Hi and thanks for the reply Melanie, your right some sensors are really modified from 4-20mA loops and don't go to 0V. However these do, also with the sensor unpluged (ie. PIC input is open circuit) the input goes to 5V which makes me sure that it is pulled up to rail.
As I understand the device there are no internal weak pull-ups on portA so I am going to try using that to see if I have everything else OK, but I need to find a way to use portB.
Hope you can provide another possible solution.
Thanks, Steve