An absolute calibration method for displacement sensors

In the present study, a new in situ absolute calibration method for a displacement sensor is proposed, and a calibration system is developed. This new method is capable of determining not only the linearity error but also the mean sensitivity (inclination of linear calibration line) on the base of the wavelength. The new measurement system consists of a compact laser interferometer and a previously developed in situ calibration system. The laser interferometer is used only to determine the necessary displacement shift quantity with an integer multiple of half wavelengths of the laser light source. Using this known displacement shift quantity, the mean sensitivity and the Linearity error of a displacement sensor can be determined absolutely. The accuracy of the proposed method depends only on the stabilities of the calibrated displacement sensor itself and the wavelength of the laser light source. A capacitance-type non-contact displacement sensor was calibrated successfully to the limit of stability of this sensor, which is determined from the signal-to-noise ratio. (C) 2001 Elsevier Science Ltd. All rights reserved.