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POS-123-*-2030
5.7 Output signal adaptation
5.7.1
MIN (Deadband compensation)
5.7.2
MAX (Output scaling)
5.7.3
TRIGGER (Response threshold for the MIN parameter)
Command
Parameters
Unit
Group
MIN:i
x
MAX:i
x
TRIGGER x
i= A|B
x= 0… 6000
x= 3000… 10000
x= 0… 4000
-
0,01 %
0,01 %
0,01 %
STD
The output signal to the valve is adjusted by means of these commands. A kinked volume flow characteristic is
used instead of the typical overlap step for the position controls. The advantage is better and more stable
positioning behavior. At the same time, kinked volume flow characteristics can also be adjusted with this
compensation
11
.
CAUTION
: If there should also be adjustment options for deadband compensation on the valve or
valve amplifier, it must be ensured that the adjustment is performed either at the power amplifier or
in the module.
If the MIN value is set too high, this has an effect on the minimum speed, which can then no longer
be adjusted. In extreme cases this leads to oscillation around the controlled position.
MAX:A
MIN:A
MIN:B
MAX:B
Input
O
u
tp
ut
non lineare Flow
compensation
Standard deadband
compensation
TRIGGER
11
Various manufacturers have valves with a defined nonlinear curve: e.g. a kink at 40 or 60 % (corresponding to 10 % in-
put signal) of the nominal volume flow. In this case the TRIGGER value should be set to 1000 and the MIN value to 4000
(6000).
If zero lapped or slightly underlapped valves are used, the volume flow gain in the zero range (within the underlap) is twice
as high as in the normal working range. This can lead to vibrations and jittery behavior. To compensate this, the TRIGGER
value should be set to approximately 200 and the MIN value to 100. The gain in the zero point is thus halved and an over-
all higher gain can often be set.
