No subject


Sun Nov 2 21:23:46 UTC 2008


the difference between two voltage sources if one uses a lot of care and =
applies some form of extra filtering.=20
A  1nV  (1e-9) is way below the noise level of any voltage standard that =
puts out volts.
This means reference measurements are not limited by the noise level =
when using a good but simple setup until the references gets to be in =
the 3e-10 precision range.


The answer to "What can an amateur do to get a good low noise reference =
for less than, say, $500"
IS shop at the US eBay site.

WarrenS

***********************
----- Original Message -----=20
From: "Bill Hawkins" <bill at iaxs.net>
To: "'Discussion of precise time and frequency measurement'" =
<time-nuts at febo.com>
Sent: Sunday, November 30, 2008 1:16 PM
Subject: Re: [time-nuts] Voltage standards


> Group,
>=20
> The subject elicited a fine hardware discussion, as always.
>=20
> There was some casual talk about measuring fractions of
> microvolts, implying 10E-7 or -8 accuracy.
>=20
> There are lots of possible thermoelectric effects that may be
> in series with the source.
>=20
> Without describing how it's done, what is the lower measuring
> limit in nanovolts? That's the limit where the last digit
> moves randomly by more than one increment. Does the method
> involve cryogenics?
>=20
> I'd look it up, but I expect some of you are more current
> with the science than anything I could find with Google.
>=20
> Given that extreme accuracy and stability are expensive, what
> can an amateur do for less than, say, $500 or 400 Euros?
>=20
> Thanks for any enlightenment.
> Bill Hawkins
>=20
>=20
>=20
>=20
>=20
>


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