"Ignition serverA" reads tag values from "Ignition serverB" via an OPC UA connection.
However, when viewing values on "Ignition serverA" that are originally read from OPC (IEC61850) by "Ignition serverB", there is a discrepancy.
The tag type on "Ignition serverB" is float, and on "Ignition serverA" it was initially double. We suspected that the difference in data types may be causing the discrepancy, so we matched both to float, but the values still differed.
When we created a test tag as a memory tag on "Ignition serverB", the values matched correctly when read by "Ignition serverA".
What should be done in this case?
We have attached the connection settings for "Ignition serverA" and the OPC UA server settings for "Ignition serverB".
serverA setting
serverB OPCUA server setting
Can you show us an example of the discrepancy you're seeing and some details about how you're reading the tags between servers? Is it scripted reads? A subscription by creating an OPC tag?
“Va” is the tag from serverB, and “V_AN” is the tag from serverA.
We suspected that the value difference might be due to the tag group's scan time, so we set the scan rate to 2 seconds (2000 ms) to test, but the values still differ.
• Test: When writing the current value to a memory tag using a tag change script and then reading that memory tag, the values match correctly.
What is the timestamp on the V_AN tag?
Kevin,
After seeing your question, I checked the timestamps and noticed that the two are not the same.
When they occasionally match, the displayed values are also the same.
The tag group is set to 30,000 ms (Polled), so it should update every 30 seconds,
but in reality, the update interval sometimes exceeds 3 minutes.
Why is that happening?
I've attached the current Tag Group settings below.
What were the timestamps? Which tags/gateway do that tag group belong to?
Why are you using Polled instead of Subscribe? Nine times out of ten this is a mistake, often due to misunderstanding how these work.
I don’t quite understand the question about "what the timestamp was."
At the time, I didn’t check the timestamp, but after seeing your question, I checked the timestamps of the tags from “serverA” and “serverB.”
I noticed that the timestamp of the tag read from “serverA” occasionally matches the timestamp of the tag from “serverB.”
When this happens, the values are the same.
This tag group belongs to “serverA.”
The reason I used Polled is that I opened a Modbus server and set it to periodically write values.
Would it be better to use Subscribe?
I mostly want to know if when the value in A doesn't match the value in B, if A has a more recent timestamp. Tags won't update when they receive a new value that has an older timestamp.
I cannot even begin to imagine what you're talking about here. I did notice you for some reason called your Tag Provider "Modbus", which makes no sense, because on ServerB we appear to be dealing with tags from a 61850 device connection, and ServerA is accessing these tags over OPC UA via the exposed tags feature enabled on ServerB.
Almost always better. If you can't explain why you chose Polled you shouldn't have changed it from Subscribe.
I think you're going to need to call into support so they can get a look at this and figure out what your system actually looks like, and then maybe turn some loggers on if it's not something simple like the timestamps being too old for the value to update.
ServerA reads data from ServerB, but the timestamp of the data on ServerB is earlier (or ahead of) than on ServerA.
The data is received via OPC UA and then sent to the Modbus server.
"Earlier" and "ahead of" have opposite meanings, but I suspect you mean the latter, that server b's tag values always have timestamps that are after the same same tags in A?
The timestamp of the data from "ServerB" is [2025-07-24 13:25:52], while the data from "ServerA" is [2025-07-24 13:23:27]. Therefore, the data from "ServerB" is more recent.
