What is the OPC UA PLC Tag Path

I established OPC UA connection to my CompactLogix PLC in Ignition 8. My OPC Name is OPC_2 and it is connected and I can see PLC Tags and r/w them as well.
When I subsribe a tag it gives me below address:
Server> OPC_2
Address> ns=1;s=[My_CLogix_ERM]Program:MainProgram.Start_PB

I entered below path to check the status of Start_PB, but it does not work:

opc.tcp://localhost:62541/OPC_2/[My_CLogix_ERM]Program:MainProgram.Start_PB

Entered it into what? That path has no meaning to anything in Ignition.

Entered into an Excel cell to show tag value.

I can tell you two things:

  1. the endpoint URL to the Ignition OPC UA server is opc.tcp://localhost:62541
  2. the NodeId of the Node you’re trying to read is ns=1;s=[My_CLogix_ERM]Program:MainProgram.Start_PB

You’ll have to read the documentation of whatever software you’re using to make Excel talk to an OPC UA server to figure out what to do with that information.

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I understand. But I have created 3 OPC UA in Ignition and all of them are connected.
What is the specific address of each of them? I mean if I use `opc.tcp://localhost:62541, which one is called? I should add something after the port number to address only one of them at the time. something like:

opc.tcp://localhost:62541/OPC_1/

or

opc.tcp://localhost:62541/OPC_1/Discovery

or …

Why? Ignition comes with what you need already created. You need to create the connection to Ignition inside your Excel OPC plugin. However that plugin’s documentation says.

It is just for experimenting. Personally I would like to know how I can call one of my 3 OPC UA servers created in Ignition. As I can add OPC UA servers, some how I should be able to specifically address them through other OPC Servers or clients.

You’ll have to give each one its own set of ports for discovery and for operations, I think.

You haven’t created 3 OPC UA servers. You’ve created 3 connections to Ignition’s OPC UA server, 2 of which are pointless.

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I got it. So what is the benefit of being able to create more connections to one server?

There isn’t a benefit. The ability to create more than one connection is so you can have connections to other OPC UA servers.

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Appreciate you.
By the way, have you ever connected Ignition OPC UA server to OPC expert server?
As I enter the Ignition OPC UA address (opc.tcp://localhost:62541/discovery) in OPC expert, it says it could not connect to that address. !!! I already set all server security to NONE in Ignition side to ease of operation.