can I use 5 pt100 sensors with single Arduino? how?
I am guessing you have an Arduino with more than two analog-digital pins. Which one?
What are you measuring.
Platinum sensors have very little resistance change per degree C, so should be used with special interface boards.
Those boards have digital (SPI) outputs, so any Arduino is likely to handle five or more sensors.
If the temperature of interrest falls more in the "human" range, then DS18B20 could be better and cheaper.
but as above re DS18B20. Another aspect is that PTs are available as screw-in fittings and thus usable in pipes under pressure, but I stuck with DS18B20, and made thermowells instead.