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How Mr. Johnson, the one after which Johnson–Nyquist noise was named measured/discovered this phenomena? Details about equipment and method are most welcome.

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  • \$\begingroup\$ Measured is one thing and discovered is another. discovering is not as interesting as measuring. Obviously, there was no low-noise broadband AC voltmeters in the era. So it is very intersting question. the one about measuring. \$\endgroup\$ – user924 Jul 16 '11 at 16:52
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Here's Johnson's original 1928 paper. May give you some clue :-)

Note that there are two papers - one by Johnson and the immediately following one by Nyquist. Both are from Physical Review July 1928 with Johnson's paper immediately followed by Nyquist's. J's title is "Thermal agitation of electricity in conductors" and N's is "Thermal agitation of electric charge in conductors".

Johnson:

Nyquist:

Richmond.edu link below has a number of interesting papers.


Useful "modern" comment

http://www.claysturner.com/dsp/Johnson-Nyquist%20Noise.pdf

Related:

Various papers including Johnson's from above:

http://www.claysturner.com/dsp/Johnson-Nyquist%20Noise.pdf

http://kiwitobes.com/wiki/Thermal_noise.html

http://uk.ask.com/wiki/Johnson%E2%80%93Nyquist_noise

http://en.wikipedia.org/wiki/Talk%3AJohnson-Nyquist_noise

http://en.wikipedia.org/wiki/Johnson-Nyquist_noise

http://ocw.mit.edu/courses/physics/8-13-14-experimental-physics-i-ii-junior-lab-fall-2007-spring-2008/labs/lab13/

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    \$\begingroup\$ all the links are very nice and such, but the more there are listed, the more I get the impression they are copied from a Google results page. I prefer reading here. (also because some of the links may be dead in a few months) \$\endgroup\$ – Federico Russo Jul 16 '11 at 11:19
  • \$\begingroup\$ You are welcome to your preferences and impressions :-). The key references are the top two, from, you'll note, two different sites, which give the original 1928 paper by Johnson, which I think answers the question "tolerably well" PLUS the paper that immediately followed it giving Nyquists perspectives - icing on the cake. If you prefer the documents to be located elsewhere you are welcome to copy and link to them for the benefit of others. That's the beauty of a site such as this - if you wish something extra to be done you can do it. \$\endgroup\$ – Russell McMahon Jul 16 '11 at 15:19
  • \$\begingroup\$ Re "from a Google results page ..." You'll find that the majority of the other links are not just "cannon fodder" but have a reasonable degree of relevance to the query, but are not in the same class as two primary 83 year old journal transcripts. Presumably you are happy with people who know what they are looking for and who are willing and able to use such a rough tool discerningly, to use a search engine AND then provide the essential filter of an informed and experienced mind to subset usefully? And fwiw, no, not Google - Alta Vista in this instance (at the top level anyway). \$\endgroup\$ – Russell McMahon Jul 16 '11 at 15:26

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