Advanced Topics; Input Selector (Isel) Function Block - Emerson Rosemount OCX8800A Manual

Manual
00809-0500-4880
8.11

Advanced topics

8.11.1 Arithmetic types
The parameter ARITH_TYPE determines how PV and the compensation terms (t)
are combined. You may select from nine commonly used math functions
depected below. COMP_HI and COMP_LO are compensation limits.
If there is a divide by zero and the numerator is positive, f is set to COMP_HI; if the
numerator is negative, then f is set to COMP_LO.
The square root of a negative value will equal the negative of the square root of
the absolute value. Imaginary roots are not supported.
If there is a divide by zero and the numerator is positve, f will be limited to
COMP_HI; if the numerator is negative, f will be limited to COMP_LO.
Compensation inputs which are not usable are not included in the calculation. PV
is always included.
8.11.2 Troubleshoot
8.12

Input selector (ISEL) function block

The input selector (ISEL) function block can be used to select the first good, hot
backup, maximum, minimum, or average of as many as four input values and
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