Talk:Bolometer

Hmm... seems substantially different then the following:

the most sensitive thermometer known to science. Invented in 1880 by astronomer Samuel P. Langley, the bolometer is used to measure light from the faintest stars and the sun's heat rays. It consists of a fine wire connected to an electric circuit. When radiation falls on the wire, it becomes very slightly warmer. This increases the electrical resistance of the wire. The difference in conductivity is proportional to the incident irradiance. rredc.nrel.gov/solar/glossary/gloss_b.html


 * I don't know what you are referring to, but to me seems consistence with the definitons given in the article. The definition given in the article is the correct one. The quote you give maybe descrive a pioneer bolometer. The only inconsistence is that a bolometer is not a thermometer but it contains a thermometer (but in any way you can made it) AnyFile

Units of measure and Category
I have corrected again 50 millikelvins into 50 mK. Please use the correct SI forms as stated in Manual_of_Style, Manual_of_Style_%28dates_and_numbers%29 SI. I can not consider valid the question we are inside a sentence. The satments of SI said that every time the unit is after a number it must go in form like K or mK. The long form (but always in sigular) like kelvin should use only when speaking of the unit of measure itslef (in which it is not preceded by any numbers)

I also reinsert this page in the Category:Particle detectors as I condider it interesting that this article is shown in that category. From waht I can see there is no reason why a page should stay in the minor possible category and that if a page should or not be present in a category have to depend on if we wants an article to be shown in the category pages and not if we consider if he article is in its whole in this category. Now Category:Particle detectors is also a subcategory of Category:Particle physics which has no link with Category:Measuring instruments. If you really have some good reason why it should not be palcede in Category:Particle detectors,I'll will move in Category:Particle physics, but of course it is prefearred the Category:Particle detectors category. AnyFile 10:20, 2 May 2005 (UTC)


 * The proper long form is millikelvins. The plural does indeed have an "s" at the end.
 * Many people get confused about this, because in the old days when Kelvin was an adjective, in English the adjectives do not add an "s" in "degrees Kelvin"; the "s" is added to the unit, the noun part, degree. But now kelvin is the noun, and it forms the normal English plural.
 * It may be used in text.
 * It often should be used spelled out in first occurence, symbols thereafter.
 * There is no requirement by the various standards agencies which oversee the SI that these units are never spelled out when used with numbers.
 * 11:21, 2 May 2005 (UTC)

I have got a question about the millikelvin comment
Hello,

in the article it is stated "Bolometers are therefore used for astronomy at these wavelengths. However, to achieve the best sensitivity, they must be cooled down to a fraction of a degree above absolute zero (typically from 50 millikelvins to 300 mK); this makes their operation technically somewhat challenging."

Now, as far as I understand it, the bolometers used in astronomy are mostly hot electron bolometers, which employ superconductive microbridges. However I was under the impression that they would be cooled to the transition temperature, so that an increase in temperature due to radiation actually causes a leap in resistance. If that is the case, then further cooling from 4 Kelvin or whereever the transition temperature of the material is, wouldn't yield an increase in sensitivity.

Could the author of the article elaborate on the 50-300 mK, as I am apparently missing some detail here and don't quite understand it.

Thanks in advance.


 * As someone who makes hot electron bolometers (HEBs), I can say that you are generally right here. HEB physics are still not completely understood, though temperature, LO power, biasing, etc all do appear to play somewhat of a role in sensitivity (really noise temperature). Lowering the temperature of your entire receiver system would reduce overall noise, but strictly speaking wouldn't have such a big effect on the HEB itself. I think what the author is referencing here are probably bolometric direct detectors, which would not even necessarily require superconductors. --Jschultz 03:42, 28 October 2006 (UTC)

I believe what you're talking about is the Transition Edge Sensor (TES). General bolometers, which employ semiconductors as their detectors/thermometers, improve as heat sink temperature goes down. You are right in that a TES must be kept at it's transition temperature or else it looses sensitivity. —Preceding unsigned comment added by 128.118.147.129 (talk) 07:06, 21 September 2007 (UTC)

OK. In astronomy, hot electron bolometers (HEBs) are often used as mixers in heterodyne systems (which is what Jschulz is describing). For direct detection, HEBs are not often used; the thermistor is either a semiconductor (silicon or germanium) or a superconductor. While it's true that the absorber and thermometer of a TES must be kept at its transition temperature or it loses (all) sensitivity, the heat sink temperature must be lower than the absorber (this is how any bolometer works, even an HEB, though here the heat sink is the crystal lattice and the electrons are the absorber and thermistor). The absorber will maintain itself at the transition temperature by an automatic feedback mechanism, but (to a point), lowering the heat sink temperature improves performance. Also, you can choose the transition temperature of your TES, and again you get the best performance by choosing lower temperatures, usually at least as low as 300 mK. The lowest transition temperatures used are around 100 mK, with heat sink temperatures lower than that.

TESs are also used as calorimeters to measure X-ray radiation by detecting the heating due to a single photon being absorbed; here, temperatures as low as 50 mK can be needed. Incidentally, hot electron TES bolometers can be used to detect optical and infrared radiation, with the wavelength being determined by measuring the heat due the absorption of a single photon.

AdamW (talk) 11:16, 22 August 2008 (UTC)

Microbolometer Generality
It seems to me that the section on microbolometers is way too specific to a particular kind of bolometer. I think a hot electron bolometer (HEB) could probably be called a microbolometer, though it doesn't match the description in this section at all. Maybe it would be more appropriate to have a section called 'Microbolometric IR Camera' instead. Any thoughts here? --Jschultz 03:42, 28 October 2006 (UTC)

Bolometers
How about a larger overview of bolometers? There are various different types that can also be used in X-rays, photon counters, composite bolometers... etc. Also, maybe a discussion of some of the science and results that they have done?

The Bolometer Limerick
This version found in J.M. Pasachoff, Contemporary Astronomy (Saunders College Publishers, Philadelphia, 1985) page 47:

Langley invented the bolometer, A very fine sort of thermometer. It can measure the heat, Of a polar bear's feet At the distance of half a kilometer. — Preceding unsigned comment added by Lori.goldner (talk • contribs) 19:11, 22 June 2017 (UTC)

Which I recall coming across in the 70's

Langley invented the bolometer, It's really a kind of thermometer, That can measure the heat, From a polar bears feet, At a distance of half a kilometer.

WhaleyTim 09:18, 23 November 2006 (UTC)

My recollection:

Langley invented the bolometer, A wonderful kind of thermometer. It can measure degrees On a grasshopper's knees At a distance of half a kilometer.

Herb Helbig, hhelbig@roadrunner.com — Preceding unsigned comment added by 67.255.201.86 (talk) 03:05, 2 March 2016 (UTC)

Secretary Charles G. Abbot with Bolometric Apparatus.jpg
Hi everyone! I just uploaded an image of Charles Greeley Abbot utilizing a "Bolometric apparatus." It might be a cool thing to feature in this, or a related article! You can see the image. Thanks! Sarah (talk) 19:24, 11 April 2012 (UTC)

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