Deep Hole Extensometer

Deep Hole Extensometer

More Information


Australia Tel: +61 (0)3 8720 6700
Indonesia Tel: +62 21 3040 4422
New Zealand Tel: +64 (0)7 850 2610
South Africa Tel: +27 (0)10 900 2055


The Model 4020 Deep Hole Extensometer system uses stainless steel high tensile wires connected to spring anchors mechanically placed in the borehole (borehole not grouted). At the collar, these wires are connected to spring loaded sensors in a head frame. This provides a physical means of measuring the displacement in the zone between workings and surface displacements. Displacement ranges available are 1m, 2m and 3m. Up to 20 anchors can be placed in one hole. Read using Model 9600-2 readout or log using datalogger.


Measurement of settlements, subsidence, displacements and deformation in:

  • Tunnelling
  • Open cut mines
  • Dam construction
  • Underground mines
  • Large excavations
  • Construction control


  • Large depth capacity up to 900m
  • On-site anchor location decision
  • No grouting or drill rod setting
  • Head Frame easily re-locatable
  • Real time data in millimetres
  • Full borehole ventilation
  • Three options for obtaining data including digital counter, hand held readout and datalogger
  • Made of/coated with corrosive proof materials


  • Displacement ranges: 0-1m, 0-2m, 0-3m
  • Resolution: 0.5mm
  • Borehole diameter: 100 ~ 300mm
  • Max borehole depth: 900m
  • Dimension (head assembly): Up to 800mm x 800mm
  • Dimension (anchor): 60mm, expands up to 250mm
  • Weight (head assembly): 20kg