AddHistorianExpressionLine Method

AddHistorianExpressionLine is a method for a Trend Invoke method action.

  • Purpose: AddHistorianExpressionLine
  • Advanced Configuration: AddHistorianExpressionLine

Purpose: AddHistorianExpressionLine

To use expressions when plotting historical data from one or more Historian databases to the runtime Trend Control when Invoke Method is triggered by an event.

Historian expression lines display expressions that include a combination of runtime and archived data. Both types of data are reported by Historian. The behavior of the Historian line type depends on the Allow Runtime Scrolling property

Important: Expression functions related to alarms (e.g. ANA, NACK) are not supported when evaluating historical data.

Advanced Configuration: AddHistorianExpressionLine

Click Advanced on the Action tab of the Procedure Information dialog box.

The Edit Method dialog box opens for the AddHistorianExpressionLine method

Configuration is as follows.

Field Description
Method name Name of the selected method. Note: Another method can be selected from the drop-down list.
Method result (Optional) Setpoint that contains the status value.
Class Boolean
Structure Type BOOL
Allowed Device or global Point ID.
When a user invokes the method, the method result contains one of the following values.
Value Method Result
1 The line was successfully added to the trend.
0 The line was not added to the trend.
Parameters LineID String that provides a name for the Line ID. The name will display in the Legend to identify the added line.
Expression String That evaluates to an expression, which is one or more tags from either single or multiple Historian servers. Syntax for Historian tags that are included in the expression is. \\<Data Collector Name>\<Tag Name> Where
<Data Collector Name> Server that is connected to Historian.
<Tag Name> Format is defined in the Project Properties dialog box.
Note:
  • The source for an Historian line can be a tag collected by any Historian Collector.
  • If the values are not being logged to Historian, a line will not display; however, the point ID will display in the legend with empty values (***).