A new linear encoder-like capacitive displacement sensor

In this paper, a new encoder-like capacitive sensor filled with dielectric material is proposed for measuring relatively long range displacements with high accuracy regardless of the gap alignment of the sensor. The proposed sensor consists of two plates with zigzag-shaped electrodes coated with thin dielectric films. When one substrate slides over the other, long range displacements can be measured with high accuracy because variation in the capacitance in one period is measured with high accuracy and repeated signals are counted, as is done in linear encoders. Moreover, the thin and uniform nature of the dielectric layer on each sensor plate means that the proposed sensor is highly sensitive and stable against misalignments such as tilting. Through experimental tests, it is demonstrated that the proposed sensor can measure displacements of up to 20 mm with a resolution of about 126 nm. (C) 2006 Elsevier Ltd. All rights reserved.