Detecting PLC stopped scanning?

[vdsvds]

Hi all,

ClearSCADA 2014, communicating with TSX Premium PLC via Modbus TCP driver on local network.

Scenario: PLC faults due to scan overrun. Ethernet module still online and ping-able, but values on the screen hold last state as PLC no longer on scan & updating.

This leaves ClearSCADA looking like everything is running and healthy, but that's not the case.

In my experience, some scanners remain "Online".

Has anyone implemented a neat solution that could somehow mark the I/O scanners offline/bad upon some kind of heartbeat value becoming stale, e.g. a RTC minute value not changing within, say, 10 minutes? I'd prefer to handle at the Scanner level to take advantage of the point statuses showing pink colour etc, instead of showing a loss of comms watermark on every page.

Or maybe there's a property in the comms driver that we haven't discovered yet?

All suggestions welcome and thanks in advance!

[sbeadle]

ClearSCADA 2014? Please consider upgrading.

I'm sure others here would agree this is the right thing to do for support, functionality and cybersecurity.

[vdsvds]

Hi @sbeadle 

Appreciate your time to respond, thank-you!

There are plans to to upgrade the control system (TSX Premium PLC included!). Do you know if the latest GeoSCADA offers a way to solve my original problem with the latest Modbus driver?

Thanks!

[sbeadle · Accepted solution]

From what you wrote, I think you have to solve this with the PLC. If you stop the ClearSCADA scanner to render it's points magenta, how would you start it again? 

Perhaps no-change alarms on analogues would be a suitable canary, or add a PLC sequence as a watchdog and look for no changes using Logic? Either way you will have separate failure indication from the rest of the points.

Steve

[vdsvds]

Thank you, the separate stale value monitoring (via logic) was my initial thought - by reading the PLC RTC minute tag. I’ve previously explored the NoChange alarm, but in order to trigger the alarm, it requires the value to have changed so this is not suitable in my situation. I’ll proceed with deriving an independent “Stale data” point and display a warning on the page banner.

Would be awesome if the driver had an OOB feature to “ping and monitor” a specified tag and somehow be able to change the OPC quality to some kind of indeterminate state if the heartbeat value stops changing.

Anyway, thanks again!

vds