Value
A read connection. You can assign a tag or an expression to this connection. The application reads the value of the connection at the data source and changes the fill level on the bar graph to reflect the value.
If you assign an expression, the application calculates the value of the expression and updates the object’s display to reflect the value.
Configure the bar graph (General tab)
How the bar graph works at run time
Columns on the Connections tab of a graphic object's Properties dialog box