Ground hydraulic settlement gauge
The Vibrating Wire Liquid Settlement System for soil is extensively used for differential monitoring of settlement or heave in soils and other structures such as embankments, earth and rockfill dams.
The main components of this system are: a reservoir (single or multiple), liquid-filled tubing and VW transducer cells located under the soil.
Each VW sensor is connected via hydraulyc tubing with the reservoir positioned in one inamovable site. The quote variation between reservoir and one or more sensors (attached to a settlement plate) positioned under the soil subject to settlement or heave is converted in pressure variation and in the quote changes (in mm of movement).
Every pressure’s variation on the each VW sensor make a variation of frequency of vibration of trasducer which is acquired by specific unis of measurement. The pressure sensor transducer uses a pressure sensitive diaphragm with a vibrating wire element attached to it which is mounted inside an evacuated and hermetically sealed housing. The transducer operates on the principle that a tensioned wire, when plucked, vibrates at its resonant frequency. The square of this frequency is proportional to the strain in the wire.Fluid pressures acting on the diaphragm causes a deflection of the diaphragm which then changes the tension in the vibrating wire thus altering the resonant frequency of the wire.
For greater accuracy moreover these readings are netted from the atmospheric pressure and temperature changes in the time.
- Type of sensor: vibrating wire;
- Standard Range: 6.9 m, 17 m (69 kPa, 170 kPa);
- Barometric sensor: piezoelectric sensor 10 kPa;
- Output signal: Hz;
- Overpressure: 2x F.S.;
- Range: from 2200 to 3500 Hz;
- Electrical power supply: 8-28 Vdc;
- sensory accuracy: +/- 0,1% F.S;
- Non linearity: <0,5% F.S.;
- Total thermal error: 0.05% F.S./°C;
- Temperature range: from -20 °C to +80 °C;
- Sensor protection class : IP 68;
- Thermistor: 3kW;
- The reservoir can have from 1 until 9 cells (depends on tube length).
- dimensions plate and material: 400x400x1,5 mm, stainless steel
- dimensions sensor and material: 175X75X60 mm, stainless steel and aluminum
- dimensions tubing and material: 6 mm O.D., polyethylene
- dimensions reservoir and datalogger box and material: from 400x300x150 mm until 800x800x250 mm, anodized aluminum