Electricity meter with variable gain sigma-delta converter

An electricity metering device comprising:

• means for measuring voltage and current at a predetermined location and including at least one sigma-delta converter adapted to output a series of digital pulses representative of consumed power, said power being the product of the measured voltage and current;
• a digital counter means for summing the output of the sigma-delta converter;
• a signalling means to deliver an output signal when the sum reaches a predetermined value;
• and
• a means for digitally adjusting the gain of the sigma-delta converter including:
• a programmable digital memory means adapted to store a parameter representing the gain of the metering device, the value of the parameter being externally programmable;
• and
• a digital logic means for logically combining the gain parameter with the digital sum stored in the counter means to determine the number of pulses required before the predetermined value is reached and an output pulse delivered by the signalling means.