problem in Analog signals siemens

[finskhan]

Hello Everybody,
I am facing a problem with my analig signals.I have siemens PLCs 400.Four CPUs 412 and a network of four CPs profibus.Now in my 2,3 analoge cards there is a spike(rise)of analog signals for 2 mints after every 13 mints form 3 days.what can be the problem?anybody can help me?

[KalleOlsen]

If I interpreted your question correctly, it sounds to me as you have a classic el. noise or grounding problem. Does this happen when other equipment switches on or off?
Kalle

[finskhan]

no its not happend on switch ON/OFF to any equipment.its just recycle of 2mints after every 13mints.

[KalleOlsen]

1: What do you mean with "2,3 analoge cards"?

2: If you read the raw values (PIW), what value do you get normally and during the error state?

3: What input type is it, current, voltage, resistance,...

Kalle

[finskhan]

i check the all raw values and know that all analog cards of one satation after 13mints gives a spike(first 0 then goes to rise)and after 2 mints its becomes normal.I am worry about its cyclic interupt there is no diffrence in seconds.time is same 2 mints disturbance and 13 mints normal.

[finskhan]

and all signals are 4 to 20 mA.

[KalleOlsen]

You must give more info. Note that I have numbered the questions so it shall be easier for you to reply systematically.

1: What do you mean with "2,3 analoge cards"?

2: If you read the raw values (PIW), what value do you get normally and during the error state?

3: (already answered to, thanks)

4: How do you read and scale the PIW?

5: What kind of ana-card do you use?

6: Is M-ANA connected to M?

Kalle

[finskhan]

You must give more info. Note that I have numbered the questions so it shall be easier for you to reply systematically.

1: What do you mean with "2,3 analoge cards"?

2: If you read the raw values (PIW), what value do you get normally and during the error state?

3: (already answered to, thanks)

4: How do you read and scale the PIW?

5: What kind of ana-card do you use?

6: Is M-ANA connected to M?

Kalle


1.its means the problem is in 2 cards.total analoge
cards are 7.

2.Raw PIW value is difrent for every signal.for example if a normal value is 30721 then after problem it will become 8FD70 like this.

3.already answered

4.I read this in WinCC.and also in a trends.I simatic program iread this value from analoge FC and its scale is diffrenet for every signal like 0-100,0-300,0-980.

5.Analoge card is 13 bit, 431-0FF00-0AB0

6.Yes M-ana is connected to M

It was normal but its a problem for 2 days

[finskhan]

I am sending the picture of that trend of two signals.You can check the Behavior of these signals

[KalleOlsen]

With such a frequent error, it would be very easy to check if it comes from the field side. Did you try conventional error tracing? To disconnect the front plug from one of the failing cards and check if the other still has got this hickup? Then try opposite. If you can relate the error to one of the cards, start disconnecting the analog signals. It is very important that you check the PIWs. If you get signals like 7FF0-7FFF its indicating overrange errors and if its 8000hex onwards it is a negative value.

Kalle