Electronic watt/watthour meter with automatic error correction and high

Abstract

An improved solid state semiconductor integrated circuit electronic watt/watthour meter circuit having analog and high frequency digital outputs with automatic error correction. The meter comprises first and second transformers for developing first and second voltage and current indicating signals for supply to a multiplier circuit that multiplies the two signals together and derives an output analog product signal representative of the instantaneous power being supplied by a source of electric energy. A multiplier low pass filter circuit is coupled to the output from the multiplier circuit for deriving from the product signal an average value power signal V. An analog-to-pulse rate converter is supplied with the average value power signal V and serves to convert it into a high frequency train of output signal pulses wherein each output signal pulse represents a predetermined quantized amount of electric energy. An automatic offset error correction circuit comprising polarity reversing switches is responsive to the output from the analog-to-pulse rate converter for automatically switching the polarity of the average value power signal V supplied to the analog-to-pulse rate converter midway through the quantizing period of the analog-to-pulse rate converter to cause an up/down integration of the average value power signal V over each quantizing period of operation and simultaneously producing a sequential addition/subtraction of like polarity offset error signals over each quantizing period of operation to thereby cancel out the offset error signals automatically.