Suppression Efficiency of the Correlated-noise and Drift of Self-oscillating Pseudo-differential Eddy Current Displacement Sensor

摘要

The suppression efficiency of the correlated noise and drift of self-oscillating front-end circuit in a pseudo-differential eddy-current displacement sensor (ECDS) is investigated using COMSOL and MATLAB. The transfer characteristic of the sensor coil, excited at 200 MHz, is obtained through a FE model in COMSOL. The characteristic is linearized to a second-order fit around a standoff distance to the target (x_(so)) of 55 μm. The nonlinearity of the interface is modelled in MATLAB. It is found that, in order to tolerate 1% drift in the oscillator amplitude, a maximum 2nd harmonic distortion (HD2) of the interface has to be less than -72 dB when the sensor HD2 is -51.5 dB for 5 μm displacement range around x_(so) = 55 μm.