[time-nuts] Recommended parameters for Timelab ADEV analysis

Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Nov 20 09:28:43 UTC 2012


Its actually Tau with a subscript 0.
This is the the time interval between successive measurements.
e.g. if a measurement is taken every second then Tau0 is 1 sec.

Bruce

Edgardo Molina wrote:
> Dear John Ackermann,
>
> I find your reply to my request to be very interesting. Without fear of asking. May I know how do I achieve a Tau 0 measurement in a 1 second interval with my setup? (HP-53132A + TimeLab).
>
> Please tell me if I am wrong.  I assume I would take the 10 MHz output from the 53132A and plug it into the Channel 1 input, while the external reference of 10 MHz is disconnected.
>
> As far as I am concerned, TimeLab does not allow a value of 0 for Tau. If I enter zero as the measurement time duration I get an error and actual acceptable Tau range. The smaller value is in the order of 1E-6s. Am I getting it right? I am sorry for my confusion.
>
> Regards,
>
>
>
> Edgardo Molina
> Dirección IPTEL
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> On Nov 14, 2012, at 8:13 PM, John Ackermann N8UR<jra at febo.com>  wrote:
>
>    
>> 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
>>>
>>> T : 55 55 55202444
>>> M : 04455 10045822
>>>
>>> Piensa en Bits SA de CV
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