PLC Comms Monitoring

[Ones_Zeros]

I have several plc’s that I’d like to monitor
Into our SCADA when the comms break or plc faults.

These are (SLC-505 & Compact Logic PLC’s)
I normally use the Wonderware bit $Sys$Status bit but
this seems to randomly show out of replay but it’s not. So
It’s not accurate.

Is there a simple and better way to monitor these plc comms?


Thanks

 

[Plantationpark]

Depending on the SCADA, the driver may have a error code that will show if the comms are ok or not - thinking of VTScada. With regards to faults etc. I sometimes create a heartbeat for the SCADA to monitor (and visa-versa if required) which can trigger an alarm.

 

[TheWaterboy]

Do you use Kepware? It has tags for this kind of thing.

If more remote I always have a running number I use as a heartbeat.

 

[JaxGTO]

For a PLC fault its best to add a fault routine that sets a bit indicating the PLC faulted. You can also use that routine to capture the fault codes.


As far as comm faults, a heartbeat works with most HMI software. Just monitor that a continuous counter has stopped changing and generate an HMI fault.


For example in Wonderware I use a Data Change script to monitor a tag that changes every 5 seconds. If that event does not happen for 10 seconds I set a local alarm tag.

 

[Ones_Zeros]

Thanks everyone for the feedback
I’ll give these a go
I appreciate it

 

[Bit_Bucket_07]

It's hard to beat a heartbeat routine for monitoring communications. It will even detect a PLC that has been switched out of run mode.

 

[I_Automation]

A heartbeat is a bare minimum, pulse a bit and make sure it's changing state at least every second. For a better watchdog have each PLC increment an integer and if it doesn't change in the PLC that reads for 1 second then the other PLC is offline for what could be a few reasons (Comm's failure, Program Mode, Faulted, Power off in that enclosure, CPU smoked itself)