The Development Of The Embedded Low-Cost Electrical Parameter Measuring Instrument

This paper focuses on the design and development of the instrument monitoring one and three phase AC, which is based on the single-chip ADuC841 and covers the electric parameters of voltage, current, power, virtual power and power factor. According to the trend of virtual instrument development, web monitor of electric parameters has been introduced based on Ethernet and TCP/IP protocol, which cuts down the cost, reduces the instrument volume and provides the flexible use. In order to cut down the cost of the whole system, the optimization of sampling circuit scheme has been performed that removes the sample-and-holder and decreases the number of ADC. Also, the circuit for periodic interruption has been improved to debase the noise existing in the low-cost hardware scheme and the interruption priority has been arrangement with reason in the result of the precise frequency. Random errors have been eliminated through the algorithm averaging the sample values,and phase difference has been compensated by adjusting the relative relationship of sample value for voltage and current. These measures are taken whose effect is proved by many experiments and simulated on computer. The conclusion is to make it sure.The instrument monitoring the electric parameters developed by this paper has the characters of low-cost, convenience, satisfied precision, and has a bright future in actual application.