Tom Van Baak wrote: >> Big question: If the single shot resolution is only 3-4 times better >> that that of the 53131 and much inferior to the 20 ps of my SR620, how >> does the 53132 manage to be THAT GOOD A PERFORMER? Magic? Black art? >> > > Hi Ulrich, > > My understanding is that 1) the 53132A has a single-shot > resolution of about 150 ps, but also 2) it can do something like > 200,000 phase measurement per second for CW RF inputs. > > In frequency mode, the frequency computed and displayed > each second is the result of internal statistics on those > 200,000 samples, which in general is much better than two > single TI measurements made 1 second apart. > > In the best case of no correlation between input and timebase > the frequency resolution would be 150 ps / sqrt(200 000), which > is sub-ps. > > In reality, depending on the numerical character of the input RF > frequency, you don't get the full sqrt(200000) factor. Page 3-13 > of the 53132A user manual tries to explain this. But for most > input frequencies it is in the low picoseconds, which is why it > can be called a 12-digit per second counter. Google for > 53132a user manual for a copy of the manual. > > (As an aside, if you use a 53132A on a slowly warming OCXO > you can see the display resolution change when the magic n/m > threshold, mentioned in the back of the manual, is crossed). > > The bottom line is that the SR 620 or hp 5370 is a better counter > for TI (single-shot) measurements (e.g., comparing 1 PPS ticks). > But for CW frequency measurements, the 53132A is much quicker > due to this extreme internal oversampling. To be fair, I'm pretty > sure that other modern counters (e.g., Philips, Pendulum) also > use this frequency resolution trick. > > /tvb > > The Australian IEEE paper details are:
/Considerations on the Measurement of the Stability of Oscillators with Frequency Counters, /Samuel T. Dawkins, John J. McFerran, Andre N Luiten. All authors are from the School of Physics, university of Western Australia. 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.