Hmm I did the measurement in entirely controlled conditions, no drafts.
I can understand these kind of spikes on a system that has a response curve with a feedback loop, but here, I am just measuring a thermometer, not a fan controller. The fan is at a constant position and at a constant speed.
My own guess is that you are reading a 10 bits ADC, and fail to do the conversion to base 10 properly.
My guess is a strong one, I write embedded software for a living
