Radiometric point level detection 

Radiometric point level detection operates with a radioactive source that emits focussed gamma radiation.
The radiation is picked up by a detector on the opposite side of the vessel. If the gamma rays are blocked by the medium, the detector receives little or no radiation. The intensity changes of the incoming radiation are forwarded as signals by a relay.
PROTRAC point level detectors for radiometric measurements can be used either as minimum or maximum detectors.

The advantages

The resulting measurement is unaffected by all the physical and chemical properties of the medium.