High-resolution vibration measurements using a posiltion-sensitive photosensor

Abstract

An integrated two-dimensional position-sensitive photosensor is used for contactless measurements of vibration amplitudes down to the sub-micron region. The sensor includes a position-sensitive silicon photodiode with high linearity over the full sensitive area and analog electronics integrated by thick-film hybrid technology for signal amplification and conditioning. Using hybrid integration of the transducer element with the following electronics we get a position-sensitive transducer, which is easy to handle under industrial conditions and gives output signals (response of the light-spot motion) that are easy to transmit over large distances. Vibration measurements have been carried out on a calibrated vibration exciter to test the sensor and on industrial equipment. The evidence of vibration amplitudes up to 0.01 μm shows that the position-sensitive hybrid circuit has the same sensitivity as the inductive displacement transducer but a better linearity in the lower frequency range from 0–100 Hz. The device is capable of performing two-dimensional sensing of the light beam from the vibrating part and does not need additional calibration, e.g., in the case of object drift during the measuring process.