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Vibrating Wire Piezometers

Vibrating wire piezometers are used to measure pore-water pressure and water levels. Datasheet

Applications

Typical applications include:

  • Monitoring pore-water pressures to evaluate slope stability.
  • Monitoring dewatering systems and wick drains at construction sites.
  • Monitoring pore pressures to check the performance of earth fill dams.
  • Monitoring containment systems at landfills and tailings dams.
  • Monitoring water levels in stilling basins and monitoring wells.
Vibrating Wire Piezometer

Vibrating Wire Piezometer Photo courtesy of Geokon Inc

Operation

The vibrating wire transducer inside the piezometer converts water pressure to a frequency signal via a diaphragm, a tensioned steel wire, and an electromagnetic coil.

The transducer is constructed so that a change in water pressure on the diaphragm causes a change in the tension of the wire. The electromagnetic coil excites the wire, which vibrates at its resonant frequency. The coil then acts as a pickup, senses the frequency of vibration, and transmits a signal readout device.

The readout or data logger then converts the frequency signal to a pressure in engineering units by applying calibration factors.

Advantages

Groutable: VW piezometers can be installed in boreholes that are backfilled with a bentonite- cement grout. This technique makes it possible to install multiple piezometers at different elevations in the same borehole.

High Resolution: VW piezometers provide a resolution of 0.025% FS.

High Accuracy: Most ranges provide an accuracy of ±0.1% F.S.

Rapid Response: VW piezometers respond very quickly to even small changes in pore- water pressure.

Reliable Signal Transmission: Signals from the VW piezometer can be transmitted long distances

Compatible: VW piezometers are compatible with loggers such as the Campbell CR6 or GeoCloud Vibrating Wire Nodes.

Specifications

Sensor Type: Pluck-type vibrating wire sensor with built-in thermistor and tripolar plasma surge arrestors.

Range: Standard ranges include 50, 100, 250, and 500 psi. Custom calibration ranges are available.

Resolution: 0.025% F.S. with suitable readouts.

Accuracy: ±0.1% F.S.

Linearity: <0.5 % F.S.

Materials: Stainless steel wetted surfaces, including the sintered steel filter.

Length x Diameter: 5.2 x 0.75 inch.

Signal Cable: Four conductor cable attached at factory. Vented cable available on request.