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The history of this entry seems to be surrounding two issues:

1) Whether to define a sling psychrometer, or to consider that as a special case and define psychrometer as any hygrometer. I did some digging to find out what was up with that--it was a puzzle, because other types of hygrometers aren't called psychrometers in general useage, but why the need for the adjective "sling" if psychrometer already means that type? I found the answer in the AMS glossary--psychrometer uses dry-bulb/wet-bulb, but the air flow can be effected by slinging or by aspiration.

2) Possible copyright problems. To solve that I threw out all the text and re-wrote it in my own words. I think I made the explanation clearer--I hope I haven't gone too far towards making it an encyclopedia entry.

I think I screwed up the formatting--I hope someone who is more of a Wiktionary expert than I can fix that. —This unsigned comment was added by (talkcontribs) 2006-06-30 15:27:38.

There was no copyright problems since the entry was from US Army FM 3-6, a US Government publication, which cannot be copyrighted. CORNELIUSSEON 00:26, 1 July 2006 (UTC)
GDFL is pretty strict, so there was a copyright problem (see Wiktionary:GNU Free Documentation License for details). Thanks for rewriting the entry! Rod (A. Smith) 03:38, 4 July 2006 (UTC)

From rfv:

The prehistory of the rfd was that we found that CORNELIUSLEON had Actually describes a sling psychrometer, one of many forms of psychrometer (cf whirling psychrometer which looks like a football rattle). Also a copy-vio, with a large chunk copied word-for-word from [1] "Copyright © 2000-2006 All rights reserved." from which the error derives. (Thanks SB for alerting me.) --Enginear 12:55, 18 June 2006 (UTC)

I see User:CORNELIUSSEON has now reverted to his definition (which is actually for a sling psychrometer) from User:SemperBlotto's correct definition added yesterday. He has also cited a source, different from the copyrighted source SB & I found, which looks like a military pamphlet on weaponry. Does anyone know whether his new source is, as he claims, public domain? If so, I suggest copying his def to a new entry at sling psychrometer, where it belongs, and leaving SB's definition at psychrometer. Meanwhile, I have put back the RFV, which CS has removed (possibly innocently during his revert). Enginear 09:07, 20 June 2006 (UTC)
Done the changes as suggested. Andrew massyn 20:37, 28 July 2006 (UTC)
Correction. Have asked SB to do the changes. Andrew massyn 20:44, 28 July 2006 (UTC)

I was responsible for the unsigned June 20 edit, and the first comment listed on this page. (Didn't have an account yet then.) Andrew and SB appear to have undone those contributions based on a critique of a previous version that was no longer relevant, with no comments about any deficiencies in the version they deleted. The present version is OK, but the June 20th version has advantages over the current version: it includes references and it includes the derived term aspirated psychrometer. I also dispute the claim that psychrometer is a broader term than wet-and-dry-bulb hygrometer. My position is backed by the references (and by the wikipedia entry on hygrometer); the present version is not backed by any references. So unless I hear reasons not to I'll plan an edit to put the content of the June 20th edit into the present better format, and to include the link to wet-and-dry-bulb hygrometer that is in the present version. I'll also move the information about an aspirated psychrometer to a new entry. OK? Ccrrccrr 02:12, 13 August 2006 (UTC)

I initially checked the entry because we noticed that CORNELIUSSEON had recently added some entries (including this one) which appeared to be copy violations (see above) and, in spite of request, he never produced evidence that the document he quoted allowed our usage rather than, for example, saying "all rights reserved". Copying work verbatim from a recent dictionary or (as in this case) glossary, can often be a breach of copyright, and military publications frequently have very strict copyright conditions. Obviously, it is better to give the reference for a quote rather than to quote it unreferenced, but it may still be illegal. Have you checked any copyright reference on the document (or in the absence of one, checked with the publishers, since copyright may now exist even if not specifically asserted in the document)?
Also, the reference document quoted in the 20 Jun entry Field Behavior of Chemical, Biological and Radiological Agents is not really "on-topic" so it is not terribly surprising that its definition is inexact. You are likely to find better definitions in a publication from meteorological or HVAC publications (eg from ASHRAE).
In this case, the entry was also a clear description of a sling psychrometer rather than a psychrometer. As it happens, sling psychrometers are not common in the UK (in fact they're becoming less common everywhere, as electronics provide the possibility of a direct readout of temperature and humidity, rather than needing to take tables for wet & dry bulb readings and deduce from them what the humidity is). In the UK, when HVAC professionals, etc, (like myself) still use non-electronic instruments, we usually use a whirling psychrometer which is small enough to be used in areas where there "is not enough room to swing a cat" rather than a whirling psychrometer, which is more suited to outdoor use.
Thus any entry for psychrometer ought to be broad enough to encompass whirling psychrometers, and aspirating psychrometers which tend to be used in fixed installations (and are generally more appropriate for electronic readouts of humidity). The present entry achieves that, although it could be improved. In my opinion, by far the best (most accurate) edit so far was the definition written by SemperBlotto on 19 Jun 06, unfortunately overwritten a day later.
It is possible your researches were skewed due to the fact that psychrometer has only recently become much used in the UK (where previously we used to use hygrometer) so you will probably find many more references to whirling hygrometer than whirling psychrometer.
Regarding the generality of psychrometer I certainly believe it, in modern usage, to refer to any means of measuring humidity. Few, if any, electronic psychrometers use thermometers, and I believe electronic versions are now the most common type of psychrometer. However, it is true that the etymology, and (according to the OED) original 18th century English usage, means "cold measurer" which does sound like a thermometer. So perhaps instuments using "old fashioned" humidity measuring techniques (eg measuring changes in length of a hair) should preferably still be referred to as hygrometers.
But that still leaves modern (last 30 - 40 yrs) electronic psychrometers (which use the change in conductivity with humidity of various chemicals, rather than thermometers), so a growing proportion of psychrometers do not use wet and dry bulb thermometers. --Enginear 09:53, 20 August 2006 (UTC)

Thanks for the extensive discussion.

In most of the usage I see, there is no distinction between sling and whirling--both are used whether the instrument is on a string (properly sling) or on a bearing (properly whirling). So I don't think it's worth bothering to make that distinction.

AS for electronic psychrometers, I looked at that a little, and it seems that the term is used for an instrument that incorporates some other form of hygrometer, a thermometer, and the abiltiy to calculate and display wet bulb temperature, in order to provide the same data as one would obtain from a wet-and-dry bulb instrument. So I don't think it has become a synonym for hygrometer. Ccrrccrr 21:54, 12 September 2006 (UTC)