Pressure Transducers

SISGEO manufactures a range for piezometers for various applications.  Broadly speaking, a piezometer measures water levels or water pressures within a borehole or in the ground.  There are various methods of doing this, ranging from a simple tube set at depth in a gravel filter zone, from which a water level reading is taken, to more sophisticated instruments which measure pore water pressures.
Standpipe piezometers are used to monitor piezometric water levels.

Observation wells are used to monitor ground water levels. Typical applications include:
• Monitoring pore-water pressure to determine the stability of slopes, embankments, and landfill dikes.
• Monitoring the effectiveness of dewatering schemes.
• Monitoring seepage and ground water movements in embankments, landfill dikes, and dams.

CASAGRANDE AND STANDPIPE PIEZOMETERS

Geozone Geoservices_Geotechnical instrumentation_Casagrande & Standpipe Piezometers
The standpipe piezometer, alternatively known as a Casagrande piezometer, comprises a filter tip joined to a riser pipe. The filters are made from high density polyethylene with a threaded cap joint for a standpipe arrangement of two ‘half inch’ tubes or one ‘1 inch’ tube. The riser pipe is typically made from PVC plastic pipe.  After the filter tip and standpipe are installed in the hole, a sand filter zone is tremied into place around the filter tip, following which the top of the filter zone is sealed with a bentonite plug which isolates the filter zone.  The annular space between the standpipe and the borehole is backfilled to the surface with a bentonite grout to prevent vertical migration of water. The standpipe is terminated above ground level with a vented cap and protective cover.  If the soil is very soft, standpipe piezometers can be pushed into position using a steel well point with an integral filter tip.

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WATER LEVEL INDICATORS (WLI) [Dipmeters]

Geozone Geoservices_Geotechnical instrumentation_Water level indicators
Dipmeters (WLI) are used for ground water level measurements in standpipes, wells and Casagrande
piezometers. The dipmeter is a battery powered portable device equipped with a dipping probe connected to a graduated cable wrapped on a cable reel. When the dipping probe comes into contact with water, it activates either an audible alarm and a light indicator mounted on a reel faceplate. The C112T version is also equipped with a dipping probe for temperature measurements. A LCD on the reel faceplate displays the temperature value directly in ˚C.

Technical Specifications

MODEL C112 class II flat cable with markings every millimetre
Probe water level detector
Available cable lengths 30, 50, 100, 150, 200, 300, 400, 500 m
MODEL C112T class II flat cable with markings every millimetre
Probe water level detector and temperature sensor
Available cable lengths 30, 50, 100, 150, 200, 300, 400, 500 m
Reel diameter 260 mm, 320 mm, 420 mm
Probe diameter 10 mm
Display 3.5 LCD (only for C112T)
Battery 9V DC disposable

STAFF GAUGES
(Product code 0HIDR100000)
Staff gauges are used for direct readings of water level in reservoirs, rivers and open channels. They consist of 1 m long porcelain enameled hydrometric rod with centimetre graduation and reference plate.

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WATER LEVEL LOGGER (WLL)

Geozone Geoservices_Geotechnical instrumentation_Water level logger
Water Level Logger (WLL) is an integrated system designed for automatic continuous monitoring of water level and temperature inside wells, standpipes and Casagrande piezometers. WLL system is equipped with an accurate ceramic pressure sensor which provides high accuracy and long-term stability measurements. The Water Level Logger records absolute pressure, which is later converted to water level readings by the Hoboware software using barometric measurements. The optical USB connection interface provide safe and reliable data download also in bad environmental conditions.

Technical Specifications

Water level range* 9, 30, 76 m
Temp. range -20°C +50°C
Accuracy
– water level* ±0.05% F.S.
– temperature ±0.5°C
Memory type Non-volatile
Memory capacity 64k-byte >21.000 combined measurements
Measuring Interval Programmable min 1 sec, max 18 hours
Communication port Optical USB interface
Temp.operating range -20°C +60°C
Battery life*** 5 years typical with min. measuring interval             1 min

* nominal value based on using WLL at sea level
** typical error using reference level measurement and the barometric compensation
*** depending also from working temperature

HOBOWARE MANAGER SOFTWARE
(Product code 0WSBHW10000)
This software is the next generation software for logger management, data graphing and data analysis; it permits to check the logger status: verify logger set-up before launch, verify logger operation while logging, display real-time sensor readings and display memory used and battery voltage. Software’s powerful graphing features let you plot and filter data for a customized data presentation. Barometric compensation assistant allows for compensation of water level measurements for barometric pressure.

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ELECTRICAL PRESSURE TRANSDUCERS

Geozone Geoservices_Geotechnical Instrumentation_Electrical pressure transducers
A wide range of electrical piezometers and pressure transducers are available for different applications. Electrical piezometers and pressure transducers are equipped with a deformable diaphragm with screen printed resistor gauges forming a 4-arms Wheatstone bridge. The P235S piezometers are used to monitor pore pressure when a fast response, dynamic measurements and/or high accuracy are required. The model P252A is supplied with a 1/2-inch male thread to be coupled with a hydraulic pressure line (for up-lift water pressure monitoring).

Technical Specifications

MODEL P235S1 with HAE value filter
MODEL P235S4 with LAE value filter
MODEL P235I Drive-in version to be pushed into a soft soil
Standard ranges 100, 200, 500 kPa
1, 2, 5, 10, 20 MPa
Sensitivity 0.01% FS
Accuracy < 0.3% FS
Temp. Operating range -10°C +55°C
Filter unit characteristic
– HAE (100 kPa) 1 µ ceramic stone
– LAE stone 40 µ sintered s/steel
40/50 µ syntherized PE
Diameter / length 27 mm / 200 mm

VENTED PRESSURE TRANSDUCER
The P252R pressure transducer is equipped with a vented sensor, which provides automatic compensation for barometric pressure changes. This transducer provides ground water table monitoring in Casagrande piezometers, wells and standpipe piezometers.

REMOVABLE PORE PRESSURE TRANSDUCER
P252C is a removable pressure transducer for soil pore pressure monitoring. It is suitable for long-term monitoring, as the instrument can be removed for calibration checks, maintenance or re-used in other boreholes. When inserted into the P101 filter unit, the pressure seal is assured by its conical tip with an O Ring kept in place on the cable by a string of dead weights.

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FLOW METERS

Geozone Geoservices_Geotechnical instrumentation_Flow meters
Water flow monitoring in open channels is widely employed in the environmental and geotechnical fields. Leakage measurement is one of the most important indicators of the overall performance of earth/rock-fill and concrete dams. The leakage rate is a function of the water level in the reservoir and depends either on the construction and/or the integrity of the dam.
Consequently, leakage monitoring provides data for the evaluation of the long-term stability of the dam structure.
Leakage water is usually impounded downstream from the dam and diverted to a basin in a weir station.

Technical Specifications
V Notch Weirs
The purpose of the weir is to transform the instantaneous flow values into the pressure/level by means of specific measuring equipment.

0QV45LS1000 10 litre/sec.  V-angle 45 Degrees
0QV60LS2000 20 litre/sec.  V-angle 60 Degrees
0QV90LS5000 50 litre/sec.  V-angle 90 Degrees

Measuring Equipment
QVLIV100 Level Transducer
Product Code 0QVLIV10000

Transducer Type floating unit with high sensitivity load cell
Measuring Range 1000 mm of water level variation
Sensor resolution 1mm
Accuracy > 0.3 % FS
Output Signal 4-20 mA (current loop)

P25 1Q100 Level Transducer
(Product Code 0P251Q10000)

Transducer Type Pressure transmitter
Measuring Range 1000 mm variation in water level
Accuracy >0.5 % FS
Output Signal 4-20 mA (current loop)

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VIBRATING WIRE PIEZOMETERS

Geozone Geoservices_Geotechnical instrumentation_Vibrating wire piezometers
Vibrating Wire piezometers are strongly recommended for long term monitoring of soil pore pressure or groundwater levels. The VW piezometer consists of a stainless steel body equipped with a filter unit (porous stone) and a pressure sensitive diaphragm with tensioned steel wire. The vibrating wire is tensioned inside a hermetically sealed and evacuated space. VW piezometers guarantee fast response, long-term stability and immunity to voltage surges (lightning). Readings of VW piezometers are obtained by vibrating wire readout or datalogger. Filter units are available with different porosity: either HAE (high air entry) or LAE (low air entry) value filters are suitable for piezometer applications in impervious, saturated and permeable soils.

Technical Specifications

MODEL PK45A with HAE value filter unit
MODEL PK45S with LAE value filter unit
MODEL PK45I drive-in version to be pushed into a soft soil by push-in rods
Standard ranges 200, 350, 500, 700 kPa
1.0, 1.7, 2.0, 3.5 MPa
Sensitivity ± 0.025% FS
Accuracy < 0.5% FS
Temp. operating range -20°C +100°C
Filter unit features
– HAE (100 kPa) 1 µ ceramic stone
– LAE stone 40 µ sintered s/steel
40/50 µ sintered PE
Diameter / length 27 mm / 200 mm

SATURATION DEVICE
(Product code 0PF01SAT000)
The filter saturation is a decisive factor of a successful installation of embedded piezometers. Sisgeo provides a device for field use for the saturation of the HAE value filter (ceramic stone). It consists of a stainless steel pump with manometer and a threaded port to fit the filter unit.

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