Q: OPC UA location of sensor data

0
votes

I have done some research on OPC UA and noticed that all sensor data on the Prosys sample server is stored in subfolders of the Object (i=85) folder. On the OPC UA server of a machine I have seen that the sensor data like the measured value, the unit etc. can ONLY be accessed via the Types (i=86) folder.

The path here would be i=84 -> i=86 -> i=88 -> i=58... There is really no other path through which you can reach these nodes otherwise.

I have never seen such an implementation.Is this normal that such data is also stored in the Types folder or are there any guidlines that forbid this? The machine is also a bit older.

Thanks for your help

UPDATE: the further path of i=58 looks like this, where --(i=45)-> symbolizes the Referencetype from the previous to the following node (in this case i=45, HasSybtype) and the word in the parentheses next to the NodeId is the NodeClass.

i=58 --(i=45)-> ns=2;i=1(ObjectType) --(i=35)-> ns=2;i=2(Object)
--(i=35)-> ns=2;i=3(Object) --(i=47)-> ns=2;s=@setPressure(Variable) --(i=46)-> ns=2;i=5(Variable)

ns=2;s=@setPressure contains the value 250.0 and ns=2;i=5 an Engineering unit

1
opc-uaopc

1 Answers

1
votes

This is not normal. It sounds like a bad implementation done by somebody who didn’t know any better.

Depending on the reference types they used to build this structure you could argue it is forbidden. DataType Nodes should only be the source of HasProperty, HasSubtype, and HasEncoding references.

edit: The path you mention is Root -> Types -> ObjectTypes -> BaseObjectType. Are you sure the Nodes you're finding under here are Variable Nodes with values or are you just seeing additional types defined by this server?