Tag is not existed

Hi. I have one question. There are two different OPC-UA servers, working on a different PC’s. One server (let’s call it “Server 1”) has a module, wich creates some tags. This server connected to other server (let’s call it “Server 2”). In Ignition Designer, started from Server 2, in a Translation Groups window I can view that tags. But when I try to read one of that tags, using system.tag.read(“path_to_tag”).value, I got Null. What can I do to read that kind of tags?


There are probably 2 things that could help:

  1. In the transaction group, you may be referencing the OPC item directly. If so, in your script, you probably want to read directly from the opc server as well, using [tt]system.opc.readValue(…)[/tt] (see here).

  2. If you are, in fact, reading a SQLTag that points to the opc item, you may not be using the full path to the tag, including the tag provider name. For example, it would look like: [tt]system.tag.read("[default]Path/To/Tag")[/tt]

It important to understand the difference. You can read from the opc server directly, using its item path, or you can read from a SQLTag- which might be subscribed to that opc item in turn. Which you use is up to you, but each will have their own syntax.


Thank you very much. The way number 1, you tell me, works.