[time-nuts] Mentorship needed in learning about Allan Deviation and variation.

[Tom Van Baak]

Alberto,

Thanks for asking. The correct spelling is Allan variance or Allan 
deviation, named after David Allan, of NBS (NIST). Yes, on rare 
occasions it is misspelled Allen, as in the hex key wrench. Note it's 
spelled correctly in the Subject line of this thread. I'm not aware of 
national explanations for the misspelling; it could simply be that allen 
is more popular a name than allan and a spell checker allows either one.

The ADEV statistic itself is spelled Allan because that's his name: Dr. 
David W. Allan. Similarly, the hex wrench is spelled Allen because of 
Mr. William G. Allen.

More fun: When you google word search it displays a hit count:

"allan deviation" About        84,300 results (0.46 seconds)
"allen deviation" About         2,460 results (0.40 seconds)

"allan variance"  About        85,400 results (0.41 seconds)
"allen variance"  About        21,300 results (0.37 seconds)

"allen wrench"    About     4,820,000 results (0.52 seconds)
"allan"           About   213,000,000 results (0.77 seconds)
"allen"           About 1,190,000,000 results (0.87 seconds)

You can see that the word allen is 5x more popular than allan. That 
alone may explain the occasion misspelling of ADEV. Also, apparently, 
Allen wrench tools are 50x more popular than Allan deviation tools ;-)

More examples in popular vocabulary:

https://en.wikipedia.org/wiki/Hex_key
https://en.wikipedia.org/wiki/Allen_(brand)
https://en.wikipedia.org/wiki/Steve_Allen
https://en.wikipedia.org/wiki/Woody_Allen
https://en.wikipedia.org/wiki/Tim_Allen

vs.

https://en.wikipedia.org/wiki/David_W._Allan
https://en.wikipedia.org/wiki/Allan_variance

Some papers on the history of ADEV:

"Introduction to the Special Issue on Celebrating the 50th Anniversary 
of the Allan Variance"
https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7445935
(yes, open access! thank you, ieee)

"The Evolution of Frequency Stability Analysis Software", W.J. Riley
http://www.wriley.com/The%20Evolution%20of%20Frequency%20Stability%20Analysis%20Software.pdf

"BYU and CU Alumni Master's Thesis 50th Anniversary is Celebrated in 
IEEE UFFC Special Issue"
https://itsabouttimebook.com/wp-content/uploads/2016/05/50th-anniversary-for-allan-variance.pdf

"Technical Background on the Fundamental Noise Problem"
https://ethw.org/w/images/e/e5/Allan_OH_-_FundamentalNoiseProblem.pdf

/tvb


On 10/27/2020 11:00 AM, Alberto di Bene wrote:
> On 2020-10-27 17:38, Andy Talbot wrote:
>> They use Allen variance, TDEV and MTIE plots.
>
> Is "Allen variance" just the British way of spelling "Allan variance", 
> or are they two different things ?
>
> 73  Alberto  I2PHD
>
>
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