Magnetostrictive level measurement technique

A Magnetostrictive level equipment measures the level by measuring the time of flight of a wave between the instrument and the material interface. But it does not work like ultrasonic or radar level measuring techniques.

Main components of the magnetostrictive level instruments are:

  • Sensor

  • Magnetic float

  • Waveguide: Rod, which has the full length of the vessel

The main part of the magnetostrictive instrument is the Float centred around a long metal rod, which is called as the waveguide. The waveguide is hung from the top of the vessel, which is long enough to from the top to bottom. An electric pulse is sent periodically from top to bottom through the waveguide.

Unlike the echo technology in the ultrasonic and guided radar system, From the top of the waveguide, an electric pulse is sent through the waveguide. The float positions at the liquid level, the electric pulse pass throughout the waveguide.

A magnetic pulse is produced due to the electric pulse. This magnetic pulse produced by the electric pulse, combined with the magnetic flux of the magnetic float generates a torsional stress pulse exactly at the float position. This torsional pulse travels through the rod to either end with a speed of sound. Though it reaches the sensor too, at the bottom end there is Dampener to the absorb the mechanical wave.

The sensor detects the torsional wave. To be clear, we are not sensing the reflected wave, the torsional wave is a mechanical wave produced at the float contact.

The microprocessor circuit attached to the sensor calculates the time elapsed between the electric pulse generation and receiving the torsional pulse. The time delay is strictly a function of the distance between the float and the sensor as we know the speed of the signal is constant.


  • Importantly for interface measurement.

  • Widely used in storage tanks, because of low maintenance and low cost.