Temperature difference

[bkimura]

Hi everyone,
For those of you using a digital thermostat, (herpstat, etc.) and a glass tank setup, how much of a difference in temperature do you generally see between the thermostat and the digital probe inside the tank? I have the following setup:

Zoo Med 10-20 UTH with Herpstat probe foil taped to the center on the outside. Acu-Rite thermometer with the probe hot glued directly to the glass over the center of the UTH on the inside. I'm finding that I need to set my Herpstat to 98 in order to achieve a temp of 92. Does this sound reasonable? I guess I was expecting a difference of 1-2 degrees so I'm wondering if something's not right. Just curious what others are seeing in their setup.

Thanks!
- Bill

[RichsBallPythons]

Need to buy IR temp gun to be sure then you will know which device is off.