> 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 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
