Scanclass rate and tag quality unknown

I am trying to increase the responsiveness of my main operator interface. Currently when, for example, something passes a sensor it is generally 2-4 seconds before it is registered on the screen. What I am ultimately trying to do is reduce that as much as possible. I have separated each PLC into it’s own scanclass which the gateway status page tells me runs at an average duration of about 4ms. The rate is 900ms.

If i reduce the 900ms rate the tag quality intermittently becomes unknown and the graphics flicker to indicate a bad tag? Is this normal behavior? How often should I be able to run a scan class? Should I be doing something else to speed up indication on my screens?

Ignition 7.9.0. No database querys.

When it comes to subscribe mode OPC tags, the term “Scan Class” is a misnomer. All it does it indicate the subscription rate that should be requested of the OPC server. The execution time is irrelevant.

You really should be looking at the diagnostics page (if there is one) for the devices in question. You’ll probably find that you’re asking for too many tags at too fast a rate and are exceeding the PLCs communication load capabilities.

Okay I see that now so the 4ms is the response between the Ignition gateway and the OPC server, I thought 4ms sounded a little fast. Thanks for clearing that up. I have found the device details page in the status section that gives me a nice load percentage indicator. I was running at about 400%. Now I know how to monitor that I can further divide my tags.