Troubleshooting PLC SCADA systems.

This is in reply to a discussion on CR4 where the commentor suspected sensor wiring method to be root cause of extended troubleshooting time. My reply below...

Actually it does not matter if you have hardwired, Modbus, Devicenet or wireless sensors as far as troubleshooting time goes. (although any of the above can add to number of problems to be found. Like Modbus communication going out.)

The two primary factors in troubleshooting with a PLC is training and documentation. Using a PLC, it typically takes 5-10 minutes for a properly trained technician with discriptored ladder logic and an electrical layout diagram, to find a problem, no matter how complex the system. Time to fix varies on actual problem found.

Items that can increase troubleshooting time in order of most negative effect are ...

• Lack of proper training.
• Lack of proper PLC program documentation.
• Over complicated PLC ladder logic.
• Lack of electrical layout and schematics.

System Designs in order of most timely to troubleshoot are ...

• DCS (Mostly proprietary and designed for only OEM to use.)
• SCADA (Often proprietary, non-user friendly and training deficiencies. Seek Wonderware® and Factorytalk® training.)
• PAC (Ladder Logic easy, but function block diagram is not always, structured text is a more complex computer programming language.)
• PLC (Ladder Logic, easy for electricians and mechanics too if taught properly.)

The bottom line is that all the above systems could be easy (quick) to troubleshoot if one is constantly trained, the system is well documented and designed for the laymen to easily understand.

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Don (Follow me on Industrial Skills Training Blog and on Twitter @IndTraining .)