Low-Cost Data Acquisition And Power Quality Analyzing System

A low-cost customizable PC-based power quality analyzer is proposed. It consists of a data acquisition unit built using a ARM microcontroller, which performs measurement functions and primary filtering and processing of the voltage and current signals, and can either transmit data to computer via virtual serial port and/or store the measurement results to a flash SD memory card for subsequent processing and analysis. The data acquisition unit has built-in real-time clock (RTC), can operate in autonomous mode, without PC connection. It is possible to define software triggers for start/stop recording conditions, including recording in specified periods of time (using RTC). For convenience, 4 discrete inputs were added with universal operating voltage range (24...220 V AC/DC) to allow recording triggering by external signal. The objective was to built a low-cost system, so data acquisition unit has no display; to reduce gain and phase errors of current clamps, a negative impedance converters were used as their loads; furthermore, an additional software filtering is performed to compensate for residual errors. A simple software for PC was also developed to allow simple signal processing and ability to export signal data to MathCad for further analysis.