Problem: Modbus TCP device is getting polled every second, despite Tag Group settings
Device: Modbus TCP connection to Rotronic room temperature monitor
S/W: 8.0.7 / Modbus Driver 6.0.7
I am capturing two serial numbers, temp, and humidity from a Rotronic device. They feed standard OPC tags with hardcoded paths (e.g. ns=1;s=[Rotronic]Reading1). The tags are assigned to a custom Tag Group (Direct mode, Polled, Rate= 15,000). When the moon aligns and I create the device / addresses / tags from scratch, the tags follow the polling rate of the group and the device gets two Modbus requests every 15 seconds.
The problem is that on a whim the tags will start refreshing every second. This has happened when I’ve renamed the device, created the tags via drag-n-drop from the tag browser, and has even happened after 12 hours of stable functionality when I restarted a tag in the OPC browser.
Once the fast polling starts, all the tags go to that rate and it’s irreversible. To the point that it is currently hammering out Modbus requests even though I just recreated the device, added the addresses, but have NO TAGS CREATED.
This polling rate causes periodic tag health issues from overquerying the device - and this data is supposed to be used for audit trail on a temp controlled room.
Anyone else seen anything like this? I’ve been experimenting for days and can’t find how to precisely reproduce (or avoid) the problem.