High accuracy and high stability magnetic displacement sensor in the presence of electromagnetic interferences

Abstract

An accurate and stable displacement sensor that reads through coated metal substrates achieves better than one micron accuracy includes: an electromagnetic coil positioned in a first enclosure; (ii) means for generating a magnetic field from the electromagnetic coil; (iii) a second enclosure which is spaced apart from the first enclosure, wherein the second enclosure includes dual magnetic sensors, such as fluxgate sensors, that are configured to measure the magnetic field; and (iv) means for calculating the separation between the operative surfaces of the enclosures from magnetic field measurements. A permanent magnet can be used instead of the electromagnetic coil and associated driving energy source. A precise displacement measurement is given by a mathematical function (such as the ratio or difference) of the two magnetic sensors demodulated signals. The displacement sensor can be mounted on a maneuverable C-frame to monitor the caliper of anodes and cathodes produced for lithium ion batteries.