Description
The Vibrating Wire Piezometer is fabricated from stainless steel components, selected to minimise thermal effects, and electron beam that is welded together to ensure a hermetically sealed cavity for Vibrating Wire element. The Model 1200 is suitable for long term Application in embankment and borehole monitoring. The unit can be read conveniently by most common Vibrating Wire readouts and loggers.
HMA Geotechnical Vibrating Wire Piezometers are based on the simple principle of resonance. The instrument consists of a vibrating wire element connected to a sensitive diaphragm. Electromagnetic coils located nearby ‘pluck’ the wire causing it to vibrate at its natural resonant frequency. A change in pressure causes a deflection of the diaphragm that in turn alters the tension in the wire and the resonant frequency.
The electromagnetic coils are used to convert this frequency as that of the wire. For each frequency there is a corresponding pressure. Unlike conventional strain gauges, the vibration frequency in a Vibrating Wire Piezometer is not affected by changes in lead wire resistance. This mean water penetration, temperature variations and contact resistance do not affect the output signal. Geotechnical Systems’ Vibrating Wire Piezometers also offer excellent zero stability.
The piezometer is read using a digital readout or data logger. Readings can be in either frequency squared or period. Calibration data is provided with each instrument to permit the calculation of pore pressure.
. The vibrating wire element is held in place using an extremely high pressure swaging technique. Each piezometer is laser marked with serial numbers and pressure ratings. A variety of filter permeabilities is available to meet different application requirements. The standard filter size is 40 micron pore diameter.
SPECIAL FEATURES
– Long term stability
– High resolution
– Remote readout capability
– Very Sensitive
– Hermetically sealed
– Stainless steel construction
– Rugged construction
– Not affected by long cable lengths