OPC DA connector variable properties

LastSample

The last sample written to the historical stream of samples.

Stream value

SampleTypeCode

The data type of the sample stream for the variable.

The data type must be compatible with the data type of the variable that is mapped to on the OPC DA server.

Boolean, DateTime, Double, Event, Int32, Int64, Single, String.

Value

The value of the last sample written to the historical stream of samples.

AVEVA™ Production Management usually reads the variable tag on the OPC DA server to derive the value; however, you can also change the value of the OpcVariable item directly with the Value property, or by the execution of running code.

AVEVA Production Management writes the changed value back to the OPC DA server immediately, and updates the OpcVariable sample after the next event notification.

Active

Indicates whether the OPC DA server monitors the variable item and raises event notifications on the item's change of state.

True, False

OpcItemID

The tag name of the variable on the OPC system that the OpcVariable item maps to. This property is case-insensitive, and it keeps the name of the variable tag in the OPC system separate from the name in the Name property.

When you add an OpcVariable item with the Add Item menu command of the OpcDataSource item, rather than the OPC variables configuration tool, the AVEVA Production Management initially gives the OpcItemID property and the Name property the same value.

If you do not change the value of the OpcItemID property; that is, it still contains the same value as the Name property, changes to the Name property cause AVEVA Production Management to give the OpcItemID property the same value.

Samples

The stream of historical samples. Each sample contains a value, a quality, and a time stamp.

Sample stream