On Fri, 4 Dec 2015 20:22:25 +0000, piglet <erichpwagner@hotmail.com> wrote:>On 04/12/2015 17:39, John Larkin wrote: >> It might be possible to detect electron charge steps in a discrete fet >> of some sort, but the capacitance involved will be hundreds of times >> the capacitance of an eprom (or ram, or CCD) cell. One electron >> charges 1 pF to 0.4 uV, which is intimidating. I wonder if there is >> some statistical way to tease 400 nV random steps out of a lot of >> noise. > >I think it is less than 400nV. By V=Q/C I get Qe/1pF = 160nV > >pigletThat's right. Slightly more intimidating. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Keithley 610C repair
Started by ●December 1, 2015
Reply by ●December 4, 20152015-12-04
Reply by ●December 7, 20152015-12-07
On Friday, December 4, 2015 at 3:28:47 PM UTC-5, John Larkin wrote:> On Fri, 4 Dec 2015 10:06:21 -0800 (PST), George Herold > <gherold@teachspin.com> wrote: > > >On Friday, December 4, 2015 at 12:40:01 PM UTC-5, John Larkin wrote: > >> On Fri, 4 Dec 2015 09:13:19 -0800 (PST), George Herold > >> <gherold@teachspin.com> wrote: > >> > >> >On Thursday, December 3, 2015 at 4:01:51 PM UTC-5, John Larkin wrote: > >> >> On Thu, 3 Dec 2015 09:34:49 -0800 (PST), George Herold > >> >> <gherold@teachspin.com> wrote: > >> >> > >> >> >On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote: > >> >> >> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer > >> >> >> <robertbaer@localnet.com> wrote: > >> >> >> > >> >> >> >Phil Hobbs wrote: > >> >> >> >> On 12/01/2015 10:18 AM, piglet wrote: > >> >> >> >>> On 01/12/2015 14:05, Phil Hobbs wrote: > >> >> >> >>>> The switch and meter movement are pretty nice, so even if you can't > >> >> >> >>>> get replacement MOSFETs, you could do a brain transplant with > >> >> >> >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. > >> >> >> >>>> > >> >> >> >>>> Cheers > >> >> >> >>>> > >> >> >> >>>> Phil Hobbs > >> >> >> >>>> > >> >> >> >>> > >> >> >> >>> If you search back postings in this NG a year or two ago John Larkin > >> >> >> >>> posted schematic and photos of a box he built around an LMC6001 which do > >> >> >> >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. > >> >> >> >>> > >> >> >> >>> piglet > >> >> >> >>> > >> >> >> >> > >> >> >> >> I think it was the same discussion where I was talking about using a > >> >> >> >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of > >> >> >> >> thing. It's easier without resistors. > >> >> >> >> > >> >> >> >> Voltage measurement is pretty easy--you can make a follower and measure > >> >> >> >> its output with a normal DVM. > >> >> >> >> > >> >> >> >> I have a couple of dozen MOSFETs without gate protection, and you can > >> >> >> >> still get 2N7002Es, some of which leak only a few electrons per second. > >> >> >> >> > >> >> >> >> Cheers > >> >> >> >> > >> >> >> >> Phil Hobbs > >> >> >> >> > >> >> >> >...which brings up a question: can one count the electrons (like > >> >> >> >Millikan oil drop bit)? > >> >> >> > >> >> >> I've thought that some simple semiconductor experiment could > >> >> >> demonstrate charge quantization. It would make a nice science project. > >> >> >> > >> >> >> The numbers are intimidating but maybe not impossible. You might not > >> >> >> see single electrons, but could dig out something statistically. > >> >> >> > >> >> >> An eprom is a possible detector. Or maybe a cmos imager. > >> >> > > >> >> >What are you thinking? > >> >> >Charge quantization.. things. > >> >> > > >> >> >Shot noise. > >> >> > >> >> That's not as appealing as seeing single-electron steps. Some day I > >> >> may try the eprom thing. > >> > > >> >I don't know eproms that well... what are you going to see? > >> > >> > >> The charge stored in an eprom cell is fC. And it's accessable to UV to > >> discharge it. > >> > >> The idea would be to scan an eprom and snoop the cell contents. > >> Modulate Vcc and apply UV, and look for bits that are marginal, namely > >> toggling 1/0 as Vcc changes slightly. That will plot as a step > >> function. Now apply some UV; maybe absorbing one UV photon will cause > >> one (or possibly more) electrons worth of discharge, which would make > >> a horizontal jump on the plot. Multiple jumps should be quantized to > >> the value of e. > >> > >> It might be possible to detect electron charge steps in a discrete fet > >> of some sort, but the capacitance involved will be hundreds of times > >> the capacitance of an eprom (or ram, or CCD) cell. One electron > >> charges 1 pF to 0.4 uV, which is intimidating. I wonder if there is > >> some statistical way to tease 400 nV random steps out of a lot of > >> noise. > >Well some synchronous, lockin type detection. > > OK, mesure the transition point, make a UV blip, measure again, > repeat. > > > > > > >ramping a current back and forth into a cap and seeing voltage steps > >would be awesome. > >Currents from a voltage source through a resistor have no shot noise.. > >which I think means the electrons are coming at you in a well ordered > >train.... hmm I guess there is no guarantee that the first "train" of > >electrons and the next have any phase relationship.. steps are smeared > >into the expected ramp. > > I expect that low currents have very small electron correlations, so > shot noise returns.Hmm, do you have some model for that, or just an idea? How low a current? I don't know anything about resistors that are greater than 1 G ohm.. One might see a lot more 1/f type noise in big R's? George H.> > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
Reply by ●December 7, 20152015-12-07
On Mon, 7 Dec 2015 07:32:06 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Friday, December 4, 2015 at 3:28:47 PM UTC-5, John Larkin wrote: >> On Fri, 4 Dec 2015 10:06:21 -0800 (PST), George Herold >> <gherold@teachspin.com> wrote: >> >> >On Friday, December 4, 2015 at 12:40:01 PM UTC-5, John Larkin wrote: >> >> On Fri, 4 Dec 2015 09:13:19 -0800 (PST), George Herold >> >> <gherold@teachspin.com> wrote: >> >> >> >> >On Thursday, December 3, 2015 at 4:01:51 PM UTC-5, John Larkin wrote: >> >> >> On Thu, 3 Dec 2015 09:34:49 -0800 (PST), George Herold >> >> >> <gherold@teachspin.com> wrote: >> >> >> >> >> >> >On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote: >> >> >> >> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer >> >> >> >> <robertbaer@localnet.com> wrote: >> >> >> >> >> >> >> >> >Phil Hobbs wrote: >> >> >> >> >> On 12/01/2015 10:18 AM, piglet wrote: >> >> >> >> >>> On 01/12/2015 14:05, Phil Hobbs wrote: >> >> >> >> >>>> The switch and meter movement are pretty nice, so even if you can't >> >> >> >> >>>> get replacement MOSFETs, you could do a brain transplant with >> >> >> >> >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. >> >> >> >> >>>> >> >> >> >> >>>> Cheers >> >> >> >> >>>> >> >> >> >> >>>> Phil Hobbs >> >> >> >> >>>> >> >> >> >> >>> >> >> >> >> >>> If you search back postings in this NG a year or two ago John Larkin >> >> >> >> >>> posted schematic and photos of a box he built around an LMC6001 which do >> >> >> >> >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. >> >> >> >> >>> >> >> >> >> >>> piglet >> >> >> >> >>> >> >> >> >> >> >> >> >> >> >> I think it was the same discussion where I was talking about using a >> >> >> >> >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of >> >> >> >> >> thing. It's easier without resistors. >> >> >> >> >> >> >> >> >> >> Voltage measurement is pretty easy--you can make a follower and measure >> >> >> >> >> its output with a normal DVM. >> >> >> >> >> >> >> >> >> >> I have a couple of dozen MOSFETs without gate protection, and you can >> >> >> >> >> still get 2N7002Es, some of which leak only a few electrons per second. >> >> >> >> >> >> >> >> >> >> Cheers >> >> >> >> >> >> >> >> >> >> Phil Hobbs >> >> >> >> >> >> >> >> >> >...which brings up a question: can one count the electrons (like >> >> >> >> >Millikan oil drop bit)? >> >> >> >> >> >> >> >> I've thought that some simple semiconductor experiment could >> >> >> >> demonstrate charge quantization. It would make a nice science project. >> >> >> >> >> >> >> >> The numbers are intimidating but maybe not impossible. You might not >> >> >> >> see single electrons, but could dig out something statistically. >> >> >> >> >> >> >> >> An eprom is a possible detector. Or maybe a cmos imager. >> >> >> > >> >> >> >What are you thinking? >> >> >> >Charge quantization.. things. >> >> >> > >> >> >> >Shot noise. >> >> >> >> >> >> That's not as appealing as seeing single-electron steps. Some day I >> >> >> may try the eprom thing. >> >> > >> >> >I don't know eproms that well... what are you going to see? >> >> >> >> >> >> The charge stored in an eprom cell is fC. And it's accessable to UV to >> >> discharge it. >> >> >> >> The idea would be to scan an eprom and snoop the cell contents. >> >> Modulate Vcc and apply UV, and look for bits that are marginal, namely >> >> toggling 1/0 as Vcc changes slightly. That will plot as a step >> >> function. Now apply some UV; maybe absorbing one UV photon will cause >> >> one (or possibly more) electrons worth of discharge, which would make >> >> a horizontal jump on the plot. Multiple jumps should be quantized to >> >> the value of e. >> >> >> >> It might be possible to detect electron charge steps in a discrete fet >> >> of some sort, but the capacitance involved will be hundreds of times >> >> the capacitance of an eprom (or ram, or CCD) cell. One electron >> >> charges 1 pF to 0.4 uV, which is intimidating. I wonder if there is >> >> some statistical way to tease 400 nV random steps out of a lot of >> >> noise. >> >Well some synchronous, lockin type detection. >> >> OK, mesure the transition point, make a UV blip, measure again, >> repeat. >> >> >> >> >> >> >ramping a current back and forth into a cap and seeing voltage steps >> >would be awesome. >> >Currents from a voltage source through a resistor have no shot noise.. >> >which I think means the electrons are coming at you in a well ordered >> >train.... hmm I guess there is no guarantee that the first "train" of >> >electrons and the next have any phase relationship.. steps are smeared >> >into the expected ramp. >> >> I expect that low currents have very small electron correlations, so >> shot noise returns. > >Hmm, do you have some model for that, or just an idea? >How low a current?There is a paper online somewhere that demonstrates that physically short resistors have shot noise. Electrons take some time to arrange themselves in an orderly queue. I suspect that low electron density will also reduce the self-ordering effect. The limiting case is obvious: only one average free electron within the length of the resistor, no electron interaction.>I don't know anything about resistors that are greater than 1 G ohm.. >One might see a lot more 1/f type noise in big R's?I needed some high-value resistors, 10s of megs, that had low current noise, so I experimented some. This is NOT an easy thing to measure. My pretty firm conclusion was that I was seeing a lot more current noise in thickilms than in metal film resistors. I didn't do a spectral analysis to separate 1/f from shot noise; that would be an interesting prokect. Problem is, you have to order 20M thinfilms as specials, axials, and buy a reel. It's impressive how little the resistor manufacturers know about this. Interesting: imagine a long strip of metallic resistance element on a substrate. e-e interaction along its length makes the electrons correlate and kills the shot noise. Now cut the element midway and bridge the gap (magically somehow)... each half now has half the electron interaction distance. Keep doing that until the segments become very short, below the e-e interaction distance, or until there's less than one free electron per section. Seems like you should have full shot noise. If I understand the mechanism. I wonder if a curved or spiral or zigzag resistor has less e-e interaction. The bends would have to be smaller than the e-e interaction distance. If you made a 2-layer resistor, with a really thin metal and really thin insulating gap between the layers, would electrons interact between the layers? An interesting device is a resistor (or whatever) that allows a flow of strictly periodic, clocked electrons, exactly one electron per clock. I think they exist.
Reply by ●December 7, 20152015-12-07
On 12/07/2015 12:12 PM, John Larkin wrote:> On Mon, 7 Dec 2015 07:32:06 -0800 (PST), George Herold > <gherold@teachspin.com> wrote: > >> On Friday, December 4, 2015 at 3:28:47 PM UTC-5, John Larkin wrote: >>> On Fri, 4 Dec 2015 10:06:21 -0800 (PST), George Herold >>> <gherold@teachspin.com> wrote: >>> >>>> On Friday, December 4, 2015 at 12:40:01 PM UTC-5, John Larkin wrote: >>>>> On Fri, 4 Dec 2015 09:13:19 -0800 (PST), George Herold >>>>> <gherold@teachspin.com> wrote: >>>>> >>>>>> On Thursday, December 3, 2015 at 4:01:51 PM UTC-5, John Larkin wrote: >>>>>>> On Thu, 3 Dec 2015 09:34:49 -0800 (PST), George Herold >>>>>>> <gherold@teachspin.com> wrote: >>>>>>> >>>>>>>> On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote: >>>>>>>>> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer >>>>>>>>> <robertbaer@localnet.com> wrote: >>>>>>>>> >>>>>>>>>> Phil Hobbs wrote: >>>>>>>>>>> On 12/01/2015 10:18 AM, piglet wrote: >>>>>>>>>>>> On 01/12/2015 14:05, Phil Hobbs wrote: >>>>>>>>>>>>> The switch and meter movement are pretty nice, so even if you can't >>>>>>>>>>>>> get replacement MOSFETs, you could do a brain transplant with >>>>>>>>>>>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. >>>>>>>>>>>>> >>>>>>>>>>>>> Cheers >>>>>>>>>>>>> >>>>>>>>>>>>> Phil Hobbs >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> If you search back postings in this NG a year or two ago John Larkin >>>>>>>>>>>> posted schematic and photos of a box he built around an LMC6001 which do >>>>>>>>>>>> pretty much the same job as the 610C for femto/pico ampere sleuthing. >>>>>>>>>>>> >>>>>>>>>>>> piglet >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> I think it was the same discussion where I was talking about using a >>>>>>>>>>> charge dispensing loop with a 100-pF Teflon cap to do the same sort of >>>>>>>>>>> thing. It's easier without resistors. >>>>>>>>>>> >>>>>>>>>>> Voltage measurement is pretty easy--you can make a follower and measure >>>>>>>>>>> its output with a normal DVM. >>>>>>>>>>> >>>>>>>>>>> I have a couple of dozen MOSFETs without gate protection, and you can >>>>>>>>>>> still get 2N7002Es, some of which leak only a few electrons per second. >>>>>>>>>>> >>>>>>>>>>> Cheers >>>>>>>>>>> >>>>>>>>>>> Phil Hobbs >>>>>>>>>>> >>>>>>>>>> ...which brings up a question: can one count the electrons (like >>>>>>>>>> Millikan oil drop bit)? >>>>>>>>> >>>>>>>>> I've thought that some simple semiconductor experiment could >>>>>>>>> demonstrate charge quantization. It would make a nice science project. >>>>>>>>> >>>>>>>>> The numbers are intimidating but maybe not impossible. You might not >>>>>>>>> see single electrons, but could dig out something statistically. >>>>>>>>> >>>>>>>>> An eprom is a possible detector. Or maybe a cmos imager. >>>>>>>> >>>>>>>> What are you thinking? >>>>>>>> Charge quantization.. things. >>>>>>>> >>>>>>>> Shot noise. >>>>>>> >>>>>>> That's not as appealing as seeing single-electron steps. Some day I >>>>>>> may try the eprom thing. >>>>>> >>>>>> I don't know eproms that well... what are you going to see? >>>>> >>>>> >>>>> The charge stored in an eprom cell is fC. And it's accessable to UV to >>>>> discharge it. >>>>> >>>>> The idea would be to scan an eprom and snoop the cell contents. >>>>> Modulate Vcc and apply UV, and look for bits that are marginal, namely >>>>> toggling 1/0 as Vcc changes slightly. That will plot as a step >>>>> function. Now apply some UV; maybe absorbing one UV photon will cause >>>>> one (or possibly more) electrons worth of discharge, which would make >>>>> a horizontal jump on the plot. Multiple jumps should be quantized to >>>>> the value of e. >>>>> >>>>> It might be possible to detect electron charge steps in a discrete fet >>>>> of some sort, but the capacitance involved will be hundreds of times >>>>> the capacitance of an eprom (or ram, or CCD) cell. One electron >>>>> charges 1 pF to 0.4 uV, which is intimidating. I wonder if there is >>>>> some statistical way to tease 400 nV random steps out of a lot of >>>>> noise. >>>> Well some synchronous, lockin type detection. >>> >>> OK, mesure the transition point, make a UV blip, measure again, >>> repeat. >>> >>> >>> >>> >>> >>>> ramping a current back and forth into a cap and seeing voltage steps >>>> would be awesome. >>>> Currents from a voltage source through a resistor have no shot noise.. >>>> which I think means the electrons are coming at you in a well ordered >>>> train.... hmm I guess there is no guarantee that the first "train" of >>>> electrons and the next have any phase relationship.. steps are smeared >>>> into the expected ramp. >>> >>> I expect that low currents have very small electron correlations, so >>> shot noise returns. >> >> Hmm, do you have some model for that, or just an idea? >> How low a current? > > There is a paper online somewhere that demonstrates that physically > short resistors have shot noise. Electrons take some time to arrange > themselves in an orderly queue. I suspect that low electron density > will also reduce the self-ordering effect. The limiting case is > obvious: only one average free electron within the length of the > resistor, no electron interaction. > >> I don't know anything about resistors that are greater than 1 G ohm.. >> One might see a lot more 1/f type noise in big R's? > > I needed some high-value resistors, 10s of megs, that had low current > noise, so I experimented some. This is NOT an easy thing to measure. > My pretty firm conclusion was that I was seeing a lot more current > noise in thickilms than in metal film resistors. I didn't do a > spectral analysis to separate 1/f from shot noise; that would be an > interesting prokect. Problem is, you have to order 20M thinfilms as > specials, axials, and buy a reel. > > It's impressive how little the resistor manufacturers know about this. > > Interesting: imagine a long strip of metallic resistance element on a > substrate. e-e interaction along its length makes the electrons > correlate and kills the shot noise. Now cut the element midway and > bridge the gap (magically somehow)... each half now has half the > electron interaction distance. Keep doing that until the segments > become very short, below the e-e interaction distance, or until > there's less than one free electron per section. Seems like you should > have full shot noise. If I understand the mechanism.No, because the other segments function like emitter degeneration in a BJT amplifier. Another way of saying it is that the shot noise of each segment is effectively shunted by the segment resistance, in parallel with the resistance of the rest of the segments in series. If you cut the element into N pieces, then from each current source's POV, only 1/N worth of the shot noise current would reach the terminals--the rest just goes round in a tight loop and never gets out of the segment. That cutting approach predicts the wrong asymptotic falloff of the noise with length, iirc. (It's been awhile since I read up on the Rolf-Landauer-contra-mundum dust-up on that point.)> > I wonder if a curved or spiral or zigzag resistor has less e-e > interaction. The bends would have to be smaller than the e-e > interaction distance.The mean free path is on the order of 100 angstroms, so the bends would have to be pretty tight. ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●December 7, 20152015-12-07
On Monday, December 7, 2015 at 12:13:03 PM UTC-5, John Larkin wrote:> On Mon, 7 Dec 2015 07:32:06 -0800 (PST), George Herold > <gherold@teachspin.com> wrote: > > >On Friday, December 4, 2015 at 3:28:47 PM UTC-5, John Larkin wrote: > >> On Fri, 4 Dec 2015 10:06:21 -0800 (PST), George Herold > >> <gherold@teachspin.com> wrote: > >> > >> >On Friday, December 4, 2015 at 12:40:01 PM UTC-5, John Larkin wrote: > >> >> On Fri, 4 Dec 2015 09:13:19 -0800 (PST), George Herold > >> >> <gherold@teachspin.com> wrote: > >> >> > >> >> >On Thursday, December 3, 2015 at 4:01:51 PM UTC-5, John Larkin wrote: > >> >> >> On Thu, 3 Dec 2015 09:34:49 -0800 (PST), George Herold > >> >> >> <gherold@teachspin.com> wrote: > >> >> >> > >> >> >> >On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote: > >> >> >> >> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer > >> >> >> >> <robertbaer@localnet.com> wrote: > >> >> >> >> > >> >> >> >> >Phil Hobbs wrote: > >> >> >> >> >> On 12/01/2015 10:18 AM, piglet wrote: > >> >> >> >> >>> On 01/12/2015 14:05, Phil Hobbs wrote: > >> >> >> >> >>>> The switch and meter movement are pretty nice, so even if you can't > >> >> >> >> >>>> get replacement MOSFETs, you could do a brain transplant with > >> >> >> >> >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. > >> >> >> >> >>>> > >> >> >> >> >>>> Cheers > >> >> >> >> >>>> > >> >> >> >> >>>> Phil Hobbs > >> >> >> >> >>>> > >> >> >> >> >>> > >> >> >> >> >>> If you search back postings in this NG a year or two ago John Larkin > >> >> >> >> >>> posted schematic and photos of a box he built around an LMC6001 which do > >> >> >> >> >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. > >> >> >> >> >>> > >> >> >> >> >>> piglet > >> >> >> >> >>> > >> >> >> >> >> > >> >> >> >> >> I think it was the same discussion where I was talking about using a > >> >> >> >> >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of > >> >> >> >> >> thing. It's easier without resistors. > >> >> >> >> >> > >> >> >> >> >> Voltage measurement is pretty easy--you can make a follower and measure > >> >> >> >> >> its output with a normal DVM. > >> >> >> >> >> > >> >> >> >> >> I have a couple of dozen MOSFETs without gate protection, and you can > >> >> >> >> >> still get 2N7002Es, some of which leak only a few electrons per second. > >> >> >> >> >> > >> >> >> >> >> Cheers > >> >> >> >> >> > >> >> >> >> >> Phil Hobbs > >> >> >> >> >> > >> >> >> >> >...which brings up a question: can one count the electrons (like > >> >> >> >> >Millikan oil drop bit)? > >> >> >> >> > >> >> >> >> I've thought that some simple semiconductor experiment could > >> >> >> >> demonstrate charge quantization. It would make a nice science project. > >> >> >> >> > >> >> >> >> The numbers are intimidating but maybe not impossible. You might not > >> >> >> >> see single electrons, but could dig out something statistically. > >> >> >> >> > >> >> >> >> An eprom is a possible detector. Or maybe a cmos imager. > >> >> >> > > >> >> >> >What are you thinking? > >> >> >> >Charge quantization.. things. > >> >> >> > > >> >> >> >Shot noise. > >> >> >> > >> >> >> That's not as appealing as seeing single-electron steps. Some day I > >> >> >> may try the eprom thing. > >> >> > > >> >> >I don't know eproms that well... what are you going to see? > >> >> > >> >> > >> >> The charge stored in an eprom cell is fC. And it's accessable to UV to > >> >> discharge it. > >> >> > >> >> The idea would be to scan an eprom and snoop the cell contents. > >> >> Modulate Vcc and apply UV, and look for bits that are marginal, namely > >> >> toggling 1/0 as Vcc changes slightly. That will plot as a step > >> >> function. Now apply some UV; maybe absorbing one UV photon will cause > >> >> one (or possibly more) electrons worth of discharge, which would make > >> >> a horizontal jump on the plot. Multiple jumps should be quantized to > >> >> the value of e. > >> >> > >> >> It might be possible to detect electron charge steps in a discrete fet > >> >> of some sort, but the capacitance involved will be hundreds of times > >> >> the capacitance of an eprom (or ram, or CCD) cell. One electron > >> >> charges 1 pF to 0.4 uV, which is intimidating. I wonder if there is > >> >> some statistical way to tease 400 nV random steps out of a lot of > >> >> noise. > >> >Well some synchronous, lockin type detection. > >> > >> OK, mesure the transition point, make a UV blip, measure again, > >> repeat. > >> > >> > >> > >> > >> > >> >ramping a current back and forth into a cap and seeing voltage steps > >> >would be awesome. > >> >Currents from a voltage source through a resistor have no shot noise.. > >> >which I think means the electrons are coming at you in a well ordered > >> >train.... hmm I guess there is no guarantee that the first "train" of > >> >electrons and the next have any phase relationship.. steps are smeared > >> >into the expected ramp. > >> > >> I expect that low currents have very small electron correlations, so > >> shot noise returns. > > > >Hmm, do you have some model for that, or just an idea? > >How low a current? > > There is a paper online somewhere that demonstrates that physically > short resistors have shot noise. Electrons take some time to arrange > themselves in an orderly queue. I suspect that low electron density > will also reduce the self-ordering effect. The limiting case is > obvious: only one average free electron within the length of the > resistor, no electron interaction.Maybe Soldi state Shot Noise by R. Landauer? http://journals.aps.org/prb/abstract/10.1103/PhysRevB.47.16427 (I couldn't find a free copy on line. I've got a copy I could send you if you promise not to share online.) For me it's heavy slogging at times... some QM that can leave me with a vague feeling. At the very small level I've got only a fuzzy image of what charge transport looks like. My understanding is that it's not the e-e interactions with the other "moving" electrons, but the number of collisions of a single electron as it travels the length of the conductor. (so the magnitude of the current shouldn't matter.) And what comes out the other end (of the resistor) are a series of little mini pulses, one from each scattering event. Each pulse being much smaller than the electron charge... (But as I say this... I find the details fuzzy.)> > >I don't know anything about resistors that are greater than 1 G ohm.. > >One might see a lot more 1/f type noise in big R's? > > I needed some high-value resistors, 10s of megs, that had low current > noise, so I experimented some. This is NOT an easy thing to measure. > My pretty firm conclusion was that I was seeing a lot more current > noise in thickilms than in metal film resistors. I didn't do a > spectral analysis to separate 1/f from shot noise; that would be an > interesting prokect. Problem is, you have to order 20M thinfilms as > specials, axials, and buy a reel. > > It's impressive how little the resistor manufacturers know about this. > > Interesting: imagine a long strip of metallic resistance element on a > substrate. e-e interaction along its length makes the electrons > correlate and kills the shot noise. Now cut the element midway and > bridge the gap (magically somehow)... each half now has half the > electron interaction distance. Keep doing that until the segments > become very short, below the e-e interaction distance, or until > there's less than one free electron per section. Seems like you should > have full shot noise. If I understand the mechanism.Yeah well (I think) that's where you need the QM. You really small sections are indeed very small... and that gives you these quantized conductance steps that I showed in my (crappy) bouncing gold wire data. But that is a whole nother ball of wax compared to your typical resistor.> > I wonder if a curved or spiral or zigzag resistor has less e-e > interaction. The bends would have to be smaller than the e-e > interaction distance. > > If you made a 2-layer resistor, with a really thin metal and really > thin insulating gap between the layers, would electrons interact > between the layers? > > An interesting device is a resistor (or whatever) that allows a flow > of strictly periodic, clocked electrons, exactly one electron per > clock. I think they exist.Yeah Phil mentioned it (in this thread?) electron turnstiles. George H.
Reply by ●December 8, 20152015-12-08
On Tue, 01 Dec 2015 10:07:53 -0800, Jeff Liebermann (jeffl@cruzio.com) said:> On Tue, 1 Dec 2015 10:22:23 -0000, RBlack <news@rblack01.plus.com> > wrote: > > >Any advice? For $100 I'm tempted to take a gamble and have it delivered > >to our US office, one of our guys can bring it over next time he visits. > >OTOH if the parts are unobtainium I'll wait for a working one to appear. > > At $100, there's almost certainly something wrong with it. Still, > methinks it's worth trying to fix it. 610c manual at: > <http://122.physics.ucdavis.edu/course/cosmology/sites/default/files/files/Ferro%20Electricity/Keithley610manual.pdf> > The schematic is dated 1968 so I would suspect that the big > electrolytics in the power supply have dried out. If that doesn't do > the trick and it looks like the two input FETs are fried, carefully > remove them (using static protection) and replace them with whatever > you can find that's close, just to see if it works. If it works, but > leaks badly on the higher sensitivity scales, try to find suitable > substitute FETs. The manual does not list a replacement part number > for the input FETs, which are designated as part of the input PCB, > Keithley 23733A. However, the photo looks like they're easily > replaced: > <http://holzleitner.com/el/keithley-610c-electrometer/keithley-610c-input-section.jpg> > Note the black Fairchild xsistors above the FETs. They're epoxy > filled and might be IR light sensitive. > > Internal detail and photos: > <http://holzleitner.com/el/keithley-610c-electrometer/index-en.html> > > Calibration costs about $250 to $300 which might make it more > attractive to buy something that works and is calibrated. > > Interesting readings and photos: > <http://www.eevblog.com/forum/projects/electrometer-input-stage/> >I had a closer look on eBay's US site and as John L pointed out, there is more than one available - unfortunately all non-working. One has the meter glass missing, I don't think the movement would survive the shipping. The one I was originally looking at has the protective cap for the input connector missing, I'm assuming this is important for protection from contamination and ESD? Looking at the completed listings, 610Cs in complete working order don't sell for much more than the $100 being asked for the broken ones, so I'll wait for one of them to turn up.
Reply by ●December 8, 20152015-12-08
On Tue, 8 Dec 2015 09:56:35 -0000, RBlack <news@rblack01.plus.com> wrote:>On Tue, 01 Dec 2015 10:07:53 -0800, Jeff Liebermann (jeffl@cruzio.com) >said: >> On Tue, 1 Dec 2015 10:22:23 -0000, RBlack <news@rblack01.plus.com> >> wrote: >> >> >Any advice? For $100 I'm tempted to take a gamble and have it delivered >> >to our US office, one of our guys can bring it over next time he visits. >> >OTOH if the parts are unobtainium I'll wait for a working one to appear. >> >> At $100, there's almost certainly something wrong with it. Still, >> methinks it's worth trying to fix it. 610c manual at: >> <http://122.physics.ucdavis.edu/course/cosmology/sites/default/files/files/Ferro%20Electricity/Keithley610manual.pdf> >> The schematic is dated 1968 so I would suspect that the big >> electrolytics in the power supply have dried out. If that doesn't do >> the trick and it looks like the two input FETs are fried, carefully >> remove them (using static protection) and replace them with whatever >> you can find that's close, just to see if it works. If it works, but >> leaks badly on the higher sensitivity scales, try to find suitable >> substitute FETs. The manual does not list a replacement part number >> for the input FETs, which are designated as part of the input PCB, >> Keithley 23733A. However, the photo looks like they're easily >> replaced: >> <http://holzleitner.com/el/keithley-610c-electrometer/keithley-610c-input-section.jpg> >> Note the black Fairchild xsistors above the FETs. They're epoxy >> filled and might be IR light sensitive. >> >> Internal detail and photos: >> <http://holzleitner.com/el/keithley-610c-electrometer/index-en.html> >> >> Calibration costs about $250 to $300 which might make it more >> attractive to buy something that works and is calibrated. >> >> Interesting readings and photos: >> <http://www.eevblog.com/forum/projects/electrometer-input-stage/> >> > >I had a closer look on eBay's US site and as John L pointed out, there >is more than one available - unfortunately all non-working. One has the >meter glass missing, I don't think the movement would survive the >shipping. The one I was originally looking at has the protective cap >for the input connector missing, I'm assuming this is important for >protection from contamination and ESD?That probably doesn't matter. The insulator in the connector is easy to clean.
Reply by ●December 8, 20152015-12-08
On Tue, 8 Dec 2015 09:56:35 -0000, RBlack <news@rblack01.plus.com> wrote:>I had a closer look on eBay's US site and as John L pointed out, >there is more than one available - unfortunately all non-working. >One has the meter glass missing, I don't think the movement would >survive the shipping. The one I was originally looking at has >the protective cap for the input connector missing, I'm assuming >this is important for protection from contamination and ESD?It appears that you do not want to do much in the way of repair work. Replacing a BNC cover, meter glass, or even input FET's are not major repairs. Broken glass on meters will not destroy the meter movement, but might destroy the needle. Attaching a new needle to the meter movement is tricky, but not impossible. I've done it a few times. The real danger is having scrap metal and dirt enter the meter movement causing erratic operation. Fishing out the scrap metal requires a steady hand, needle point tweezers, and a binocular microscope. I've done it a few times. I've also replaced an analog meter with a digital panel meter.>Looking at the completed listings, 610Cs in complete working order don't >sell for much more than the $100 being asked for the broken ones, so >I'll wait for one of them to turn up.Don't use eBay "Completed" listings. Use "Sold Listings". Completed listings include those items that did not sell in the last 30 days while sold listings go back 90 days. <http://pages.ebay.com/help/search/questions/search-completed-listings.html> <http://www.ebay.com/sch/i.html?_nkw=keithley%20610c&LH_Complete=1&LH_Sold=1> Looks like $140 to $180 were the selling prices with 0 sold in Sept, 3 sold in Nov, and 1 in Dec. You shouldn't have long to wait. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●December 8, 20152015-12-08
On Tue, 08 Dec 2015 08:22:21 -0800, Jeff Liebermann <jeffl@cruzio.com> wrote:>On Tue, 8 Dec 2015 09:56:35 -0000, RBlack <news@rblack01.plus.com> >wrote: > >>I had a closer look on eBay's US site and as John L pointed out, >>there is more than one available - unfortunately all non-working. >>One has the meter glass missing, I don't think the movement would >>survive the shipping. The one I was originally looking at has >>the protective cap for the input connector missing, I'm assuming >>this is important for protection from contamination and ESD? > >It appears that you do not want to do much in the way of repair work. >Replacing a BNC cover, meter glass, or even input FET's are not major >repairs. > >Broken glass on meters will not destroy the meter movement, but might >destroy the needle. Attaching a new needle to the meter movement is >tricky, but not impossible.Might the weight of the needle affect the meter linearity?
Reply by ●December 8, 20152015-12-08
On 12/08/2015 04:56 AM, RBlack wrote:> On Tue, 01 Dec 2015 10:07:53 -0800, Jeff Liebermann (jeffl@cruzio.com) > said: >> On Tue, 1 Dec 2015 10:22:23 -0000, RBlack <news@rblack01.plus.com> >> wrote: >> >>> Any advice? For $100 I'm tempted to take a gamble and have it delivered >>> to our US office, one of our guys can bring it over next time he visits. >>> OTOH if the parts are unobtainium I'll wait for a working one to appear. >> >> At $100, there's almost certainly something wrong with it. Still, >> methinks it's worth trying to fix it. 610c manual at: >> <http://122.physics.ucdavis.edu/course/cosmology/sites/default/files/files/Ferro%20Electricity/Keithley610manual.pdf> >> The schematic is dated 1968 so I would suspect that the big >> electrolytics in the power supply have dried out. If that doesn't do >> the trick and it looks like the two input FETs are fried, carefully >> remove them (using static protection) and replace them with whatever >> you can find that's close, just to see if it works. If it works, but >> leaks badly on the higher sensitivity scales, try to find suitable >> substitute FETs. The manual does not list a replacement part number >> for the input FETs, which are designated as part of the input PCB, >> Keithley 23733A. However, the photo looks like they're easily >> replaced: >> <http://holzleitner.com/el/keithley-610c-electrometer/keithley-610c-input-section.jpg> >> Note the black Fairchild xsistors above the FETs. They're epoxy >> filled and might be IR light sensitive. >> >> Internal detail and photos: >> <http://holzleitner.com/el/keithley-610c-electrometer/index-en.html> >> >> Calibration costs about $250 to $300 which might make it more >> attractive to buy something that works and is calibrated. >> >> Interesting readings and photos: >> <http://www.eevblog.com/forum/projects/electrometer-input-stage/> >> > > I had a closer look on eBay's US site and as John L pointed out, there > is more than one available - unfortunately all non-working. One has the > meter glass missing, I don't think the movement would survive the > shipping. The one I was originally looking at has the protective cap > for the input connector missing, I'm assuming this is important for > protection from contamination and ESD? > > Looking at the completed listings, 610Cs in complete working order don't > sell for much more than the $100 being asked for the broken ones, so > I'll wait for one of them to turn up. > > >They come along periodically. Inspired by this thread, I bought one with a 30-day DOA warranty for a $125 (best offer) a week or so ago. Should be here Thursday. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
