Electric power measuring appts. - has converters for voltage dependent values into signal trains of different frequencies and has signal duration detectors

The appts. may be in the form of a Watt-hour meter in which both the voltage and current values are converted into signal trains of different frequencies in order to attain a higher precision. These frequencies are mutually multiplied by counting the higher frequency signals during a time-limited signal period of the lower frequency. The counting takes place via a frequency reduction stage (19) in a counter (20). Pref. the two signal trains are interconnected via an AND-gate (18). The signal period duration may be determined by timing elements (15, 17). The meter is pref. used for limiting the cost of electric consuming appliances, such as battery driven vehicles, in which both the current and the volt. are fluctuating. It enables a highly precise determination of power consumption by digital techniques.