High Quality White Noise Gen
in [Design]
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From: Martin Brown on 7 Jun 2010 10:59 On 07/06/2010 14:55, John Larkin wrote: > On Mon, 7 Jun 2010 02:16:57 -0700 (PDT), Bill Sloman > <bill.sloman(a)ieee.org> wrote: > > >> Modern wines are often made to be instantly drinkable. This doesn't >> mean that they can't get better with age, but many don't. If the wine- >> maker has a gas-chromatograph - ideally with a tandem mass- >> spectrometer as a detector - they can have a very clear idea of what >> their wine tastes and smells like, and the good ones know how to >> create an attractive mixture of sensations, and have a pretty good >> idea of how that mixture will change and develop with time, > > Can a GC tell that the vines grew in water that had been filtered > through glacial gravel, slate and shale? GC can't but ICP-MS can. I worked on techniques used to prove provenance of very expensive French wines a long time ago based on the pattern of various alkali metals and rare earths present at ultra trace levels. We required about 10ml of wine of which only a couple of ml were analysed. That left the rest of the bottle to be disposed of. They were concerned about rather high quality forgeries. A more recent paper (not by our group) but using similar kit is online at: <http://www.thefreelibrary.com/Geology+and+wine+9%3a+regional+trace+element+fingerprinting+of+Canadian...-a0139717400> SIRA can also spot adulteration by adding cane sugar to grape juice. Regards, Martin Brown
From: Bill Sloman on 7 Jun 2010 11:41 On Jun 7, 3:55 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Mon, 7 Jun 2010 02:16:57 -0700 (PDT),Bill Sloman > > <bill.slo...(a)ieee.org> wrote: > >Modern wines are often made to be instantly drinkable. This doesn't > >mean that they can't get better with age, but many don't. If the wine- > >maker has a gas-chromatograph - ideally with a tandem mass- > >spectrometer as a detector - they can have a very clear idea of what > >their wine tastes and smells like, and the good ones know how to > >create an attractive mixture of sensations, and have a pretty good > >idea of how that mixture will change and develop with time, > > Can a GC tell that the vines grew in water that had been filtered > through glacial gravel, slate and shale? Beats me. Why not ask a wine-maker? In theory, the mineral content of the water could influence the volatile organic compounds that give wine its odour and flavour, but I'd be surprsied if the comment was much more than decorative verbiage. The GC can detect what you can smell, with somewhat more discrimination, allowing a more rational approach to wine-making than was possible in previous centuries, not that the more subjective approach couldn't produce great wines. -- Bill Sloman, Nijmegen
From: John Larkin on 7 Jun 2010 12:06 On Mon, 7 Jun 2010 08:41:20 -0700 (PDT), Bill Sloman <bill.sloman(a)ieee.org> wrote: >On Jun 7, 3:55�pm, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Mon, 7 Jun 2010 02:16:57 -0700 (PDT),Bill Sloman >> >> <bill.slo...(a)ieee.org> wrote: >> >Modern wines are often made to be instantly drinkable. This doesn't >> >mean that they can't get better with age, but many don't. If the wine- >> >maker has a gas-chromatograph - ideally with a tandem mass- >> >spectrometer as a detector - they can have a very clear idea of what >> >their wine tastes and smells like, and the good ones know how to >> >create an attractive mixture of sensations, and have a pretty good >> >idea of how that mixture will change and develop with time, >> >> Can a GC tell that the vines grew in water that had been filtered >> through glacial gravel, slate and shale? > >Beats me. Why not ask a wine-maker? In theory, the mineral content of >the water could influence the volatile organic compounds that give >wine its odour and flavour, but I'd be surprsied if the comment was >much more than decorative verbiage. In other words, delusional fat-headedness. There's a lot of that going around. He should be careful about chewing on rocks... it's bad for your teeth. > >The GC can detect what you can smell, with somewhat more >discrimination, allowing a more rational approach to wine-making than >was possible in previous centuries, not that the more subjective >approach couldn't produce great wines. So the GC knows more about what wines I like than I do? No, thanks. The Bandit tastes great. John
From: Phil Hobbs on 7 Jun 2010 12:26 George Herold wrote: > On Jun 7, 12:10 am, Phil Hobbs > <pcdhSpamMeSensel...(a)electrooptical.net> wrote: >> George Herold wrote: >>> On Jun 4, 4:40 pm, Phil Hobbs <pcdhSpamMeSensel...(a)electrooptical.net> >>> wrote: >>>> On 6/4/2010 12:01 PM, Bill Sloman wrote: >>>>> On Jun 4, 4:41 pm, George Herold<gher...(a)teachspin.com> wrote: >>>>>> On Jun 4, 10:07 am, Phil Hobbs >>>>>> <pcdhSpamMeSensel...(a)electrooptical.net> wrote: >>>>>>> On 6/3/2010 11:12 PM, George Herold wrote: >>>>>>>> langw...(a)fonz.dk wrote: >>>>>>>>> On 3 Jun., 23:11, Phil Hobbs<pcdhSpamMeSensel...(a)electrooptical.net> >>>>>>>>> wrote: >>>>>>>>>> On 6/3/2010 9:49 AM, George Herold wrote: >>>>>>>>>>> On Jun 2, 4:36 pm, John Larkin >>>>>>>>>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>>>>>>>>> On Wed, 2 Jun 2010 12:30:19 -0700 (PDT), George Herold >>>>>>>>>>>> <gher...(a)teachspin.com> wrote: >>>>>>>>>>>>> On Jun 2, 1:59 pm, whit3rd<whit...(a)gmail.com> wrote: >>>>>>>>>>>>>> On Jun 2, 10:37 am, George Herold<gher...(a)teachspin.com> wrote: >>>>>>>>>>>>>>>>>>> Yup, and if the voltage asymmetry is a problem you can add the signal >>>>>>>>>>>>>>>>>> >from two diodes, one biased from the positve supply and the other from >>>>>>>>>>>>>>>>>>> the negative. >>>>>>>>>>>>>>> Hmmm, you are right.... I still don't think that summing the voltage >>>>>>>>>>>>>>> noise from a bunch of unipolarized zeners is going to get rid of the >>>>>>>>>>>>>>> voltage asymmetry. >>>>>>>>>>>>>> You can use two zeners on a single power supply, in bridge >>>>>>>>>>>>>> configuration; couple the output through a transformer to get >>>>>>>>>>>>>> the difference. Symmetry is guaranteed if you balance the bridge >>>>>>>>>>>>>> correctly. >>>>>>>>>>>>> Ahh, more than one way to skin that cat. >>>>>>>>>>>>> Say speaking of noise sources, a colleague put together a digital >>>>>>>>>>>>> noise source. A counter steps through a look up table that feeds a >>>>>>>>>>>>> DAC. The lookup table holds a whole comb of sine waves equally spaced >>>>>>>>>>>>> in frequency space up to 32kHz. (I don t recall the frequency spacing >>>>>>>>>>>>> but I could find out.. a few Hz or so.) The phases of all the sine >>>>>>>>>>>>> waves were chosen randomly. The DAC was 12 bit (an AD7541 I >>>>>>>>>>>>> think). The whole thing was clocked several times lower than Nyquist >>>>>>>>>>>>> limit (~128 kHz). Now the problem we observed, (and could never >>>>>>>>>>>>> cure), was intermodulation distortion above the 32 kHz cutoff.. The >>>>>>>>>>>>> signals above the cutoff frequency were down by only 50 dB, and my >>>>>>>>>>>>> colleague was expecting something closer to 70 dB down. (Is that >>>>>>>>>>>>> right for 12 bit resolution on the DAC? ) I worked on all the layout >>>>>>>>>>>>> and analog portions of the circuit but could never make it any >>>>>>>>>>>>> better. There was talk about clock jitter on SED recently and I >>>>>>>>>>>>> wondered if this could be the source of the problem? Or maybe you >>>>>>>>>>>>> have some other idea. >>>>>>>>>>>> The DAC quantization, and any nonlinearity, will add harmonic >>>>>>>>>>>> distortion. Plus the sines may occasionally peak together and clip the >>>>>>>>>>>> dac. Plus it's not trivial to get -70 dB distortion at these >>>>>>>>>>>> frequencies. >>>>>>>>>>>> We use random number generators and boxcar filters to generate >>>>>>>>>>>> Gaussian noise to feed into dacs. This little box does this, all in a >>>>>>>>>>>> Spartan3 FPGA... >>>>>>>>>>>> http://www.highlandtechnology.com/DSS/T346DS.html >>>>>>>>>>>> Rob cleverly, somehow, allowed the user to program the noise bandwidth >>>>>>>>>>>> from mHz to 2 MHz without affecting the RMS amplitude. >>>>>>>>>>> Very nice, (Are prices listed on your website?) Y'all make stuff >>>>>>>>>>> that's several orders of magnitude above what we're doing. >>>>>>>>>>> You know what I'd really like to make (and could probabbly sell too.) >>>>>>>>>>> is a random pulse generator. Short little pulses maybe 10nS or less >>>>>>>>>>> coming at an average rate of 1us or so. This would be a psuedo shot >>>>>>>>>>> noise generator. With a pot on the output one could change the >>>>>>>>>>> amplitude of the pulses and see how the noise scaled. ... Hmm it >>>>>>>>>>> would be nicer if the average pulse rate could be changed too. So >>>>>>>>>>> that one could keep the average 'current' the same, but made with >>>>>>>>>>> bigger 'electrons'. Sounds like a digital circuit. (Which I find a >>>>>>>>>>> bit boring) an analog 'something' would be more fun. >>>>>>>>>>> George H. >>>>>>>>>>>> John- Hide quoted text - >>>>>>>>>>>> - Show quoted text - >>>>>>>>>> How about avalanching a phototransistor? ;) >>>>>>>>> point it at an Americium source from a smokedetector :) >>>>>>>>> real random noise >>>>>>>> Something optical is nice because you can change light intensity with >>>>>>>> a knob. >>>>>>>> George H. >>>>>>>>> -Lasse >>>>>>> I was just janking your chain--I had no idea that anybody had actually >>>>>>> tried that. Phototransistors are so horrible on so many levels that >>>>>>> it's pretty amusing to see someone trying to make fast pulses out of them. >>>>>>> Cheers >>>>>>> Phil Hobbs >>>>>>> - Show quoted text - >>>>>> Oh...(Silly me) Well so how 'bout a photo-transistor with three >>>>>> terminals (one where the base has a lead connected to it.) I'll short >>>>>> the base and collector together and then reverse bias the EB >>>>>> junction. With the bias voltage set just below where the thing wants >>>>>> to zener. Then a photon could set the whole thing off? >>>>>> I thought I had a photo transistor around here someplace, but I >>>>>> couldn't find it. (The original prototype of optical puming used a >>>>>> phototransistor, until I convinced every one that a photodiode was, >>>>>> more sensitive (larger area), less noisy and faster.) >>>>>> Ahh the other silly thought that this generated was using an avalanche >>>>>> zener diode as a photo detector. I know the Zener's I use are >>>>>> sensitive to light, so again if I was to park them just below the knee >>>>>> voltage and then hit them with light could I get some gain out of >>>>>> them? Kinda a poor man's APD. >>>>> You might want to search on single photon avalanche photo-detection. >>>>> http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-3-2232 >>>>> I haven't looked at the full paper but the list of references includes >>>>> some useful stuff. >>>>> -- >>>>> Bill Sloman, Nijmegen >>>> Geiger-mode APDs are mostly a crock unless you need timing accuracy >>>> better than, say, 10 ns. Their dark count rate is a good six orders of >>>> magnitude worse than a PMT of the same area, and their dead time is 10 >>>> times longer. >>>> On the other hand, they don't die if you put them in a helium >>>> atmosphere, and they last longer than 5 years. >>>> Cheers >>>> Phil Hobbs >>>> - Show quoted text - >>> PMT's and APD's are too expensive, for a simulation, PD shot noise >>> should be easy, or a zener. (how much does an APD cost, in hundreds?) >>> George H. >> The nice thing about PIN photodiodes is that there's a first-principles >> relationship between the DC and noise currents. That's a great >> calibration principle for instruments. > > Yeah, Lafe Spietz does shot noise thermometry with tunnel junction > diodes. I've got an idea for a similar circuit trick that will, > balance shot noise and johnson noise to measure temperature... The > shot noise gives you the circuit gain and bandwidth, which then drop > out in a ratio.... looks good on paper but I still have to try it. > (You run the same DC current from the shot noise through the resistor > that gives you the johnson noise and it's DC voltage is then the > thermal voltage. (or maybe two times it.) > > George H. > Fun. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: John Larkin on 7 Jun 2010 14:55
On Sun, 6 Jun 2010 06:43:13 -0700 (PDT), Bill Sloman <bill.sloman(a)ieee.org> wrote: >On Jun 6, 12:52�am, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Sat, 5 Jun 2010 15:00:09 -0700 (PDT),Bill Sloman >> >> >> >> <bill.slo...(a)ieee.org> wrote: >> >On Jun 5, 8:18�pm, John Larkin >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> On Sat, 5 Jun 2010 10:47:26 -0700 (PDT),Bill Sloman >> >> >> <bill.slo...(a)ieee.org> wrote: >> >> >On Jun 5, 1:24�am, John Larkin >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> On Fri, 4 Jun 2010 14:56:44 -0700 (PDT),Bill Sloman >> >> >> >> <bill.slo...(a)ieee.org> wrote: >> >> >> >On Jun 4, 10:40�pm, Phil Hobbs >> >> >> ><pcdhSpamMeSensel...(a)electrooptical.net> wrote: >> >> >> >> On 6/4/2010 12:01 PM,Bill Slomanwrote: >> >> >> >> >> > On Jun 4, 4:41 pm, George Herold<gher...(a)teachspin.com> �wrote: >> >> >> >> >> On Jun 4, 10:07 am, Phil Hobbs >> >> >> >> >> >> <pcdhSpamMeSensel...(a)electrooptical.net> �wrote: >> >> >> >> >>> On 6/3/2010 11:12 PM, George Herold wrote: >> >> >> >> >> >>>> langw...(a)fonz.dk wrote: >> >> >> >> >>>>> On 3 Jun., 23:11, Phil Hobbs<pcdhSpamMeSensel...(a)electrooptical.net> >> >> >> >> >>>>> wrote: >> >> >> >> >>>>>> On 6/3/2010 9:49 AM, George Herold wrote: >> >> >> >> >> >>>>>>> On Jun 2, 4:36 pm, John Larkin >> >> >> >> >>>>>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> � � �wrote: >> >> >> >> >>>>>>>> On Wed, 2 Jun 2010 12:30:19 -0700 (PDT), George Herold >> >> >> >> >> >>>>>>>> <gher...(a)teachspin.com> � � �wrote: >> >> >> >> >>>>>>>>> On Jun 2, 1:59 pm, whit3rd<whit...(a)gmail.com> � � �wrote: >> >> >> >> >>>>>>>>>> On Jun 2, 10:37 am, George Herold<gher...(a)teachspin.com> � � �wrote: >> >> ><snip> >> >> >> >> >> > You might want to search on single photon avalanche photo-detection. >> >> >> >> >> >http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-3-2232 >> >> >> >> >> > I haven't looked at the full paper but the list of references includes >> >> >> >> > some useful stuff. >> >> >> >> >> Geiger-mode APDs are mostly a crock unless you need timing accuracy >> >> >> >> better than, say, 10 ns. �Their dark count rate is a good six orders of >> >> >> >> magnitude worse than a PMT of the same area, and their dead time is 10 >> >> >> >> times longer. >> >> >> >> >> On the other hand, they don't die if you put them in a helium >> >> >> >> atmosphere, and they last longer than 5 years. >> >> >> >> >Horses for courses. They can be a lot more compact and robust than >> >> >> >PMTs - on which I'm rather more expert. >> >> >> >> Vain fathead. >> >> >> >I've worked with PMT's - which is more than I can claim about SPAD's - >> >> >and I've persuaded the IEEE that I do know a little about PMTs - see >> >> >the IEEE Transactions on Electronic Devices volume 38 pages 679-680, >> >> >published in March 1991. >> >> >> >You do need to base your abuse on something more than your right-wing >> >> >intuition. Going off half-cocked like this does rather expose your >> >> >enthusiasm for believeing what you want to believe despite the absence >> >> >of any evidence to support your point of view. >> >> >> All you do here is claim how "expert" you are, or maybe were, without >> >> ever making actual contributions. >> >> >Nothing that you'd be willing to acknowledge, particularly since most >> >of my contributions are references to the publshed literature, a >> >source that you seem ill-equipped to exploit >> >> >> You never *do* anything. >> >> >Not at the moment, and I find it frustrating. >> >> >> And when I don't have convincing evidence, I experiment and collect >> >> some. A mouse isn't a soldering iron. >> >> >You burble about 140dB of ripple rejection >> >> Burble? I questioned whether the Spice models of the c-multiplier were >> accurate at mid-frequencies. None came close to 140, or even 80, dB at >> frequencies where Early slope matters. So I tried some experiments. >> >> �and then post the results >> >> >of your experiment that shows 67dB. You've got a lab full of expensive >> >equipment - if we are to take your boasting seriously - and boast like >> >a lion about your "insanely good" electronic designs, but then post a >> >result that might qualify you as a mouse in an undemanding >> >environment. >> >> This is the sort of thing you could do. It doesn't take expensive >> equipment to measure, say, 80 or 100 dB of ripple rejection. Just a >> little thought and patience. > >Not to mention the transistors, the capacitors and the resistors - I >don't keep a stock of components, and while I could get them, there is >a mininum order charge which menas that I'd better order all of what >I'd need in one hit > >> So try it - for real - and we'll compare numbers. > >I'm still trying to use the gEDA circuit design software to prepare a >schematic - and the concommitant parts list - for my oscillator >project, which is more interesting, if still not interesting enough to >motivate me to spend enough time rooting around in the gEDA >hierachical design system. > >> If not for money, just to keep your mind from rotting. > >My mind is fine, but my motivation isn't what it could be. > >> >Somebody with your experience ought to be aware that if you want 140dB >> >of attenuation you are going to need more than a single stage of >> >filtering - stray impedances usually make it difficult to get more >> >than 60dB in a single stage. >> >> My experience was entirely inadequate to make such a pronouncement. > >It probably isn't, but you clearly didn't think hard about the earlier >experience you were getting while you were getting it. I've always ignored Hre up to now, because it's generally swamped by other parameter variations. I certainly never had a reason to map Hre vs Ie and Vce. The Fairchild 2N3904 datasheet actually has a curve, sadly only at 10 volts. > >> I did some tests. Now I know more than I did before. You don't >> approve? > >It is certainly a step in the right direction - but one that you might >have taken a few decades earlier. In your case, it obviously needs the >right sort of customer asking the right sort of questions to get you >interested. People with academic curiousity tend to get more out of >the experience they have had because they put more time into making >sense of their results. They often find that some academic had written >up the whole issue a few decades earlier. It's hard to avoid re- >inventing the wheel if you did't know that the wheel existed in the >first place. I don't have a lot of "academic curiousity"... I'm motivated by solving real problems. I've never before explored nanovolt-noise-level LDO regulators because I'd never needed one. Given an essentially infinite list of things to explore, I'd just as soon pick the ones that are potentially useful. Exceptions occasionally made for super-cool stuff, of course. John |