Details:

VP11N   VP11FFlat detectorDetector is a flat vibration plate and only a small portion is projected into the tank, ensuring little degradation over time.Extremely robustWith piezoelectric crystal, no moving parts are required. The sensor is made very simple, offering long service life.User adjustable sensitivitySensitivity is adjustable to suit specific applications.Easy installation and low costThreaded (G 3/4) and sanitary flange type (1-1/2S) process connections are available.Compact and lightweightVibration plate O.D. 22.5, approximately 220g (VP11N) or 300g (VP11F)

Principle of Operation

The sensor uses a piezoelectric crystal to cause pulsed vibration on the plate. The vibration is followed by ringing.
The ringing decreases as time passes. How it decreases depends on the force applied to the plate.
With material covering the plate, the ringing decreases more rapidly than without material. The sensor compares how the ringing decreases to determine material presence.
The pulsed vibration is synchronized with the ringing to achieve a wide sensitivity adjustable range.