Structure And Mode Of Operation; Transducer; Strain Gage Covering Agent - Hbm U9C Montageanleitung

Structure and mode of operation

4 Structure and mode of operation
4.1

Transducer

The measuring body is a steel loaded member on which strain gages (SG) are
installed. The influence of a force deforms the measuring body, so there is
deformation in places where the strain gages are installed. The SG are
attached so that two are stretched and two are compressed when a force is
applied. The strain gages are wired to form a Wheatstone bridge circuit. They
change their ohmic resistance in proportion 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 gage arrangement is chosen
to compensate, as much as possible, for parasitic forces and moments (e.g.
lateral forces and eccentricity influences), as well as the effects of temperature.
4.2

Strain gage covering agent

To protect the SG, the force transducers have thin cover plates that are welded
on the bottom and, in versions with a nominal (rated) force of up to 200 N, on
the top. This method offers very good protection against environmental
conditions so that the U9C reaches the protection class IP67. In order to retain
the protective effect, these plates must not be removed or damaged in any
way.
Fig. 4.1 The thin plate on the top side must not be damaged in the variants with
nominal (rated) forces 50N, 100N and 200N; the same applies for the plate
on the bottom of all force transducers.
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A03815_03_YI0_01 HBM: public
U9C