hi All
i have rather basic question which i would rather ask than assume.
I have Kepserver connected to Ignition Edge using OPC UA.
My understanding is that OPC UA works by exception which means that OPC UA server sends only the changes in the tag values but Edge is in my case OPC UA client to Kepware so my understanding is that reporting by exception is not applicable.
In the kepserver\Device\Properties\Scan mode there to select the scan mode which i have set as "Respect-client specified scan rate". In my case Edge is a OPC UA client so whatever Edge tag group scanning rate is set to it will be executed (with the limitations of the actual source device and native kepware channel). What would be ideal scan mode if i had 10 Edge stations connected to one kepware server ? My understanding is that it would not be ideal as there would be 10 requests for the same data - is it correct? In that case " Request Data No Faster Than Scan Rate" would be probably the most efficient - is that right?
Regards
Thanks Phil it makes sense but can you please comment on my example below?
The default in OPC UA is to report no faster than the requested pace.
If there is a device with 1 signal changing every 100ms and there are 10 ignition edge clients (each with 1 tag polled every 1s) with identical tag group settings connected to 1 Kepware - is the communication somehow streamlined or will there be 10 independent connections which might read different values ?
A single Kepware instance for all ten Edge units? (That sound's like a less than ideal architecture, but ok.) I would be shocked if Kepware didn't consolidate into a single device poll, distributed to all consumers. Not sure if the spec absolutely requires that, though.
This is implementation specific, so just a guess, but I would think Kepware will consolidate the polls as long as each of the clients had requested the same sampling interval.
Alternatively you could disable the "respect requested client scan rate" (or whatever it's called) setting in Kepware, set up the polling at whatever fixed interval you want, and then the number of clients and their requested sampling interval won't have any affect.
I am not familiar with Edge licensing or modules but could you use 1 of the Edge gateways to talk to Kepware and then use the gateway network to have the other Edge systems talk to the Edge with Kepware?
Using remote tag providers?