OPC arrays as event PI points

Multiple scan classes can have the same scan period, and event classes are a logical grouping of PI points. For efficiency, put event arrays into their own scan classes with any other points that need to be read with the array.

Configuring arrays that are read as event tags is complex: because only the first array item (with userint1 = 1) causes a read, you must create a dummy trigger PI point to use with the rest of the array items. That PI point must have a pointsource that is either unused or used for manual entry points (lab data usually is entered manually, so L is often used as the pointsource for manual entry PI points).

In the following example, the trigger PI point is called TriggerTag and the dummy trigger PI point is called DummyTrigger.

Because all the tags in an array must belong to the same group, even if the OPC server is v2.0 and some part of the array data comes from a different device than the rest of the array data, all the array tags must be configured to be in the same event group.