The electric piezometer is widely used in piezometers of the Casagrande, standpipe, open well type or can be directly installed in boreholes. It measures groundwater level and pore water pressure variations.
It consists of a cylindrical stainless steel casing, a strain gauge pressure transducer and a filter. Water entering through a filter acts on a metal diaphragm to which a Wheatstone bridge is fixed.
The deflection sustained by this bridge is measured as to resistance variations and this value is converted by an external converter into an electrical signal. This signal can be easily acquired by a dedicated electric control unit. Reliable instruments are essential for long-term measurements.
The piezometric casing must therefore be periodically flushed and the pressure transducer serviced by making sure that the filter functions correctly and checking the zero value. The transducer allows the sensitized metal diaphragm to which the water pressure is applied, to communicate with the outside air through a connection tube. This prevents the water level measurements from being affected by air pressure fluctuations. Air pressure fluctuations are not compensated in the absolute transducer, which is therefore used in completely filled in boreholes, for measuring pore water pressure.
- Piezoelectric sensor
- Full scale: 0.35 – 700 bar absolute and relative
- Overpressure : 2x F.S.
- Power supply: 8-28 V DC
- Output: 4-20 mA
- Non linearity: +/- 0.1% F.S.
- Repeatability: +/-0.01% F.S.
- Total thermal error: <0.04% / °C
- Long-term stability: 0.1 % F.S./1year
- Insulation: >100 MΩ
- Operating temperature: -40/+125 °C
- Protection class: IP68
- Material: stainless steel
- Dimensions (mm): 21 x 74
- Weight (g): 325