Hello. I’ve imported tags directly from a SLC-5/05 PLC using the ‘Browse OPC Servers’ button within the designer, but the tags are alternating between good and bad quality every 10 or so seconds. I understand that I can disable the overlay and continue working on the HMI, but I’m worried that bad quality tags will be an issue once the HMI is deployed.
Are there steps that I can take to correct this? I’m located roughly 20 miles from the PLC and an HMI running on RSView32 seems to be connected without any issues. I’ve attached a diagnostics screenshot. Thank you.
You’re subscribed to the tags from that PLC at a drastically faster rate than they’re actually able to be polled at. The tags you’re asking for get grouped into 375 requests and you’re asking for them @ 1000ms, which would mean you need to achieve a throughput of 375 req/s. The diagnostics indicate you’re getting ~8.6 req/s.
There’s no really great solutions for this right now, but here are your options:
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Use a significantly slower scan class for the tags coming from this PLC.
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Increase the ‘stale multiplier’ setting (under Ignition OPC-UA Server > Settings) to something so highly it effectively disables the stale detection the server does. A change in this setting requires the UA module to be restarted to take effect.
The way the stale detection in the server works is that it takes the rate a tag is subscribed at, applies the multiplier, then periodically checks to make sure the tag is being updated no slower than that. So in this case (rate=1000ms) your tags would have to be updated at least every 5 seconds (at the default multiplier setting) to avoid getting marked stale. It looks like in reality your tags are probably only updated every ~45 seconds.
So… either move them a 60,000ms scan class or increase the stale multiplier.
Thank you very much Kevin. I’ve implemented your scan class suggestion while I work on the design and all is good. I figured latency may play a role, as you have suggested, and I will set up a server at the remote site as soon as possible. Thank you for your help.