Allen-Bradley LOGIX 5000 Reference Manual page 397

Statistical Instructions
Output Parameter
EnableOut
Out
Average
Status
InstructFault (Status.0)
InFaulted (Status.1)
NumberOfSampInv (Status.2) BOOL
Structured Text
Operand
block tag
StorageArray
See Structured Text Syntax for more information on the syntax of expressions
within structured text.
Description
The MSTD instruction supports any input queue length. Each scan, if
SampleEnable is set, the instruction enters the value of In into a storage array.
When the storage array is full, each new value of In causes the oldest entry to be
deleted.
The MSTD instructions uses these equations for the outputs:
Condition
Average
Out
The instruction will not place an invalid In value (NAN or
storage array. When In is invalid, the instruction sets Out = In, sets Average = In,
and logs an overflow minor fault, if this reporting is enabled. When In becomes
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
Data Type Description
BOOL Indicates if instruction is enabled. Cleared to false
if Out overflows
REAL The calculated output of the algorithm.
REAL The calculated average of the algorithm.
DINT Status of the function block.
BOOL The instruction detected one of the following
execution errors. This is not a minor or major
controller error. Check the remaining status bits
to determine what occurred.
BOOL In health is bad. InFault is set.
NumberOfSamples invalid or not compatible with
array size.
Type Format
MOVING_STD_DEV structure
REAL array
Action
Chapter 5
Description
MSTD structure
Holds the In samples. This
array must be at least as large
as NumberOfSamples.
INF) into the
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