LVDT On-sample Strain Sensors (Local Strain Measurement)

On-sample transducers consist of smaller size, submersible LVDTs which are mounted on soil samples using calipers. They are used to measure the actual soil deformation during a triaxial test, eliminating the errors produced by the frame deflection, load cell compression, etc. VJ Tech’s On-sample system consists of three LVDTS that are used to measure the radial (x1) and axial (x2) deformation. The calipers that hold the LVDTs in place are pined into the specimen and glued on the rubber membrane to ensure an accurate measurement of the deformation. On-sample transducers are very important for the determination of the small-strain deformation and stiffness occurring in a soil specimen.

A complete set consists of 2 Axial Calipers, 1 Radial caliper, 3 LVDTs fitted to the Calipers (each with cable, cable exit port, and male LEMO) & Signal Conditioning Unit with entry and exit cables. When used in a static Triaxial frame, the data will be processed by the LVDT Signal Conditioning Unit, and the results passed on to a datalogger. When used in a Dynamic system, the data can be processed by the Dynamic Servo Controller, without the need of the Signal Conditioning Unit.

Clisp Studio incorporates the measurements of the on-sample transducers into the Advanced Triaxial, Unsaturated Triaxial, and Dynamic Triaxial modules for the determination of the sample’s diameter change, allowing to perform Ko consolidation in triaxial specimens. The readings from the Axial Strain sensors can be used to determine the true sample’s axial strain.

  • Available on 50mm, 70mm and 100mm triaxial specimens.
  • Usually combined with static or dynamic triaxial systems.
  • Triaxial cells with exit ports or extension rings are required.
  • LVDTs have identical body size and they fit to any size caliper.
  • They can be used to measure the radial deformation (i.e., change in diameter) and the axial deformation (i.e.., change in height). When combined, Poisson’s Ratio can be determined.
  • Sample volume change can be determined in unsaturated soil specimens.
  • Axial strain is determined in the middle section of the soil specimen, which is not affected by the boundary effects (e.g., friction between the top cap and the soil specimen).
LVDT Strain measurement range
+/- 2.5mm, +/- 5 mm and +/- 10 mm
LVDT Sensitivity
375 mV/V
Calipers for the following Sample Sizes
50, 70 and 100 mm triaxial specimens
Test Performed

Unsaturated Triaxial tests
Triaxial Tests (UU, CU, CD)
Stress Path tests
Advanced Triaxial and Cyclic Tests


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