A magnetoacoustic position sensor
T. K. Worthington, D. Thompson · IEEE Transactions on Magnetics · 1980
We have developed an absolute position sensor using a magnetostrictive plated wire delay fine. Position is calculated by measuring the time for a torsional acoustic pulse to propagate from a moving multigap head to fixed sense coils at either end of the wire. The sensor provides positonal information over a 2 meter span every few milliseconds, with an accuracy of better than 100 micrometers.