Siemens: Calibrating Analog Input Cards

[MartyW]

I am using an Siemens SM 331 analog input card (314 CPU). I am noticing about a 0.1% error on the A/D conversion. Is there a way to adjust this directly on the card?

I'd rather not fudge with my Rosemount Transmitters which I know are correct. There also seem to be some institutional resistance here to handling this in the software.

 

[L D[AR2P#0.0]]

How are you determining the error ?
Is this voltage or current ?

 

[MartyW]

The input is a 4-20 mA signal from a Rosemount 3051T pressure transmitter. I used a Hart Communicator attached to the Rosemount to have the Rosemount output exactly 4 mA. I confirmed the output was 4.000 using a Fluke 787 multimeter.

Monitoring my PLC, the input PIW input to my FC that scales my analog signal is negative at 4.000 mA. It is zero at about 4.004 mA (on average - there is some noise at these levels).

The FC I am using is FC1105 (different from FC105). I inherited it for this project and it is locked so I can't see inside it. I only input the raw counts (PIW integer input) and the high & low range. I assume it is set up specifically for 4-20 mA.

 

[TurpoUrpo]

what value does piw itself show?

 

[Paul B]

What specific part number on the analog module? Siemens makes 12-bit, 14-bit, and 16-bit analog input modules.

 

[MartyW]

PIW values:
4 mA: -10 (+/- 5)
20 mA: 27580 (+/- 5)

Part #: 331-7NF10-0AB0, 8 x 16bit AI

 

[Paul B]

It looks like the module is within spec. From the S7-300 Module Data Manual 08/2009, A5E00105505-06, on page 278 it says the Operational Limit of the 331-7NF10 module is +/- 0.1% and the Basic error limit is +/- 0.05%. There is also Temperature error listed and a Linearity error of +/- 0.1%.

I do not think there is a way to adjust this on the card as you asked, nor within the hardware configuration.

I have ran into situations where S7-300 analog modules replaced a Honeywell DCS and the techs in the plant were not as pleased with their performance.

 

[MartyW]

Thanks.

 

[John Gaunt]

Modified FC105 may be your problem.

I too use a version of FC105 that I have modified. It may be that yours has been set up to provide zero and span calibration of your AI.
In any case it is something you could consider doing yourself.
There are ways to unlock your existing version.
If you post a cut down project with little else other than your version of FC105 I will unlock it and post it back. Somebody else will almost certainly unlock it and post it back before I see it.

 

[MartyW]

I deleted everything from the project except the single FC including all hardware; then exported to a zip file. I still couldn't get below the size limit for attaching zip files. The FC size in Simantic Manager is listed as 244. The exported zip file is 716 kb.

I'm I doing something wrong?

 

[erdemsvri]

I too use a version of FC105 that I have modified. It may be that yours has been set up to provide zero and span calibration of your AI.
it.

I am curious if the unlocking procedure works for Siemens Standart functions. I mean can you unlock a SFC or FC like FC105 106 from the standart library?

And how and why do you upgrade FC105?

Thanks.

 

[John Gaunt]

You can certainly unlock functions like FC105. I am not sure about SFC's though.
Marty if you send me a PM I can send you my email address and then you can send me the zip file. You will need to hurry as I am going away and then won't have access to Step7.