Digital power consumption meter for displaying instantaneous and consumed electric power of an electrical device

Claim 1

An electric power consumption meter circuit for measuring real and consumed power of an electrical load, comprising: means for connecting the load to a power source which provides a load supply voltage and including a load current sensing resistor connected between the load and the power source, the load current through the resistor resulting in a load current induced voltage; a FET arranged as an electronic switch and connected through a current limiter resistor to the load current sensing resistor to sink the load current induced voltage when switched on; an adjustable phase shift circuit connected to produce a 90 degree phase delayed voltage wave form of the load supply voltage; an open loop comparator connected to the phase shift circuit to provide a square wave output of the delayed voltage wave form to the gate of the FET to provide switching thereof; an amplifier connected to the current limiter resistor and the FET to produce an amplified output signal; a voltage peak detector connected to the amplifier to detect the peak voltage of the amplifier output signal; a voltmeter calibrated in power units for displaying the real power as a function of the peak voltage; a voltage to frequency convertor for converting the peak voltage to a frequency signal; a counter calibrated in power consumption units for counting the frequency signal and displaying the total consumed power.