6
5 Function
5.1 Measuring principle level
The unit operates on the capacitive measuring principle� In direct contact with
the medium the unit detects whether the requested level (point level) has been
reached�
The relative permittivity (before: dielectric constant) of a medium is important
for its detection� Media with a relative permittivity greater than 1�8 are reliably
detected�
Electrically conductive and non conductive media are detected�
Relative permittivity of common media
Mineral oil
≈ 2
Coolant emulsion
≈ 25...75
Glycol
≈ 37
Water
≈ 80
The unit operates with radial detection
characteristics� Therefore media below the active
zone (A) are not detected.
When the unit is perfectly adjusted, the
presence of certain media can be detected
while build-up or foam is suppressed�
A: Active zone (28 mm)
5.2 Measuring principle temperature
The temperature is detected by a temperature element at the lower end of the
probe and electronically evaluated�
