I’ve been using some of these https://www.phoronix.com/scan.php?page=article&item=ebest-temper-linux&num=1 USB temperature sensors with an RPi to log a number of house heating/power generation/use parameters.
I’ve found them to have a pretty whacky offset error (2-3C at room temp) which is easy to correct, but they have a horrendous “sticky” temperature characteristic. It isn’t a ceiling, as shown above, it’s a sticky value. If the temps pass a long way away from this point it continues to update – it just seems to get locked into a value rather than update it. This was noted by Steve Timms (http://www.thermohid.co.uk/) too and seems to happen at fixed temps on each device. For me, it’s infuriating as it’s right around temperatures I want to have accurate data at. I honestly couldn’t recommend these to anyone because of this, but they do the job for now.