A planar capacitive sensor for 2D long-range displacement measurement

A planar capacitive sensor (PCS) capable of 2D large-scale measurement is presented in this paper. Displacement interpretation depends on independently measuring the periodic variation in capacitance caused by the change in the overlapping area of sensing electrodes on a moving plate and a fixed plate. By accumulating the number of quarters in each direction and the specific position in the final quarter, the large-scale measurement is fulfilled. Displacements in X- and Y-direction can be measured independently and simultaneously. Simulation shows that a shorter gap distance and a longer electrode guarantee better sensitivity. Experiments based on a PCS test bench demonstrate that the PCS has a sensitivity of 0.198 mV/μm and a resolution of 0.308 μm. An electric fringe effect and other possible measurement errors on displacement interpretation accuracy are discussed. The study confirms the high potential of PCSs as innovative 2D long-range displacement sensors.