Rockwell Automation FactoryTalk Metrics User Guide - Manual (Page 109)

Collecting Performance Data Chapter 3
Use the following advanced functions:
Item Description
Parse() The Parse function uses four parameters to return the requested
value from a data point array.
• The first parameter is the data point to parse. The data point is
usually created as a starting data table address and a length, for
example, N7:0,L8 returns an array of eight elements from N7:0
to N7:7 in one data point.
• The second parameter is the starting offset in bytes of data to
be extracted from the array.
• The third parameter is the length in bytes of data to be
extracted.
• The fourth parameter is the data type of the extracted data.
Data extracted from the data point array is converted to this
data type.
The Expression Editor supports a data point range syntax that
compares a data point value over a series of transactions. Each time
the transaction runs, a new value is added to the data range for a
given transaction. The expression is then evaluated using the range
of values.
Data Point Range The MIN(), MAX(), SUM(), and AVG() functions use the data point
range for multiple parameters of historic data from a single data
point. Transactions using the Data Point Range expression fail until
there is enough historical data to evaluate the expression.
For example, the expression AVG(data_point1[0:4]) computes the
average of the current value of temperature plus the previous four
historical values of temperature. The first four occurrences fail
because historical data is not available. Error 32769 is returned
(invalid argument passed to a function).
How do I access the dialog box?
1. In the left pane of the Configure Performance Parameter
Event dialog box, click Event Value.
2. Under Event Value / Reason Code Lookup List, click
Create List.
Advanced Functions
Creating Event Value Reason
Code Lookup Lists
Rockwell Automation Publication PLTMT-UM001M-EN-P-June 2014 109