Choosing the Right Transducer

This table presents a number of advanced transducer and control options that are available to determine soil properties typically unobtainable with conventional systems, or soil response that is more closely representative of in-situ soil conditions.

TransducerMain Function
Compatibility
RangeSoil / Rock
Hall Effects Transducers
Greater accuracy strain can be measured by using local strain transducers.
  • 1.7MPa
  • +/- 3mm
Soil

LVDT Transducers
GDS’ LVDT transducers are available in two types, low pressure and high pressure, they mount directly onto the specimens membrane to record on-sample small strain measurements of axial and radial strain.
  • Triaxial Systems (range from 50mm+ diameter specimens) (requires access ring)
  • EMDCSS (used for vertical measurement and direct pedestal to topcap measurement)
  • Up to 3.5MPa       +/-2.5mm,         +/-5mm,           +/- 10mm
  • Up to 100MPa     +/- 2.5mm         +/- 5mm
Low pressure (Soil)

High pressure
(Rock)
Mid Plane Pore Pressure Transducer
To increase the accuracy of pore pressure measurement during consolidation and shear, mid-plane pore pressure transducers can be fitted within a triaxial system.
  • 1500kPa
Soil
Bender Elements System
The very small strain response of a soil specimen can be determined through bender element testing.
  • 50mm+ diameter specimens
  • Up to 3.5MPa
Soil  

Laser Displacement Sensors
The lasers take a point measurement of the centre of the specimen at either 2 or 3 locations and provide a specimen profile from outside of the triaxial cell. 
  • 2 or 3 Lasers
Soil
Wet Wet Differential Transducer
GDS offers two types of Wet Wet transducer. One is used with the HKUST UNSAT method to measure volume change by means of hydrostatic head pressure changes. The other is to measure the back-base pressure differential for permeability testing.
  • Up to +/- 1.5kPa (HKUST version)
  • 200 or 50kPa range (differential pressure transducer for permeability)
Soil / Rock
Internal Submersible Load Cells
Designed to be submersible, the confining pressure does not affect the load readings recorded by the transducer. This in-turn removes friction of the ram and the up-thrust created from the test recordings, creating more accurate results. 
  • Load Cells up to 100MPa with
  • Loads up to 1500kN
Soil / Rock
Linear Strain Displacement Transducers
GDS’ Linear Displacement Transducers are the next new generation of strain gauge type transducers. Used in a wide variety of industries and applications, the linear displacement transducers are precision engineered with a robust construction.
All GDS Systems
  • 0 - 10mm
  • 0 - 25mm
  • 0 - 50mm
  • 0 - 100mm
Soil / Rock
Potentiometer Displacement Transducer
The transducers are supplied with a spring loaded shaft biased to the fully extended position. Being a potentiometric divide with coated windings, the transducers produce an output with limitless resolution.
All GDS Systems
  • +/- 12.5mm to
  • +/- 25mm
  • +/- 50mm
Soil/Rock
Pore Pressure Transducers
Pore Pressure Transducers are used to measure pressure during testing.  Typically used for pore pressure measurement, the transducers can be combined with remote feedback modules to provide additional reading for cell/back or lower chamber pressure.
All GDS Systems
  • Up to 100MPa
Soil/Rock

The S-Beam Load Cells are designed to measure load during testing. Non-submersible, these load cells are situated outside of the triaxial cell, between the top of the ram and the reaction bar of the load frame, or attached to a force actuator.
Up to 100kN
Soil/Soft Rock
Acoustic Velocity Transducer
Acoustic Velocity (AV) sensors are generally used where pressures and load exceed those where bender elements can be used. AV sensors are based on the same principle as bender elements however, the piezo ceramic elements are not exposed to the environment so they can be used at pressures up to 100MPa and loads up to 2MN.
  • GDS Triaxial Cells (typically high pressure)
Up to 100MPa 
Up to 2MN
Rock
Acoustic Emission Transducers
The Acoustic Emission transducers enable micro-fractures occurring within a rock specimen during testing to be recorded and analysed. Analysis of rock micro fractures can give information as to the failure mechanisms of a sample under tests well as determining the onset of failure.
  • Hoek Cell
  • GDS Triaxial Cells (Modified base required)
Up to 100MPa 
Up to 2MN
Rock