Difference between surface and substrate in temp with uth

[The Serpent Merchant]

Ooh, I guess it just read the nearest surface then. I just bought the temp gun and missed that. I have an ambient thermometer about 7" from the floor that reads 79F.

The cool uth is warming the bottom. I know it doesn't heat air. Without it, the substrate was measuring under 74. I use it with the thermostat to bump it closer to 80.

Air temperature in the cage is just as important as the cool side substrate temperature. As long as the air temp stays above 75 you are fine.