Eddy-Current Displacement Sensing Using Switching Drive Where Baseband Sensor Output Is Readily Available

In eddy-current displacement sensing, existing techniques mostly involve a high-frequency sinusoidal carrier wave and deal with the demodulation of this signal. In this paper, we give a new design idea. We use switching circuits, in which the sensing coil is included as an inductor and driven by a switching voltage, and some baseband sensor output is readily available. Thus, no explicit demodulation is needed, and the electronics are simplified. We give three designs of such switching circuits. The first is based on coil inductance, the second is also based on coil inductance but is different from the first in many ways, and the third is based on eddy-current power loss. These circuits are tested on hardware electronics. The results seem to indicate that the presented techniques would permit performances comparable to those achieved by existing techniques.