Control System Network Diagnostics

Hi All,

I have noticed delays in communication between PLCs and IOServers.

I am looking for a way to use my control system devices to monitor network performance/issues.

My thinking was the following. I have a heartbeat in each PLC, 1 second pulse. The idea is to monitor the edges of the pulse to determine when my IOservers updates this data from the PLC. Within my control system SCADA i will monitor timestamps for updated values of this heartbeats and when i have delays over a certain period i flag missed pulse counters.

Im thinking of doing something similar for inter PLC communications.

The idea is then to have this information displayed within my control system on a diagnostics page and try to analyze network performance.

My questions.

1. Do you think this data can be analyzed in this way to identify areas of the network that need attention?

2. Considering i want this to be part of my control system what recommendations do you have on how to interpret data between devices within the control system to build such a model?

3. Am i wasting my time thinking this can be done, i am looking for a simple model that can be implemented over many sites with minor adjustments?

Thank you in advance.

R

I think that reading a number is more accurate than looking for a heartbeat
eg use 30.000 seconds on a 16 bit number (60.000 Unsigned)
This gives you all the information that you require
1) item is operating (value changing)
2) Update rate (difference in value)

Can be used PLC to PLC or PLC to SCADA

I have not had to monitor the update rates continuously - just for FAT and system acceptance

Hi Michael.

Thanks for your feedback.

So i have done some test and realised that actually measuring response is propably the best way to do this.

So i do the following at the moment. I set a bit and start my timer within the PLC. This bit is either communicated to a PLC or the SCADA PC. I reset the bit in what i call the client device(PLC or SCADA)

When i get the bit reset within my Master PLC i stop that timer. I repeat this every minute and record these times to an array of 120 Values. Just so i can have some visibility for 2 Hours or so. Eventually i will record this to a Historian so no requirement for the array.

At the moment I am looking at implementing the analysis from the Scada side at the moment. So i will make the SCADA my Master for all SCADA <-> PLC times. I will eventually just implement the PLC code for when i want to measure PLC <-> PLC.

I have used some networking tools to measure what i am doing at the moment and it seems pretty close. Offcourse i have the advantage of being able to meausre between PLCs which no network tool gives me.

Rheinhardt