General columns in the signal table
For a description of the general signal table columns see Columns in tables with analog and digital signals.
Expression
This column contains the definition of a virtual signal (or alarm). You may enter simple numerical or Boolean equations or complex mathematical expressions. Mathematical expressions are created with the expression editor. If you know the syntax, you may also manually enter the expressions in the table.
Click the <fx> button to open the expression builder.
For more information, see .
Clicking on the <?> button executes a syntax check for the expression in the same row. A dialog window with diagnostic information about the expression opens. This is a good help when looking for errors in long and complex expressions.
Virtual analog signals are always REAL type values. In order to get a virtual digital signal or alarm, the result of the expression must be a Boolean quantity (TRUE or FALSE).
Adding signals
For virtual signals, there is always an empty row in the signal table. As soon as you start typing in a row, a new empty row will be added automatically.