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: [email protected] [mailto:time-nuts-
[email protected]] 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
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