I after agree with Aaron but in this case I do not. I simply do not like the thought of a snake being able to come between a heat source and the probe. I would recommend dangling it about 3 inches or so below the RHP. I have been testing this method for some time (3 different probe placements) and found it to be a good compromise. I don't get exact temps on the floor but it is not as dramatic as on the RPH and IMO safer than on the floor.

0% RH is almost non existent, I suspect a faulty hygrometer. They are can be very fussy and can go out of calibration very easily. Digital units are especially prone to this. I would remove it blow out the probe as best you can (blower brush would be great vacuum set reversed would work well too.) and try again. If that does not work I'd replace the unit with a second one. My personal preference is these ...

http://www.cheaphumidors.com/p_analo...CC-ANALOG.html

All mine have a magnetic attachment it works ok but not stellar I often just pull the metal disk off the brass housing and tack it with some hot melt glue. Or use a rare earth magnet to replace the original one. I have tested 26 so far and out of the box they all have been with in 7%RH accurate and are easily adjusted to accurate again. The best digital unit I tested was about 5% Rh of correct and the worst was over 30% off. The best of this model I found to be as accurate as a salt test is capable of 1% this is in fact the majority tested out spot on. Much better than any digital I have ever checked. They also resist dust and debris super well I have actually plucked one out of a water bowl and it continues to work accurately and with out problem after it dried out.