Re: [time-nuts] Standards for units
> "Bruce" == Bruce Griffiths <[EMAIL PROTECTED]> writes: >> back around 1954 or so. Bruce> The change occurred in July 1959. I usually remember things abstractly or aurally, but that appears to be a visual (mis-)remembrance. ;-/ Thanks for the (time) correction. :-) -JimC -- James Cloos <[EMAIL PROTECTED]> OpenPGP: 1024D/ED7DAEA6 ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
From: [EMAIL PROTECTED] Subject: Re: [time-nuts] Standards for units Date: Wed, 4 Apr 2007 01:46:57 EDT Message-ID: <[EMAIL PROTECTED]> Said, > In a message dated 4/3/2007 19:29:25 Pacific Daylight Time, [EMAIL PROTECTED] > > writes: > > An Arianne 5 rocket had to be destroyed with its cargo when it veered > off course because of a faulty conversion from English to metric in the > guidance software. What a bummer! > I hate it when that happens!!! > > > Hi Didier, > > actually unless there was a second explosion I don't know about, the first > Arianne-5 proto-rocket exploded due to a variable parameter overflow > (missing > saturation check) in a calculation. A very spectacular overflow indeed. http://www.around.com/ariane.html > The conversion problem you mentioned happened on a Mars mission. This should shed some light over the manuvering details of that particular mission: http://lamar.colostate.edu/~hillger/toles-orbiter.gif (From http://lamar.colostate.edu/~hillger/cartoon.htm) > BTW: I didn't expect my email about our strange US units to start such a > lengthy discussion on the board... OK, thanks for reminding us who's fault it is. :) Cheers, Magnus ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Hi Said, Thanks for the correction. Now I recall... That's what happens when shooting from the hip without proper backup :-) Didier KO4BB [EMAIL PROTECTED] wrote: > > In a message dated 4/3/2007 19:29:25 Pacific Daylight Time, [EMAIL PROTECTED] > > writes: > > An Arianne 5 rocket had to be destroyed with its cargo when it veered > off course because of a faulty conversion from English to metric in the > guidance software. What a bummer! > I hate it when that happens!!! > > > Hi Didier, > > actually unless there was a second explosion I don't know about, the first > Arianne-5 proto-rocket exploded due to a variable parameter overflow > (missing > saturation check) in a calculation. > > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Hi Poul: Yes, that's the 747 that ran out of gas at 41,000 feet due to an error in converting liters of JP4 to pounds. http://en.wikipedia.org/wiki/Gimli_Glider and it was not the only time this happened: Similar incidents In 2001, in a similar incident involving a Canadian airline, Air Transat Flight 236 made an emergency landing in the Azores without fuel. In 2000, Hapag-Lloyd Flight 3378 landed in a powerless glide 500 meters short of the runway in Vienna, Austria, with all aboard surviving. Have Fun, Brooke w/Java http://www.PRC68.com w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com Poul-Henning Kamp wrote: > In message <[EMAIL PROTECTED]>, Brooke Clarke writes: > >>Hi: >> >>There was a recent incident when a passenger aircraft (maybe Canada) had >>to make an emergency landing because of a wrong metric - English >>conversion resulted in not enough fuel to get to the destination. > > > Not recent, but famous: The Gimli Glider. > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
In message <[EMAIL PROTECTED]>, Brooke Clarke writes: >Hi: > >There was a recent incident when a passenger aircraft (maybe Canada) had >to make an emergency landing because of a wrong metric - English >conversion resulted in not enough fuel to get to the destination. Not recent, but famous: The Gimli Glider. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
In a message dated 4/3/2007 19:29:25 Pacific Daylight Time, [EMAIL PROTECTED] writes: An Arianne 5 rocket had to be destroyed with its cargo when it veered off course because of a faulty conversion from English to metric in the guidance software. What a bummer! I hate it when that happens!!! Hi Didier, actually unless there was a second explosion I don't know about, the first Arianne-5 proto-rocket exploded due to a variable parameter overflow (missing saturation check) in a calculation. The conversion problem you mentioned happened on a Mars mission. There was a lengthy and technically detailed report in the German CT' magazine, it said the designer of the routine proved extensively that the routine would never overflow on Arianne 4 due to it's flight configuration, and in fact it never did. He left the company, and the guys who followed just copy-pasted his code into the Arianne 5 flight software were the code did overflow due to missing saturation tests and a different flight configuration. BTW: I didn't expect my email about our strange US units to start such a lengthy discussion on the board... bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Hi Brooke, Metric screws are spec'd by major diameter, and the number of mm between the peaks of the threads. English are spec'd by diameter, and the number of threads per inch. A 40TPI screw corresponds to a (1/40) * 25.4 = 0.635 mm pitch. There are standard metric pitches of 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, and 1.0 mm. What you are seeing is probably an M3-0.5, M3-0.6, or an M4-0.7 screw. -Chuck Harris Brooke Clarke wrote: > Hi: > > There was a recent incident when a passenger aircraft (maybe Canada) had > to make an emergency landing because of a wrong metric - English > conversion resulted in not enough fuel to get to the destination. > > Are there metric equivalents to different series of English threads. > For example I recently purchased a tap for 8-40 threads after mistakenly > purchasing a 6-40 tap. Most good hardware stores in the US have 4-40 > taps, dies, various lengths screws and nuts. Although 6-40 and 8-40 are > standard sizes they are not commonly stocked. Are there a a number of > alternative combinations of root diameter and pitch in the metric system? > > Have Fun, > > Brooke Clarke ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
>I have read some weird discussion about measurement units. How about weird units? Velocity in attoparsecs (official SI abbreviation apc) per microfortnight? A standard lecture being a microcentury? http://en.wikipedia.org/wiki/List_of_strange_units_of_measurement LtCol Keith E. Brandt, MD, MPH USAF-NASA Aerospace Medicine Liaison Officer Johnson Space Center, Houston, Texas [EMAIL PROTECTED] Goodbye cruel world that was my home- there's cleaner space out here to roam Put my feet up on the moons of Mars- sit back, relax, and count the stars *This message transmitted with 100% recycled electrons ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Thomas A. Frank wrote: >> Are there actually US people on this list who actually continue to >> advocate the use of non-metric units in their country? Speak up! >> > > Of course. > > >> Well the USA ever go metric? >> > > No. > > >> I find it hard to understand why a country as advanced as the US sticks >> with such an antiquated system. I don't get it. >> > > Once this French fade has run its course, you'll all switch back to > English units. > > Tom Frank, KA2CDK > :-) Didier KO4BB ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
An Arianne 5 rocket had to be destroyed with its cargo when it veered off course because of a faulty conversion from English to metric in the guidance software. What a bummer! I hate it when that happens!!! Didier KO4BB Brooke Clarke wrote: > Hi: > > There was a recent incident when a passenger aircraft (maybe Canada) had > to make an emergency landing because of a wrong metric - English > conversion resulted in not enough fuel to get to the destination. > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
> Are there actually US people on this list who actually continue to > advocate the use of non-metric units in their country? Speak up! Of course. > Well the USA ever go metric? No. > I find it hard to understand why a country as advanced as the US sticks > with such an antiquated system. I don't get it. Once this French fade has run its course, you'll all switch back to English units. Tom Frank, KA2CDK ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Hi: There was a recent incident when a passenger aircraft (maybe Canada) had to make an emergency landing because of a wrong metric - English conversion resulted in not enough fuel to get to the destination. Are there metric equivalents to different series of English threads. For example I recently purchased a tap for 8-40 threads after mistakenly purchasing a 6-40 tap. Most good hardware stores in the US have 4-40 taps, dies, various lengths screws and nuts. Although 6-40 and 8-40 are standard sizes they are not commonly stocked. Are there a a number of alternative combinations of root diameter and pitch in the metric system? Have Fun, Brooke Clarke w/Java http://www.PRC68.com w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com Magnus Danielson wrote: >From: Hal Murray <[EMAIL PROTECTED]> >Subject: Re: [time-nuts] Standards for units >Date: Tue, 03 Apr 2007 17:14:50 -0700 >Message-ID: <[EMAIL PROTECTED]> > > > >>>The US has been metric since 1988, however the continued use of >>>customary units during the indefinitely long transition time is the >>>problem. Fundamentally it seems there is a lack of political will to >>>place a definite cutoff date on the use of customary units. >>> >>> >>I have friends who work in the auto industry. They reported (over 10 years >>ago?) that all new designs are metric. >> >>I wonder how much it would help if GSA gave a serious preference to things >>that were metric? >> >>What's 8.5x11 in metric? >> >> > >An odd-shaped A4ish paper for which there is no propper envelope. > >This fact I had to learn from an American professor that was enligthened when >he came to Sweden. Since then he converted to A4 even in his NYC flat where his >wife mostly lives (there is a downside to being professors at different >universities divided by the atlantic). > > > >>Do we have to convert to A4 too? >> >> > >Preferably. :) > > > >>For real fun, look at bicycle parts. I remember seeing one part that had >>25.4 threads per inch. >> >> > >:) > > > >>What fraction of the military is metric? Do they buy potatoes in kilos or >>pounds? >> >> > >The aviation side certainly have alot of imperial measures. Figures. > >Look at GPS. Certainly metric all the way as far as I have seen. Like all >aviation stuff that part may ofcourse use a mixture. Wonder what nice orbit >errors they would have if they used metric and survey inches as basis. >Hmm 2 ppm would be some 50 m or so. > > > >>>One would have thought that with the advent of computers using the >>>"survey inch" and related units for new surveys would have vanished by >>>now. >>> >>> >>There is probably a lot of legal baggage there. I'll bet they will be one of >>the last holdouts. >> >> > >I wonder just how many metric related laws they would have to write before >all things is metric. There is already a few to go around you know. > >Cheers, >Magnus > >___ >time-nuts mailing list >time-nuts@febo.com >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Palfreyman, Jim L wrote: > Are there actually US people on this list who actually continue to > advocate the use of non-metric units in their country? Speak up! > > Well the USA ever go metric? > > As an Australian, why would I care, you may ask? > > Well because of the dominance of the US market, some things can be sold > here using imperial units. My biggest beef is televisions. Some (mainly > CRTs) are sold in cm. Others (plasmas and LCDs) are marketed in inches. > You walk into a shop and you a greeted with dual units. It is terrible! > > The key to making metric work is to completely chuck out the use of > non-metric units. Having to convert is the hard bit. We've been metric > for 35 years and still having to convert from inches to cm because of > the United States is so annoying! > > I find it hard to understand why a country as advanced as the US sticks > with such an antiquated system. I don't get it. Because we like it? Because we can? -Chuck Harris ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
From: Hal Murray <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Standards for units Date: Tue, 03 Apr 2007 17:14:50 -0700 Message-ID: <[EMAIL PROTECTED]> > > > The US has been metric since 1988, however the continued use of > > customary units during the indefinitely long transition time is the > > problem. Fundamentally it seems there is a lack of political will to > > place a definite cutoff date on the use of customary units. > > I have friends who work in the auto industry. They reported (over 10 years > ago?) that all new designs are metric. > > I wonder how much it would help if GSA gave a serious preference to things > that were metric? > > What's 8.5x11 in metric? An odd-shaped A4ish paper for which there is no propper envelope. This fact I had to learn from an American professor that was enligthened when he came to Sweden. Since then he converted to A4 even in his NYC flat where his wife mostly lives (there is a downside to being professors at different universities divided by the atlantic). > Do we have to convert to A4 too? Preferably. :) > For real fun, look at bicycle parts. I remember seeing one part that had > 25.4 threads per inch. :) > What fraction of the military is metric? Do they buy potatoes in kilos or > pounds? The aviation side certainly have alot of imperial measures. Figures. Look at GPS. Certainly metric all the way as far as I have seen. Like all aviation stuff that part may ofcourse use a mixture. Wonder what nice orbit errors they would have if they used metric and survey inches as basis. Hmm 2 ppm would be some 50 m or so. > > One would have thought that with the advent of computers using the > > "survey inch" and related units for new surveys would have vanished by > > now. > > There is probably a lot of legal baggage there. I'll bet they will be one of > the last holdouts. I wonder just how many metric related laws they would have to write before all things is metric. There is already a few to go around you know. Cheers, Magnus ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
> The US has been metric since 1988, however the continued use of > customary units during the indefinitely long transition time is the > problem. Fundamentally it seems there is a lack of political will to > place a definite cutoff date on the use of customary units. I have friends who work in the auto industry. They reported (over 10 years ago?) that all new designs are metric. I wonder how much it would help if GSA gave a serious preference to things that were metric? What's 8.5x11 in metric? Do we have to convert to A4 too? For real fun, look at bicycle parts. I remember seeing one part that had 25.4 threads per inch. What fraction of the military is metric? Do they buy potatoes in kilos or pounds? > One would have thought that with the advent of computers using the > "survey inch" and related units for new surveys would have vanished by > now. There is probably a lot of legal baggage there. I'll bet they will be one of the last holdouts. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Palfreyman, Jim L wrote: > Are there actually US people on this list who actually continue to > advocate the use of non-metric units in their country? Speak up! > > Well the USA ever go metric? > > As an Australian, why would I care, you may ask? > > Well because of the dominance of the US market, some things can be sold > here using imperial units. My biggest beef is televisions. Some (mainly > CRTs) are sold in cm. Others (plasmas and LCDs) are marketed in inches. > You walk into a shop and you a greeted with dual units. It is terrible! > > The key to making metric work is to completely chuck out the use of > non-metric units. Having to convert is the hard bit. We've been metric > for 35 years and still having to convert from inches to cm because of > the United States is so annoying! > > I find it hard to understand why a country as advanced as the US sticks > with such an antiquated system. I don't get it. > > > Jim Palfreyman > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Jim The US has been metric since 1988, however the continued use of customary units during the indefinitely long transition time is the problem. Fundamentally it seems there is a lack of political will to place a definite cutoff date on the use of customary units. With the supposed current emphasis on SI units in the education system hopefully the use of customary units will vanish with a generation or two. One would have thought that with the advent of computers using the "survey inch" and related units for new surveys would have vanished by now. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Are there actually US people on this list who actually continue to advocate the use of non-metric units in their country? Speak up! Well the USA ever go metric? As an Australian, why would I care, you may ask? Well because of the dominance of the US market, some things can be sold here using imperial units. My biggest beef is televisions. Some (mainly CRTs) are sold in cm. Others (plasmas and LCDs) are marketed in inches. You walk into a shop and you a greeted with dual units. It is terrible! The key to making metric work is to completely chuck out the use of non-metric units. Having to convert is the hard bit. We've been metric for 35 years and still having to convert from inches to cm because of the United States is so annoying! I find it hard to understand why a country as advanced as the US sticks with such an antiquated system. I don't get it. Jim Palfreyman ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Hello to all,
and thank you very much Enrico, a very nice and comprehensive
document.
There is a book on the market (2005) "The Measure of all Things" by
Ken Alder, Free Press New York, translated version in german (2006)
"Das Mass der Welt". It tells on about 500 pages quite precise and
very detailed (based on a lot of original french and other documents)
the long history and big work principally of J.- B.-J. Delambre, P.- F.-A.
Méchain
and J.-J. Lalande fighting for the definition and introduction of the meter
in the 18. century.
Worth to be read I believe.
I like all the discussions on this Time-Nuts platform. Concerning the
relation between inch and meter I thought that the definition
is fixed long time ago.
When the meter was defined to be multiples of the wavelength
of light in vacuum, in 1959, the relationship between inches and
centimeters was redefined to be that one inch is equal to 2.540
centimeters, exactly. The new foot, derived from 1 inch = 2.54 cm
(exactly),
is referred to as the "international foot".
There are a lot of informations about to find in the internet, but to be on the
safe
side I had a look on the NIST homepage:
http://emtoolbox.nist.gov/Faq/Faq.asp#FAQ-Miscellaneous-6
(") Quote:
What is the definition of the meter and the inch?
The inch has always been tied to the meter in the U.S. After the Civil War, the
Surveyor General of the U.S. set the inch as 39.37 inches to the meter. The
British had a yard bar, the Canadians had 25.4 mm per inch,
and the other English speaking nations had chosen one of these or some
variation. They were all close, but not exactly the same. The yard bar was in
fact shrinking. In 1959, a conference attended by the directors of
the National Measurement Institutes from all of the English speaking countries,
those who still used inches, met to standardize the inch. The 25.4 mm per inch
(exactly) was chosen, and since then this is the inch used
by NIST (formerly NBS). Except . . . Yes, there is always an exception.
Surveyors still use the old inch because all of the mountains of measurements
in place defining the positions of everything in the US are in these
inches, and the job of changing them was considered too large a task. So
surveyors still use the surveyor inch, 39.37 inches per meter.
(") End of quote.
and :
http://physics.nist.gov/cuu/Units/meter.html
(") Quote:
...in 1983 the CGPM replaced this latter definition by the following definition:
The meter is the length of the path travelled by light in vacuum during a
time interval of 1/299 792 458 of a second.
Note that the effect of this definition is to fix the speed of light in
vacuum at exactly 299 792 458 m·s-1. The original international prototype of
the meter, which was sanctioned by the 1st CGPM in 1889, is still kept
at the BIPM under the conditions specified in 1889.
(")
End of quote.
As well:
Eric Weisstein's World of Physics
http://scienceworld.wolfram.com/physics/Inch.html
An nonmetric unit of length, originally defined as the lengths of
three "average size" barleycorns laid end-to-end, but now more
rationally defined as 2.54 cm. An older definition no longer used
was 1 meter = 39.37 inches, giving 2.54000508 cm/inch.
Surprisingly, these two conversions are both exact. For details on
the current definition of the inch, see
A Tale of Two Feet OR The Case of The Double Standard - T. J. Keefe
http://physics.ccri.cc.ri.us/keefe/twofeet.htm
Finally, the conversion is finally in a concrete form, as long the speed of
light
in vacuum does not turn out to be not constant ;-)
keep watching the time and units,
regards
Arnold, DK2WT
On Tue, 3 Apr 2007 11:37:16 +0200, Enrico Rubiola wrote:
>Dear all,
>I have read some weird discussion about measurement units.
>There is a wonderful book I come across, by Francois Caldarelli
>You may take a look
>http://rubiola.org/shared/caldarelli.pdf
>then it's up to you
>Best
>Enrico Rubiola
>professor of electronics
>web: http://rubiola.org
>e-mail:[EMAIL PROTECTED]
>FEMTO-ST Institute
>32 av. de l'Observatoire
>25044 Besancon, FRANCE
>voice: +33(0)381.853940 (E.Rubiola)
>voice: +33(0)381.853999 (switchboard)
>fax: +33(0)381.853998
>___
>time-nuts mailing list
>time-nuts@febo.com
>https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
___
time-nuts mailing list
time-nuts@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Dear all, I have read some weird discussion about measurement units. There is a wonderful book I come across, by Francois Caldarelli You may take a look http://rubiola.org/shared/caldarelli.pdf then it's up to you Best Enrico Rubiola professor of electronics web:http://rubiola.org e-mail: [EMAIL PROTECTED] FEMTO-ST Institute 32 av. de l'Observatoire 25044 Besancon, FRANCE voice: +33(0)381.853940 (E.Rubiola) voice: +33(0)381.853999 (switchboard) fax:+33(0)381.853998 ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Now I thought the NTSC frame-rate was reduced so that the line frequency was an exact sub-multiple (1/286) of the sound subcarrier at 4.5 MHz, and hence sidebands of the color subcarrier were equally positioned around the sound carrier. Using exactly 30 Hz frame rate (15750 Hz line rate) would have necessitated increasing the sound subcarrier by 4.5 KHz in order to minimise picture-on-sound interference. My understanding is that whilst this was the most obvious this to do, and the major television manufacturers had no problem with that, one or two minor manufacturers of black-and-white televisions objected vociferously that the new signal would be incompatible with their old televisions, and so the FCC insisted the sound carrier had to remain at 4.5 MHz - a decision everybody in television has regretted ever since! I thought I had learnt the above from the SMPTE NTSC specification 170M, but on re-reading that now, I can't find the reference :-( I'd love to read that RCA document if it is available electronically. Peter Vince (BBC Television, London) >This precise sort of error reminds me of the error that RCA >introduced into the frame rate for NTSC color when they discovered >that the chosen color burst frequency was right on top of a diathermy >machine or something silly like that. They bumped the frame rate down >by exactly 0.1%, creating the 29.97 frames/second that >cinematographers have grown to love to hate. > >There's a volume of the RCA Review that came out in 1953 that is all >about the NTSC color system development process. It's fascinating >reading. Available at your local university library. > > >-- > >--David Forbes, Tucson, AZ >http://www.cathodecorner.com/ ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
This was sent before, but never seemed to get to the net. > It is interesting to look in the front of the International > Critical Tables, an encyclopedic set of books containing detailed > scientific information about 1920. Every nation, (hundreds of them) > had their own units which were used in commerce and trade. > Unfortunately the only access on the net to these tables is blocked > by a pay barrier. > Their are now very few nations hanging out for their own units. > The story I heard about the inch/metre relationship was that during > WW2 there were problems making spare parts for aeroplane engines to > specification, and it was discovered that the French had supplied a > replica standard metre to the bureau of standards of each major > country and that these could be quickly used to standardise > engineering measurements. My version said that 25.4000 mm > per inch was the accepted relationship. > > Clocks were made in Napoleons time with ten hour dials with one > hundred minutes. > > Cheers, > Neville Michie > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
From: David Forbes <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Standards for units Date: Mon, 2 Apr 2007 23:22:24 -0700 Message-ID: <[EMAIL PROTECTED]> > At 9:57 PM -0700 4/2/07, Tom Van Baak wrote: > >> >1/meter/39.37 inches = 0.025400051 meters/inch ... > > > >> The interesting thing is that this result is off by 2.04000 ppm. > >> That's a rather precise error! > >> > >> The calculator I used is here: > >> http://homepage.ntlworld.com/r.howitt/Calculator.htm > > > >David, > > > >There are two ways to compute relative error, depending on > >which one you call the reference. > > > >For extra credit, note your number is actually this cool-looking > >fraction* whose pattern you will immediately recognize. > > > >2.0408163264000128000256000512001024... > > > >/tvb > >http://www.LeapSecond.com > > > >* calculated with: echo "80k .002 999.998 / 10 6 ^ * p" | dc > > > Yes, I had a feeling it was that case, but I didn't bother to chase it too > far. > > This precise sort of error reminds me of the error that RCA > introduced into the frame rate for NTSC color when they discovered > that the chosen color burst frequency was right on top of a diathermy > machine or something silly like that. They bumped the frame rate down > by exactly 0.1%, creating the 29.97 frames/second that > cinematographers have grown to love to hate. We *STILL* suffer from this. With CCIR-601 we where doing good, everything about PAL and NTSC joins in with 27 MHz as a common frequency, but when they went for HD-SDI they broke things bigtime as they chose to have 11/2 times higher rate than SD-SDI. So now we have to support 1.485 Gb/s AND 1.485 / 1.001 Gb/s. Sigh! I would have settled for 5 or 6 times instead, that 11 is what breaks the magic. This 1.001 error is a major headache since you can't use the same crystal and pull it either way. If you do many channels it is infeasable to have multiple crystals and choose between them (we have done that once already) and the resynthesis chips doesn't have godo enought phase noise to be useable when they do the 1.001 term. It also shows up in sample-rates, so we see things like 44056 Hz samplings etc. It is still broken and its a PINA to get fixed. (Sorry for the strong wording) > There's a volume of the RCA Review that came out in 1953 that is all > about the NTSC color system development process. It's fascinating > reading. Available at your local university library. Somehow I doubt that. :P Would like to read it thought. Cheers, Magnus ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
James Cloos wrote: >> "David" == David Dameron <[EMAIL PROTECTED]> writes: >> > > David> (I was taught that 1 meter was 39.37 inches, to define the > David> inch, but now I see more of 1 inch = 2.54 cm, as someone just > David> referred to.) > > That was the old inch. It was changed back around 1954 or so. They > decided they didn't want to have an SI unit looking like it was > defined in terms of a legacy unit, and so changed from 1 meter = 39.37 > inches to 1 inch = .0254 meters so that the inch was defined in terms > of the meter. > > Or, as likely, from 1 meter = 3937/1200 feet to 1 foot = .3048 meters. > > The old length is still used for so called survey feet in the US. > > Many conversion routines -- including unix's units(1) and HP's line of > RPL calculators -- call them US feet. > > -JimC > Jim The change occurred in July 1959. At which time the UK, USA, NewZealand etc officially adopted the new definition of the inch. Canada had adopted it somewhat before this. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
From: Chuck Harris <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Standards for units Date: Mon, 02 Apr 2007 22:09:49 -0400 Message-ID: <[EMAIL PROTECTED]> Chuck, > > The other inch defined by > > > > 1 inch = 25.4mm exactly > > > > is used for everything else. > > My recollection when I posted the earlier letter was 24.5 mm/inch was > exact by definition, and I recalled that 39.37 inches/meter was also > exact... a quick calculator check to 6 figures showed that it was exact, > then I tried to 9 figures, and saw that pesky little 0.00051. I was telling you that it was of by about 2 ppm. > > For confirmation read the appendix C of NIST Handbook 44, where these > > and other units of measurement are described. > > Why on earth one has to have different units all called barrels for oil, > > cranberry juice, dried fruits, liquor (this one varies from state to > > state) etc., defies imagination. > > I think the biggest push for metric is the chance to start fresh. But > when metric includes piezes, and poises, and sthenes and steres and stokes... > I guess it ain't all that fresh. Huh? Where did you get that from? Cheers, Magnus ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
At 9:57 PM -0700 4/2/07, Tom Van Baak wrote: >> >1/meter/39.37 inches = 0.025400051 meters/inch ... > >> The interesting thing is that this result is off by 2.04000 ppm. >> That's a rather precise error! >> >> The calculator I used is here: >> http://homepage.ntlworld.com/r.howitt/Calculator.htm > >David, > >There are two ways to compute relative error, depending on >which one you call the reference. > >For extra credit, note your number is actually this cool-looking >fraction* whose pattern you will immediately recognize. > >2.0408163264000128000256000512001024... > >/tvb >http://www.LeapSecond.com > >* calculated with: echo "80k .002 999.998 / 10 6 ^ * p" | dc Yes, I had a feeling it was that case, but I didn't bother to chase it too far. This precise sort of error reminds me of the error that RCA introduced into the frame rate for NTSC color when they discovered that the chosen color burst frequency was right on top of a diathermy machine or something silly like that. They bumped the frame rate down by exactly 0.1%, creating the 29.97 frames/second that cinematographers have grown to love to hate. There's a volume of the RCA Review that came out in 1953 that is all about the NTSC color system development process. It's fascinating reading. Available at your local university library. -- --David Forbes, Tucson, AZ http://www.cathodecorner.com/ ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
> "David" == David Dameron <[EMAIL PROTECTED]> writes: David> (I was taught that 1 meter was 39.37 inches, to define the David> inch, but now I see more of 1 inch = 2.54 cm, as someone just David> referred to.) That was the old inch. It was changed back around 1954 or so. They decided they didn't want to have an SI unit looking like it was defined in terms of a legacy unit, and so changed from 1 meter = 39.37 inches to 1 inch = .0254 meters so that the inch was defined in terms of the meter. Or, as likely, from 1 meter = 3937/1200 feet to 1 foot = .3048 meters. The old length is still used for so called survey feet in the US. Many conversion routines -- including unix's units(1) and HP's line of RPL calculators -- call them US feet. -JimC -- James Cloos <[EMAIL PROTECTED]> OpenPGP: 1024D/ED7DAEA6 ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
> >1/meter/39.37 inches = 0.025400051 meters/inch ... > The interesting thing is that this result is off by 2.04000 ppm. > That's a rather precise error! > > The calculator I used is here: > http://homepage.ntlworld.com/r.howitt/Calculator.htm David, There are two ways to compute relative error, depending on which one you call the reference. We start with 39.37 * 25.4 = 999.998 (exactly) and note that it is 0.002 (exactly) away from 1000. You can compute the relative error two ways: 1) 0.002 / 1000.0 = 2 ppm (exactly), or 2) 0.002 / 999.998 = your 2.04000 ppm number. I'd guess convention is to use the first number, not the second. For extra credit, note your number is actually this cool-looking fraction* whose pattern you will immediately recognize. 2.0408163264000128000256000512001024... /tvb http://www.LeapSecond.com * calculated with: echo "80k .002 999.998 / 10 6 ^ * p" | dc ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
> >As long as exact means within a few parts per million: > >1/meter/39.37 inches = 0.025400051 meters/inch ... > The interesting thing is that this result is off by 2.04000 ppm. That's a rather precise error! The calculator I used is here: http://homepage.ntlworld.com/r.howitt/Calculator.htm -- --David Forbes, Tucson, AZ http://www.cathodecorner.com/ ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
> My recollection when I posted the earlier letter was 24.5 mm/inch was > exact by definition, and I recalled that 39.37 inches/meter was also > exact... a quick calculator check to 6 figures showed that it was > exact, then I tried to 9 figures, and saw that pesky little > 0.00051. I did things like that for a while, then I multiplied 3937 by 254. The answer is 98. So those 2 constants are off by 2 ppm from being an exact inverse of eachother. I assume the decimal points/units work out right. I just shifted to integers to avoid any rounding quirks. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
>>> 1 meter/39.37 inches = 0.02540 meters/inch = 2.54 cm/inch = 25.4 mm/inch >>> >>> Exactly. >>> >> As long as exact means within a few parts per million: >> >> 1/meter/39.37 inches = 0.025400051 meters/inch ... >> >> >>> -Chuck Harris >>> >> ___ >> time-nuts mailing list >> time-nuts@febo.com >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> >> > Chuck > > That's a little sloppy for this list surely. > > In fact the US currently uses 2 different inches the "survey" inch (plus > yard, mile etc) which is defined by the relation > > 1 metre = 39.37 "survey" inches exactly. > > This inch is used purely for surveying purposes. > > The other inch defined by > > 1 inch = 25.4mm exactly > > is used for everything else. My recollection when I posted the earlier letter was 24.5 mm/inch was exact by definition, and I recalled that 39.37 inches/meter was also exact... a quick calculator check to 6 figures showed that it was exact, then I tried to 9 figures, and saw that pesky little 0.00051. > For confirmation read the appendix C of NIST Handbook 44, where these > and other units of measurement are described. > Why on earth one has to have different units all called barrels for oil, > cranberry juice, dried fruits, liquor (this one varies from state to > state) etc., defies imagination. I think the biggest push for metric is the chance to start fresh. But when metric includes piezes, and poises, and sthenes and steres and stokes... I guess it ain't all that fresh. -Chuck ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Chuck Harris wrote: > Chuck Harris wrote: > >> David Dameron wrote: >> >>> Hi all, >>> I just realized that a meter is defined by the speed of light., see >>> http://physics.nist.gov/cuu/Units/meter.html >>> It is only to 9 significant digits, so if the speed of light (in some >>> controlled environment) is measured more precisely than this, the meter and >>> all other derived length units will change? >>> >>> (I was taught that 1 meter was 39.37 inches, to define the inch >>> , but now I see more of 1 inch = 2.54 cm, as someone just referred to.) >>> >> 1 meter/39.37 inches = 0.02540 meters/inch = 2.54 cm/inch = 25.4 mm/inch >> >> Exactly. >> > > As long as exact means within a few parts per million: > > 1/meter/39.37 inches = 0.025400051 meters/inch ... > > >> -Chuck Harris >> > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Chuck That's a little sloppy for this list surely. In fact the US currently uses 2 different inches the "survey" inch (plus yard, mile etc) which is defined by the relation 1 metre = 39.37 "survey" inches exactly. This inch is used purely for surveying purposes. The other inch defined by 1 inch = 25.4mm exactly is used for everything else. For confirmation read the appendix C of NIST Handbook 44, where these and other units of measurement are described. Why on earth one has to have different units all called barrels for oil, cranberry juice, dried fruits, liquor (this one varies from state to state) etc., defies imagination. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Chuck Harris <[EMAIL PROTECTED]> wrote: > > 1 meter/39.37 inches = 0.02540 meters/inch = 2.54 cm/inch = 25.4 mm/inch > > > > Exactly. > > As long as exact means within a few parts per million: > > 1/meter/39.37 inches = 0.025400051 meters/inch ... Nobody needs that kind of precision when dealing with inches... Just kidding!!! could not resist :-) Didier KO4BB ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Chuck Harris wrote: > David Dameron wrote: >> Hi all, >> I just realized that a meter is defined by the speed of light., see >> http://physics.nist.gov/cuu/Units/meter.html >> It is only to 9 significant digits, so if the speed of light (in some >> controlled environment) is measured more precisely than this, the meter and >> all other derived length units will change? >> >> (I was taught that 1 meter was 39.37 inches, to define the inch >> , but now I see more of 1 inch = 2.54 cm, as someone just referred to.) > > 1 meter/39.37 inches = 0.02540 meters/inch = 2.54 cm/inch = 25.4 mm/inch > > Exactly. As long as exact means within a few parts per million: 1/meter/39.37 inches = 0.025400051 meters/inch ... > > -Chuck Harris ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
David Dameron wrote: > Hi all, > I just realized that a meter is defined by the speed of light., see > http://physics.nist.gov/cuu/Units/meter.html > It is only to 9 significant digits, so if the speed of light (in some > controlled environment) is measured more precisely than this, the meter and > all other derived length units will change? > > (I was taught that 1 meter was 39.37 inches, to define the inch > , but now I see more of 1 inch = 2.54 cm, as someone just referred to.) 1 meter/39.37 inches = 0.02540 meters/inch = 2.54 cm/inch = 25.4 mm/inch Exactly. -Chuck Harris ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
It is interesting to look in the front of the International Critical Tables, an encyclopedic set of books containing detailed scientific information about 1920. Every nation, (hundreds of them) had their own units which were used in commerce and trade. Unfortunately the only access on the net to these tables is blocked by a pay barrier. Their are now very few nations hanging out for their own units. The story I heard about the inch/metre relationship was that during WW2 there were problems making spare parts for aeroplane engines to specification, and it was discovered that the French had supplied a replica standard metre to the bureau of standards of each major country and that these could be quickly used to standardise engineering measurements. My version said that 25.4000 mm per inch was the accepted relationship. Clocks were made in Napoleons time with ten hour dials with one hundred minutes. Cheers, Neville Michie On 02/04/2007, at 4:08 PM, Dr Bruce Griffiths wrote: > David Dameron wrote: >> Hi all, >> I just realized that a meter is defined by the speed of light., see >> http://physics.nist.gov/cuu/Units/meter.html >> It is only to 9 significant digits, so if the speed of light (in some >> controlled environment) is measured more precisely than this, the >> meter and >> all other derived length units will change? >> >> (I was taught that 1 meter was 39.37 inches, to define the inch >> , but now I see more of 1 inch = 2.54 cm, as someone just referred >> to.) >> >> I find the standard for the Ampere, mentioned in the nist pages >> above more >> difficult, as 2 infinite wires to measure the force between cannot be >> found! Was the coulomb the standard before? Does anyone have other >> web >> pages to recommend? >> (Am still learning about the 1948 changes to electrical units, >> international and absolute volts, etc. Before finding this list, >> did not >> think much about the differences, about 500 ppm., with a 3 1/2 >> digit dvm.) >> >> David D. >> > David > > The 1m = 39.37 inch definition applies to the US survey inch, a unit > only used in surveys. > Since around 1958 or 1959 the US customary inch has been identical to > the international inch: > 1 international inch = 25.4mm. > The 2ppm difference is significant in geodetic survaeys. > > In practice realising the ampere used to mean building a current > balance. > The abstract definition employing infinite wires can easily be used > together with a little calculus to calculate the force between non > infinite wires of wound into ci=oils and other shapes. > > Before the advent of the current balance the unit of charge was > defined > electrochemically in terms of the weight of a standard metal > (platinum??)electroplated from solution on to the cathode of a > electroplating cell. The unit of current being defined by extension > from > the unit of charge. Note the SI units as we know them today were not > then in use. > > Bruce > > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
From: "David Dameron" <[EMAIL PROTECTED]> Subject: [time-nuts] Standards for units Date: Sun, 1 Apr 2007 20:45:49 -0700 Message-ID: <[EMAIL PROTECTED]> > Hi all, > I just realized that a meter is defined by the speed of light., see > http://physics.nist.gov/cuu/Units/meter.html > It is only to 9 significant digits, so if the speed of light (in some > controlled environment) is measured more precisely than this, the meter and > all other derived length units will change? Incorrect. You have as many significant digits as you want. It is defined to that number which just happends to use only 9 digits in decimal system. This is a convenience that was chosen, but the significant digits is as many as you need. > (I was taught that 1 meter was 39.37 inches, to define the inch > , but now I see more of 1 inch = 2.54 cm, as someone just referred to.) The US Metric law defined 1 meter to be 39,37 inches, but this is unpractical since you often build precission inch measures (in the world of C E Johansson) from meter buildingblocks and then 25,4 mm is much more convenient. The difference is about 2 ppm. Except in a few cases you must use the 25,4 mm definition (which is now part of the SI system) rather than the 1/39.37 definition. > I find the standard for the Ampere, mentioned in the nist pages above more > difficult, as 2 infinite wires to measure the force between cannot be > found! They are stapleware! :-) No, it's indeed a strange definition but it can be converted into a more realizeable thing. I beleive that one will be redefined eventually. We can count the amount of electrons passing a cross-section per second and having the defined the element charge we simply use the second definition which is the most precise SI unit we can realize anyway. Go to BIPM and you can download the SI document from them. Includes parts of the history. They also have more info online. Cheers, Magnus ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
David Dameron wrote: > Hi all, > I just realized that a meter is defined by the speed of light., see > http://physics.nist.gov/cuu/Units/meter.html > It is only to 9 significant digits, so if the speed of light (in some > controlled environment) is measured more precisely than this, the meter and > all other derived length units will change? > > (I was taught that 1 meter was 39.37 inches, to define the inch > , but now I see more of 1 inch = 2.54 cm, as someone just referred to.) > > I find the standard for the Ampere, mentioned in the nist pages above more > difficult, as 2 infinite wires to measure the force between cannot be > found! Was the coulomb the standard before? Does anyone have other web > pages to recommend? > (Am still learning about the 1948 changes to electrical units, > international and absolute volts, etc. Before finding this list, did not > think much about the differences, about 500 ppm., with a 3 1/2 digit dvm.) > > David D. > David The 1m = 39.37 inch definition applies to the US survey inch, a unit only used in surveys. Since around 1958 or 1959 the US customary inch has been identical to the international inch: 1 international inch = 25.4mm. The 2ppm difference is significant in geodetic survaeys. In practice realising the ampere used to mean building a current balance. The abstract definition employing infinite wires can easily be used together with a little calculus to calculate the force between non infinite wires of wound into ci=oils and other shapes. Before the advent of the current balance the unit of charge was defined electrochemically in terms of the weight of a standard metal (platinum??)electroplated from solution on to the cathode of a electroplating cell. The unit of current being defined by extension from the unit of charge. Note the SI units as we know them today were not then in use. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
David Dameron wrote: > Hi all, > I just realized that a meter is defined by the speed of light., see > http://physics.nist.gov/cuu/Units/meter.html > It is only to 9 significant digits, so if the speed of light (in some > controlled environment) is measured more precisely than this, the meter and > all other derived length units will change? > > (I was taught that 1 meter was 39.37 inches, to define the inch > , but now I see more of 1 inch = 2.54 cm, as someone just referred to.) > > I find the standard for the Ampere, mentioned in the nist pages above more > difficult, as 2 infinite wires to measure the force between cannot be > found! Was the coulomb the standard before? Does anyone have other web > pages to recommend? > (Am still learning about the 1948 changes to electrical units, > international and absolute volts, etc. Before finding this list, did not > think much about the differences, about 500 ppm., with a 3 1/2 digit dvm.) > > David D. > David You may find this link somewhat amusing http://www.sizes.com/units/miners_inch.htm If one moved around the various mining fields one could become somewhat confused by this unit of measurement. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
David Dameron wrote: > Hi all, > I just realized that a meter is defined by the speed of light., see > http://physics.nist.gov/cuu/Units/meter.html > It is only to 9 significant digits, so if the speed of light (in some > controlled environment) is measured more precisely than this, the meter and > all other derived length units will change? > > (I was taught that 1 meter was 39.37 inches, to define the inch > , but now I see more of 1 inch = 2.54 cm, as someone just referred to.) > > I find the standard for the Ampere, mentioned in the nist pages above more > difficult, as 2 infinite wires to measure the force between cannot be > found! Was the coulomb the standard before? Does anyone have other web > pages to recommend? > (Am still learning about the 1948 changes to electrical units, > international and absolute volts, etc. Before finding this list, did not > think much about the differences, about 500 ppm., with a 3 1/2 digit dvm.) > > David D. > David No, the speed of light in vacuum has in effect been fixed by this definition. All that will happen is the meter will be able to be realised more accurately. The 1 meter = 39.37 inches is a relatively inaccurate (2ppm) approximation. At one time the US, UK and Canada all had slightly different length inches. The fractional differences weren't very large several orders of magnitude lower than the fractional differences between the imperial gallon and the US gallon for example. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] Standards for units
Hi all, I just realized that a meter is defined by the speed of light., see http://physics.nist.gov/cuu/Units/meter.html It is only to 9 significant digits, so if the speed of light (in some controlled environment) is measured more precisely than this, the meter and all other derived length units will change? (I was taught that 1 meter was 39.37 inches, to define the inch , but now I see more of 1 inch = 2.54 cm, as someone just referred to.) I find the standard for the Ampere, mentioned in the nist pages above more difficult, as 2 infinite wires to measure the force between cannot be found! Was the coulomb the standard before? Does anyone have other web pages to recommend? (Am still learning about the 1948 changes to electrical units, international and absolute volts, etc. Before finding this list, did not think much about the differences, about 500 ppm., with a 3 1/2 digit dvm.) David D. >Oh, is that SI Inch or US Metric act Inch? There is about 2 ppm of difference >you know (we are time-nuts after all, right?). It was actually C E Johansson >that tricked the world into beleiving the Inch was 25.4 mm and when they found >out the US motor industry was running of Johanssons version of the Inch and >refused to change. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
