Use the Expression pane of the Tag Picker

Use the Expression pane at the bottom of the Tag Picker to add an expression that will show in your trend. See Expressions (wwexpression) for information about the syntax and usage for expressions.

Add an expression

1. In the Expression field, add the expression you wish to display in the trend.

   Select the Expanded Expression Editor button to open a larger expression window. This is helpful for entering longer expressions.

   In Historian Client Trend, validation is performed on the expression’s syntax. If the syntax is incorrect, an error displays. Tag names are not validated; if an expression includes an invalid tag name, the expression will not return data, and no error will display.

2. In the Alias field, a default alias is assigned. If it is changed, the revised alias will show as the tag name of the expression in the trend. If the alias is left at default, the value from the Expression field will be used instead.

3. Select Add to add the expression to the trend.

   Note: A trend with an expression must use extension tables for the source. If you configure a trend with a source other than Extension tables in the options, the trend is automatically processed with extension tables. A message to that effect appears in the log.