It is possible for 100k secondary standards average to be skewed if they were calibrated to the same primary standard. All the primary standards would have to different for the secondary average to be an real average. Coin toss analogy would be slightly different if the coins were all different shapes and sizes.. but probably not! >It is not impossible that for a sample of 100,000 secondary standards, that the errors would be all be off in the same direction, compared to the standard's value. > >Now, granted, this would be a small probability indeed. But it is possible to toss a coin fifty times and have fifty "heads". The smart bet is that it won't. > -- Raj, VU2ZAP Bangalore, India.

Roy, The standard is based on the Analog Devices AD588 chip. http://www.analog.com/static/imported-files/data_sheets/AD588.pdf You can buy the magazine article at http://siliconchip.com.au/cms/A_111365/article.html Regards, Nic Hi Nick Is it possible to let us have the schematic/details of this SC Magazine Voltage Reference project, thanks Roy

Wow thats a nice chip indeed On Tue, Jan 12, 2010 at 2:58 PM, Nic McLean <mcleann@bigpond.com> wrote: > Roy, > The standard is based on the Analog Devices AD588 chip. > http://www.analog.com/static/imported-files/data_sheets/AD588.pdf > You can buy the magazine article at > http://siliconchip.com.au/cms/A_111365/article.html > Regards, > Nic > > > Hi Nick > Is it possible to let us have the schematic/details of this SC Magazine > Voltage Reference project, thanks > Roy > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

Were you guys around (about a year back, I think) when this reference was mentioned? http://www.voltagestandard.com/ Seems like excellent price/performance to me. I see he has a more accurate, more expensive model too. paul swed wrote: > Wow thats a nice chip indeed > > On Tue, Jan 12, 2010 at 2:58 PM, Nic McLean <mcleann@bigpond.com> wrote: > > >> Roy, >> The standard is based on the Analog Devices AD588 chip. >> http://www.analog.com/static/imported-files/data_sheets/AD588.pdf >> You can buy the magazine article at >> http://siliconchip.com.au/cms/A_111365/article.html >> Regards, >> Nic >> >> >> Hi Nick >> Is it possible to let us have the schematic/details of this SC Magazine >> Voltage Reference project, thanks >> Roy >> >> >> >> >>

Mike Naruta AA8K wrote: > > Sure Chuck. What I was talking about was a part of statistics that we > in our gnat-hair-splitting compulsive group may forget about. > > Let's assume that our 100,000 standards were carefully calibrated > against THE standard. There is a small amount of error in the > calibration process. Let us even assume that the error in the > calibration process is normally distributed. > > It is not impossible that for a sample of 100,000 secondary standards, > that the errors would be all be off in the same direction, compared to > the standard's value. > > Now, granted, this would be a small probability indeed. But it is > possible to toss a coin fifty times and have fifty "heads". The smart > bet is that it won't. Well, if the distribution of these is only random and of benign randomness like gaussian noise. If you have an aging mechanism for instance, over time this huge set would drift in that direction and that would produce a moving average value... The rate of calibration to a primary standard would be one of the parameters needed to set the limit of drift. So, systematic drift is not canceled by large number statistics. It just doest not obey the underlying assumption. Long-term noise of clocks obery the f^-3 noise which does not converge nicely and statistical measures needs to be adapted to provide reasnoble measures. This is why we have ADEV and friends. Again, this is why you need to separate stability with reproducability aspects. Cheers, Magnus