Piezometers and Water Level Meters

Water Level Measuring System – Pressure Transducer

///Water Level Measuring System – Pressure Transducer


Water level measurement in tanks or open tanks can be by vibrating wire piezometer or strain gauge bridge.

Transducers for the measurement of levels, are products with varying measuring ranges between 1m and 200m of water column (higher on request).

There are many uses for this instrument, essentially the two main applications are as below:

  1. Application with sensor immersed in the liquid whose level is being measured, inaccessible after installation. This instrument is also referred as ” water level measurement system – outdoor applications”
  2. Application in locations that are always accessible.

This instrument is also referred to as “water level measurement system – indoor applications”.

In the first case the instrument is equipped with a protective tubular structure, in stainless steel.
In the second case the instrument, consisting of the transducer and the piezometric pressure outlet group, is contained in a resin protection panel and equipped with an external Bourdon pressure gauge for local measurement of pressures in the hydraulic circuit.


Typical applications for this instrument are the measurement of water levels in:

  • basins
  • tanks
  • dams
  • rivers
  • channels
  • wells
  • various

Features and benefits

The instrument is characterized by:

  • wide variety of measuring ranges
  • simplicity of installation
  • accuracy and reliability
  • High resolution and repeatability
  • Direct reading of data
  • adaptability to different installation requirements
  • readable outputs 4-20mA for standard measuring instruments
  • robust and durable
  • High resolution and sensitivity
  • Low cost
  • Long life under normal working conditions
  • Possibility of automatic measuring

Measuring Principle

Measurement of the level is obtained by determining the hydrostatic load, i.e. the hydrostatic level, acting on the piezometric sensor’s membrane.

The output signal is transmitted via cable to a local manual or automatic reading unit – automatic readings are transmitted to a remote control center.
The simplicity of the sensor and ease of use allows a variety of applications  for a various situations

System composition:

Piezometric level meter for external use, using immersion application (inaccessible)

The fitting can be straight or angled. The application can be with locked or removable sensor.

Piezometric level meter for internal use, with application via taking pressure group (accessible) Installation is generally in dam tunnels or outside tanks, with the realization of a direct taking pressure group.

The sensor is supplied in a protective casing, taking pressure group with siphon and auxiliary Bourdon type manometer

Figure 1 shows

a) piezometric transducer

b) connection between transducer and protective cable tubing

The connection can be straight or squared. The application can be with a locked or removable sensor

Figure 2 shows:

  • Piezometric transducer
  • Connection cable to the readout unit
  • Blowdown device for air accumulated in the pipe
  • Gate valve separating the transducer from the pressure intake

Figures 3 and 4 show the most common applications

Both figures show the use of further sensors, to cover the entire measuring range of the level, creating some areas with reading at differential accuracy.

Fig. 3 shows an installation scheme for a dam already built; in this case the transducers are fitted outside the structure.

Fig. 4 shows the insertion of transducers during construction of the structure

In the example, the transducer at the bottom can be installed either in the tunnel, connected to the basin with a hydrostatic pressure outlet, or directly immersed in the basin.

Transducers for level measurement can normally be read by portable DEC readout units or connected to automatic acquisition systems.

Technical Features

Vibrating Wire Piezometer 
Technology Vibrating Wire
Range (kg/cmq) 3 or 5 or 10 or 15 or 20 or 30   (greater ranges upon request)
Sensitivity 0,02% f.s.
Accuracy <0,2% f.s. (upon request 0,1% f.s.)
Resolution  0,02% f.s.
Linearity <0,4% f.s.
Operation Range (Hz) 500 – 1000
Drift in temperature 0,025% f.s. for °C
Filter In bronze or sintered steel, porosity 10mm or 30mm
Material Stainless steel AISI 304
Dimensions 35mm x 110mm
Weight 750 gr
Membrane sealing Electrowelding TIG
Cable sealing  By weld metal glass, resin and cable sleeve
Signal Cable
Type Rubber insulated 2×1 mm2 ; 3x1mm2
Outside diameter 11mm
Maximum allowable traction 15 N/mm2  movable installations; 50 N/mmfixed installation
Weight for 100m 3x1mm2: 18Kg
2x1mm2: 16kg
Analogical  Piezometer  
Range From 1 to 300 meters of water column
Precision ≤ ±0,25 % f.s.
≤ ±0,1% f.s.
≤ ±0,05% f.s.
Overcharge 3 x f.s.
Thermal Drifts [± % F.S./°C]
– Zero: 0 … +70 °C
– Span 0 … +70 °C
0,06 … 0,02
Long-term stability (1 year) < 0,2% f.s. for ranges > 1 bar – 4 m bar for ranges 0,5 < 1 bar
Operating Temperature -5 … +50 °C
Fluid Temperature -5 … +50 °C
Power Supply 9 … 30 Vdc
Output Signal 4-20 mA
Material of pressure sensor AISI (Ceramic upon request)
Material instrument body Stainless steel 316 (Titanium upon request)
Cable Material PUR

Related products

Tubular element and sensor protection Outdoor application, in stainless steel
Case and sensor protection Indoor Application, accessible; Gewiss in resin
Bourdon Manometer auxiliary in class 1 Indoor Application
Siphon and taps Indoor Application

Technical Assistance

If you have any requests or questions about our instruments or if you have special needs that require different solutions from the standard, please contact us. Our team will provide all the necessary information and will be very happy to work with you to study, develop and customize instruments and solutions suitable for your specific needs.


All information in our datasheet is subject to change without prior notice.

Please check the datasheet/details carefully and contact Pizzi Instruments for further information