HBM U2B, Инструкция по монтажу, Страница: 9 / 60

9
U 2B
H BM A03823.3en/de/fr
2.3 M eas u reme n t p r o cess, ou t pu t si gn al
A force acting upon the transducer w ill elasticall y deform the SGs applied to
the measuring bod y . Their electrical resistance then changes in proportion to
the change in their length. This disturbs the balancing of the measurement
s
y stem w ired in the form of a Wheatstone bridge, resulting in an output v ol
tage U
A
at contacts 1 and 4 if a bridge e x citation v oltage U
B
is present at
points 2 and 3 on the bridge.
The ratio bet w een the v oltages, U
A
/ U
B
, e x pressed in mV/V, is a measure of
the sensiti v it y of the force transducer. The change in output v oltage U
A
is
linear to the acting force. Pro v ided the force transducer is connected in ac
cordance w ith Fig. 5.1 and as specified in the U ser Manual for the amplifier
concerned, compressi v e forces are displa y ed w ith a positi v e operating sign
and tensile forces are sho w n w ith a negati v e operating sign. The force trans
ducer is electricall y connected in 6 w ire mode (see Section 5.2). To re v erse
the polarit y , the w hite and red w ires in the cable should be transposed.
2.4 Co m p e n sati ng f o r d ist u rba n ce variables
The geometr y of the measuring bod y and the positioning of the SGs ensure
that the output signal from the transducer suffers onl y minimal distortion if the
force being measured is affected b y superimposed lateral forces and/or torsio
nal and bending moments. The specifications for this can be found in the
Technical Data. In the interests of greater accurac
y , ho w e v er, it is generall y
better to tr y to pre v ent spurious loadings of this kind altogether. The U 2B also
has separate lateral force compensation w hich reduces lateral force influ
ences to a minimum (see Technical Data).
The influence of temperature on the zero signal and sensiti
v it y are compensa
ted. C hanges in ambient pressure ha v e the same effect as additi v e (substrac
ti v e) forces (see Section 3.3).