Design Of And Experiment On Eddy Current Displacement Sensor Of Wide Detecting Range

Eddy current displacement sensor as an analyzer in the TSI system of online monitoring of rotating machinery vibration feature has good reliability, fast response speed and strong anti-interference advantages. However, there is a need to develop such kind of sensors with constant probing diameter and linear range extender because of the restricted factors such as the measured dimensions and installation space. This thesis, based on the theoretical analysis and by means of experiments, aims to expand the eddy current sensor linear range through the optimization of the structure of probe coil size and measurement circuit.Firstly, according to the working principle of the eddy current sensor and the hollow transformer model, this thesis established a mathematical model to solve the equivalent impedance of the coil. Because the random error between the theoretical value and the measured value of the equivalent resistance and the equivalent inductance has been big in the previous studies, this thesis, based on the displacement change, proposed the corrected function and it made the random error of models-calculating under different coil size reduce by 10%.Secondly, as for the optimization of coil parameters, the method of double objective function optimization is put forward. For the optimization of wire diameter, this thesis considered AC resistance and quality factor of coil temperature change rate as the double objective function, and employed the experimental method to choose the optimal value for target function; for coil slot width and diameter optimization, this thesis considered nonlinear error of sensors and sensitivity as double objective function, and employed the direct comparison method to select the optimal value for target functionThirdly, this thesis designed the variable frequency amplitude modulation measurement circuit matched the probe by using the modular design in order to realize the transition from displacement signal to electrical signal. The main circuit structure consists of oscillator detector and radio detector and so on. Using Multisim12 software to debug and simulate each function circuit, this thesis had each circuit module met the design requirements.Finally, through the sensor probe equivalent components concatenate oscillator, this thesis conducted the simulation experiment on measurement circuit. After analyzing the compensating sensor output value, it is concluded that the linear range is 19 mm, the sensitivity is 0.4 V/mm. Compared to the Φ25 mm sensor produced by Bentley company which is usually used by power plants, its linear range is increased by 6.3 mm.The simulation experiment through the objective function by optimization design method of probe structure and measurement circuit can implement the expanded linear range of the sensor in the probe diameter unchanged.