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APPENDIX B
Manual Tuning
Tune the controller if any of the following occurs:
•
Installation in a new system
•
Installation replacement in an existing system
•
The input sensor is relocated or changed
•
The output device is relocated or changed
•
The setpoint is significantly changed
•
Any other condition that will alter the dynamics of the system
Proportional Band
The proportional band is a band around the setpoint of the controller
where the output is between 0% and 100%. The percentage of output is
proportional to the amount of error between the setpoint variable (SV)
and the process variable (PV). Outside of the proportional band the out-
put is either 0% or 100%
The proportional band on the controller is equidistant from the main set-
point as illustrated below.
Reverse Action
Main Setpoint
PB
PV
100%
0%
Output
Note: PB = Proportional Band
PB
PV
100%
0%
Output
Direct Action
Main Setpoint
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