[time-nuts] Primary Standards...
Tom Holmes, N8ZM
tholmes at woh.rr.com
Wed Feb 24 00:56:48 UTC 2010
My recollection of the definition of an Ampere is 6.02 x 10^23 electrons per second (Avogadro's Number, I believe) passing a point in a conductor. To this day, I wonder how they managed to count all those electrons. But it does suggest that the silver deposit approach might be a better method of building a standard. Seems, though, like you'd have to make a darned high resolution weight measurement.
Now with tongue still planted firmly in cheek, I have to think that THE primary standard time interval reference is whatever NIST (and other such outfits) tells me it is. Anything else would seem to be a secondary standard as it would have to be compared to NIST to be sure it is right (OK, its error to NIST is known), especially based on all of your comments.
But as even NIST pointed out, primary vs. secondary seems to be in the context of the beholder.
Thanks for the enlightening discussion; you've really encouraged me to think about this a bit.
Tom Holmes, N8ZM
Tipp City, OH
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Don Latham
Sent: Tuesday, February 23, 2010 7:33 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Primary Standards...
Gosh. I remember the ampere as the current that would deposit a given
weight of silver in a fixed time...
Also saw a note about one part in e-20. As the universe is apparently
about 5e17 sec old, can we make a standard that is good to 1 sec in 1e20
Dr. David Kirkby
> David C. Partridge wrote:
>> No they cannot be - yet. At the point where (e.g.) the second is
>> in terms of the aluminium quantum clock, then the aluminium quantum
>> are then by definition the primary standards of time, and all the Cs
>> are now secondary standards as the second is no longer defined in terms
>> the Cs beam clock.
> Does that mean that there is no primary standard for the Ampere?
> An Ampere is defined as the current which will produce an attractive force
> of 2
> Ã— 10â€“7 newtons per metre of length between two straight, parallel
> conductors of
> infinite length and negligible circular cross section placed one metre
> apart in
> a vacuum.
> Since its impossible to build such a system, does that mean there is no
> standard for an amp?
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> and follow the instructions there.
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
Huson, MT, 59846
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
More information about the time-nuts