E17 Rod Extensometer System

The Rod Extensometer system accurately measures settlement and/or heave at single or multiple anchor points in a borehole relative to its reference head. It employs up to eight rods, anchored along the axis of a borehole with a diameter from 50mm up to 200mm, terminating in the reference head at the borehole entrance.

The Rod Extensometer system can be assembled on-site or can be supplied pre-assembled to specified lengths and coiled to ensure a quicker and easier installation.

Product Features 

  • Rods and heads are available pre-assembled to customer specified lengths
  • Fibreglass rods (GRP)
  • Various anchor types available
  • Remote monitoring using Vibrating Wire displacement transducers and wireless systems such as GTec Link
  • Up to 8 measuring points per borehole
  • Lighter, condensed construction

Product Benefits

  • Quicker deployment than conventional rod extensometer systems
  • Less sensitive to temperature changes than steel
  • Enabling installation in varied soil conditions and orientation
  • Ideal for remote and difficult to access locations
  • Provides greater visibility of the settlement profile
  • Lower shipping costs and easier to manoeuvre on site
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Relative movement between the end anchor and the reference tube is measured with either a digital depth gauge, or a displacement transducer inserted through the reference tube and registering on to the free end of the rod.

The ground condition determines the type of anchor to use:
• Groutable anchors for downhole installation in rocks
• Hydraulic anchors (single or double-ended) for soft soils
• Packer anchors for jointed rocks, where there is flowing water, or uphole installations

The extensometers have reference heads with provision for up to eight measuring points per borehole. Borehole diameters may be in the range of 100mm-200mm.


Continuous Rod Extensometers are used to monitor small-scale rock and soil movements to a high degree of accuracy, including settlement and heave of foundations and relaxation or subsidence of rock around tunnels, shafts, caverns, and abutments.

Typical applications include:
• Monitoring settlement and heave in foundations
• Monitoring tunnels, shafts, caverns and abutments
• Control of natural and cut slopes, quarry and mining excavations
• Monitoring deformation of retaining walls, bridge piers and abutments


Contact us for more information on the E17 Rod Extensometer system by Soil Instruments.