Magnet targets sliding on a central access tubing are fixed in the ground at locations where movement is to be monitored. Various types of magnet target are available; they are retained by leaf springs in boreholes or plate fixtures in soil or fill. A suspended probe incorporating triple reed switches travels within the access tubing and senses the position of magnet targets outside the tubing.

The reed switches close on entering a magnetic field, activating visual and audio indicators in the cable drum. The probe is suspended by a composite cable and steel measuring tape and measurements are taken from the top of the access tubing to each magnet target in turn.

One probe reads at many locations; only the access tubing and magnet targets are permanently installed in the ground.

Displacements can be measured in three dimensions by combining this instrument with an inclinometer installation.

Reliable, accurate, simple to install and to read.
Any number of points can be monitored at little extra cost and with no increase of borehole diameter.
Magnet targets and portions of access tubing can be excavated or added.
Ideal for monitoring heave and settlement in cut and fill operations.

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