Where to put thermostat probe

[PitOnTheProwl]

Deborah,

I recently purchased a temperature-control thermometer for my ball python's terrarium. Currently, I have it placed inside the warm hide. Are you saying that I should have it tapped to the outside of the terrarium, on the under tank heater? Between the bottom of the tank and the surface on which it is sitting? That will measure the same temperature as on top of the substrate, where my ball python is?

Yes.
1 It should not be inside the enclosure. Too many variables that can cause a false reading.
2 You should be monitoring the hottest surface your animal can touch. This would be under the substrate as they can and will burrow.