Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] IR thermometer buy

this "really" complicates it:


IR2 Two Color-Ratio Thermometry <http://www.omega.com/pptst/iR2.html> Two coloration Thermometry
Given that emissivity plays such a vital role in obtaining accurate temperature data from infrared thermometers, it is not surprising that attempts have been made to design sensors which would measure independently of this variable. The best known and most commonly applied of these designs is the Two coloration Thermometer. This technique is not dissimilar to the infrared thermometers described so far, but measures the ratio of infrared energy emitted from the material at two wavelengths, rather than the absolute energy at one wavelength or wave band. The use of the word "color" in this context is somewhat outdated, but nevertheless has not been superseded. It originates in the old practice of relating visible color to temperature, hence "color temperature."


from:

http://www.omega.com/prodinfo/infraredthermometer.html

bc, continuing search.



Bernard Cleyet wrote:

Excellent point. To determine I would necessarily dismantle the bolometer. OR sit on my arse and use Google. We'll see. (FOS)

bc

Ludwik Kowalski wrote:


On Jan 24, 2007, at 3:31 PM, Bernard Cleyet wrote:



I doubt a $10 IR thermometer. is that sophisticated *, even in this
21st. cent. They likely make use of the T^4 relation,


What is proportional to T^4 is the total intercepted intensity. But that intensity is also proportional to 1/r^2, where r is the distance
from the source. Therefore, the reading, for a given T, would change

with r. Does the indicated T change when r is changed?

The only things that do not change with r are the location of the maximum and ratios of partial intensities at two different wavelengths. My guess is that T is determined from a ratio of two partial intensities. Some kind of a filter, and two detectors, would make this possible, at least in principle.


cut.