Thermal Leak Detector & Digital Thermometer question

[The Serpent Merchant]

First off, is a thermal leak detector the same thing as a temp gun used for seeing the temp in a BP's cage? I am using my boyfriend's dad's right now, and I wasnted to make sure it was accurate.
This is it: http://www.amazon.com/dp/B001LMTW2S/...SIN=B001LMTW2S

Secondly, I have a digital thermometer in his tank right now. The main "machine" is on the cold side, and the wire and little sticky pad thing to measure "outside temperature" is attached to the glass on the hot side.
However, it's saying that the inside temp is warmer than the outside temp... What am I doing wrong?

You have it set up right. Remind me again what heat sources you have and where they are.

To everyone else she has an Acurite digital thermometer with probe. She has the probe on the hot side. The actual thermometer itself has a second temperature sensor and a hydrometer. That is on the cold side of her tank.

It's probably this one or at least similar: