Page 9
PROGRAMMING AND OPERATION FOR PID
Theory of Operation
The PID method of control is based on the individual tuning of proportional
band values, integral time values, and derivative time values to help a unit
automatically compensate for changes in a control system. The proportional
band is the range around the set point in which the control’s proportioning
takes place. The control increases or decreases the output proportionately
to the process temperature’s deviation from the set point. The integral time
eliminates undershoot and overshoot of the set point by adjusting the
proportioning control based on the amount of deviation from the set point
during steady state operation. The derivative time eliminates undershoot and
overshoot by adjusting the proportioning control based on the rate of rise or
fall of the process temperature. The integral deviation offset correction (ioFn)
improves the speed in which the process value reaches the set point value.
If this parameter is set to zero, the output will be zero when the process
value is equal to the set point value. If the integral time parameter is used
only to eliminate steady state error, it may take a long time to reach the set
point because it needs time to accumulate the error. This parameter defines
the default output level on start up. When the integral time is set at 0, then
the proportional derivative offset correction (PdoF) would replace the integral
deviation offset correction, but serves the same function.
Program Set Up
In order to use the PID function in the C series controllers, the Control Mode
will have to be set to PID in the Initial Setting Menu. After changing the
Control Mode, the PID parameters can be accessed in the Regulation Menu.
The PID parameters can either be programmed manually or they can be set
by the controller using the auto tune function. The auto tune will use trial and
error to tune the PID parameters to give the control the most precise control.
Since the time to accurately tune the control may differ depending on the
process, the controller can also be manually tuned to known PID values
prior to running auto tune. The Run/Stop parameter must be set to run in
order to start auto tuning.
Page 10
DESCRIPTION OF MENU STRUCTURE
The programming for the controller is broken down into three menus
(Operation, Regulation, and Initial Setting). Upon normal operation, control
will be in the Operation Menu.
OPERATION MENU
Pressing the INDEX key will cycle through the below menu items. The
parameter will be displayed in the top display, while its value will be
displayed in the bottom display, except for the set point which is displayed
in the bottom display on the Home Display. The UP and DOWN arrows
change the values of the parameters. The ENTER key must be pressed after
any changes.
Adjust the set point value - Can be any numerical value
between the upper and lower limit of the temperature range.
Select Run - Stop Output Control.
Activates outputs.
De-activates outputs.
Alarm 1 High Set Point. May not appear depending on ALA1
setting in Initial Setting Menu.
Alarm 1 Low Set Point. May not appear depending on ALA1
setting in Initial Setting Menu.
Alarm 2 High Set Point. May not appear depending on ALA2
setting in Initial Setting Menu.
Alarm 2 Low Set Point. May not appear depending on ALA2
setting in Initial Setting Menu.
Set front panel security lock.
Lock all settings.
Lock all settings except the set point.
Display the % output value for output 1. In manual mode, this
value can be changed using the up and down arrows.
1234
r-S
rUn
StoP
AL1H
AL1L
AL2H
AL2L
LoC
L0C1
L0C2
oUt1
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