The PW piezometer consists of a vibrating wire sensing element enclosed in a protective steel housing. The sensing element is formed essentially of a steel wire clamped to both ends of a hollow cylindrical body. An electromagnetic coil is used to excite the wire and to measure its vibration period. The period is sensitive to the pressure applied onto the sensing element. The excellent long-term reliability of the PW results from the use of the latest developments in vibrating wire technology. For instance, the wire is clamped by a proven hydraulic swaging technique that ensures high stability. The sensing element is hermetically sealed in order to protect the steel wire against corrosion. All parts of the sensing element other than the wire are machined from a high-grade stainless steel. The PW is fitted with a surge protector and resists electrical and radio frequency interferences, as determined by tests compliant to IEEE and CEI specifi cations.
Five models of PW piezometers are available:
The PWS is designed to be embedded in earth fi lls, at concrete/earth interfaces or inserted into boreholes
and small-diameter pipes. The end of the PWS is fi tted with a high or low air entry fi lter, which protects the
sensing element from solid particles, allowing this model to sense only the fl uid pressure to be measured.
The fi lter is easily removable in case of saturation. The PWF is a thick-walled version of the PWS for use in
direct burial applications. The PWC is provided with a pipe thread adapter, thus enabling the piezometer to be used as a pressure transducer.
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