Analog-to-digital measurement and calibration system for electrical energy

A system for measuring the energy output from one or more electrical energy sources first makes an analog power measurement, and converts the resultant output into digital form. The A/D converter includes a sigma-delta modulator in series with a digital filter. Then, the output from the A/D converter is inputted to a digital quantizer via a serial interface. A programmable calibration value is also inputted into the digital quantizer from a computer via a non-volatile memory, such that the operating level/calibration of the digital quantizer is controllable by the computer.