The Research Of Key Technology Of Digital I/F Converter

I/F converter is a kind of convert current signal to frequency signal of the device, has been widely applied to various fields. Aiming at the problem of converting the I/F converter has low precision, anti-interference ability, this paper designed a kind of less than 5 x 10-5 high performance digital I/F converter based on single chip ADuC847 conversion and digital signal controller MC56F8037 accuracy.I/F converter is designed mainly from the front-end signal conditioning circuit, A/ D sample value of digital filtering, nonlinear compensation, digital frequency synthesis algorithm, anti-interference measures introduced in five aspects. Amplifier without the front end of the signal conditioning circuit structure, which is a differential signal transmission structure, improve the external electromagnetic anti-interference ability, to identify small signal, ensures that the bipolar signal fidelity and stability. The original moving average filtering algorithm is improved and designed based on the algorithm of butterworth low-pass digital filter, in the original inherits the outstanding performance of the algorithm, and improves the sensitivity and the ability to inhibit pulse interference. Due to the small signal input microcontroller ADuC847, there are serious nonlinear, using variable gain compensate nonlinear compensation principle, namely the different range of input current, different gain method, experimental tests show that nonlinear improved. In this paper, the frequency synthesis technology based on MC56F8037 on chip PWM timer or digital frequency synthesis algorithm, not only the output frequency of the signal and the stability of the resolution is very high, but also greatly reduces the cost. Finally, this paper from two aspects of hardware and software to improve the anti-interference ability of the I/F converter, the hardware design including power supply, grounding, front-end signal modulation, frequency output isolation module circuit anti-interference design; Software design including power supply monitor, software trap, instruction redundancy, watchdog technology and the anti-jamming design of digital filter.Modulation signal circuit converts the input signal current dual polarity can be identified in the input voltage signal to the microcontroller ADuC847, A/D converter, sampling the voltage signal into the digital quantity through filter filter to remove interference signal, calculates the output frequency value, then according to the frequency synthesis algorithm, through MC56F8037 output frequency signal.For testing in this paper, design of the I/F converter test, through the analysis of test data, its performance fully meet the design requirements.