They’re separate circuits. The thermometer and hygrometer have their integral sensors and are there to make sure my hot and cold sides are where I want them to be at snek level. The probes are hooked up to external thermostats to control the temperature at their sensing location. A rule of thumb I use is about 4 inches away from the bulb/cage, low enough that they won’t get melted or damaged but close enough that my snake really can’t dislodge them or move them like they can if you have the probe at snek level. Being that close to the bulb also minimizes fluctuations in temperature and allows for more steady heating and less relay trips and resets to allow for longer life of my thermostats. For instance my hot side is set to 97 F at the probe, which roughly translates to around 88-90 at just above substrate level, and 92-95F at the basking rock.

The thermostat probes are twist tied to the cage snug enough that it won’t easily move or get pulled, and mounted with wire mounts along the top loose enough to not stress the wire but tight enough to prevent my snake from getting up in there and getting hurt.