Hello osama;
First thing, I suggest you download the manual "S7-300_Module data" from the Siemens support website, it has a chapter that covers in detaiol the procedures for analog sensor connections and configuration.
Next, here is a brief list of things to do to connect your RTD and read values in the PLC:
1) configure the module in the HardwareConfig editor; select the channel you will connect to, the type of sensor and other parameters.
This will give you 2important informations: the input address for the channel you are configuring, and the position of the measuring range module. This measuring range module is a square jumper, marked A,B,C and D along its sides. You must position the module so the correct letter (as indicated in the hardware configuration) is lined up with the marking arrow. this will ensure the input card reads the correct voltage levels.
2) connect the 2-wire sensor as described in the manual I suggested, or on the accompanying diagram for your module (if it is new, it was in the box). Here is a general connexion diagram for 2-wire RTD sensor:
The exact pin numbers to connect to will vary depending on the module model you are using.
3) download the configuration to the CPU, and (for example)use the FC105 "Scale" function to read and scale the PIWxxx address you were given in the HardwareConfig editor for the channel you want to read.
Note that the above mentionned manual will also explain the analog value representation scheme for Siemens S7 PLCs.
Hope this helps,
Daniel Chartier
