Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Plural inputs
Patent
1982-02-24
1985-01-22
Karlsen, Ernest F.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Plural inputs
324127, 324130, G01R 2106, G01R 120
Patent
active
044954638
ABSTRACT:
An electronic watt and kilowatt hour measuring circuit susceptible of being fabricated for the most part in solid state semiconductor monolithic integrated circuit form is provided. The electronic measuring circuit uses an active load terminated current transformer sensor for sensing alternating load current and a voltage transformer for sensing the alternating current voltage supplied from a source of alternating current electric energy being monitored. The output of the active load terminated current sensor transformer has an inherent DC-offset error voltage added to the alternating voltage which is proportional to the current being measured. This DC-offset error voltage is caused by the operational amplifier employed in the active load terminated current transformer sensor. By using time division multiplier circuits employing CMOS electronic switches as a means for multiplying the current and voltage signals together, the DC-offset error caused by the active load terminated current transformer sensor automatically will be zeroed out. The circuit can be employed as a straightforward multiplier to derive an output indication of instantaneous watts, or can be employed together with an analog-to-digital pulse rate converter for obtaining kilowatt hours of electrical energy consumed, and can be further modified to provide both instantaneous watts and kilowatt hours measurements, by appropriate design of the circuit together with system-wide correction of any DC-offset error voltages produced within the measuring circuit.
REFERENCES:
patent: 3947763 (1976-03-01), Milkovic
patent: 3955138 (1976-05-01), Milkovic
patent: 4066960 (1978-01-01), Milkovic
Brunson Robert E.
General Electric Company
Karlsen Ernest F.
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