GBO Magnetic Ekstensometer


The GBO Magnetic Extensometer are available in 2 main configurations. All 2 configurations listed below use an GBO Reed Switch Probe to provide a reading in magnetic zones allocated along the lenght of borehole.
Installation as a single purpose device to monitor settlement
Installed in conjuction with GBO Inclinometer Casing to
obtain both vertical and horizontal deformation data from a
single installation.

The GBO magnetic extensometer is used to monitor settlement and heave in excavation, foundations, and embankments. Readings obtained with the extensometer indicate the depths at which settlement has occured as well as the total amount of settlement.

• Stainless Steel Probe Material
• Replaceable 9V Battery
• Visible andAudible Indicators
• Waterproff Construction
• Stretch Resistant Measuring Tape

Reed Switch Probe : The reed switch probe is a reading unit
that will produce sound and light (at main unit) when it
encounters a magnetic field.
Access Pipe : Subsurface access for the probe is provided by
inclinometer casing or 1 inch (33mm O.D) PVC pipe.
Plate Magnet : The plate magnet is used in fill. It is positioned
at the specified elevation and then covered with fill material.
Spider Magnet : The spider magnet is used in boreholes. The
legs are compressed for installation and released when the
magnet is positioned at the specified depth.
Datum Magnet : The datum magnet is fixed directly to the
botom section of access pipe where the soil is stable.
Index Mark : Index Mark is used to mark the depth of reading
on the measuring tape.

Technical Spesifications

Cable Lengths
50 m, 100 m, 150 m, 200 m
± 1 mm
Probe Construction
Stainless Steel and Hard Nylon
Probe Dimension (L x Ø)
182 x 19 mm
Acces Tube
33 mm (1.3") O.D Sch. 80 PVC
Plate Magnet Material
Plate Magnet Material
Plate Magnet Dimension (L x W x D)
300 mm x 300 mm x 9.5 mm
Spider Magnet Material
Body : PVC
Legs : Spring Steel
Spider Magnet Dimension(L x O.D x I.D)
Closed : 445 x 70 x 34 mm
Released : 445 x 203 x 34 mm
Datum Magnet Material
Datum Magnet Dimension
54 x 60 mm
Borehole Size
102 - 152 mm (4 - 6")
9V Alkaline Battery


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