Saharan Sand Boa heating pad?

[UnloosedCake]

Hi! Just got my first snake today, he's a ~2y Saharan sand boa. I got a 150W UVB bulb that I have on a timer and a heating pad that I have under the enclosure. I'm just looking for advice, I'm not sure if I should leave the pad on all the time or keep it on the same timer as the lamp? Also, the thermometer I have on the wall of the tank displays about 80 degrees, should I invest in a digital one to measure the temperature on the ground or is it sufficient to assume the lamp is heating the tank up appropriately?

Any advice is much appreciated, I've been around snakes for a while but never had to do everything on my own. Thank you!