Magnetostrictive Deadband Limitations | APG

Magnetostrictive level sensors work by detecting magnetic interaction between the stem and float.

Magnetostrictive level sensors are a great way to get highly accurate and repeatable level readings. A .1-inch resolution and the ability to read 2 levels with the same sensor sound pretty bulletproof. However, there are a few limitations to magnetostrictive level sensors.

Dead Band Limitations

There are 2 different dead bands on the magnetostrictive sensors: A top dead band and a bottom dead band.

The top dead band is due to the waveguide and the pulse transmitted. Depending on the length of the stem and the floats being used, the top dead band can be as small as 6” from the top of the head to as large as 12” from the top of the head.

The bottom dead band is caused by the magnet placement in the middle of the float. The stem has a float stop on the bottom, stopping the float from falling off the end of the stem. With the float at the bottom of the stem, the magnet in the float (depending on which float is being used) can be anywhere from 1” to 3” above the bottom of the stem causing a 1”- 3” dead band from the bottom of the stem.

If the application is for dual level, the same dead band principal applies to the floats when they come together.  There will be a 2” to 6” dead band between the floats.

The magnetostrictive level sensors are highly accurate, have .1” resolution, and are repeatable. But, they do have their limitations. When dead bands are not an issue for the application, a magnetostrictive sensor is a great solution for level readings.

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Photo Credit: Oguraclutch

Photo Source: Wikimedia Commons

Photo License: GFDL (applies to the image only)

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