High-performance eddy current sensor interface for small displacement measurements

This paper presents an improved interface for eddy current displacement sensor for accurate displacement measurement of thin targets in harsh environment. Two recently proposed state-of-the-art interfaces are analyzed and experimentally verified. The experimental results confirm high level of performance: displacement measurement of a 100 um thin target; displacement range ±1.5 mm; 15 bits dynamic range; 1 kHz signal bandwidth; 18-mW power consumption. The most important application constraints of the two interfaces are discussed, which facilitates a correct choice when targeting a specific set of application requirements. A new interface, which demonstrates the above mentioned performance, and at the same time allows continuous time displacement measurement useful in control loops and servo systems, is presented and evaluated.