Hi Magnus; I hope this is not to far off thread. Has anyone in the group done real world measurements of single shot res, and jitter on the new Agilent and Tektronix/Pendulum counters compared to the SR620 and Agilent 53132A. I would imagine that counter designs would be an area that really benefits from ongoing advances in digital technology. I have also found that it is much easier to claim specs then meet specs. Thanks; Thomas Knox
> Date: Sat, 3 Nov 2012 16:28:42 +0100 > From: mag...@rubidium.dyndns.org > To: time-nuts@febo.com > Subject: Re: [time-nuts] A counter for phase measures > > On 11/03/2012 03:10 PM, Volker Esper wrote: > > > > Thank you for the interesting information. Now, the time has come to > > look for an adequate counter - anyone who has experience with the HP > > 53132A and the SR620? If they both where at - say 1000 USD - what would > > you prefer for the job of phase measurement? I've read about that > > massive single shot capability of the SR, but - as being a newbie - is > > there anything I overlook at this moment? > > For short time-scales, single shot resolution and trigger jitter > dominates your measurement floor. > > Single-shot resolution is the time resolution by which you make a single > measurement. > > Trigger jitter is the noise at the trigger point. it's a combination of > thermal noise and the slew-rate at the trigger points. It is often that > trigger jitter is dominated by slew-rate, but there is also internal > sources of trigger jitter. The slope dependent trigger jitter follows > the formula: > > t_jitter = v_noise / s_slew > > t_jitter is the trigger jitter (s) > v_noise is the noise power (V) > s_slew is the slew rate (V/s) > > When the time-span of a measurement is long, long-term stability comes > in as well as systematic drifts. Also, systematic noise such as hum also > becomes important. > > To see how much you depend on slew-rate limitation, you can reduce the > amplitude, and as this reduces the slew-rate you can separate the > slew-rate dependent jitter from the intrinsic jitter of the input. It > also helps you to identify if you need to work on the slew-rate limit > rather than anything else. > > So, it may not be the single-shot resolution which limits you, but a > combination of things. > > I would recommend you to pick up a SR620. It has 4 ps single shot > resolution and about 25 ps jitter (but you can get less). That is > significantly better than the 53152A provides. > > SR620 manual (one of many links): > http://ilrs.gsfc.nasa.gov/docs/timing/sr620_manual.pdf > > Cheers, > Magnus > > _______________________________________________ > 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.
