Access Property Tags

You can use the Root Group branch of the OPC Data Bar to access the properties of any database item to which the ViewX client and your User Account has access. The name of each property is stored in the database as an OPC Tag.

To access such a property:

1. Display the OPC Data Bar (see Display an Explorer Bar in ViewX in the Geo SCADA Expert Guide to ViewX and Virtual ViewX Clients).
2. Expand the Root Group branch of the system (database) for which you want to access a property.
   The uppermost entries within the branch correspond to the database setup (the entries
3. mirror those of the Database Bar).

   

   The lower entries within the branch provide access to OPC properties associated with the Root Group’s configuration fields, data fields, database aggregates (some of which appear as tabs on the Root Group’s configuration Form), and status attributes.

   

   

4. Expand the tree structure further, as required, to access the OPC properties in which you are interested.

   (If required, you can place the cursor over an entry in the OPC Data Bar, to display a ToolTip providing more information about that entry.)

   The entries within each Group, Group Template, or Group Instance are organized in a similar way to those of the Root Group: the uppermost entries provide access to the database items and any Groups within that branch of the database; the lower entries provide access to the OPC properties associated with that particular Group, Group Template, or Group Instance.

5. Either:
   • Right-click on an item other than an OPC property to display a context sensitive menu, then select the Display Values menu option.
     A window is displayed, showing the current values of the OPC Data Access properties that are associated with that item.

     

     (Reference fields, such as ‘EventAreaOfInterest’ shown above, store the Object Id number of the target database item. The Object Id is the number that uniquely identifies an item in the database. An Object Id of 0 (zero) indicates the Root Group (or ‘World’ Area of Interest, if referring to an AOI reference field). An Object Id of -1 indicates a reference field to which no database item has been assigned. In this particular case, no Area of Interest has been assigned to events associated with the Guest User (as can also be seen by the blank ‘Area of Interest’ field on the ‘Guest User’ tab of the configuration Form shown in step 2).)

     Or:

   • Double-click on an OPC property to display a window providing information about that specific property.

     

     (With a property that also appears as a field on a configuration Form, a Timestamp of 01/Jan/1601 typically indicates that the property’s setting has never been changed from the default. In the figure above, for example, the ‘AllowGroupAlarmOps’ property appears as an ‘Allow Group Alarm Operations’ check box on the Guest User tab of the Root Group’s configuration Form (as shown in the figure in step 2). The check box is blank (indicating that the feature is disabled, or false) by default. The Timestamp shown above indicates that the check box’s setting has never been changed from the default.)

     Or:

   • Right-click on an OPC property to display a context sensitive menu. The options vary, depending on the type of property, but may include:
     • Display Value—Displays a window providing information about that property (as shown above).
     • Display Trend—Displays the property’s value in the form of a current Trend.

       

     • Set Value—Displays a window enabling you to set the property’s value.

       

6. If you want to use an OPC property elsewhere (for example, in a Logic program or on a Mimic), you can either:
• Copy and paste the OPC Tag from the window that is displayed when you double-click on the property or select Display Value from the property’s context sensitive menu. For more information, see Use the Status Display Buttons in the Geo SCADA Expert Guide to ViewX and Virtual ViewX Clients.
• Drag the required property (OPC Tag) from the OPC Data Bar onto a Mimic or other display. For more information, see Add Live Values to a Mimic in the Geo SCADA Expert Guide to Mimics.

Further Information

For more information on any of the OPC properties that are available from the OPC Data Bar’s Root Group branch, see the database Schema.

Using the Schema, see Working with the Database Schema in the Geo SCADA Expert Guide to the Database.

Trends: see the Geo SCADA Expert Guide to Trends.

Geo SCADA Expert supports several types of Trend. The type of Trend that you can display using the OPC Data Bar is a ‘standard’ Ad Hoc Trend (see Pre-Configured Trends and Ad Hoc Trends in the Geo SCADA Expert Guide to Trends).

Use the OPC Historic Data Bar to Access Historic Property Tags.

Access status attribute properties such as Alarm Count tags: see Use the OPC Data Bar to Access Alarm Count Information in the Geo SCADA Expert Guide to Alarms.