[time-nuts] Recommended parameters for Timelab ADEV analysis

John Ackermann N8UR jra at febo.com
Thu Nov 15 02:13:35 UTC 2012


Edgardo, the minimum sample rate in practice is determined by the noise floor of the measurement system.  I would suggest that you do a baseline test by measuring the counter reference against itself with a tau0 (sample rate) of 1 second.  You'll see a best-case result and from it you can determine at which sample rate your noise floor is better than the predicted performance of the oscillator under test.  You'll probably find that you are measurement-noise limited below several hundred seconds.

Also, you'll generally get a lower noise floor doing time interval rather than frequency measurements, so you might experiment with that, which normally involves using a low-rate signal such as PPS for "start" and "stop" channels.

John

On Nov 14, 2012, at 8:43 PM, Edgardo Molina <xe1xus at amsat.org> wrote:

> 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
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