Appendix
I
B-3
PID Parameters
STEPS:
Set Default Parameters
1
Turn off all derivative control by setting
Er
and
EH
to “0”.
2
Minimize integral control by setting
nt
and
nH
to “800”.
3
Set proportional control of
bn
and
PBH
to an initial value of approximately
10% of setpoint.
For example, if your setpoint is 150°F {66°C}, set these
parameters to “15”.
Run a Test - Proportional
4
Start the Thermolator and observe it attempting to reach setpoint.
5
Decrease the values of
bn
and
PBH
until the system beings to oscillate around
the setpoint.
You may have to cool-down your system and repeat the experiment
several times so you can accurately observe the process temperature approaching
setpoint.
6
Multiply the value determined by step 5 by “2” and enter it as parameters
bn
and
PBH
.
Continue the Test – Propor Integral
7
Decrease the integral setting
nt
and
nH
by a factor of two and run the system
through a thermal cycle.
For example, change it from “800” to “400”, then “200”,
then “100, etc. Repeat as necessary. You should observe the steady-state error
disappear and the system reach setpoint. If the system begins to oscillate around the
setpoint, you have gone too far.
8
Cool-down your system and repeat the experiment so you can truly observe the
process temperature approaching setpoint.
You will probably observe the
temperature overshooting the setpoint. If overshoot is acceptable for your process,
there is no reason to continue tuning. If you would like to eliminate overshoot in
exchange for slightly longer times until setpoint it reached, read on, as overshoot can
be eliminated using the next step.
Continue the Test – Propor In Derivative
9
Set the derivative parameters
Er
and
EH
to “1”.
Run the system through a
thermal cycle and observe the overshoot the first time it reaches setpoint.
10
Double the derivative parameters
Er
and
EH
and run the machine through
another thermal cycle.
If you have a floating valve, you may wish to observe its
position, since derivative control will help the system properly anticipate the slow
operating time for such a valve.
11
Repeat the doubling process of parameters
Er
and
EH
until overshoot is
satisfactorily eliminated.
If the system stutters or temporarily reverses temperature
direction as approaching setpoint, your derivative response is too aggressive and you
need to decrease this parameter.
(Continued)
(Continued)
Summary of Contents for Thermolator TW-P
Page 6: ...iv I Table of Contents ...
Page 12: ...1 6 I Introduction ...
Page 36: ...3 14 I ...
Page 58: ...4 22 I Operation ...
Page 72: ...5 14 I Maintenance ...
Page 128: ...E 4 I Appendix ...
Page 134: ...G 4 I Appendix ...
Page 136: ...H 2 I Appendix ...