Branching Bus for Sensor
I have a page about connecting Arduinos using RS485. You can connect multiple devices up like this:



That has a reasonable range, 20 metres or more.



On that page I describe a Rolling-master system where each device takes turns to be the master and transmit information to the other devices. It also manages some devices not responding.

This screenshot shows the various devices "talking" during their timeslot:



In that particular case there were 3 devices active out of 4 configured.




  I have a master ardunio polling a number of sensors. 


I'm assuming in my answer that you have an Arduino at each sensor point (you could use a cheap ATtiny85 or something). That would be needed to run the rolling master code.