S7 Analoge Inputs Go Crazy!

Coops

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• Oct 27, 2006

• #1

Hi guys,

I have a S7 system (CPU315-2P) with a couple of analog cards on it. Never had this problem before and I have used there cards on numerous occasions. The cards in question are a Analog Input Module, 8 Channel.

The cards work (2 in total) fine and then all of a sudden (can take up to half an hour) all the channels go high and stay high until i power down the system and power it back up again.

Anybody no why???? The problem is on both cards....both brand new. So this is very strange. Dont know what the problem is, tried swapping the cards over and still the same.

Any Suggestions gratefully accepted.

 

SimonGoldsworthy

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• Oct 27, 2006

• #2

What is the hex value read from the PIW address under the fault condition ?

 

Coops

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• Oct 27, 2006

• #3

The strange thing is the card doesnt go into fault....but all the values goto hex FFFF. Very strange.

 

SimonGoldsworthy

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• Oct 27, 2006

• #4

If all the bits are on, this implies overflow and wire break detected. How are the inputs configured ?

 

Coops

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• Oct 27, 2006

• #5

Configured for 4-wire transmitter. Never had a problem before though like i said.

 

BryanG

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• Oct 28, 2006

• #6

Hi Coops

Have had similar problems when the supply powering the inputs was ocasionally shorting to earth. In my case I realised it only happened when it rained, water was getting into one sensor and grounding the supply. The supply output was short circuit protected and so just sat down when the problem occured which then affected all readings.

Bryan

 

Pandiani

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• Oct 28, 2006

• #7

Have you read diagnostic buffer (module informations) of your PLC when this thing happen?

 

[FIN]Pete

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• Oct 28, 2006

• #8

Is the card type 6ES7 331-7KF00-0AB0?
Years ago I had a pretty similar case -> I just connected the terminals 10, 11 and 20 together. All the problems disappeard permanently.
-Pete-

 

Coops

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• Oct 30, 2006

• #9

Isolated the problem down to 1 sensor....so there was nothing wrong with the card..thank god. Thanks for your help guys.

 

Pandiani

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• Oct 30, 2006

• #10

Can you describe what exactly was problem with the sensor?
What did you find?

 

Coops

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• Oct 30, 2006

• #11

Havent stripped it down yet but I think there is something shorting on the pcb board...will replace the pcb board alter and all should be fine

 

bebecall

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• Oct 30, 2006

• #12

Hope this link will help.


http://support.automation.siemens.com/WW/llisapi.dll/23857901?func=ll&objId=23857902&objAction=csView&lang=en&siteid=cseus&aktprim=0&extranet=standard