AC500 - analog modules ac523


I have a problem with an module, specifically with an AI523.

The values are non 'stable': if i turn off and restart the plc (PM590), some channels have value '32700...'. If i exctract and recconnect the module or restart the plc, the values become 'normal', trusted.

That appens often.

Thanks for the tips.


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asked 1 year ago



Hi Mario

As you describe it, it looks like a typical fake contact or bad shielding of the analog signal cable.
You can try to test all your HW connections in your application, especially if subject to vibration.

You can also check with an oscilloscope if the signal in input at the PLC is clean or "dirty" by disturbances, so as to accurately determine the source of signal variations.

If necessary, you can filter the SW signal input at input level when configuring the analog input card

Let us know about the results

Flavio Mussolin   

answered 1 year ago


By mario478 on 5/24/2017 | Like (0) | Report

Hi Flavio.
We verified the connections, and whatever... but is the same. The values continue to be 'fake'... Only two values in analog input card.... If restart the plc or recharge the program...the same story. It could it be the base of modules?

By mario478 on 5/24/2017 | Like (0) | Report

Sorry Flavio...i forgot....
When the plc 'is off' and after is fed, when i login with codesys, each time appears "the program are changed....ecc...ecc..." and the CPU goes on STOP-START... I have verified MOD...ecc...ecc.
Other checks?

By Flavio Mussolin on 5/24/2017 | Like (0) | Report

Hi Mario

the changing after one reconnection with codesys could be depend that into pc the values are "stored" and freeze at the time when you have made the last backup.
Every values changed dinamically when you are not connected with pc means the message that you have described.
Have you tried to substitute the AI card? Only two values can indicate that the unit AI is broken or damage...may be you have electrical disturbances in the power supply?

By mario478 on 6/12/2017 | Like (0) | Report

Hi Flavio, sorry for the delay...
I tried to change the AI card, but it's the same...
Moreovor, a strange fact appens: if i control this values online 'on hardware', the values change constantly with the process...but if i pull out the card where the values are configured...the values continue to change. How is it possible?

By Flavio Mussolin on 6/12/2017 | Like (0) | Report

Hi Mario

It is definitely a special case that is quite difficult to remotely solve.
In what geographical area of Italy is the plant? I could suggest you some ABB service technicians to contact in this case

By mario478 on 6/13/2017 | Like (0) | Report

HI Flavio,
the plant is in Lazio

By Flavio Mussolin on 6/13/2017 | Like (0) | Report

Ok Mario
contact me in PVT :

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