Rockwell Automation T8019 Trusted Process Control Algorithm Software Package - Manual (Page 14)

Trusted
TM
Process Control Algorithms T8019
Issue 8 Sep 07 PD-T8019 14
2.4. High Value Select
HVS
OUT PV1
PV2
SEL
The process variables (PV1 and PV2) and the output (OUT) are all REAL 4 . The output (OUT) is set to
the higher process variable value.
( )
PV2 PV1, MAX OUT =
The selected output (SEL) indicates which of the process variables is being used to generate OUT.
SEL is of type Boolean, and is FALSE if using PV1 and TRUE if using PV2.
If PV1 or PV2 is a NaN, the function is to set OUT to PV1, SEL to FALSE and increment the “Param”
error counter. OUT is not a NaN if, and only if, PV1 is not a NaN and finite if, and only if, the higher of
PV1 and PV2 is finite.
2.5. Median Value Select
MVS
PV1
OUT PV2
PV3
LIMIT
DEVIATION
The median value select sets OUT to the mean of the three process variables (PV1, PV2 and PV3) if
the deviation between their values is less than the maximum (DEVIATION). If the variation in inputs is
less than the allowed deviation the LIMIT output is set to FALSE. If the input values vary by more than
DEVIATION, OUT is set to the median value and LIMIT is set to TRUE.
If an overflow condition occurs during the execution of the function, e.g. if the deviation is huge, the
function is to set OUT to the median value, LIMIT to TRUE, and increment the “overflow” error counter.
All input parameters (PV1, PV2, PV3 and DEVIATION) must be finite, i.e. not ±infinities or NaNs.
4 The standard ISaGRAF MAX function provides the equivalent functionality for integer values
(without the SEL output).