Omega CN4321, Руководство пользователя, Страница: 77 / 83

db Deadband/Overlap: Deadband is that area where neither out-
puts are energized. Overlap is that area when both outputs
are energized. This function lets you decide where you want
the heating action to stop and the cooling action to begin.
Notes:
1. The Heat/Cool Option is available on the CN4321 controller only.
Output #2 can be a relay output only.
2. Integral and Derivative Times are the same for both the heating and
cooling sides of a process with PID control because the response
frequency or time constant of the system does not change at main
setpoint when cooling is added.
3. The Proportional Band for heating and cooling are almost always
different. Rarely does the same amount of cooling output remove the
same percentage of process error as the heating output does. The
Cooling Proportional Band must be manually and separately tuned.
4. If the heating side is set for On/Off control, the cooling side will be
set for On/Off control also. Regardless of what the COOL parameter
is set for, if the Proportional Band is set to zero, the Heating Propor-
tional Band and the Cooling Proportional Band will always be zero.
5. If the cycle times of one or both outputs are long and the process
dynamic, there is a good chance that both outputs will be cycling on
and off at the same time around main setpoint. This is evident if one
or both outputs are relays.
6. Autotune is not effective on the cooling side of Heat/Cool control.
Autotune the controller for heat only and then manually tune the
cooling parameters.
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