Research And Design Of Data Acquisition System Of Current Meter

Data acquisition system of Current Meter is an important part of current meter calibration system,one of the key factors to complete this design is whether the frequency of current meter can be measured accurately.Based on current meter calibration system,this thesis deeply understands the working principle of rotor type current meter and signal characteristics,and analyzes current meter data collection system's role in the current meter calibration system and the function needs to be done,and then according to the linear slot in the rotor type current meter calibration of the national standard requirements,designs the structure and working process of the acquisition system of current meter.Through the analysis of the rotor type current meter signals,find that they are affected by various interference,including water resistance interference,high frequency interference and interference jitter.Current meter signals range and duty ratio range are both big,which serious influence on the precision of the current meter signal detection.Base on this background,this thesis analysis in detail all kinds of interference and put forward reasonable solution,and designs the current meter data acquisition system based on the combination of hardware and software.(1)This thesis chooses the combination of hardware and software method which the linear optical coupling circuit combined with "threshold" filtering algorithm to filter out water resistance interference.(2)This thesis selects Butterworth low-pass filter hardware circuit filter out high frequency interference.According to the speediness and stability requirements of system design,the 6 order Butterworth low-pass filter circuit is modified.(3)According to the characteristics of the random jitter interference,this thesis abandons the existing of pulse signal detection method combined with time delay,but choose A/D sampling method to select real current meter signals,at the same time,this thesis uses cross-correlation detection algorithm to filter out interference jitter.And then get the signals cycle and transfer rate value of the current meter.(4)Finally,the detailed design of hardware circuit of the system is carried on in this thesis as well as a variety of important components are analyzed and calculated.The experimental results show that the design using the threshold value filtering algorithm can effectively and fast filter water resistance interference.Modified 6 order Butterworth low-pass filter circuit satisfies the requirement of experiment,because it has a fast response time and a small overshoot volume.Cross-correlation detection algorithm can effectively filter out interference,regardless of its occurrence in what position,and then get the accurate signal cycle and high precision current meter rate value.In this thesis,the design of current meter data acquisition system has high efficiency and precision,which meets the design requirements.