Thank you for the info Jeff5may. Looking at the links, it says one wire, but really this is what I came across...
or this
So if I understand this correctly, there is a ground wire, power and then the data wire? They say one wire because the data goes on one wire and each sensor is unique?
I have a 250' spool of underground solid core sprinkler system wire in my stash and wonder if that would work, or does it have to be stranded?
Since this is going to be direct buried, I could go with the sensor that are premade or make my own with pigtails and solder them up. I suppose the wires and sensor must be protected from moisture and the elements. Would enclosing them in epoxy and then attaching them to the pipe suffice?