Research On Open-loop High Voltage And Wide Range Current Sensor Based On Wireless Transmission

The measurement of electric power parameter plays a basic role in the maintenance and improvement of the electric power system. With the smart-grid concept having been put forward and implemented, it becomes a more and more important issue to accurately and efficiently measure current, voltage and other electric power parameters. The performance of sensors must be improved accordingly. It is necessary to use information technology, sensing technology and other modern technological methods to design a new type of current sensor which can meet the practical requirements of the smart-grid under high voltage conditions. At present, the high voltage and wide range current sensor has disadvantages of large size, low digitization, wire transmission of limited service life, being easy to be disturbed and close-loop sensor head of being inconvenient to operate and possible danger on the measurement workers working in the high voltage environment. In order to effectively improve the above disadvantages, this paper proposes a new type of open-loop high voltage and wide range current sensor working under high voltage conditions based on Bluetooth wireless transmission technology.The open-loop high voltage and wide range current sensor proposed in this paper is comprised of the hardware unit and the software unit. The hardware unit includes the sensor head, the sensor structure framework, the function implementation circuit board and the portable terminal. The software unit includes the program of function implementation circuit and the receiving and displaying program of portable terminal. The current sensor is designed based on the HALO-I ammeter framework and the high performance sensor head of HALO-I ammeter is used as the sensitive part. Firstly, the sensor head transforms the desired current into the voltage signal. Secondly, the voltage signal is subjected to the polarity conversion,the amplification, the anti-aliasing filtering and the analog-to-digital conversion of the function implementation circuit. And then, the digital signal is sent into the HC-05 Bluetooth module by the MSP430F149 microprocessor. Finally, it is transmitted to the portable terminal by the Bluetooth wireless transmission technology and displayed on the portable terminal.The function implementation circuit is the basis of signal processing and Bluetooth transmission and the MSP430F149 microprocessor is the operating and controlling core of the whole circuit. The program of the function implementation circuit is written by C language in IAR Embedded Workbench for MSP430 integrated development environment. The portable terminal is an Android smart phone which is portable, easy to operate and integrated with the Bluetooth module. The receiving and displaying Android application is written by Java in Eclipse integrated development environment.The test shows that the current sensor proposed in this paper has a high measuringaccuracy and it achieves the purposes that the tester can operate the sensor and read the data in a safe place and the data can transmit to the portable terminal by using Bluetooth transmission technology, it also lays the foundation of high-level digital processing. The field test shows that the current sensor proposed in this paper has high practical values in the current measurement.