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

So, cross post to alt.psychology

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.

...

Jerry

Have fun... Javascript calculator of the many distances involved in cosmology

Fluke 75, shorted leads, VDC range: steady .000

Fluke 87, ditto: steady 0.000

AlwaysWrong.

John

Femtovolts, with an FM receiver? Good ones need microvolt or so. A 3 dB noise figure, optimistic for a radio, is ballpark 1 nV RMS noise per root Hz, and an FM radio has a couple of hundred KHz bandwidth.

AlwaysWrong.

John

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

In comp.dsp John Larkin wrote: < Femtovolts, with an FM receiver? Good ones need microvolt or so. A 3 < dB noise figure, optimistic for a radio, is ballpark 1 nV RMS noise < per root Hz, and an FM radio has a couple of hundred KHz bandwidth.

How about traditional satellite TV? As I remember, it is about six watts per channel. If the signal covers most of the continental US, a 10m dish has about 1/(500000)**2 the area of the US, so about

On the other hand, my cable modem has about +16dBm input at 75 ohms. About 1.7V, maybe enough for a small light bulb. (I believe that is only for the specific signal it is receiving, not counting the hundreds of other cable channels.)

-- glen

opps 'wait for "the" measurement.

George

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

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

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

Try that without the feed horn and dish to supply a fair amount of gain.

The early 'Galaxy' birds were 10 watts per transponder.

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 hasn=92t been any new (experimental) particle physics in a while.

George H.

Are you going to return these meters for repair?

Rick

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