An acoustic position sensor
This article presents an acoustic method-the resonance acoustic field sensor or piezoelectric-sound-resonance cavity (PSRC)-for object position detection. This method utilizes the change of acoustic radiation impedance as a sensing mechanism. The PSRC both generates and detects a resonance acoustic field, along both the axial and transverse directions. We have discovered that an inserted object or an object motion in the sound radiation field results in changes in both the voltage and phase of the PSRC. Results have shown that a minimum object displacement of <10 mum can be detected in the axial direction (and <100 mum in the transverse) by this method. (C) 2003 American Institute of Physics.