8
U2B
HBM 24.5.2000
2.2
Housing
The housing with its integral measuring spring is closed by a floor plate
welded to its underside. The measuring spring on the force transducer has a
threaded pin which acts as a force conductor. A removable adapter is
screwed to the lower part of the housing and acts as a force conductor via
jointed eyelets (see Section 7).
1
2
3
4
5
7
8
9
6
1
1 = Strain gauges
2 = Housing with integral measuring spring
3 = Adapter
4 = Lock nut
5 = Threaded pin for force conductor
6 = Glass bushing
7 = Cable chest
8 = Welded cover
9 = Internal thread
Fig. 2.1:
Schematic diagram: U2B
2.3
Measurement process, output signal
A force acting upon the transducer will elastically deform the SGs applied to
the measuring body. Their electrical resistance then changes in proportion to
the change in their length. This disturbs the balancing of the measurement
system wired in the form of a Wheatstone bridge, resulting in an output volt-
age U
A
at contacts 1 and 4 if a bridge excitation voltage U
B
is present at
points 2 and 3 on the bridge.
The ratio between the voltages, U
A
/U
B
, expressed in mV/V, is a measure of
the sensitivity of the force transducer. The change in output voltage U
A
is lin-
ear to the acting force. Provided the force transducer is connected in accor-
dance with Fig. 5.1 and as specified in the User Manual for the amplifier con-
cerned, compressive forces are displayed with a positive operating sign and
tensile forces are shown with a negative operating sign. The force transducer
is electrically connected in 6-wire mode (see Section 5.2). To reverse the po-
larity, the white and red wires in the cable should be transposed.
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