Design And Research Of The Calibration System For Current-Meter

Current meter is the commonly used device that used to measure the river and lake's hydrological data. In order to keep the accuracy of the current meter measuring the flow velocity, current meter must be tested on the current meter verification system regularly to determine its parameters.Based on an extensive investigation and research about technology development of the current meter verification system at home and abroad, this thesis further studies the principles of current meter calibration system and analyzes the verification process, designs a set of calibration system:the control system adopts dc Speed Regulation Systems, dc speed regulator controls speed of the separately excited dc motor. Industrial computer gives calibration vehicle a range of velocities, and controls PLC on calibration vehicle to complete direction adjustment of the current meter, data collection and data transmission, and so on; data collection of current meter is completed by three microcontrollers; the system establishes wireless communication on the basis of wire communication, using the Siemens'Profmet wireless communication protocols real-time transferring current meter verification data. Finally, this thesis adopts Labview which is on behalf of the virtual instrument represents software and manufactured by NI company as the upper machine programming software, carrying on software design such as system monitoring, data fitting and printout, realizing the upper machine monitoring of hardware devices, controlling the amount of output as well as the management of the experimental data.The dc speed control system adopted in this thesis has a wider speesd range, a good starting and braking performance, which can satisfy the requirements of the system. The digital dc speed controller and velocity measurement encoding disk are used to improve the steady precision of the system, so as to ensure the accuracy of testing data and the reliability of test results in system. On analysis of some factors affecting the speed in practice, this thesis has improved control algorithm in view of the original speed control system, put forward parameter self-tuning PID control algorithm based on fuzzy control, and tested and verifyed it by simulink. The improved control algorithm can effectively suppress all kinds of interference that the system encounters in the process of operation and improve the accuracy of the results and the stability of the operation.In the full analysis of the flow characteristic curve and methods of data fitting, this thesis chooses segmentation least square method to handle calibrating data, this method of data fitting satisfies the requirements of system and obtains good fitting effect. To low speed part of the flow characteristic curve, this thesis chooses three-step fitting mathematical model of least square method; To medium and high speed speed part of the flow characteristic curve, this thesis chooses liner fitting mathematical model of least square method. Parameter calculation, drawing and measuring point, the output of the test results in the process of data fitting are done by the computer, which can help the operator eliminate subjective factors influence on test results and reduce the work intensity as well as improve work efficiency.