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GDS Hall Effect Local Strain Transducers

Product Code : GDSHE

On Sample Hall Effect Transducers (HE) are very light and easy to handle, therefore can be mounted to the sample for small strain measurement with minimal disturbance to the sample.

Small strain stiffness values are becoming more commonly required by consultants due to the parameters required for FE models.  It has been recognised for many years that small strain measurement is more representative to the operational strain, and that the small strain stiffness curve is required for any advanced modelling of the soil. Need advice choosing the right transducer, view our options table here.

Further Information:

Discover more transducers and load cells equipment for soil testing.

GDS Hall Effect Local Strain Transducers
specification datasheet (PDF)
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Key features Benefits to the user
Axial and radial deformation measured directly on the triaxial test specimen: Removes bedding errors or “end effects”.
Light compact semiconductor chip: The Hall Effect semiconductor chip is very light, has compact assembly and is compensated against changes in ambient temperature and changes in DC voltage supply.
Accurate determination of soil stiffness: True soil strains can be masked by deflections which originate in the compliances of the loading system and load measuring system. Such equipment compliance errors add to a variety of sample bedding effects to give a poor definition of the stress strain behaviour of the material under test, particularly over the small strain range.
Small strain measurement: Recent work has demonstrated that soils can be equally as brittle as rocks and that an understanding of their behaviour at levels of shear strain below 0.05% is very important.
Measurement is taken in the middle third of the sample which is less restrained than the end zones: Therefore, it is highly desirable that radial and axial deformations are measured locally in this region if realistic deformation moduli are to be found.
Displacement Range

+/-3.0mm
Pressure Range (MPa)

Up to 2000kPa
Sample Sizes

38mm, 50mm,70mm,76mm, 100mm,150mm, custom
Weight Approx (kg)

: Radial Caliper Weight, 38mm caliper = 24g, 70mm caliper = 46g, : Axial Apparatus Weight (1 off) = 16g, : Transducer Weight (1 off encapsulated Hall Effect Chip) = 5g


 

Tests supported by the GDS Hall Effect Local Strain Transducers, transducers and load cells equipment for soil testing :-

Axial or Radial Deformation

Axial deformation is measured by a displacement transducer in all GDS systems (LVDT, LDT or digital gauge).  Radial deformation is calculated as standard by measuring the volume change to 1mm3 directly on the back pressure controller.  For direct measurements of radial strain (i.e. transducers mounted upon the sample, and direct measurements of axial strain in the same way, GDS can supply a Hall Effect local strain set or an LVDT local strain set. Please note: Some apparatus may require additional components or software modules to perform certain tests.

Axial or Radial Deformation soil test equipment
Local Strain Measurement

Accurate determination of soil stiffness is difficult to achieve in routine laboratory testing. Conventionally, stiffness of a triaxial test specimen is based on external measurements of displacement which include a number of extraneous movements.  By placing transducers directly on the sample, accurate measurements of strain may be obtained, particularly in the small strain area of the sample loading cycle where strain dependancy of soil stiffness (stiffer at low strains) can be otherwise be masked when using external transducers.

Local Strain Measurement soil test equipment
Maximum Shear modulus

Determination of the maximum (i.e., very small strain) shear modulus of a specimen. Please note: Some apparatus may require additional components or software modules to perform certain tests.

Maximum Shear modulus soil test equipment

Standards for the GDS Hall Effect Local Strain Transducers, transducers and load cells equipment for soil testing :-