Patent ID: 6291985
Filing Date: 2001-09-18
Classification: G01R

Abstract:
An electronic wattmeter for use with a source of alternating current, a.c., electrical power supplying alternating current, a.c., voltage across a load that is connected to an alternating current, a.c., ground, the electronic wattmeter comprising:a direct current, d.c., power supply, floating relative to the a.c. ground, for producing from the a.c. voltage a direct current, d.c., voltage relative to, and impressed upon the a.c. voltage;a resistor located in series between, at a first terminal, the source of a.c. electrical power and, at a second terminal, the load;a first resistive voltage divider having two resistive legs, located between (i) the first terminal of the series resistor and (ii) the a.c. ground, for developing at a point between its two resistive leas a first voltage;a second resistive voltage divider having two resistive legs, located between (i) the first terminal of the series resistor and (ii) the a.c. voltage, for developing at a point between its two resistive legs a second voltage; anda third resistor voltage divider having two resistive legs, located between (i) the second terminal of the series resistor and (ii) the a.c. voltage, for developing at a point between its two resistive legs a third voltage;a sensing means, full floating relative to a.c. ground and connected between the d.c. voltage and a d.c. ground,for first sensing the first voltage as indicative of an instantaneous a.c voltage of the source of a.c. electrical power, andfor second sensing the difference between the second voltage and the third voltage as indicative of an instantaneous alternating current provided from the source of a.c. electrical power to the load; anda multiplier means, receiving an instantaneous voltage and the instantaneous current from the sensing means, for multiplying the instantaneous voltage by the instantaneous current to develop instantaneous power that is being provided by the source of a.c. electrical power to the load.