Vibrating Wire Piezometer Manual
The RST Vibrating Wire Piezometer provides excellent long-term accuracy, stability of readings and reliability under demanding geotechnical conditions.
The RST Vibrating Wire Piezometer provides excellent long-term accuracy, stability of readings, and reliability under demanding geotechnical conditions. Vibrating Wire Piezometers are the electrical piezometers of choice as the frequency output of VW devices is immune to external electrical noise and able to tolerate wet wiring common in geotechnical applications.
Vibrating Wire Piezometers contain a high tensile steel wire with a fixed anchor at one end and are attached to a diaphragm in contact with water pressure at the other end. The wire is electrically plucked, with the resonant frequency of vibration proportional to the tension in the wire. This frequency induces an alternating current in a coil which is detected by the readout unit, such as the VW2106 Vibrating Wire Readout, and can then be converted to a pressure. The frequency output is immune to external electrical noise.
The frequency signal is exceptionally immune from cable effects, including length (to several kilometers), splicing, resistance, noise pickup, and moisture. The vibrating wire coil circuit contains no semiconductor devices and has built-in ionized gas discharge device protection against transient damage. As a result, the vibrating wire piezometer provides excellent reliability in typical geotechnical situations – i.e. long outdoor cables buried in saturated soil.
The piezometer is equipped with a standard sintered stainless steel porous filter to prevent soil particles from contacting the diaphragm. A thermistor is built into the piezometer body to permit temperature measurement and temperature compensation of the piezometer. Standard construction is all stainless steel. RST vibrating wire piezometers are shipped with extremely tough polyurethane-jacketed foil-shielded cable for maximum endurance in field conditions.
|Over range||2 X F.S.|
|Resolution||0.025% F.S. minimum|
|Operating Temperature||-20 to 80°C (-4 to 176°F)|
|Diaphragm Displacement||<0.001 cc at F.S.|
|Thermal Zero Shift||<0.05% F.S./°C|
|Materials||Hermetically sealed stainless steel housing|
|Thermistor Type||NTC 3K Ohms @ 25°C|
|Filter||50 micron sintered filter. (High air entry alumina filter 1 Bar available)|
|EL380004||Two twisted pairs cable with polyurethane jacket|
|EL380004HDL||Two twisted pairs heavy-duty cable with a thick polyurethane jacket mold for added protection|
|EL380004K||Two twisted pairs Kevlar® reinforced, non-stretch polyurethane jacketed cable for rigorous installations where the stretching of cable is a concern|
*Other types of cables, depending on site conditions and atmospheric reference requirements, are available upon request. These include vented, FEP, PVC, polyurethane, and armored varieties.
Vibrating Wire Piezometers are commonly used for:
View illustrations on how Vibrating Wire Piezometers are used for:
|PART #||DESCRIPTION||PRESSURE RANGE||DIMENSION|
|VW2100||Standard model for general applications||0.35, 0.7, 1.0, 2.0, 3.0 MPa||19 mm Ø X 130 mm|
|VW2100-HD||Heavy duty piezometer for direct burial in fills and large dam embankments or for high pressure borehole installations||0.35, 0.7, 1.0, 2.0 3.0, 5.0, 7.5, 10, 20 MPa||25.4 mm Ø X 146 mm|
|VW2100-DPC||Drive point model with CPT thread||0.07, 0.175, 0.35, 0.7, 1.0, 2.0, 3.0, 5.0, 7.5 MPa||33.4 mm Ø X 508 mm|
|VW2100-DPEW||Drive point model with EW thread||0.07, 0.175, 0.35, 0.7, 1.0, 2.0, 3.0, 5.0, 7.5 MPa||34.6 mm Ø (body) X 304.8 mm|
|VW2100-L||Low Pressure, unvented||70, 175 kPa||25 mm Ø X 133 mm|
|VW2100-LV||Low Pressure vented||70, 175 kPa||25 mm Ø X 133 mm|
|VW2100-M||Miniature version – 17.5 mm diameter||0.35, 0.7, 1.0, 2.0, 3.0 MPa||17.5 mm Ø X 133 mm|
|VW2100-MM||Micro-miniature version – 11.1 mm diameter||0.35, 0.7 MPa||11.1 mm Ø X 165 mm|
|VW2190||Heavy duty piezometer with bladder for brine environment||0.07, 0.175, 0.35, 0.7, 1.0, 2.0, 3.0, 5.0, 7.5 MPa||42 mm Ø X 319 mm|
|VW2191||Heavy duty piezometer with bladder for acidic environment with secondary corrosion protection||0.07, 0.175, 0.35, 0.7, 1.0, 2.0, 3.0, 5.0, 7.5 MPa||42 mm Ø X 319 mm|
|VW2106 Vibrating Wire Readout|
|Cable splice kits|
I’m very happy with the quality of the instrumentation and technical support from RST, as always. They worked with us from the initial stages of the project to ensure that we were fully prepared and equipped to use the RSTAR network for the first time. They delivered everything within the tight project time frame to ensure that there were no delays on site, and the submersible tilt meters looked like new even after over twelve months of being submerged in Thames water!
-Richard Lipscombe, BEng (Hons), Director & Principle Consultant - RL Geotechnical Ltd