Half a croissant, on a plate, with a sign in front of it saying '50c'
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Black-/white-bulb thermometers

Compensation for radiative heat transfer
  [vote for,

Meteorological thermometers are usually enclosed in white louvered enclosures (Stevenson screens—[link]) to keep them from being affected by radiative heat transfer. This is not just heating by sunlight, but cooling by exposure to the night sky—[link]. Stevenson screens generally work okay, but they're expensive and bulky.

I propose using two separate thermometers, equally exposed to the radiative environment, where one has its bulb painted white (to absorb/emit little radiation) and the other has its bulb painted black (to absorb/emit lots of radiation). The black and white paints don't have to be perfect; calibration can take care of any nonzero emissivity/absorptivity of the 'white' paint and and nonone emissivity/absorptivity of the 'black' paint. The only requirement is that the have very broad emission/absorption spectra. Spectralon for white and carbon black for black would work well, I think.

By comparing the temperatures measured by each thermometer and doing a bit of math, one can then determine both the radiative temperature and the thermal temperature of the environment, even though both are affected by both (but in different proportions). (This is similar in concept to wet-/dry-bulb thermometers used to measure both humidity and temperature.)

To ensure equal exposure to the radiative environment (i.e. not shielding each other), the thermometers could be rotated around each other continuously, or have their absorbers/radiators intercalated like the colors on a beachball. Other solutions are welcome too.

41/277 [2018-01-31]

[In addition to my count of how many ideas from my list I've posted so far, I'm now going to include the date I put the idea on the list, if I recorded that date.]

notexactly, Feb 03 2018

Stevenson screen https://en.wikipedi...ki/Stevenson_screen
[notexactly, Feb 03 2018]

Cooling by exposure to the night sky Cosmic Background Refrigeration
by [BunsenHoneydew] [notexactly, Feb 03 2018]




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