Quote Originally Posted by dpcsquid View Post
I'm probably wrong, but if you have a heat sensor in there, as well as your heat light, I would personally put the probe about an inch off of the "ground"/substrate on the side of the tank with the heat lamp--that way, the warmer side of the tank will be controlled by the thermostat, because if you were to put it on the cool side, I would think that the heat lamp would heat up the "hot" side too much.

I don't know if that made any sense. It did in my head. : D
I agree with 'dp'.
However get a few inexpensive aquarium type thermometers in there to double check the probe devices.
I have had some prob devices act really whacky ! drives me nuts !!
So, I have gone back to 4$ aquarium thermometers. You know, the one that bob in the water. They are never wrong !!