Data sources for the Trend Client

The Trend Client can use real-time data from Application Server and the InTouch HMI software and historical data from the Historian or InTouch LGH files. You identify the historical data source when you configure a pen. For more information, see Configuring Historical Sources.

At run time, the Trend Client initializes the trend with historical data from the data source (if configured) and then appends real-time data for the pens. If the pen is not associated with a historical data source, the trend initially shows no data. It then starts charting information as real-time data becomes available. If you refresh a pen configured with historical data, the chart re-queries the historical information, after which it appends the real-time data as it becomes available. Refreshing does not change a pen configured only for real-time data. If you refresh a trend that is charting both historical and real-time data, the historical information is recharted immediately, after which the trend charts real-time data as it becomes available.

The Trend Client supports the same syntax as the Industrial Graphics. It also supports the built-in functionality of the OwningObject property for trends configured with relative naming. For information about Industrial Graphics data configuration syntax and OwningObject functionality, see the Creating and Managing Industrial Graphics User Guide. For more information on relative and absolute references, see the Application Server User Guide.

There are primary settings for specifying the time period you want to plot, such as a relative reference (the preceding two hours), or an absolute reference (July 15th at 10am for 2 hours) using scripting.

As an example, suppose you opened two trends created with the Trend Client. Both of them have a duration of 15 minutes, but the first one is only trending real-time data (meaning that the pen is associated with an expression but not with a historical tag) and the second is trending historical data (meaning that the pen is associated with both an expression and a historical tag). If you open both of these trends at the same time, what you see is described in the following table.