How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Phil Your Own Question
Phil, Mechanical Engineer
Category: Electrical
Satisfied Customers: 8512
Experience:  Retired electrical contractor, 51 years experience.
Type Your Electrical Question Here...
Phil is online now
A new question is answered every 9 seconds

PLC troubleshooting

Customer Question

PLC troubleshooting
Submitted: 2 years ago.
Category: Electrical
Expert:  Phil replied 2 years ago.


Tell me a lot about your technical background so that I can coach you most effectively.

To trouble shoot the PLC you need a ladder logic diagram of the PLC programming and inputs. you can see what inputs are active or should be active, and if an input, such as a resistance read from a sensor is absent when you should be getting a resistance reading.. then you know that the problem is not in the PLC but in that particular input.

Most PLC's have many inputs and they vary in type from various DC voltage inputs, to switches, to voltage inputs of various sorts.

You verify the inputs first... If the inputs are all good and inputting as they should under the conditions, then you see if the outputs of the PLC are outputting as shown on the ladder logic diagram that defines what combination of inputs result in what combination of out puts, the outputs can be mere switches open or closed, or variable voltages for instance 0 to 10 VDC to input another device such as a variable speed pump or fan speed controller.

There can be various timers internal to the integrated circuit chip, or from various inputs that delay the action of an output... those are called I/O's input and outputs.

That is the gist of it. We can go from there, you will need a ladder logic diagram of how that particular PLC has been programmed.



Related Electrical Questions