[time-nuts] Recommended parameters for Timelab ADEV analysis

Adrian rfnuts at arcor.de
Thu Nov 15 02:59:07 UTC 2012


Hi Edgardo,

however, the 53132A is considerably more sensitive in frequency mode as 
we have recently discovered.
I saw an astoundingly low ADEV noise floor of some 6E-13 at t=10 sec as 
opposed to only 2.5E-11 in TI mode.
I don't have a 53132A, only a 53131A that I don't use anymore for ADEV, 
so I can't be more specific.

In TI mode, the noise floor is determined by the _resolution_ of your 
counter.
If the resolution is 500ps, you are looking into 5E-10 at t=1 second, if 
it is 200ps then 2E-10 etc.
When you increase t by a factor of 10, your noise floor goes down by the 
same factor of 10.
That is, with the same 200ps counter, you get 2E-11 at t=10 sec, 2E-12 
at t=100 sec etc.
Just don't expect that to continue endlessly. There are other limiting 
factors to the ADEV noise floor that come into play like thermal drift, 
including the cables.

A very interesting option with TIMELAB is that you can use your 53132A 
counter in continuous printing mode via RS232. This mode is faster than 
what GPIB gets you. And, you don't even need a GPIB interface... that's 
really cool, isn't it?

Last but not least, somehow you have to figure out what you are actually 
measuring, the DUT and / or your reference, or simply the noise floor of 
your test setup. This can be the hardest part. You might want to compare 
your test results with some trustworthy reference measurements like 
this: http://www.leapsecond.com/museum/manyadev.gif

Adrian


John Miles schrieb:
> Hi, Edgardo --
>
> Your counter's noise near t=1s will dominate most measurements you're likely
> to make, so there's nothing to be gained by acquiring data at even faster
> rates.  This will probably be true out to at least 10-100 seconds or even
> longer, depending on what you're measuring.
>
> For best ADEV fidelity you'd want to use TI measurements rather than
> frequency measurements, but frequency measurements are obviously much easier
> to set up.  They can give you a good overall idea of what's going on.
>
> -- john
> Miles Design LLC
>
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-
>> bounces at febo.com] On Behalf Of Edgardo Molina
>> Sent: Wednesday, November 14, 2012 5:44 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: [time-nuts] Recommended parameters for Timelab ADEV analysis
>>
>> Dear Group,
>>
>> Now that I have setup TimeLab along with the Prologix GPIB to USB adapter
>> and the HP-53132A frecuency counter, I am starting to get some data from
>> my frequency standards. Still I think I have a long way to go in front of
> me.
>> One of the main concerns that cross my mind at this point are:
>>
>> a. What is the recommended sampling duration to consider for Quartz,
>> Rubidium  and other types of oscillators?
>> b. What are the recommended sampling intervals for the above mentioned
>> oscillator types?
>> c. I am using a 10 MHz Rb FE-5806A frequency standard as an external
>> reference for the HP-53132A.
>> d. I am connecting my DUT at the frequency counter channel 1
>> e. I am setting Timelab for Data Type = Frequency
>> f. My graphs somehow have the same geometry of classical ADEV examples,
>> I can differentiate the ADEV noise types quite easily.
>> g. Should I use sub-second sampling intervals for my graphs to start
> closer to
>> the vertical axis of the graph? Or should I use a conservative 1s sampling
>> rate?
>>
>> With the previous questions I am looking for consistency in my ADEV
>> studies.. Are there any typical ADEV conditions to be considered when
>> analysing this way?
>> Am I missing something? My apologies to everybody if I am missing
>> something or doing it the wrong way. In the end I want to learn more than
>> anything else.
>>
>> Your kind comments are welcome. Thank you.
>>
>> Best regards,
>>
>>
>>
>> Edgardo Molina
>> Dirección IPTEL
>>
>> www.iptel.net.mx
>>
>> T : 55 55 55202444
>> M : 04455 10045822
>>
>> Piensa en Bits SA de CV
>>
>>
>>
>> Información anexa:
>>
>>
>>
>>
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