Operationg Principle
The transducer uses a pressure sensitive diaphragm with a vibrating wire element attached to it. The diaphragm is welded to a capsule which is evacuated and hermetically sealed. Fluid pressures acting upon the outer face of the diaphragm cause deflections of the diaphragm and changes in tension and frequency of the vibrating wire. The changing frequency is sensed and transmitted to the readout device by an electrical coil action through the walls of the capsule.
Piezometers incorporate a porous filter stone ahead of the diaphragm, wich allows the fluid to pass through but prevents soil particles from impinging directly on th diaphragm.