What is the smallest physically-possible voltage that can be detected or processed given the state of today's technology?

wrote:


Never the less, into the binary bin with him I say !!
Rheilly P
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All responders have been suckered by the green monster.
Bill
--
Most people go to college to get their missing high school education.

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That is true, but the femtovolt question is interesting, independent of who asked it. I base my replies on the question, not the questioner. It might be that the answer is independent of the original question.
-- glen
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On Tue, 02 Jun 2009 00:19:17 -0400, "Michael A. Terrell"

We should all refrain from replying to your horseshit then.
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Eric Gisse wrote:

Is there any one in this group with the necessary scholastic qualifications to diagnose the reason this poster asks such esoteric questions
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F Murtz wrote:

It probably needs someone from the astronomical and satellite-making communities (and maybe folk at Cern et al), who have necessarily to deal with the smallest detectable signals; and the answer will (a) probably have to do with the lowest-achievable noise (C --> Absolute Zero), and (b) change regularly as new technology is developed to see further back in space/time, and to detect smaller and smaller (etc) particles. To these folks, a photon or an electron is probably pretty loud.
The best I can suggest is to start with picovolts and work downwards, e.g. (from a quick google search):
http://www.emelectronics.co.uk/spec/P12.html http://www.maa.org/mathland/mathtrek_7_27_98.html
Are yattovolts measured anywhere? I had not known of this unit until this question popped up, so I am already grateful for learning something new, even if its everyday usage is (for me) rather limited.
sci.physics appears not to be on the list. If it is a legitimate albeit esoteric question, I would have thought they would be the most likely to enjoy both the question and its answers. Though I have observed that as a general rule, people on newsgroups prefer questions that have answers that can be both definitive and short. Perhaps this is not one of those?
Richard Dobson
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On Tue, 02 Jun 2009 12:25:54 +0100, Richard Dobson

I bought a nice old Keithley electrometer on ebay. Analog-needle meter. Its lowest range is +- 1e-14 amps. Cool stuff.
John
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wrote:

He seems interested in the issues but confused about physical units.
I suppose I should get on with writing my book, to make all this stuff plain.
John
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On Jun 2, 12:26pm, John Larkin

John, Are you really writing a book. You can sign me up for a copy.
And if you want to measure a small voltage (difference) you need to also specify how long you are willing to wait for measurement. Give me a billion years and I can do a lot of averaging.
George Herold
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On Tue, 2 Jun 2009 19:33:47 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

If you can turn the source on and off, and can do the lock-in thing, you could measure a picovolt to decent accuracy in an afternoon.
John
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On Jun 3, 5:18pm, John Larkin

Hmm, at 1nV/rtHz it's going to take me 10^6 seconds to get down to 1 pV. But that's a straight noise measurement. I guess if I've got a 1pV signal and can add that on and off to 1nV of noise I can build up to 1 SNR in 2000 seconds.
If the measurement period gets longer than a day you have to start to really worry about all sorts of strange effects. (Have you every read R.V. Jones, Instruments and Experiences (1988). Some great tales for instument builders.
I'm also reminded of a recent report, on old data, (in phyiscs today?) about nuclear decays that showed a period of one year.
George Herold
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On Wed, 3 Jun 2009 19:17:24 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

I think that works. The measurement bandwidth is 1/2000 Hz or something. OK, maybe a week or so. Somebody does sell a voltmeter that resolves 200 pV, slowly I assume.

I'll try to find that.

Yup, there are suggestions that certain isotope decays are affected by the distance to the sun or something. Strange.
John
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On Jun 3, 11:04pm, John Larkin

Try a university library for the book. I borrowed a copy from a colleague. I've been watching the used book sites on and off and it's always at least $200.00 (sigh)
My guess on the distance from the sun decay rates is that they didn't understand all the systematic errors in their apparatus. Not that I think I could have done better. Making measurements that last years has got to be hard. I do hope someone is trying to repeat it though, except for neutrino mass there hasnt been any new (experimental) particle physics in a while.
George H.
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On Jun 2, 10:33pm, snipped-for-privacy@gmail.com wrote:

opps 'wait for "the" measurement.
George
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The little twit "takes" responsibility for exercising our brains.
He feels that posts that get responses and incite discussion means that he was the one that got us going, so he feels vindicated for all the crap he never got done in real life.
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F Murtz wrote:

So, cross post to alt.psychology
--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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