Switchable impedance circuit for current sensing an electricity meter
First Claim
1. An impedance circuit for an electrical meter monitoring power usage from a service line, the meter having a current meter and a transformer having a conductor of the service line coupled to primary terminals and a sensing resistor coupled across secondary terminals, the impedance circuit comprising:
- a signal generator generating a control signal having a level dependent upon the current sensed by the current meter;
an electrically controlled switch having an ON state and an OFF state, the state of said switch being dependent upon the level of the control signal;
a resistive branch including the electrically controlled switch and a resistive element;
wherein the impedance circuit couples the sensing resistor to the current meter and wherein the equivalent resistance seen by the current meter is dependent upon the state of the switch.
3 Assignments
0 Petitions
Accused Products
Abstract
An arrangement for generating a digital current measurement signal includes an analog-to-digital (A/D) converter and an impedance circuit. The A/D converter is operable to receive a voltage input signal and generate a digital output signal having a digital value representative of the magnitude of the voltage input signal. The impedance circuit includes at least first and second alternative impedance values and a switch operable to cause the impedance circuit to have a select one of the first impedance value and the second impedance value. The impedance circuit is configured to receive a current signal to be digitized, the impedance circuit generating an output voltage signal representative of the current signal and having a magnitude dependent on the select one of the first impedance value and the second impedance value. The output voltage signal of the impedance circuit is then provided as the voltage input signal of the A/D converter.
8 Citations
15 Claims
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1. An impedance circuit for an electrical meter monitoring power usage from a service line, the meter having a current meter and a transformer having a conductor of the service line coupled to primary terminals and a sensing resistor coupled across secondary terminals, the impedance circuit comprising:
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a signal generator generating a control signal having a level dependent upon the current sensed by the current meter; an electrically controlled switch having an ON state and an OFF state, the state of said switch being dependent upon the level of the control signal; a resistive branch including the electrically controlled switch and a resistive element; wherein the impedance circuit couples the sensing resistor to the current meter and wherein the equivalent resistance seen by the current meter is dependent upon the state of the switch. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification