HBM U9B, Mounting Instructions, Page: 9 / 68

9
U9B
A0137-7.0 en/de/fr HBM
3 Construction and mode of operation
3.1 Transducer
The measuring body is a membrane that is mounted on four strain gages
(SG) so that two are stretched and two compressed. The membrane with the
SG is elastically deformed by the force acting in the measuring direction. The
strain gauge changes its ohmic resistance in proportion to its change in length
and so unbalances the Wheatstone bridge. If there is a bridge excitation volt­
age, the circuit produces an output signal proportional to the change in resist­
ance and thus also proportional to the applied force.
The force is applied to the measuring body of the U9B via two threaded bolts.
For smaller measuring ranges up to 200 N, one side is designed as an
adapter which is connected via three screws (M3) to the transducer (see
Fig 3.1). By undoing these screws, you can remove the adapter and mount
the transducer directly. The zero signal may change by max. 2% due to this. If
the adapter is mounted again, the screws must be tightened with a tightening
torque of 0.75N
⋅
m.
Fig 3.1: Adapter connection with three screws
3.2 SG cover
To protect the SG, the U9B force transducers are welded with a thin metal
plate. This procedure offers the SG a high protection against environmental
influences.