Importance

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Abstract

Methods and apparatus for metering electrical energy are disclosed in an electronic meter which includes a first oscillator for generating a first clock signal to within a first accuracy and a second oscillator for generating a second clock signal within a second accuracy. A processor, operable in relation to a clock signal, measures time and periodically compensates for the accuracy of the first oscillator. The first clock signal is used for measuring time when power is applied to the meter and the second clock signal is used by the processor for measuring time when power has been removed from the meter. The accuracy of the first oscillator is compensated periodically in relation to a compensation factor stored in memory. In one embodiment, the processor includes a counter for counting from a first value to a second value in response to the first clock signal. In such an arrangement, the processor substitutes the first compensation factor for the first value. The meter can further include a timer, wherein the processor substitutes the first compensation factor for the first value in response to the first timer. The processor also is shown to implement a process for compensating for the accuracy of the second oscillator. This process compensates for the accuracy of the second oscillator in relation to the first oscillator. To this end, the process calculates a second compensation factor. The second compensation factor is determined when power is applied to the meter, wherein after power has been removed and restored, the second compensation factor is used to compensate time measured in relation to the second oscillator during the period power had been removed.

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First Claim