Liquid level sensor: Non-mechanical optical technology extends application possibilities

Level sensing switch has no moving parts, does not depend on conductivity, detects liquids with any physical characteristics
By Control Engineering Staff November 20, 2008

Infrared technology operates independently of liquid characteristics, so conductivity is not an issue.
New optical level sensor from Baumer uses infrared light to detect the presence of liquid while minimizing intrusion into a tank or vessel. The result is accurate readings whether the liquid is conductive, non-conducting, cloudy, or clear.

The FFAR sensor detects liquids without an electrical current in the liquid or any mechanical sensor probe. Baumer says the measuring principle is based on the total reflectance of infrared light at the interior of a translucent cone. The limit angle for the total reflectance of the light changes depending on whether the sensor tip is surrounded by liquid or air. If the tip is surrounded by liquid, the light beam is diverted and the sensor exit changes its switching status.

Constructed of borosilicate glass with a stainless steel enclosure, the sensor is extremely resistant to a wide variety of aggressive substances. All parts exposed to surrounding media withstand pressures up to 40 bar (580 psi) and temperatures up to 65 °C (150 °F).

—Edited by Peter Welander, process industries editor, PWelander@cfemedia.com ,
Control Engineering Process Instrumentation & Sensors Monthly
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