Power meter for highly-distorted three-phase systems

This paper describes a low-cost three-phase power meter, which is based on a fast special-designed acquisition board coupled to a personal computer. Such a solution permits an easy design of the acquisition board and the arrangement of a compact and portable instrument. In addition, the software updating is extremely easy and the availability of a powerful graphic interface makes the instrument use rather friendly. The acquisition board is based on low cost 8 bit analogue to digital converters. The converters have a maximum sampling rate of 1 MHz and store the results in a static 512 Kbyte local RAM, which decouples the personal computer speed from the measurement necessities. Hall-effect transducers are used for the current channels and fast differential amplifiers for the voltage channels. Both Aron and complete three-phase system configurations are available. The board connection to the computer is obtained either by means of a special designed AT card or the widely diffused parallel/printer port. This last possibility makes it possible to perform in-field measurements using small subnotebook computers