Text version of the page

Description and operationLevel Sensors

Level sensors are used as sensing elements forelectrical continuous remote display of the level. They work on float principle with magnetic transmission (permanent magnet, reed switch and resistance chain) in a three wire potentiometer circuit. A toroidal magnet in the float actuates tiny reedcontacts with its magnetic field through the wall of the guide tube; they read off an uninterrup- ted measurement voltage from a resistance chain (potential divider) and this voltage is proportional to the liquid level. The resistance chain is very finely graduated and is made up of small chips soldered onto a printed circuit board. Because of this construction the measurement voltage given out is quasi-continuous. Depending on the requirements and the design there are various types of resolutions available.In connection with a control unit the value ofresistance can be converted into a standard analogous signal.
blue brown black Internal connection dia- gram for level sensor Chip-housing

Technical advantages

Simplest mounting and initial operation of level sensors , control units and indicating instruments. Constant display of the level with highly accurate repeatability, regardless of the build up of foam, varying conductivity and pressure. Nearly maintenance-free operation during many years. Applicable for temperatures up to 120°C, HT-versionup to 180°C (high temperature design on request). Nearly applicable for all mediums by use of different materials. Remote display of the level over long distances. Interface measurement of liquids with ballasted float.

Schematic diagram of the principles

134520(4)-20mA

1Level sensor2Float 3Control unit 4Display unit 5Set point relay A

Formula for calculating the measurement accuracy

ResolutionMeasuring length in mm x 100 z.B. 12,72000 x 100 = 0,635% 62