OPC Tag timing accuracy

Let’s say I have opc tags set up for a 1 sec Scan Class/Tag Group rates. Does Ignition guarantee that each tag will be updated at 1 sec or less but not more? Does this timing hold for any number of tags? If not, at what point does this timing start to slow down (10,100,1000,10000 tags) and how bad?

Also, if one or more of the tags is/are bad (disconnected) will it impact the rest of the tags timing?


It will update at ~1sec, or slower if the device can’t keep up with comms.

Depends entirely on the device and its comms load.

Individual tags don’t disconnect, but the device being offline will affect all tags on that device only, and the device not responding to a request will potentially hold up other requests to that device. Comms problems with one device do not effect other devices, though.

This information is all specific to our drivers in our OPC UA server.

OPC tags in general are just an OPC subscription to some OPC server, usually ours. The actual behavior of that server may vary.