I would suggest to use multiplexer/demulti plexer(CD4051 8 channel), follow the steps below

1. Generate proportional mV singal for each RTD sensor and amlify if necessory.
2. Connect all RTD mV signals to Mux/Demux.
3. Generate a BCD counter from uC and connect it to control lines of Mux/Demux.
4. The output of the Mux/Demux will be same as any of one the input signal according to control lines.
5. Convert this Mux/Demux output signal to digital and feed it to uC.
6. You can connect it to PC via RS232/RS485 and its your data logger.

and then you knows what to do !!!!

Note : This is a proved design.

Hope this will help.

Good luck