Structure And Mode Of Operation; Transducer; Strain Gauge Covering Agent; Disturbance Variables - HBM PWS Mounting Instructions

4

Structure and mode of operation

4.1

Transducer

The measuring body is an aluminum loaded member on which strain gauges
(SG) are installed. The influence of a force deforms the measuring body, so
there is deformation in places where the strain gauges are installed. For each
measuring circuit (measuring bridge), the strain gauges are attached so that
two are stretched and two are compressed. The strain gauges are wired to
form a Wheatstone bridge circuit. They change their ohmic resistance in pro­
portion to their change in length and so unbalance the Wheatstone bridge. If
there is an excitation voltage, the circuit produces an output signal proportional
to the change in resistance and thus also proportional to the applied force. The
strain gauge arrangement is chosen to compensate, as much as possible, for
parasitic forces and moments (e.g. lateral forces and torques), as well as the
effects of temperature.
4.2

Strain gauge covering agent

To protect the strain gauges, the load cells have a silicone covering agent, that
offers good protection against environmental influences. In order to retain the
protective effect, the silicone covering agent must not be removed, or damaged
in any way.
4.3

Disturbance variables

Torsion, bending moment and lateral forces are disturbance variables that
affect measurement accuracy, and should therefore be avoided as much as
possible.
PWS
A05750_02_XA0_00 HBM: public
Structure and mode of operation
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