Eval tags are objects that acquire values on the basis of the defined expression (formula). Maintainer of eval tags is the calculation process - SELF.CLC. This process determines values of eval tags and reports changes of these values to D2000 system. Value changes are reported via communication with process D2000 Server.
Using eval tags in D2000 system
- calculations of derived values
- handling output tags in AUTO mode
- operands in logical and arithmetical expressions
- operands in conditions to raise and finish alarms
- displaying in pictures
- displaying in graphs
- archiving and displaying in graphs
Eval tag values, via process D2000 Calc (SELF.CLC), are calculated:
- periodically - expression is calculated periodically according to the given period and offset.
- on change - expression is calculated when a value of at most one object placed in the expression notation is changed.
- trigger - expression is calculated according to the defined condition (trigger).