[time-nuts] General questions about making measurements with time interval counter.

[Bob Camp]

Hi

It varies from 5370 to 5370. You see a lot of plots that run out to 10 samples or less. Anything below 100 samples
is risky in some senses.

Bob

> On Jan 12, 2017, at 12:25 PM, Bob Stewart <bob at evoria.net> wrote:
> 
> Hi Bob,
> OK, what's a small number of data points?  Attached is a screencap of captures for 25, 50, 75, 100, and 150 seconds.  Yeah, at 25 seconds, the 1S tau is up at 4.56E-11, but it falls pretty quickly.  I will mention that this particular 5370 is much better than my other one.  So, maybe this one is an exceptional example?
> 
> Just for grins, I also included a screencap of the phase points.
> 
> Bob -----------------------------------------------------------------
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>      From: Bob Camp <kb8tq at n1k.org>
> To: Bob Stewart <bob at evoria.net>; Discussion of precise time and frequency measurement <time-nuts at febo.com> 
> Sent: Thursday, January 12, 2017 11:04 AM
> Subject: Re: [time-nuts] General questions about making measurements with time interval counter.
> 
> Hi
> 
> There is a big difference between RMS and single shot. Single shot, the 5370 is a very different beast. 
> That’s not a big deal when you have a few thousand readings and it all averages down. Unfortunately 
> we all love to do runs with a very small number of points and then draw conclusions from them. As the 
> sample size goes down, you no longer have a 2 to 4 x 10^-11 beast, it’s more like 5X that.
> 
> Bob
> 
> 
>> On Jan 12, 2017, at 11:31 AM, Bob Stewart <bob at evoria.net> wrote:
>> 
>> Hi Bob,
>> Normally I see somewhere between 2E-11 and 4E-11 at 1S tau on my 5370A, as in the blue trace on the attached plot.  Am I misunderstanding your meaning?  Granted, I am clocking the 5370A with a GPSDO, but I believe I see about the same thing with the HP10811.  This test was 1PPS vs 1PPS on two different units.
>> The plot also has a test run by Tom, in orange, using his H Maser and a Timepod to show how poor the 5370 is compared to the Timepod below about 60S tau.  These are essentially apples vs apples tests.
>> 
>> Bob
>> 
>> 
>> 
>> 
>>       From: Bob Camp <kb8tq at n1k.org>
>> To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
>> Sent: Thursday, January 12, 2017 8:27 AM
>> Subject: Re: [time-nuts] General questions about making measurements with time interval counter.
>> 
>> Hi
>> 
>> There are a number of ways to improve the resolution (and accuracy) of your data without spending 
>> big piles of cash. They have been discussed here on the list many times over the last few years. 
>> What I’m suggesting is that you dig into that ahead of taking data. You will dive into it eventually as you 
>> look more and more at devices that are locked to some sort of stable reference internally. 
>> 
>> Ideally you would like a device with a floor 5X to 10X better than what you are measuring. For ADEV style
>> data, the 5370 is a 1x10^-10 sort of device single shot (so 1x10^-9 is the limit at 10:1). With a lot of averaging 
>> (which is not something you do with ADEV) you can get about 5X better than that as a floor. In either case, it is getting in the way of any
>> readings that are much below 1x10^-9 at one second. A low cost XO can hit that level of performance.  
>> 
>> Bob
>> 
>> 
>> <ADEV.png>_______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
> 
> 
> <ADEVs.png><Phase.png>_______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.