GDS LVDT Local Strain Transducers

Product Code : LVDT

The GDS LVDT Local Strain Transducers provide on-sample small strain measurements of axial and radial strain. 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.

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. Most triaxial tests therefore tend to give apparent soil stiffnesses far lower than those inferred from field behaviour (Jardine, Symes & Burland, 1984). Need advice choosing the right transducer, view our options table here.

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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”.
Inherently robust LVDT’s as they have no physical contact across the sensing element: Zero wear ensuring longer life and lower friction effects.
Submersible low pressure version (pictured above): Water version can be used up to 3500kPa.
Vented high pressure version: High pressure version for use in non-conducting oil up to 200MPa (Pressure relieved).
Temperature limits -20°C to 60°C &
-20°C to 110°C
Suitable to use with GDS Environmental Triaxial Testing equipment, see page 8 for more information). Higher temperature versions available.
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.
Through bore configurations: Allows test to continue after the LVDT has passed its measurement range.
Radial sprung aluminium-bronze hinge for no backlash and low friction: The transducers measure sample effects not those of the measuring calipers.
Displacement Accuracy

0.1% FRO

Displacement Range

+/- 2.5mm or +/-5.0mm

Displacement Resolution

+/- 2.5mm = <0.1μm, +/- 5.0mm = <0.2μm typical values but dependant on data acquisition used

Sample Sizes

50mm, 70mm, 76mm, 100mm, 150mm, custom

Weight Approx (kg)

: Radial Caliper Weight, (based on a nominal 70mm caliper) = 74g : Axial Apparatus Weight (1 off) = 26g : Transducer Weight (1 off LVDT) = 20g