You can specify a block of historic data in the database and have Geo SCADA Expert perform a calculation on that data. The result of the calculation can form the value of an expression in a Data Grid cell. In order to perform such a calculation:
- The Field has to have a numeric Type (see Use the Field Properties Window)
- Geo SCADA Expert has to be configured to log values historically for the item for which you want to perform the calculation.
To use the result of such a calculation for an expression a cell in a Data Grid, either:
- Display the OPC Historic Data Bar (see Display an Explorer Bar in ViewX in the Geo SCADA Expert Guide to ViewX and Virtual ViewX Clients).
- Perform one of the following:
- For the path to the property to be relative to the Data Grid’s location, drag the required item from the OPC Historic Data Bar into the relevant Data Grid cell.
- For the path to the property to be absolute, hold down the SHIFT key while you drag the property from the OPC Historic Data Bar into the required cell.
By default, the result of the expression is the average value of the selected item during the current hour.
Or:
- Right-click on the required cell in the Data Grid.
A context sensitive menu is displayed. - Select the Historic Tag option.
Database items that have historic properties (historic ‘tags’) are displayed in a Select Historic Tag window
- Select the required entry from the hierarchical tree structure and then use the fields in the window to specify:
- Whether the path for the tag is to be relative or absolute
- The calculation that Geo SCADA Expert is to perform on the data
- The block of historic data that Geo SCADA Expert is to use for the calculation.
For more information on using the window, see OPC Historic Tags in the Geo SCADA Expert Guide to Expressions.
- Select the OK button.
The Select Historic Tag window is closed. The specified tag is displayed in the Data Grid cell.