This particular type of gauge is installed in
diaphragm walls, struts, piles, and tunnels as
it measures stresses and strains in concrete.
These steel bars have a Wheatstone bridge
attached to measure the stresses of the bar.
Only two of the strain gauges are active
thus removing the influence of flexing and
thermal variations.
This simplifies the readings and takes away
the need for additional complicated
calculation or instrumentation.
The sensor is protected from damage from
impact by layers of resin which also protects
the device from pressure from submersion in
liquids.
Therefore theses gauges can be attached
to reinforced cages and embedded in
concrete.