| In order to ensure the electrical network work safely and grasp its running status, the parameters of electrical network should be measured exactly. EPMI (Electrical Parameter Measuring Instrument) is just an instrument which can measure the electrical parameters. The paper introduces the development status and background of EPMI overall and expounds the measuring principle of voltage, current and other electrical parameters in detail. The whole design schemes of the system's hardware and software are also presented in the paper.The EPMI uses voltage and current mutual inductors to construct signal transition circuit. The voltage and current mutual inductors can transform strong signal to weak signal which can be processed conveniently. PIC16F877A which produced by Microchip Company is the main-control chip of the EPMI. The EPMI uses ATT7026 which is the special chip to measure electrical energy to acquire and process data. The communication between PIC16F877A and ATT7026 depends on SPI interface. The EPMI can measure voltage, current, frequency, power, energy and other electrical parameters synchronously, and display the measured parameters on LCD. Furthermore, the EPMI can transmite the measured data to the surveillance room through RS485 bus interface. If there are many EPMIs, they can be formed as a controlling network and managed easily. In the anti-jamming aspect, the EPMI adopt the way which combinated software and hardware methods. Both hardware circuit designing and software programming have provided relevant anti-jamming methods, so the anti-jamming ability and stability of EPMI has improved observably. Moreover, the EPMI which includes measuring, controlling, displaying and other function has the characteristics of multi-function, well-precision, display intuitionisticly, good performance and low cost. The EPMI has formed many series of production and can adjust the coefficient so flexibly that it can fulfil different clients demand and it will have a good future.
|
PDF Full Text Request