Step 2.5. Set OPC Group Settings Properties

OPC group settings information is required for the OPC configuration.

Enter information on the OPC Group Settings tab of the Device dialog box as follows:

Configured OPC groups

Select a group from the OPC groups field. DEFAULTPOLL and DEFAULTUNSO are groups created by the OPC client and always exist.

You can enter a group name to create a new group, then use the New Group button to add the group to the list.

New group Button

Click this button to add a new group to the Configured OPC groups list.

 

Property

Value

Description

Scan Rate

 

Default

1000 ms.

Determines how often the OPC server updates the items in this group with fresh device data. It also determines how often to send DataChange events to the OPC client. Enter the scan rate in milliseconds (ms).

If you require faster value updates, this value can be set as low as zero (0). If set to 0, the OPC server updates values "as fast as possible". However, caution is urged when setting this property to zero because it is possible for the OPC server to send the data faster than the hardware or operating system can support on a sustained basis. As the scan rate decreases, CPU usage may rise significantly and a corresponding increase in network traffic may be observed in a DCOM environment.

NoAccessPath

True

Enables OPC servers to have the Item IDs include the access path, separated by a period (.).  

Set to False if your OPC server (e.g. OMNISERVER), does not use the Access path when adding points.

 

False

Default

DelayBeforeRefresh

True

Enables the OPC server to delay before refreshing after adding the items.

 

False

Default

DeviceReadAfterSet

True

Requests that the OPC server read the data from the device.

Default

 

False

Forces the OPC server to read from its cache.

IsPolled

True

Enables polling.

Default

Note: For existing devices that were configured in earlier versions of the OPC Client using the .INI file, all groups listed in the .INI file are displayed in the OPC groups list.

More information

Configure an OPC Client device.