Electronic AC electric energy measuring circuit
First Claim
1. An AC electric energy measuring circuit comprising:
- a current responsive input for receiving a first analog signal being responsive to the time derivative of a current component of an alternating current energy quantity to be measured;
a source of square wave pulses including a frequency substantially greater than the frequency of said alternating current energy quantity to be measured;
a first modulator circuit including a first integrator circuit responsive to said first analog signal and said square wave pulses at a common input thereof and further including an output producing a constant amplitude pulse width modulated signal variable in response to variations in amplitude of said current component;
a voltage responsive input responsive to a second analog signal proportional to a voltage component of the alternating current energy quantity to be measured;
a multiplier circuit including a second modulator circuit responsive to said second analog signal and to said constant amplitude pulse width modulated signal so as to produce a variable amplitude pulse width modulated signal corresponding to the product of said current and voltage components so that the average value thereof is representative of a measure of average power produced by said voltage and current components; and
an analog to frequency converter circuit including a second integrator circuit responsive to said variable amplitude pulse width modulated signal so as to produce output pulse signals, wherein each output pulse represents a quantized amount of said alternating current energy quantity to be measured.
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Accused Products
Abstract
An electronic AC electric energy measuring circuit converts a di/dt analog input signal into a pulse width modulated signal responsive to the amplitude of a current component of an alternating current energy quantity to be measured. The pulse width modulated signal is produced by a first modulator circuit including an integrator circuit deriving both a modulating frequency signal and a current analog signal proportional to the current component. A multiplying circuit receives a voltage analog input signal and applies it to a reference input of a second modulator circuit. The modulating control of the second modulator circuit receives the pulse width modulated signal so that the multiplying circuit produces a variable amplitude and pulse width modulated signal having an average value equal to an average power measurement. An analog to frequency converter including a second integrator circuit receives the output of the multiplying circuit to produce an output pulse representative of a quantized amount of electric energy.
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Citations
11 Claims
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1. An AC electric energy measuring circuit comprising:
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a current responsive input for receiving a first analog signal being responsive to the time derivative of a current component of an alternating current energy quantity to be measured; a source of square wave pulses including a frequency substantially greater than the frequency of said alternating current energy quantity to be measured; a first modulator circuit including a first integrator circuit responsive to said first analog signal and said square wave pulses at a common input thereof and further including an output producing a constant amplitude pulse width modulated signal variable in response to variations in amplitude of said current component; a voltage responsive input responsive to a second analog signal proportional to a voltage component of the alternating current energy quantity to be measured; a multiplier circuit including a second modulator circuit responsive to said second analog signal and to said constant amplitude pulse width modulated signal so as to produce a variable amplitude pulse width modulated signal corresponding to the product of said current and voltage components so that the average value thereof is representative of a measure of average power produced by said voltage and current components; and an analog to frequency converter circuit including a second integrator circuit responsive to said variable amplitude pulse width modulated signal so as to produce output pulse signals, wherein each output pulse represents a quantized amount of said alternating current energy quantity to be measured. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification