Vibrating Wire Inline Extensometer


The Vibrating Wire Inline Extensometer is used to determine the stability and movement behavior of soil, rock, and concrete structures.


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Product Features

  • Flush with surface, no electrical head protruding out of borehole
  • Suitable for remote reading and data logging
  • Suitable for extension and compression movements
  • Can be installed in 3" borehole
  • Rigid 3/8 inch inner stainless steel rod


The Vibrating Wire Inline Extensometer is used to determine the stability and movement behavior of soil, rock, and concrete structures. The main advantage of the extensometer is that it has no electrical head protruding out of the borehole, contrary to conventional multi-point borehole extensometers (MPBX). The Inline Extensometer is installed flush with the borehole collar or ground surface and measures movement at different depths in the borehole.

By construction, all displacement transducers are located in the borehole in sealed head/anchor assemblies that are inserted in the borehole and separated by extension sections which can be of variable length depending on the required measurement depths. The extension sections consist of rigid 3/8 inch (9.5 mm) stainless steel rods protected by a telescopic outer 21/32 inch (16.8 mm) PVC pipe. The larger diameter of the rigid rod is an additional advantage as compared to the usual 1/4 inch (6.35 mm) of conventional MPBXs, as it provides more accuracy in the measured displacements, both in case of extension and compression movements.

As all displacement transducers are in series in the borehole, the total measurement range of the extensometer is the sum of the individual measurement ranges of each transducers. This allows to measure considerably larger movements than conventional MPBXs while using lower cost standard range transducers.


Sensor Range 25, 50, 100, 150, 200 mm
Accuracy +/- 0.25 % FSR
Resolution 0.02% FSR
Linearity 0.25% FSR
Thermal Zero Shift <0.05% FSR/°C
Operating Temperature -20°C to 80 °C
Extensometer Head max/min Diameter 63.5 mm / 42.5 mm
Signal Cable Two twisted pair cable with polyurethane jacket (one cable per measurement point).


Vibrating Wire Inline Extensometers are commonly used for:

  • Ground movements around tunnels.
  • Deformation of concrete piles (tell-tales).
  • Deformations of dam abutments and foundations.
  • Ground movement behind retaining walls, sheet piling, slurry walls, etc.
  • Ground movements in the walls of open-pit mines.
  • Fracturing in the roofs and walls of underground caverns.
  • Subsidence above tunnels and mine openings.
  • Settlement and heave of foundations in soft soil.

View illustrations on how the Vibrating Wire Inline Extensometers are used in underground mines.

Vibrating Wire Inline Extensometer Ordering Info

25 mm EXINLINE-1025 1 m
50 mm EXINLINE-1050 1 m
100 mm EXINLINE-1100 1 m
150 mm EXINLINE-1150 1.5 m
200 mm EXINLINE-1200 2 m

*-Please specify anchor type
*-Includes Signal Cable & Sheath


0.5 m EXIL-0500
1.0 m EXIL-1000
1.5 m EXIL-1500
2.0 m EXIL-2000
3.0 m EXIL-3000


Signal Cable Ordering

Signal Cable EL380004


End Achor Ordering

Groutable Anchor EXIL11000
Groutable Anchor with Spring Legs EXIL12000
Hydraulic Borros Anchors EXIL13000
Hydraulic Bladder Anchor EXIL14000


Ordering Info Considerations

Number of anchors, type and depths.
Specify sensor range.
Accessories required.
Cable length.
Borehole diameter.
Environmental considerations.
Extension or compression expectations.
Drilling method, soil and/or rock types.
Orientation of borehole.


Accessories & Optional Equipment Ordering

Grout and/or bleed tubes.
Portable readouts.
Hydraulic pump for anchors.
Terminal stations.
Data loggers.

File Name

Vibrating Wire Inline Extensometer

Resource Type

Language Version Download
English EXB0020F
Spanish EXB0031A

File Name

Multi-Point Inline Extensometer Installation Manual

Resource Type

Language Version Download
English EXM0097I

Speak with an Expert

I’m very happy with the quality of the instrumentation and technical support from RST, as always. They worked with us from the initial stages of the project to ensure that we were fully prepared and equipped to use the RSTAR network for the first time. They delivered everything within the tight project time frame to ensure that there were no delays on site, and the submersible tilt meters looked like new even after over twelve months of being submerged in Thames water!
-Richard Lipscombe, BEng (Hons), Director & Principle Consultant - RL Geotechnical Ltd