An interesting and useful characteristic of non-contact pyrometers is that their calibration does not
depend on the distance separating the sensor from the target object23. This is counter-intuitive to
anyone who has ever stood near an intense radiative heat source: standing in close proximity to a
bonfire, for example, results in much hotter skin temperature than standing far away from it. Why
wouldn’t a non-contact pyrometer register cooler target temperatures when it was far away, given
the fact that infrared radiation from the object spreads out with increased separation distance?
The fact that an infrared pyrometer does not suffer from this limitation is good for our purposes in
measuring temperature, but it doesn’t seem to make sense at first.