Hi The statistical fill approach is a cute way to go. The gotcha comes in when you have a structure that *may* not be monotonic.
Bob On Dec 28, 2012, at 1:04 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > Fabio Eboli wrote: >> Hello >> >> How could I test the time to analog converter >> we talked few posts ago? >> Something that can be done with things I have >> or can easily find. > One method is to use a statistical fill the buckets technique to measure the > linearity. > To do this one needs to use an incoherent source to trigger the interpolator > and plot a histogram of the results. > A noisy RC oscillator would be useful for this but care should be taken to > avoid injection locking. > To achieve useful measurement in a reasonable time interval a trigger rate > somewhat greater than 1Hz is required. > If the interpolator has 1024 time delay bins then ~ 100,000 trigger events > are required to achieve a bin width measurement error of 10%. > > Otherwise a series of measurements of a set of accurately known delays is > required. > Useful results can be produced by measuring the delay between various outputs > of a shift register clocked at a sequence of different measured frequencies. >> >> I was thinking that would be nice to try to >> feed it with signals similar to the real ones, >> but that can be controlled: PPS + 10MHz reference, >> without the PPS tipical jitter. >> > One should characterise the interpolator linearity etc first. >> To do so I was thinking to use the PPS from >> one of the 2 FE5680 and the 10MHz from the >> second ad use these to simulate the real signals. >> >> I can tune the frequency of the Rb with the >> serial interface (tested and working). >> I'd like to verify both the resolution and >> repeteability. >> >> I was trying to figure the approx jitter >> I will have using the Rb like I said above, >> so I'm giving an eye to this diagram from >> John Miles page: http://www.ke5fx.com/rb.htm >> >> If I'm understanding correctly, that 5680 >> at 1s should have most of the jitter (95% +-2sigma) >> into an interval +- 3.08x10^-11 wide, i.e. about 62pS >> on the PPS signal (non considering the PPS buffer >> inside the 5680). Is this how it work, or I'm mistaking? >> This is from only one unit, but both unit will have >> the jitter, how to take into account the jitter >> from both? >> >> Is there a better method to make this test? >> I could try to test the TAC alone feeding it >> with a 100 to 200nS pulse, but I dont know >> from where to start to generate a clean stable >> and repeteable pulse. >> > You dont need one (see above) as long as you have the means to accumulate the > results of 100,000 measurements or preferably more. >> I have the 2 5680, the counter with it's 10MHz >> inputs and outpus, and a Vectron OCXO that came >> with one of the 5680, with these markings: >> OCXO500-18 63.897600MHz >> 34537 A0715 >> and... >> soldering iron, solder and scrap electronics :) >> >> Thanks, >> Fabio. >> > Bruce > > _______________________________________________ > 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. _______________________________________________ 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.