Contactless Position Measurement of an Electrical Conductor using GMR Sensors

This article introduces a new method for contact-less position measurement of an electrical conductor (such as a current-carrying wire) using giant magneto-resistive (GMR) sensors. The readout circuit of this method is designed for high-range, high-sensitivity dynamic position measurement of proposed of thin stationary and moving wire. The developed method can be applied in precision applications such as diamond abrasive wire (DAW) sawing, wire electrical discharge machining (EDM), musical instruments and acoustics. The proposed method is based on the principle of electromagnetism, where a constant DC current is supplied to the wire to produce a magnetic field around it. This magnetic field varies non-linearly outside the wire in the radial direction; the non-linear field is sensed using a GMR sensor. The sensor's performance is evaluated in terms of characteristics such as linearity, sensitivity, resolution, and drift. The variation in the magnetic field strength affects such characteristics. The maximum signal-to-noise ratio (SNR) and, hence, the maximum sensitivity of 4.2
$V$
/ mm, and
$\pm \mathbf{3}\sigma$
resolution of 10
$\mu m$
are achieved in the operating range.