I once worked for a company that required obscene amounts of paperwork and
specs for projects. Paperwork that nobody would ever read. I wrote up a spec
where all the timing was done in ffn (femto-fortnights). It was several years
before anybody asked what an ffn was.
I avoided the effects of the most recent one by sneezing at exactly the right
time. Not a popular thing to do at the dinner table but when ya gotta sneeze,
ya gotta sneeze!
Dave, if we didn't exist who would drink the beer???
Steve
On Jul 13, 2012, at 11:23 AM, Artekmedia wrote:
> Actually
I wouldn't lose any sleep over it, but maybe I'm not "nutty" enough for the
current discussion :-o
Steve
On Jul 13, 2012, at 10:49 AM, Artekmedia wrote:
> There are 1,209,600 seconds in a fortnight (14days/fortnight x 24 hours/day x
> 60 min/hour x 60 seconds/min) so the implied error is a
Actually it is pretty easy to avoid leap seconds as they are usually
introduced on June 30 or Dec 31 and only 25 leap seconds have been
introduced in the last 40 years, the most recent one on June 30th,
2012...given that figure, the implied error due to leap seconds is much
much less than the
There are 1,209,600 seconds in a fortnight (14days/fortnight x 24
hours/day x 60 min/hour x 60 seconds/min) so the implied error is a bit
less than 1PPM.
Dave
"Experience keeps a dear school ..but a fool learns in no other" ..Ben
Franklin
On 7/13/2012 8:09 AM, Steve wrote:
But what if a
But what if a leap second occurs during the fortnight the standard is being
set? ;)
Steve
On Jul 13, 2012, at 7:22 AM, "Poul-Henning Kamp" wrote:
> In message <4fffebec.8030...@embarqmail.com>, Artekmedia writes:
>
> Yes, I'd expect the last non-metric country in the world to go for that :-
In message <4fffebec.8030...@embarqmail.com>, Artekmedia writes:
Yes, I'd expect the last non-metric country in the world to go for that :-)
>Coulombs per fortnight to be sure :-)
>
>On 7/13/2012 2:40 AM, Poul-Henning Kamp wrote:
>> In
>> message
>> , Will writes:
>>
>>> No practical quantum Amp
Coulombs per fortnight to be sure :-)
On 7/13/2012 2:40 AM, Poul-Henning Kamp wrote:
In message
, Will writes:
No practical quantum Ampere so far?
It has always surprised me that the Ampere was not defined in terms of
electron charges per second...
--
Dave& Lynn Henderson
manu...@artekmed
In message
, Will writes:
>No practical quantum Ampere so far?
It has always surprised me that the Ampere was not defined in terms of
electron charges per second...
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer |
The 1990 Josephson constant 2e/h is just an approximation which means
that the "Josephson Volt and Ohm" are not exactly the same as the SI
Volt and Ohm.
No practical quantum Ampere so far?
2012/7/12, Mike S :
> Apropos: http://www.sciencedaily.com/releases/2012/07/120711101042.htm
>
> With regar
Yes, the effect can be estimated quite easily. Also, keep in mind
that the 0.13 nV is the RMS noise, so the peak to peak excursions can
be around six times that, or almost 1 nV p-p. If the FS is 1 mA, then
it's about 1 ppm - one count on a six digit DVM, or ten times more
with each additional d
Apropos: http://www.sciencedaily.com/releases/2012/07/120711101042.htm
With regard to the discussion, since in the SI, Amps are the base unit,
Volts are derived from Amps, and Ohms from Volts - remarkable that Amps
are the least realizable in practice? (I guess it's just the difference
between
On 07/11/2012 09:01 PM, Mike S wrote:
> On 7/11/2012 5:15 AM, Frank Stellmach wrote:
>> This is the worst realized electrical unit, i.e. the 'mise en pratique'
>> is difficult to an error level of about 1e-7 only.
>
> On 7/11/2012 6:50 PM, Bob Smither wrote:
>> I may be off here, but I doubt that
On 7/11/2012 5:15 AM, Frank Stellmach wrote:
This is the worst realized electrical unit, i.e. the 'mise en pratique'
is difficult to an error level of about 1e-7 only.
On 7/11/2012 6:50 PM, Bob Smither wrote:
I may be off here, but I doubt that thermal (Johnson) noise would limit the
precision
On 07/11/2012 03:49 PM, ed breya wrote:
> That which is more fundamental to the problem is the unavoidable (at room
> temperature) noise from the resistors. Even a "perfect" resistor with zero
> tempco has noise, so if you use resistors to measure current with a
> high-precision voltmeter, eventual
That which is more fundamental to the problem is the unavoidable (at
room temperature) noise from the resistors. Even a "perfect" resistor
with zero tempco has noise, so if you use resistors to measure
current with a high-precision voltmeter, eventually you reach a
resolution where the noise be
In message <4ffca814.5080...@toneh.demon.co.uk>, Tony Holt writes:
>I've never understood why relatively expensive and sophisticated
>instruments don't have significantly lower resistance shunts
Isn't it simply because there are better ways to do it, than to
use an external shunt ?
Flux Gate cu
egards,
Laurence Motteram
-Original Message-
From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
Behalf Of Tony Holt
Sent: Wednesday, 11 July 2012 8:09 AM
To: volt-nuts@febo.com
Subject: Re: [volt-nuts] HP 3458A DC current accuracy
Frank,
Thanks for taking to trouble to r
Frank,
Thanks for taking to trouble to respond. Its interesting that the Datron
1281 has exactly the same issue - best 24hr uncertainty:
DC V: .5ppm + .3,
Resistance: 1+ .3,
DC A: 10 + 2
So its not a HP specific design trade-off. Perhaps there's something
more fundamenta
..
but it does not explain completely the mediocre specification of
resistance and current ranges, that's true.
Especially the 1µA range, measured directly by the internal 40kOhm
standard resistor (TC 1.3ppm/K, and "precise" to 2ppm within 24h )
should be on the same level of accuracy in the
Tony,
for understanding the 3458A, the HP Journal 4 / 1989 is a good read,
available on the agilent site.
There's described, that the 3458A is calibrated completely by two
sources only, i.e. 10V and 10kOhm, and all other ranges and modes are
derived from its ultra linear A/D transfer.
Each 10:
I'm new here so please be gentle with me if you think I'm asking stupid
questions.
I'm trying to understand the accuracy specifications of the 3458A. One
that I can't understand is why the DC current accuracy specs are much
worse than the DC V and resistance accuracies would imply are possible
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