Cutback --Built-in Overshoot Inhibition Software
This unique feature is part of Eurotherm's copyrighted software for PID
tuning of control loops. The Series 2000 PID algorithm features a proven
overshoot/undershoot inhibition feature called "cutback." This unique feature
is far superior to other overshoot algorithms. High and low cutback parameters
are set automatically by the self-tuning routines and they can be individually
adjusted to optimize performance. For example: the proportional band (PB)
number might be 30 degrees after performing a self tune. If Cutback Low
is set to Auto, then the instrument will calculate the lower cutback to
be 90 degrees (3 times PB) below setpoint. As the rising temperature crosses
this point, the PB window will be temporarily moved to this point in order
to slow down the increasing temperature. The PB window will be permitted
to return to its proper location based upon the thermal dynamics of the
temperature zone as learned in the self tune procedure.
Cutback Low prevents overshoot on rising temperatures. Cutback High
prevents undershoot on decreasing temperatures. Setting to "Auto" permits
the instrument to set them. You may also set them individually if you wish
to. A smaller number than 3 times the PB will result in more "aggressive"
response and some possible overshoot.
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