You can impose upper and lower limits on the modulating output.
Limitations
(MIN POS, MAX POS)
In that case, 0…100% output means "Positioning signal min (MIN
POS)…positioning signal max (MAX POS)" as shown below:
0 %
100 %
0 %
0 V
100 %
10 V
MAX POS
Y
Qs
31
01
D
05
MIN POS
Qs = load demand from the sequence controller
You can use this feature to parameterize the output for a solenoid valve with a
DC 5…7.5 V input signal, for example.
Application example
%OPEN according to
the outside
temperature
At low outside temperatures, air heating coils must be permanently heated; this is
ensured by maintaining a (minimum) valve position (controlled by an analog
output). This function prevents the air heating coils from freezing up.
Prerequisite for this function is the availability of an outside temperature signal
(refer to section 7.6, Outside temperature (OUTS)
If the outside temperature falls below the adjusted limit value (ON-OUTS), the
controller opens the analog output. The analog output and thus the valve opening
position in percent are set to the value entered in %OPEN. The analog output is
deactivated and thus the valve fully closed when the outside temperature has
exceeded the limit value by 2 K.
Notes
•
The connected controller sequence can override this process
•
This function is available with every operating mode, including Protection
8.2.3
Troubleshooting
The controller interprets external signals IN X with input values below 0 V as 0%,
and signals with values over 10 V as 100%. It performs linear interpolation on all
values in between.
Signal interpretation
Observe hardware restrictions!
Caution
If, with the %OPEN function activated, the outside temperature sensor is missing,
the valve opens until the entered position is reached and then maintains that
position.
Note
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Siemens
Universal Controllers RLU2…
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Building Technologies
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29.08.2008
