The Level Switch LS is our only Level Switch with ATEX certificate. The Level Switch Ex (LS Ex) is made to be used in Apparatus-group llB and Equipment-group 2G. The Level Switch Ex is classified for zone 1.
The The LS and LS Ex sensor is designed to work with the echo technique.
Echo Technique
The Echo technique uses echo from a reflecting surface inside the container (usually the opposite container wall) to determine if there is liquid or not inside. The ECHO-technique transmits short sounds and then measures the echo bouncing on the reflecting surface. When there is an echo, there is liquid inside and with no liquid there is no echo (ultrasound do not travel very well into air).
The liquid must not attenuate the sound too much. Small bubbles and particles in the liquid can cause attenuation and unmixed liquids having different sound velocities can cause refraction of the sound and thereby wrong indication of low level. It is important that the soundbeam from the sensor is reflected back to the sensor and not diverted in the wrong direction.
For more information download the product datasheet:
AQ Level Switch.pdf
or the manual:
Level Switch Ex manual version 2.1.pdf