The Research And Development Of Data Acquisition System

Data acquisition is the chief tool in measurement and computer-control and is wildly used in many fields, such as electric measurement,automatic control and fault diagnosis. The design of data acquisition system that meets different application fields and different function demands is always the key point in engineering field.According to the 25Hz railway circuit, this paper analyzes the functional requirements and qualifications of data acquisition system. The design of data acquisition system based on digital processor controller,on-chip ADC and RS-485 communication technology is put forward.In this paper, the hardware based on TMS320LF2407A is presented. The design of DSP minimum system contains the power system,clock system and emulation interface circuit. The dominance of ADC clock prescaler and self-calibration are expatiated. By analyzing the advantage and disadvantage of three wide used active filter circuits (Butterworth, Chebyshev and Bessel filter circuits) in practical application, the active low-pass Butterworth filter is chosen as a pre-filter. In synchronous data acquisition controlling, the multiple-channel synchronous sampling implemented by controlling ADC with divided frequency of synchronous signal in real-time sampling. The problem in the communication between DSP and PC based on RS-485 is presented, and the solution of common-mode disturbance and EMI which are generated by incorrect ground connection is stated.The program on DSP is designed on the platform of CCS. According to the cause of offset error and gain error, one method of ADC calibration is stated. In data dealing module, FFT calculation is used.On the basis of this paper, the device used for data acquisition is developed, and is proved stable and efficient by field testing.