Principle of Operation of Magnetostrictive Position Sensors

Magnetostrictive sensors detect the location of a magnetic ring that slides along a conductive metal tube; in other words this sensor operation utilizes the effect of a magnetic field on magnetostrictive wire to function. The figure below illustrates a Magnetostrictive position sensor:

To detect the position of the magnet (in this case, an electromagnetic created by energizing of the ferrite core), a pulse of DC current (not shown on the diagram) is introduced into the conductive metal tube also referred to as the magnetostrictive wire (in our case, this is represented by the ferrite core). Sometime later, the current pulse reaches the magnet and passes through its magnetic field. When current moves across a field, the conductor experiences a force. This causes a slight mechanical disturbance in the metal tube i.e. the metal tube distorts and a vibration travels back along the metal tube to a force sensor. The time elapsed between the generation of the DC current and the time of the mechanical or acoustic signal/vibration is linearly related to the position of the magnet along the metal tube.

Applications of Magnetostrictive Sensors

This technology is used in level measurement, where we have level transmitters utilizing the effect of the magnetic field (usually the magnetic field of a float) on a magnetostrictive wire to measure level in liquids. These level transmitters are typically used for liquids with enhanced foam development.

Other applications of magnetostrictive sensors are in the measurement of torque, motion, stress or force, and so forth.

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