[time-nuts] Best counter setting for ADEV?

Azelio Boriani azelio.boriani at screen.it
Tue Oct 2 08:59:14 EDT 2012


Yes, and why the 10 seconds frequency mode sigma is apparently better than
the 10 seconds TI mode sigma? Because between the two there are 200
averages taken by the frequency mode processing. This is possible also
because the input frequency in frequency mode is 10MHz or 5MHz and in TI
mode a 1Hz signal is used.

On Tue, Oct 2, 2012 at 2:51 PM, Adrian <rfnuts at arcor.de> wrote:

> No matter how much averaging takes place inside the counter, in TI mode
> the output resolution is limited to +/- 200ps (53132A) or +/- 500ps
> (53131A) which appears to translate directly into the measurement limit /
> noise floor.
>
> Adrian
>
> Azelio Boriani schrieb:
>
>> Hmm, the frequency mode sigma is the same as the TI mode sigma for
>> 200*tau.
>> That is if I take the sigma at 200*tau from the TI mode I have the same
>> figure of the frequency mode. Maybe the frequency mode 2 seconds sample
>> time uses 100 averages per second.
>>
>> On Tue, Oct 2, 2012 at 1:50 PM, Timeok <timeok at timeok.it> wrote:
>>
>>  correction: HP53132A
>>>
>>>
>>> timeok
>>>
>>> Il 2012-10-02 13:29 Timeok ha scritto:
>>>
>>>   test using HP53123A:
>>>
>>>> The pink line is the noise floor using the TI mode
>>>> The blue line is the noise floor using the Frequency mode (gate 2 sec)
>>>> The other two line are the same oscillator, an HP105B tested with
>>>> both the modes.
>>>> As you can see the range between 1 and 200 sec is "totally
>>>> compromised" by the system noise floor using the TI method.
>>>> The approximation using the freq mode can be anyway usefull to make a
>>>> comparatinon between two source.
>>>> I suppose to have right measurements, without any restriction we have
>>>> to use the Timepod or other high level instruments than this kind of
>>>> counters.
>>>>
>>>> Luciano
>>>>
>>>>  --
>>>
>>>
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