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Magnetic extensometer

A Magnet Extensometer consists of a series of magnets (spider) that are installed on the outside of an access pipe. The magnets are anchored at specified depths. Measurements are taken by lowering a Reed Switch Probe down through the access pipe to detect the depth of the magnets.


Magnetostriction is a property of ferromagnetic materials such as iron, nickel, cobalt and their alloys to expand or contract when placed in magnetic field

Initially when these ferromagnetic materials are not magnetised the magnetic domains of the ferromagnetic material are randomly distributed. But when they are placed in magnetic field the magnetic domains undergo changes and are arranged in parallel.

A magnetostrictive sensor is used to measure linear position. It basically senses the position of the permanent magnet (position magnet) to determine the distance between the permanent magnet and the sensor head.


A physical quantity unit intended to be measured. In Geotechnical instrumentation the six main measurands that are monitored are pressure, displacement, force, temperature, tilt and volume. This is then used in several calculations (computations) to quantify different parameters.

(Also see parameter)


Micro Electronic Measurement System uses modified semiconductor device fabrication technology to make specialist electronic printed circuit boards including accelerometers and  gyroscopes used for manufacturing inclinometers and tilt sensors.


Multiple point borehole extensometer which is used to measure and locate settlement, displacement and deformation in soil and rock. It consists of a reference head and one or more in-hole anchors each of which is placed at a known depth and connected to the reference head by either a rigid or flexible rods running inside sleeves which keep the rods de-bonded from the grout. 

As the soil or rock deforms the anchors’ positions change and the relative movement can be measured in the reference head.

The magnitude, distribution, rate and acceleration of deformation can be accurately measured at the reference head.


A multiplexer (or mux) is a device that selects one of several analogue or digital input signals and forwards the selected input into a single line. Multiplexers are mainly used in automatic data acquisition systems to increase the amount of sensors that can be connected to the data logger.