Piezometers (Vibrating Wire)
The model VWP vibrating wire piezometer, also known as pore water pressure gauge, is a pressure sensor for long-term monitoring of pore water pressure and groundwater level, and can simultaneously measure the temperature of the buried point. It can also be used to measure reservoir osmotic pressure, uplift pressure, water level or groundwater level. It has stable performance, high sensitivity, small size, etc. The overall stainless steel shell is durable, and is suitable for long-term automatic monitoring. It can be used in piezometric tubes, foundation drilling and other occasions with the addition of accessories. It is widely used in the monitoring of reservoir dam uplift pressure, seepage pressure, infiltration line, and pore water pressure.
Overview
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. This frequency induces an alternating current in a coil which is detected by the readout unit or automatic vibrating wire datalogger, and can then be converted to a pressure. The frequency output is immune to external electrical noise.
The pore water pressure gauge is mainly composed of stainless steel protective tube, coil frame, pressure membrane, high strength steel wire, etc.
There is a highly sensitive pressure-bearing diaphragm in the pore water pressure gauge. A high-strength steel wire is fixed on the membrane, and the other end of the steel wire is fixed on the coil frame, as shown in the figure below. When in use, the change of the pressure on the diaphragm causes the diaphragm to deform. This small deformation can change the tension of the steel string and thus affect the vibration frequency of the steel string. The change of the pressure on the diaphragm can be converted by measuring the change of the oscillation frequency. The square of the vibration frequency is proportional to the pressure on the diaphragm. The pore water pressure gauge is driven by the excitation circuit sensor coil, when the excitation signal frequency and the natural frequency of the steel string is close, the steel string quickly reached resonance state. When the excitation signal is removed, the steel string still vibrates at its natural frequency for a period of time. The sensing signal generated by vibration is filtered, amplified and shaped by the monitoring circuit of the acquisition instrument, and the vibration frequency of the string can be measured by measuring the pulse period of the sensing signal.
Characteristic:
- Range from 0.35MPa to 3MPa, 0.5%F.S accuracy;
- Vibrating wire theory;
- Super strong steel wire;
- Stainless steel material, corrosion resistant;
- High stability and precision;
- Built-in temperature sensor;
- Waterproof up to 1.2 times pressure;
Application scenarios:
- Fluid pressures for ground water elevations;
- Pore pressures of embankments, fills, soil;
- Water pressure inside boreholes, observation wells and standard piezometer riser pipe;
- Tunnel convergence monitoring;
Specifications
| Type | VWP-0.35/0.7/1/2/3 |
| Measuring Range | 0~0.35/0.7/1/2/3MPa |
| Accuracy | 0.5%F.S |
| Resolution | 0.025%F.S |
| Temperature Range | -40℃~+80℃ |
| Temperature Accuracy | ±0.5℃ |
| Waterproof | 1.2 x measuring range |
| Material | Stainless steel |
| Size | ø24mm*120mm |
Note: The size and performance parameters are conventional product parameters, and other parameters can be customized according to requirements.
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