Rockwell Automation 9307 FactoryTalk EnergyMetrix - Manual (Page 92)

FactoryTalk EnergyMetrix Software
92
Usage is:
CalcDerivedTags [-sd ] [-ed ] [-t
] [-d]
-sd
-ed if not specified, generates values until current
date
-t if not specified, generates all derived tags in
the system
-d delete old data in the selected interval before generating new
values; if not specified, existing data is not overwritten
Examples
 Simple derived tag
In this example, the 'Acme' domain includes a main meter and a meter on one of its
two feeders. The meter on the second feeder is a 'virtual' meter populated with derived
tags. The derived tag script using shortcut method tag names for the Real Power
Demand tag is:
Result = #MeterTagID456# - #MeterTagId789#
The script may also use fully qualified tag names. This usage will not permit the use of
other derived tags in the formula.
 Derived tag using functions
This example calculates a value for Real Power Demand based on a 15 minute fixed
demand period. The referenced meter tag (MeterTagId = 138) is logging Real Energy
Net at a 15 minute log rate.
Result = TagTotal(138, 0, 0, 0, 15) * 4
 Consumption derived tag (odometer-style)
This example logs an odometer-style consumption value in derived tag ID 123 by
adding the 15-minute usage of meter tags 456 and 789 to the previous logged value of
the derived tag.
Result = GetTagData(123, DateTime.utcNow.AddMinutes(-15)) _
+ TagTotal(456, 0, 0, 0, 15) _
+ TagTotal(789, 0, 0, 0, 15)
 Testing source data
In this example, the source data is tested to avoid writing an incorrect result into the
database. When the If condition is false, no Result is written.(
If (Not GetTagData(456) Is Nothing) And (Not GetTagData(789) Is
Nothing) Then
Result = GetTagData(123, DateTime.utcNow.AddMinutes(-15)) _
+ TagTotal(456, 0, 0, 0, 15) _
+ TagTotal(789, 0, 0, 0, 15)
End If