Correction of nonlinear distortion in capacitive displacement meter

A capacitive displacement meter used to measure the displacement of a vibrating object generates substantial nonlinear distortion in the case of large vibration displacements. This affects the accuracy of the measurements. The functional relationship between the output voltage and the vibration displacement is determined, and ways of expressing the displacement as a function of the output voltage are examined. To accomplish this computational process, a simple analog device (consisting of a subtractor and a divider) was developed and used to test AM and FM displacement meters. The correction principle involved analyzing the mechanism generating the distortion (expressing the output voltage as a function of the relative displacement), and obtaining the true displacement by inverse operation. The study showed that high-frequency distortion can be held to the order of 1% over a wide range of relative displacement.