Clicking on the "Virtual..." button on the Plot Properties Mapping tab launches the Virtual Item Dialog. This allows any number of Items to be combined in a mathematical expression. The result becomes a "Virtual" pen that can be trended.
See the Virtual Items page in the Basic Plot Operations for an overview of Virtual items in stPro.
Tip: Press the "..." button to select a pen from the available list.
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Field/Control Name: |
Description: |
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Item Name |
The user specified name to use for the Virtual Item. |
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Description |
A user specified textual description of the Virtual item.
Note: The Description will be displayed as contextual data with the item throughout stPro/stOCX. It is the morale equivalent of the OPC Item Property that will be read for 'genuine' OPC items during item resolution. |
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Units |
A user specified text string that defines the Engineering Units for the Virtual item.
Note: The Units will be displayed as contextual data with the item throughout stPro/stOCX. It is the morale equivalent of the OPC Item Property that will be read for 'genuine' OPC items during item resolution. |
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Formula |
The Expression to evaluate for the Virtual item. See the Syntax page for a definition of the constructs that can be used to define an expression. |
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... |
The Browse button. Used to select an OPC item for use within the specified Expression. |
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Validate |
The Validate button. Used to validate the syntax of the Expression without having to exit the dialog.
Note: Validation of the Expression will always take place when the dialog is closed via the 'OK' button. |