Magnetic Reed Switch Probe Extensometer System Model R-4

The R-4 Magnetic Extensometer is a precise multiply point settlement gage designed to accurately measure deformation in soil and rock including:

  • Heave of brace or open cut foundations
  • Subsidence
  • Settlement within soil or rock embankments and dams
  • Foundation settlements
  • Deformation around underground openings
  • The stability of natural slopes, excavations and walls
The R-4 Magnetic Probe Extensometer consists of an array of magnetic targets, surrounding a common access pipe, positioned at different depths along the length of a borehole or the height of an embankment, fill.

A reed switch probe, lowered down the access pipe detects the position of the magnet anchors outside the tube. The probe is suspended by a single graduated tape that incorporates the electrical leads. The tape graduation is used to determine the deformation along the pipe's axis between anchor points.

Close block

The magnetic anchors are available in two configurations leaf spring anchor and plate anchor. The leaf spring anchor can be pushed in place or lowered with the access pipe. The leaf spring anchor pre-mounted on the access pipe is released with a cutting device lowered through the access pipe with an external draw wire.

The paler anchor is comprised of a plate with a central hole. The magnets are mounted in each plate. The plate anchors are installed with the access pipe as the construction of the embankment or foll proceeds.

Telescoping access pipe is used where deformations exceeding 1% are expected.