A low-cost, accurate and fast capacitive displacement sensor with microcontroller interfacing

A high-performance, capacitive displacement measuring system is described. Using a very linear oscillator, shielding and a three-signal approach, most of the errors are eliminated. The accuracy amounts to 1 mu m over a 1-mm range. Since the output of the oscillator can be directly connected to a microcontroller, an analog-to-digital (A/D) converter is not needed. The system was tested in a fully automated setup, using an electrical XY table, the described sensor and a personal computer. Nonlinearity, long-term stability, and repeatability were verified.<
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