MTS Systems’ Levelplus range of level transmitters, available from ThermoFisher Scientific, utilises the highly accurate magnetostrictive technology for liquid level and interface measurement.
Magnetostriction is one of the most accurate and repeatable measurement technologies available today and has been used for many years for such precise applications as linear machine tool positioners, etc.
When the wave guide within the sensing element is stimulated by a current pulse, a magnetic field is created. External floats containing a permanent magnet interact with this magnetic field and create a "torsional strain pulse" which moves up and down the wave guide at sonic speed.
Product and interface levels are then accurately determined by measuring the time difference between the initial current pulse and the return pulse.
Unlike micro power impulse radar (MIR), microwave time domain reflectometry (TDR) and ultrasonics, which depend on the dielectric or reflective properties of the product being measured, the return magnetostrictive pulse in the MTS system can only come from the precise position of the float magnet.
The result is high overall accuracy (typically 0.51mm) and high repeatability (0.005% FS).
The sensors have no moving parts other than the freely guided float, are virtually maintenance free and come in a range of versions for ultrapure, ultraclean, or ultraharsh applications and are suitable for cleaning-in-place (CIP).
Transmitters display any combination of level, interface and temperature and have 2 x 4-20mA analog outputs. Digital output versions are also available.