Hello KA24DE;
we have already made sure that the input you are reading (PIW752) seems correctly set-up. Analog input value ranges in Siemens PLCs are range limited, either (in decimal values) 0 to 27648 (unipolar) or ±27648 (bipolar), so there is no need to set input limits or to mainpulate the value. On a 4-20 mA signal, 34 mA will always give you a (decimal) reading of 5552, 20 mA will give you 27648; any other reading will be linearly calculated on those values. Simply place PIW752 as the IN signal of FC105 (it is a INT type, so it reads as a decimal; value).
what you need to do is setup the limits for the output signal. if you want to read 0-100%, put 0.0 in the low limit, 100.0 in the high limit (note that these are REAL values, so write the value with a decimal point or setup the variables as REAL). If you want to read minus 10 to 40 degrees, write -10.0 to the low limit, and 40.0 to the high limit. Just choose your engeneering units and arrange the output accordingly. By the way the output is also a REAL value, so read it as a floating point value, or what you read will make no sense.
There is documentation in a PDF file that is included in the documentation section of Simatic installation (Start --> Simatic--> Documentation-->English) called "STEP 7 - System and Standard Functions for TI-S7-Converter"; FC105 is very well described in the Convert funstions chapter.
Hope this helps,
Daniel Chartier