Design of reliable interface system for eddy current displacement sensors in vacuum environments1

In this paper we propose a reliable interface concept for eddy current displacement sensors. The implementation of a signal conditioning approach, based on simple electronic circuits, is also discussed. The interface system is designed for medium to high-resolution applications in the sub-micron displacement measurement range. The application of the sensor is in special vacuum environment with severe restrictions of power dissipation, and increased requirements for reliability and thermal drift. The new system is expected to consume less than 20 mW, and to have a very low thermal drift. The implementation will be a system-in-package (SIP). The full-scale range of the measured displacement is 1 mm with 50 KHz signal bandwidth and 11 bits resolution (less than 500 nm). The signal conditioning interface is utilizing a standard 0.35 mum CMOS technology. The discussions are based on simulations and primary experimental results, promising a proper sensor operation.