Increase the filter constant to 100s to smoothen the signal a lot. For
online viewing, this is quite nice, but for acquisition, we should
probably look at the raw data...
Do the monster math to convert ADC readings into appropriate temperature
values. The absolute result is way off but it seems to respond sanely
in relative terms.
Additionally, apply a low pass filter with f=1Hz to smoothen the noise a
tiny bit.
