R-4 Magnetic Reed Switch Probe Extensometer

How it works

Magnetic targets are positioned at different depths along a borehole or the height of an embankment or fill, surrounding a common access pipe. A reed-switch probe, lowered down the pipe on a single graduated tape carrying the electrical leads, detects each magnet's position. The tape graduation gives the deformation between anchor points along the pipe's axis.

Installation

Two anchor types are available: a leaf-spring anchor for borehole installation, which is pushed into place or lowered with the access pipe and released with an external draw wire, and a plate anchor for embankment or fill installation, installed with the access pipe as construction proceeds. Telescoping access pipe is used where deformations exceeding 1% are expected.

The system is compatible with standard inclinometer casings, and a probe centralizer is recommended for repeatable readings.

What's included

The R-4 readout unit comprises the probe, reed switch, cable and reel. A range of accessories is available: PVC collar tape guides, push-in and standard leaf-spring anchors, magnetic plate anchors, magnetic datum ring anchors, access pipe and telescoping access pipe with couplings, installation jigs, and end caps, sized to match pipe diameters from 33 mm to 85 mm.