Volt-ampere-hour meter using a digital signal processor

An active and reactive volt-ampere-hour meter that consists of 12-b analog-to-digital converters and a digital signal processor has been developed. The meter has digital offset canceling filters and digital 90°-phaser-difference filters. The canceling filters cancel offset in the sample-and-hold circuits and in the analog-to-digital converters. Using the phase-difference filters, the meter is able to measure reactive volt-ampere-hour value, not only for the fundamental frequency but also for several orders of harmonics. The voltage and current noise is canceled by the time-domain integrals. Using a digital signal processor, it is possible to realize a smaller size and lower power consumption than for a conventional volt-ampere-hour meter. Highly accurate results were obtained by computer simulation and for a breadboard mockup construction