the solution I suggest is to place Arduino near the sensor,
so you don't introduce noise by running long cables,
and then use a usb-to-cat5 extender,
that can run up to 50-100m without noise problems.
The only downfall is that with such a long distance you can have a little delay,
you just have to think if it's a critical parameter for your application.
For an installation a couple of years ago I used these Lindy USB-to-CAT5 extenders, they're rated up to 50 meters,
but they say that for low-traffic devices you MAY achieve up to 100m distance. They cost around 50, I found them for 10 on ebay and they worked PERFECTLY.
You just need to power the "remote extender" from the arduino side with 5V,
then plug the USB from arduino into the "remote extender",
connect a 50meters LAN cable to it,
and at the other side you just get back from LAN to USB with the "local extender".
Really easy, cheap and stable.
Here's the link:http://www.lindy.co.uk/usb-extension-cat5-usb-extender-premium-up-to-50m/42801.html
And if you google "usb to cat5 100m" you will find other options:http://www.blackbox.com/Store/Detail.aspx/Single-USB-rarr-CAT5-Extender-100-Meters/IC245A-R2
These up to 100m can even cost 500,
depending on how much money the manufacturer wants to steal you,
as they're quite simple circuits...
Hope this helps,