I just finally found an acurite thermo/hygro at a local hardware store (sooo much cheaper than those silly things marketed for reptiles ) And I love it! I put the actual unit in the cool side, and the probe by the warm side, like the picture above (except I have a 40 gallon tank for my big girl I'm using it for). It took until now to realize how off my temps are I like how you can get the measurements for the hot and cool side at a glance, as well as overall humidity.