RF Admittance is a static level sensor with no moving parts. Its sensing parts are:-
Earth Extension (body)
These parts form three capacitances:-
Shield Earth Capacitance
Shield Sense Capacitance
Sense Earth Capacitance
A Sine wave of high frequency is fed into both Sensing Rod as well as Compensation Shield. Voltage at shield is equal to voltage at sense, no effective current flows between sense and shield.
This removes shield-sense capacitance from the measurement. Shield-earth capacitance is ignored by circuit.
This removes the effect of material coating on probe.
Bulk is considered as fill-level and "wet" signal is issued
Coating is ignored as insignificant capacitance and "dry" signal is issued