Ahh... the resolution question again. He already answered that one too, you just have to read what was written.
Another resolution question is the guys trying to determine the age of the universe.
I would think it quite hard to look that far back because things would be so distorted that even your determination of how far back you are "seeing" could be off an order of magnitude. 13.5 Billion years could really be 135 Billion.
See you on 12/20/2012.
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
So, cross post to alt.psychology
the
robes
.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.
...
13.5 billion is so last year! The number now is 13,500,000.001.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
6W/2.5e11 or about 2.4e-11W At 75 ohms that is about 40uV. I would expect that to be a lot less than FM radio with 100kW transmitters.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
ed
opps 'wait for "the" measurement.
George
ted
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
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.
tected
ic
.uff
eTry 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.
0
t the
probes
re.
ll
ll
wlso
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
COMMERCIALLY ?
THE ANSWER IS . 001 vOLTS
I AM PROTEUS
YOU BE MORON.
My Fluke handheld DVM resolves 100 uV. My Fluke benchtop does 100 nV. You can buy meters that resolve 200 pV.
John
CLEAN MY PROBE "BE"
I AM PROTEUS
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