Thanks Fixebr, I tried several wiring solutions with the two sensors I have and I just could not get it to work. So I capitulated and put in the UC300ETH, hey presto, everything is good. It's just the hardware limitation of the UC100 that created the problems for me. I do have to purchase some more sensors, so I am probably going to go with the two same sensors but in a different configration to enable me to bring the UC100 back into service, but I need to do more work.
Thanks all for the help.