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Wireless Multipoint Borehole Extensometer

The WMPBX is a flush-mounted, wireless, multi-point borehole extensometer designed to monitor settlements and deformations in busy locations that are difficult to access, such as city streets, highways, airport taxiways, and port facilities. Datasheet

Wireless MPBX


An MPBX includes anchors, rods, a reference head, and sensors. Anchors are joined to rods and installed at specified depths in the borehole. Rods run upwards from the anchors to the reference head, which is installed at the surface. Sensors inside the reference head monitor the rods, which follow the upward or downward movement of the anchors.

The WMPBX adds a waterproof canister containing a data logger, a radio modem, and long-life battery pack to permit the complete instruments to be installed flush with the pavement. The data logger obtains readings from the sensors at specified intervals, and the radio modem transmits the readings to a nearby base station or cell tower.

Because the radio modem is below grade, it requires a special antenna. GEO designed its flush-mount, traffic-rated Lid-Link Antenna for this application.


The WMPBX can be adapted to suit almost any site conditions. Some of the options are:

Monitored Points: The WMPBX can monitor a maximum of 5 points. Each point must have its own anchor, rod assembly, and sensor.

Anchors: A wide variety of anchors is available, including simple groutable anchors, packer anchors, hydraulic prong anchors, and snap ring anchors.

Sensors: Both vibrating wire and Linear Potentiometers are available, with measurement ranges from 2 to 6 inches.


Settlement Sensors - MPBX

Anchors and rods are pre-assembled at the factory to save time at the site. The geotextile packer anchor will be inflated with grout when the extensometer is in place.

Positioning the MPBX head

Positioning the waterproof MPBX head which contains logger sensors, radio, and batteries. Yellow grout tubing was used to inflate the packer anchor.

Placing the traffic-rated LidLink antenna

Placing the traffic-rated LidLink antenna.