Emerson Tescom ER5000 Series User Manual page 159

ER5000 — The ERTune™ Program: Basic Features
Cascade Tuning
Cascade tuning is complex and can prove daunting for the
inexperienced user and should only be attempted if the system is
persistently unstable.
NOTE NOTE
When the ER5000 is set to Cascade Mode, the PID Control Panel
has separate displays for the internal and external PID controllers. Click
CAUTION CAUTION
the Cascade Show External?/Cascade Show Internal? button to toggle
between these two displays within the panel.
WARNING WARNING
Cascade Tuning Tips
• Cascade Mode typically only requires tuning for the PID
settings of the External loop.
• For proper operation in Cascade Mode, the defaults for the
Integral Limits of the External loop are: Maximum: 32767;
Minimum: 0. These settings are optimal for most applications
and should not be changed unless you have verified that this
is required by your application.
• Increasing the Integral Term of the External PID generally
has a more pronounced effect on rise time than increasing
the Proportional Term. In some applications, increasing the
Proportional Term of the External PID in Cascade tuning may
slow down rise time.
• Alternate between increasing the Integral Term, then
increasing the Proportional Term, until you begin to see
instability in the response of the ER5000. At this point, back
off the values slightly.
• The Derivative Term should be added gradually to the
External PID after Integral and Proportional values have been
set. Unwanted effects from too much Derivative may develop
quickly, so be prepared to step back the Derivative slider as
soon as they are noted.
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