User`s guide

Appendix B - Loop Application Examples
PID Control Algorithms
Release E UMC800 Control Builder User’s Guide 241
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Example 3 - Ratio control
The RATIO control loop requires selection of the
remote SP of the PID for ratio control. The Ratio
and Bias values are available for adjustment
from the Control Setup screen of the Operator
Interface. The Bias may be a local value or come
from an external source such as an O2 analyzer
trim arrangement. You may elect to use % for
the ratioed inputs (typically for boiler
applications) or Eng. Units (EU) (for feed flows to
a reactor, for example).
External Bias
Input
Air (controlled variable)= Ratio x Fuel (RSP, or wild variable) + BIAS
Example 4 - Assigning alarm relays to loop alarms
Digital output signal from PID block AL1 will turn the Digital
Output block ON & OFF for remote alarming. This output could
be Ored with other alarm outputs if going to a common alarm
relay.
FAIL