HBM CMD Serie Bedienungsanleitung Seite 77

CMD
Tips for piezoelectric measurement technology
S This produces 115493.8 pC for the charge range at
the input (is calculated automatically and set in the
CMD).
This produces an output voltage on the charge amplifier
of +10 V at 15 kN.
Example 2: Force washer
S A maximum force of 100 kN is to be measured.
S Select a force washer with a full scale value of
140 kN, such as the CFW/140 kN with -4.3 pC/N sen­
sor sensitivity.
S Enter the unit kN in the CMD Assistant via Display ->
Unit .
S For technical reasons, the force washer must be
pre‐stressed with approx. 20% of the nominal (rated)
force. This leaves a useful range of approx. 0.8 x
140 kN = 112 kN. You can use the sensor itself to
measure this pre‐stressing force. To do this, enter the
sensor sensitivity, here 4300 (pC/kN), and approx
30% of the full scale value as the Physical input
range, here, for example, 40 (kN, the display shows
39.99893).
S Then apply a pre‐stress of approx. 28 kN (20%).
S Unfortunately, the pre‐stress also causes the sensor
sensitivity to change. So you must determine the new
sensitivity by measuring. This can be done with a ref­
erence force transducer, for example.
S To do this, enter the unit pC, a sensor sensitivity of 1
(pC/pC) and, for example, an Electrical input range
of 50000 (pC), (for 10 kN, this produces a value of
approx. 43000 pC at 4.3 pC/N).
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