Watlow F4P Series, User Manual, Page: 18 / 124

3 . 4
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O p e r a t i o n s P a g e Wa t l o w S e r i e s F 4 P
3. Next, autotune the outer loop. Go to the Autotune PID
Menu (Operations Page). Choose Cascade Outer Loop,
then choose Outer Loop PID set 1 to 5, where PID val-
ues will be stored after autotuning. Autotuning begins
when you choose the PID set. While autotuning, the
outer loop will be controlled in an on-off mode at a set
point equal to static set point x Ch 1 Autotune Set
Point. In most cases, the autotuning feature will tune
for acceptable control. If not, manually tune the outer
loop (step 4 below). Before manually tuning, record the
values generated by the autotuning feature.
4. To manually tune the outer loop, go to the Edit PID
Menu (Operations Page). Choose Cascade Outer Loop,
then choose Outer Loop PID set 1 to 5. Begin manual
tuning by setting the Proportional Band to 5, Integral
(Reset) to 0, and Rate to 0. Establish the desired set
point and let the system stabilize. When the system
stabilizes, watch the Inner Loop Set Point on the Main
Page. If this value fluctuates, increase the proportional
band until it stabilizes. Adjust the proportional band
in 3° to 5° increments, allowing time for the system to
stabilize between adjustments.
5. When Input 1 has stabilized, watch the percent power
on the Main Page. It should be stable, ±2%. At this
point, the process temperature should also be stable,
but it will exhibit droop (stabilized below set point).
The droop can be eliminated with Integral (reset).
6. Start with an integral setting of 99.9 minutes, and al-
low 10 minutes for the process temperature to come up
to set point. If it has not, decrease the setting by half
and wait another 10 minutes. Then halve the setting
again and wait another 10 minutes until the process
value equals the set point. If the process becomes
unstable, the integral value is too small. Increase it
until the process stabilizes.