A novel design of the Parallel Plate Capacitive Sensor for Displacement Measurement

The capacitive sensors because of their low-cost, low power consumption, small temperature dependence, and high sensitivity are widely used to measure various physical parameters. However, the main limitation to use a capacitive sensors is the effect of parasitic capacitances, which significantly affect the measurement accuracy. So, to avoid the parasitic capacitance, the electrodes are enclosed in a conducting grounded shield, and the sensor is interfaced with a suitable electronic circuit to minimise these stray capacitances. The main object of present work is to utilise the grounded shield to design a parallel-plate capacitor with a linear response for displacement measurement. The structure is modeled and simulated using ANSYS Maxwell software. Based on the simulation results, the optimum arrangement is fabricated using two fixed circular plates and a moving grounded electrode in the gap. The experiment was performed with the sensor to obtain a sensitivity of 38 fF/mm. The most important feature of this setup is, the capacitance value changes linearly with the movement of the grounded electrode.