Reading a value from Simatic SM431 module


Thread Starter

Nick Fedun

I have a Simatic S7-400 PLC station with SM-431 analog input module (16 inputs with 13 bits ADCs). Hardware is configured for 4-20 mA two-wire current transducer. Raw word (IWxxx or PIWxxx) read from the address of any of the
inputs is incorrect, that is, always about 58 percent of the actual input current. Already tried grounding unused channels and swapping modules, which didn't help.
Gratefull for any tip.

Daniel Chartier

Hello Mr. Fedun;
You say that the card has been configured for 2-wire transducers. Siemens Ai cards must be configured in the Hardware Config editor (object properties of the Analog Input card/INPUTS) but also physically by setting a square jumper on
the side of the card. Each of these jumpers configures 2 channels at a time (there are 8 groups on a 16-input card). For 2 wire currenttransducers,the jumpers must be turned so that the letter 'D' (as shown in the Hardware Config parameters for the Inputs) is placed directly under the pointer arrowhead etched on the side of the analog card. I have experienced a few problems with the inadequate positionning of these jumpers.
Hope this helps,
Daniel Chartier
[email protected]