Publication 1757-RM810A-EN-P - May 2002
3-40 Functional Blocks
Outputs Block has following initializable outputs:
• OP = Calculated output in percent.
• OPEU = Calculated output in engineering units
Note that the default OP connection pin is exposed on the blocks and the implicit/hidden connection function
automatically makes the appropriate value/status parameter (OPX/OPEUX) connection when required.
Output Ranges
and Limits
CVEUHI and CVEULO define full range of CV in engineering units. If this block has a secondary, it brings the
secondary’s input range through the BACKCALC and sets its CV range to that. If it has no secondary, you must specify
CVEUHI and CVEULO range.
• OPHILM and OPLOLM define normal high and low limits for OP as a percent of CV range (user-specified values).
– OP clamps to limits if calculated CV exceeds them, or another block or user program attempts to store OP value
exceeding them; operator may store OP value outside these limits.
• OPEXHILM and OPEXLOLM define extended high and low limits for OP as percent of CV range (user-entered
values).
– Prevents operator from storing OP value that exceeds these limits.
Equation
Options
• Equation A – Proportional, Integral, and Derivative on error.
• Equation B -- Proportional and Integral on error and Derivative on changes in PV.
• Equation C -- Integral on error and Proportional and Derivative on changes in PV.
• Equation D -- Integral only.
• Equation E -- Proportional only; this equation supports the following two options that affect CV:
– Output bias processing which adds fixed and floating bias to unbiased CV.
– Reverse-control action causes the sign of the unbiased CV to be reversed.
Gain Options If equation A, B, or C is selected, any of the following gain options may be chosen:
• Linear Gain -- provides proportional control action that is equal to a constant (K) times the error.
• Gap Gain -- used to reduce sensitivity of control system when PV is in user-specified band (gap) around set point.
• Nonlinear Gain -- control action is proportional to square of error, rather than error itself.
• External Gain -- gain (K) is modified by input value that can come from the process, another block or user program.
Direct or
Reverse Control
• Direct action -- increase in error increases output (OP).
• Reverse action -- increase in error decreases output (OP).
Parameters on following page
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