Rockwell Automation FactoryTalk Metrics User Guide - Manual (Page 108)

Chapter 3 Collecting Performance Data
Item Description
QualityOf() Uses one parameter to return three OPC server values. The values in
parentheses in the first column of the following table represent the
OPC bit values for quality. The corresponding converted QualityOf()
return values are displayed in the second column. This function only
applies to OPC or FactoryTalk data servers. If you are using a DDE
server, a Good value is always returned.
OPC Server QualityOf()
Bad (0) 1
Uncertain (1) 2
N/A (2) 3
Good (3) 0
If you use the Use Bad Quality option and you have chosen the
QualityOf() expression string from the Expression Editor dialog
box, along with the Substitute Previous Value option, the
FactoryTalk Live Data server sends bad quality data to the control
connector. The control connector logs the bad quality and passes it
to the Transaction Manager service. The Transaction Manager
service substitutes the previous data point's value, as well as the
QualityOf() the previous data point's value, and then passes good
quality to the enterprise connector. The enterprise connector then
logs good quality.
If you use the Use Bad Quality option and you have chosen the
QualityOf() expression string from the Expression Editor dialog
box, along with the Substitute Value option, the FactoryTalk Live
Data server sends bad quality to the control connector. The control
connector logs the bad quality and passes it to the Transaction
Manager service. The Transaction Manager service uses the
specified substitute value, and then passes good quality to the
enterprise connector. The enterprise connector then logs good
quality.
108 Rockwell Automation Publication PLTMT-UM001M-EN-P-June 2014