Very nice plot Tom!

Did you thermally insulate the CSAC to get this kind of performance?

bye,
Said

In a message dated 10/3/2012 09:24:54 Pacific Daylight Time,
tvb@LeapSecond.com writes:

forward to the day and I can afford a GPS disciplined CSAC.

The CSAC is cheap compared to the  reference you need to measure  it...

http://www.leapsecond.com/pages/csac/log96872v.gif

/tvb

On Oct 3, 2012, at 11:15 AM, SAIDJACK@aol.com wrote:

Nice plot! Yes, I'd have trouble measuring 10E-14 at 10E5 seconds.

Kevin

On Oct 3, 2012, at 6:52 PM, Kevin Rosenberg kevin@rosenberg.net wrote:

Sorry, 1E-14 at 1E5.

Hi

A 1 ns resolution TI counter will do the measuring part just fine. Hitting the number, is where it gets a bit crazy. A good GPSDO might get near that.

Bob

On Oct 3, 2012, at 8:56 PM, Kevin Rosenberg kevin@rosenberg.net wrote:

Taking 10 samples from a 1nS counter leads you to a 100pS resolution but
the noise at best (if it is really random) is reduced by SQRT(10). So, as
already pointed out here, there is no real substitute for lower noise,
higher resolution measurements.

On Thu, Oct 4, 2012 at 3:01 AM, Bob Camp lists@rtty.us wrote:

Azelio,

as an example, with a 53131A you have an output 'granularity' of +/- 500
ps.
No matter how much averaging happens inside the counter, if the least
significant digit is 500 ps, then the (ADEV) measurement limit is always
5E-10 at 1 sec as I posted in the initial post to this thread. This is
not the accuracy of the counter, it's simply the available display and
output string resolution.
At 10 sec., the ADEV limit of the same counter is 5E-11 etc. etc.
finally getting limited by the reference source and other effects.
If the DUT's ADEV is in the 1E-13's, any measurement values below 1000
sec. are void and represent just the measurement limit of the +/- 500ps
counter.

Now I'm waiting to receive 'glasses' for my 53131A that are in transit :)

Adrian

Azelio Boriani schrieb:

OK, and then what about measurements beyond 1000 sec (for the same DUT's
ADEV in the 1E-13's) taken with a 500pS counter and a 50pS counter? Nice to
hear that there is exactly no difference, just use average...

On Thu, Oct 4, 2012 at 2:34 PM, Adrian rfnuts@arcor.de wrote:

Hi

But I don't have to take data only at one second points for a one second
ADEV. I can take data faster and then process it. That's what the counter
does in frequency mode. I can do the same thing with time readings.

The big advantage there is that with higher speed time readings, I can
control how the math works and hopefully get a valid ADEV out the other
side. With the counter doing it's magic math in the frequency mode, you are
entirely at the mercy of an unknown HP coder who might or might have been
thinking ADEV when he wrote the code.

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Adrian
Sent: Thursday, October 04, 2012 8:35 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best counter setting for ADEV?

Azelio,

as an example, with a 53131A you have an output 'granularity' of +/- 500
ps.
No matter how much averaging happens inside the counter, if the least
significant digit is 500 ps, then the (ADEV) measurement limit is always
5E-10 at 1 sec as I posted in the initial post to this thread. This is
not the accuracy of the counter, it's simply the available display and
output string resolution.
At 10 sec., the ADEV limit of the same counter is 5E-11 etc. etc.
finally getting limited by the reference source and other effects.
If the DUT's ADEV is in the 1E-13's, any measurement values below 1000
sec. are void and represent just the measurement limit of the +/- 500ps
counter.

Now I'm waiting to receive 'glasses' for my 53131A that are in transit :)

Adrian

Azelio Boriani schrieb:

Hitting

https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

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Hi

For a resolution of 1.0 x 10^-14 at 1.0 x 10^5 seconds I only need a 1.0 x
10^-9 second reading out of the counter. Indeed, 5 or 10X more than that
would be better if I was after a 1 x 10^-14 accuracy.

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Azelio Boriani
Sent: Thursday, October 04, 2012 7:58 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best counter setting for ADEV?

Taking 10 samples from a 1nS counter leads you to a 100pS resolution but
the noise at best (if it is really random) is reduced by SQRT(10). So, as
already pointed out here, there is no real substitute for lower noise,
higher resolution measurements.

On Thu, Oct 4, 2012 at 3:01 AM, Bob Camp lists@rtty.us wrote:

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and follow the instructions there.

Yes, for a theoretical resolution of 10E-14@100K sec start with a 1nS and
average for 100K seconds but ending up with a noise (an error bar) of 3E-12.

On Thu, Oct 4, 2012 at 4:25 PM, Bob Camp lists@rtty.us wrote:

Hi

Maybe we're talking about two different things here.

Simplistically, resolution is simply what the counter puts out as a usable
LSB. There are a lot of examples out there that will do a one nanosecond
single shot measurement. That measurement includes the normal trigger noise
and "stuff" in the counter. There are a few assumptions about slew rate of
the input.

If I take two one shot measurements spaced 100,000 seconds apart, my
resolution over that period is 1.0x10^-14. The measurement is representative
of what the sources have done to that level. Weather the sources are stable
to that level is independent of the resolution of the measurement.

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Azelio Boriani
Sent: Thursday, October 04, 2012 12:27 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best counter setting for ADEV?

Yes, for a theoretical resolution of 10E-14@100K sec start with a 1nS and
average for 100K seconds but ending up with a noise (an error bar) of 3E-12.

On Thu, Oct 4, 2012 at 4:25 PM, Bob Camp lists@rtty.us wrote:

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and follow the instructions there.

You're right: it is better to put it down correctly:
for a theoretical resolution of 10E-14@100K seconds, start with a 1nS
counter that takes 1 second samples for 100K seconds and average those 100K
samples. You have your resolution and a noise (an error bar) of 3E-12. If
you use a 100pS counter and do the same run, you will end up with a 10E-15
reolution and 3E-13 noise, and so on. It turns out that to have a real
10E-14 measure (@100K seconds), not blurred with noise, you must start with
a 10pS counter.

On Thu, Oct 4, 2012 at 6:41 PM, Bob Camp lists@rtty.us wrote:

Hi

What if I only take two single measurements:

One at time = 0, the other at time = 100,000 seconds.

No averaging, no signal processing just two measurements. I look at the time
difference  between the two signals at time = 0, and then again a bit more
than a day later.

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Azelio Boriani
Sent: Thursday, October 04, 2012 2:48 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best counter setting for ADEV?

You're right: it is better to put it down correctly:
for a theoretical resolution of 10E-14@100K seconds, start with a 1nS
counter that takes 1 second samples for 100K seconds and average those 100K
samples. You have your resolution and a noise (an error bar) of 3E-12. If
you use a 100pS counter and do the same run, you will end up with a 10E-15
reolution and 3E-13 noise, and so on. It turns out that to have a real
10E-14 measure (@100K seconds), not blurred with noise, you must start with
a 10pS counter.

On Thu, Oct 4, 2012 at 6:41 PM, Bob Camp lists@rtty.us wrote:

noise

stable

as

near

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If you take 2 samples out of a 1nS counter than you can estimate your
measure with a 500pS resolution (5E-10) with an uncertainty (noise) of
7E-10.

On Thu, Oct 4, 2012 at 8:58 PM, Bob Camp lists@rtty.us wrote:

Hi

If I have two clocks:

1. I know they are X ns apart at time = 0
2. I know they are Y ns apart at time = 100,000 seconds
3. The resolution of the X and Y measurements is 1 ns

I know the relative time between the two clocks to a lot better than
5.0x10^10...

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Azelio Boriani
Sent: Thursday, October 04, 2012 3:43 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best counter setting for ADEV?

If you take 2 samples out of a 1nS counter than you can estimate your
measure with a 500pS resolution (5E-10) with an uncertainty (noise) of
7E-10.

On Thu, Oct 4, 2012 at 8:58 PM, Bob Camp lists@rtty.us wrote:

100K

with

seconds.

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OK, because you think: (Y-X)/100K is the drift of the two clocks for each
second over 100K seconds and for each second I have a 1nS/100K resolution.
Now think about this: repeat the measure over and over and after each 100K
seconds you have your table. This table (your counter is 1nS) can have
figures like, say, 52nS, 53nS, 58nS, that is with a 1nS step. Your drift
maybe not exactly 52: it maybe 52.1 52.3 52.4 but you only see 52. So you
are loosing an entire nS between 52nS and 53nS. If you have a 100pS counter
you can see 52.0, 52.1 and so on.

On Thu, Oct 4, 2012 at 10:13 PM, Bob Camp lists@rtty.us wrote:

Hi

Doing the repetition may give you a more fine grained idea of what the clocks are doing. It does not impact the resolution of the single measurement.

A single ns in 100,000 seconds is indeed 1.0x10^-14…

Bob

On Oct 4, 2012, at 6:11 PM, Azelio Boriani azelio.boriani@screen.it wrote:

OK, now I understand: you are not interested in anything less than 100K
seconds with your 1nS counter. Taking samples every 100K seconds from very
stable sources with a 1nS counter hides the entire step between (for
example) a 1E-14 and 2E-14. You can't see 1.1E-14, 1.2E-14, 1.3E-14 but,
yes, you have a 1E-14 resolution at 100K seconds.

On Fri, Oct 5, 2012 at 1:19 AM, Bob Camp lists@rtty.us wrote:

Hi

Yes, that's it exactly.

I knew we must be talking about to different things...

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Azelio Boriani
Sent: Friday, October 05, 2012 5:25 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best counter setting for ADEV?

OK, now I understand: you are not interested in anything less than 100K
seconds with your 1nS counter. Taking samples every 100K seconds from very
stable sources with a 1nS counter hides the entire step between (for
example) a 1E-14 and 2E-14. You can't see 1.1E-14, 1.2E-14, 1.3E-14 but,
yes, you have a 1E-14 resolution at 100K seconds.

On Fri, Oct 5, 2012 at 1:19 AM, Bob Camp lists@rtty.us wrote:

each

you

the

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