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

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

Thanks
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On Mon, 1 Jun 2009 17:15:19 -0700 (PDT), GreenXenon

You can buy nanovoltmeters that will resolve a couple of hundred picovolts, if you're careful.
Superconductive SQUID detectors can measure a picovolt.
Single-electron transistors can sense, well, single electrons.
John
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On Mon, 01 Jun 2009 17:40:20 -0700, John Larkin

PMTs can be good enough to detect single photon events.
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On Jun 1, 10:33 pm, ItsASecretDummy

Hmmm... I have a $35 digital multimeter that can measure exactly 0 volts!
Rick
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rickman wrote:

No, it can't. It can display zero, even with some voltage at the input. The issues is the resolution of the meter. Even with the probes shorted, you will have some Johnson noise which is generated by the resistors in the input circuitry, if the meter is above absolute zero degrees. That voltage is too low to be displayed, but it is still there.
--
You can't have a sense of humor, if you have no sense!

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wrote:

Yeah, but when it's exactly zero volts, that what the $35 multimeter will display, so he wasn't incorrect.
;)
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Eric Jacobsen wrote:

Sigh.
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You can't have a sense of humor, if you have no sense!

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On Mon, 1 Jun 2009 22:00:07 -0700, "Eric Jacobsen"

] Not if it is turned on it wont.

Oh yes he was, and so is most of the other responses to him.
If the meter is off, there will be no display. If it is on, it will not be very likely to read zero volts when probing a bare piece of metal or shorting the leads.
Like a scale that has been zeroed, one will see drift above and below the zero line if the scale can resolve to tenths of a gram. It will also drift as the internal electronics heats up. Not so much with a meter as with scale electronics, for some reason.
So if the meter has more than 2 digits behind the decimal point, one will likely see errant values pop in and out.
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On Tue, 02 Jun 2009 18:40:51 -0700, ItsASecretDummy

Fluke 75, shorted leads, VDC range: steady .000
Fluke 87, ditto: steady 0.000
AlwaysWrong.
John
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On Jun 3, 5:09 pm, John Larkin

Are you going to return these meters for repair?
Rick
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wrote:

We do have an Agilent 34401A benchtop DVM. It has a VF display that kicks huge noise spikes out the front-panel connectors. So on the low AC ranges, it's pretty much measuring its own spikes. So they boogered the firmware so that, just above that noise floor, the displayed value drops to exactly zero.
John
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wrote:

That was my point. It was supposed to be funny... I guess I needed to add the smiley.
One of the things I have thought about is when in court defending a ticket for not stopping at a stop sign, asserting that there is no defense possible since you can never prove a quantity is exactly zero by measurement. Somehow I suspect the interesting aspects of this defense would be lost on the judge...
Rick
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rickman wrote:

Judges don't have a sense of humor, and most have no common sense.
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Michael A. Terrell wrote:

WRONG! If you had said "many" or possibly "most" that would be something else. For over three years I sat in on local Justice of Peace every Monday. Great entertainment! It was free, educational, and entertaining to boot.
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wrote:

Yeah, and then there are those of us that, as we aged and learned, did not decide to cast out half of what we were taught and pull crap like ignoring rules, not using turn signals, flicking their cigarette butts out onto the rest of the world, forgetting what the rule is for a stop sign, and generally growing up thinking they are smart, and then doing stupid shit like applying to much precision where less is used by the rest of the world, and invariably using too little where it is needed, and then they have a wreck, and want to call it "an accident" when they should be charged with negligence.
It was an accident that we let them make laws that allow any dumb mutant to get a license to drive. Because invariably some other retarded mutant observes said mutant driving, and then picks up his mutated foul driving habits.
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Well, it would be, since stop signs don't really have anything to do with Judges, but only really concern DAs. Which is mostly why the people with actual brains started building Optical Computers, Distributed Processing, Self-Assembling Robots, Self-Replicating Machines, Holograms, On-Line Banking, On-Line Publishing, GPS, Autonomous Vehicles,, and Drones for the idiots, Rather than more roads.

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On Tue, 02 Jun 2009 00:17:44 -0400, "Michael A. Terrell"

Zero volts cannot be measured no matter what parasitics are in place or are not.
Nothingness cannot be quantified. Only tangibles can. Zero is not tangible, it is the absence of tangibility.
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wrote:

Yeah, but to how many percentage accuracy?
John
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On Mon, 01 Jun 2009 21:28:02 -0700, John Larkin

No, as in: there is no such measurement capacity available anywhere on any device.
Your statement has 'bent' grammar. Insert word "points" or choose different manner to ask same question as in: "to what degree of accuracy".
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Well, but zero volts is ancient history, rather than a measurement. Which is why the people with brains invented optcal computers, flat sceeen hdtv debuggers, c++, distributed processing, blue ray, holograms, xml, usb, on-line banking, on-line shopping, on-line publishing, diigital-terrain mapping, post Ford Batteries, and self-assembling robots, rather than idiot physics anyway.

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