A Unique Linear Position Sensor Using Magnetostriction
1 min read
Summary
Magnetostriction is a property of certain materials that causes them to change size or shape when magnetised, via the movement of tiny magnetic domains within the material.
One side effect of magnetostriction is the Wiedenmann effect, which causes an electrical conductor to experience a twisting force when a current pulse is applied to it in a magnetic field, this twisting effect then creates a mechanical wave along the wire.
This project uses the Wiedenmann effect to create a linear position sensor, it uses a nickel wire stretched tightly in the centre of a PVC tube, at one end is a coil of copper magnet wire and at the other end there is a damper to prevent reflections.
The ring-shaped cursor magnet can move up and down the tube and when it does so the exciter circuit applies a current pulse to the wire and the position of the magnet is determined by the difference in time between sending the pulse and receiving the reflection, which can be measured using an oscilloscope.
