage signal. A multiplication circuit (31) outputs the product of the voltage signals under the control of the pulse-width keying signal as a pulse signal which is proportional to the instantaneous power consumption of the feed voltage lines. A filter circuit (32) integrates the pulse signal of the multiplication circuit (31) to form an integrated voltage signal. A voltage/frequency converter (35) converts the integrated voltage signal into a pulse signal which is proportional to the consumed power of the feed voltage lines. An automatic compensation circuit (46) integrates the pulse signal of the voltage/frequency converter (35) to form a feedback signal which is supplied to the input of the voltage/frequency converter (35) as a result of which the inherent offset voltage is eliminated which is caused by the pulse width modulation circuit (14), the current/voltage converter (25) and the voltage/frequency converter (35). <IMAGE>