HI

It does not come up with a 1000 s tau ADEV by doing that. The gate time would need to be open for 1000 seconds.

If you are measuring the difference between two one 1 pps signals, and they are < 0.1 seconds apart, and the TICC has a resolution of 0.1 ns ….

Then the reference clock for the TICC only needs to be good to 0.1 ns / 0.1 s = 1x10^-9

A counter that will do 1x10^-12 at 1 second would need errors below 1 ps. I do not know of any such counter. As you go to other tau’s (like 1,000 seconds)
a counter that will keep a gate open for 1000 seconds might do the trick.

We have been doing that off list ….

Look at the counter’s stated accuracy information and do the math. If it’s a 100 ps counter, then that is 100 x 10^-12 at 1 second. If there are no other errors, and
the reference is perfect, you will hit 10X better each time the gate increases by 10X.

Bob

Hi Taka,

On 2020-02-21 23:26, Taka Kamiya via time-nuts wrote:

No problem. No worries. I hope you end up reading these and the other
replies again and acquire good knowledge. I know it's like drinking from
a fire-hoze, but you did ask some very relevant and fair questions.

ADEV is about the frequency stability. ADEV can be calculated using
phase or frequency measures. We tend to prefer using phase measures from
Time-Interval Counters for these things.

OK, so let's say that we want to output a counter which provides output
of frequency estimates but for a time-base which is longer than 1 s,
even if we output results every 1 s?

Classically counters could not do that. You acquired a start-value,
waited the time-base, acquired a stop-value, calculated a result to
display and then arm to get a new start-value for the next result. Such
counters will have a limit that the rate of readings will be limited by
the time-base, so if it is set to 10 s, only every 10 s and output is
produced.

To tackle this, one needs a counter that can interleave frequency
measurements, so that it generates new start-points at the update rate
even if the stop-point has not occurred. So, for a time-base of 10 s and
an update rate of 1 s, then every 1 s a new start-trigger is produced,
and then remembered until a stop trigger can be produced, at which time
the start-trigger 10 s back is used to estimate the frequency. In fact,
for this to work, the stop trigger time-stamp is also the start trigger
time-stamp for a new measurement. You can do this with any time-base
really, and the degree of interleaving only depends on the number of
start-points one can keep in memory.

There is benefits in time-measures over frequency measures when one
monitors long-term properties. Also, as one tries to create a
phase-curve from frequency estimates, any rounding off errors show in an
slope, as there is a tiny average frequency offset from round-offs. Only
really good such setups does not have significant slope.

The resolution of your counter tells you about where your 1/tau curve
will cut tau = 1 s, and it goes from there. There is a slight scaling
factor, but if we assume it is 1 for now, it is pretty simple. Your
5335A has 1 ns single-shot resolution, this gives 1E-9 at 1 s, but 1E-10
at 10 s, 1E-11 at 100 s and 1E-12 at 1000 s. You see very clearly when
the linear slope ends and "lands" in the noise, at which time the noise
becomes dominant and is giving you the interesting reading. The 5370A is
20 ps single-shot resolution, giving you a whopping 2E-11 at 1 s, 2E-12
at 10 s, 2E-13 at 100 s and 2E-14 at 1000 s. It's some serious
improvement. You are more likely to be limited by your oscillators as
ref and under test at 1000 s with that one, than the instrument itself.

I think you have contributed by asking some really good questions.

A setup I use a lot is this:

1. Connect a reference oscillator to produce a 1 Hz or 10 Hz signal and
   feed into a counter Channel A/TI-start channel. For PPS signals, I make
   sure to trigger a but up on the rising edge not to false-trigger. For
   some counters this means turning of automatic trigger and set it to 1 V
   manually. It is important that no false triggers occurs.

2. Connect a signal under test to Channel B/TI-stop. Adjust trigger to
   through-zero or up on the edge as suitable.

3. TI-mode, continuous trigger

4. Collect data in TimeLab, give TimeLab the frequency of the signal on
   B-channel, give it the time-base of the period on the A-channel.

5. Look at data as it comes in. Look at phase view, frequency view,
   wrapped phase. Look at the ADEV, how the upper end flaps with data, but
   how the same tau becomes more and more stable as it comes in.

Using even old counters this setup have helped a lot for many measures.
It is simple and sturdy for many measures. Remember to save traces, to
annotate it carefully so one can understand afterwards what one did.

Using this setup, I swapped a HP53132A (150 ps) for a HP5335A (1 ns) and
then PM6853A (2 ns) to show that a particular problem did not needed the
best counter in the house to be well characterized.

Almost. It's a good start. The first slope for lower taus is due to the
instrument for sure. If you look carefully you will notice that the
actual performance shifts around, because it is more complex than just
being instrument limit, but it is the right ball-park for that part of
the plots. For the upper end, you can be limited by your device under
test drift. This can be handled by simply letting them be turned on
longer. Sub-sequent measurement will have that rising slope move more
and more towards higher taus and thus becomming less like a limit-issue
for a certain tau.

Good spirit. DMTD takes some care, but once you learned it, it can be a
magnificent tool.

Cheers,
Magnus

It's not like drinking from a fire hydrant.  It's like drowning in hoover dam, get sucked into an inlet, pulverized by turbine blade, and getting spit out into a stream. 

One question : 

You said this:
"The resolution of your counter tells you about where your 1/tau curve
will cut tau = 1 s, and it goes from there. There is a slight scaling
factor, but if we assume it is 1 for now, it is pretty simple. Your
5335A has 1 ns single-shot resolution, this gives 1E-9 at 1 s, but 1E-10
at 10 s, 1E-11 at 100 s and 1E-12 at 1000 s. You see very clearly when
the linear slope ends and "lands" in the noise, at which time the noise
becomes dominant and is giving you the interesting reading."
By using the same logic, I can keep going up and up on longer gate time and tau keeps getting better and better.  I know at one point, inflection happens and that indicates noise taking over.  But what kind of noise (phase?) and how does that happen?  Only thing that changes in this equation is the gate time.  Everything is constant.  You mean gate time is no longer accurate enough to support the minute shift in phase?
I'm still confused about the precision (not accuracy) of the time base.  Am I still ultimately constrained by this?  Without DMTD, or some kind of pre-scaling of DUT, if I measure Rb with time base using another Rb, they are both rubber-bands, correct?
I'm infinitely curious by nature.  I need to know everything, even to a minute detail, to be satisfied.  I hope you don't get tired of this.   

(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG

On Friday, February 21, 2020, 9:26:47 PM EST, Magnus Danielson via time-nuts <time-nuts@lists.febo.com> wrote:  

Hi Taka,

On 2020-02-21 23:26, Taka Kamiya via time-nuts wrote:

No problem. No worries. I hope you end up reading these and the other
replies again and acquire good knowledge. I know it's like drinking from
a fire-hoze, but you did ask some very relevant and fair questions.

ADEV is about the frequency stability. ADEV can be calculated using
phase or frequency measures. We tend to prefer using phase measures from
Time-Interval Counters for these things.

OK, so let's say that we want to output a counter which provides output
of frequency estimates but for a time-base which is longer than 1 s,
even if we output results every 1 s?

Classically counters could not do that. You acquired a start-value,
waited the time-base, acquired a stop-value, calculated a result to
display and then arm to get a new start-value for the next result. Such
counters will have a limit that the rate of readings will be limited by
the time-base, so if it is set to 10 s, only every 10 s and output is
produced.

To tackle this, one needs a counter that can interleave frequency
measurements, so that it generates new start-points at the update rate
even if the stop-point has not occurred. So, for a time-base of 10 s and
an update rate of 1 s, then every 1 s a new start-trigger is produced,
and then remembered until a stop trigger can be produced, at which time
the start-trigger 10 s back is used to estimate the frequency. In fact,
for this to work, the stop trigger time-stamp is also the start trigger
time-stamp for a new measurement. You can do this with any time-base
really, and the degree of interleaving only depends on the number of
start-points one can keep in memory.

There is benefits in time-measures over frequency measures when one
monitors long-term properties. Also, as one tries to create a
phase-curve from frequency estimates, any rounding off errors show in an
slope, as there is a tiny average frequency offset from round-offs. Only
really good such setups does not have significant slope.

The resolution of your counter tells you about where your 1/tau curve
will cut tau = 1 s, and it goes from there. There is a slight scaling
factor, but if we assume it is 1 for now, it is pretty simple. Your
5335A has 1 ns single-shot resolution, this gives 1E-9 at 1 s, but 1E-10
at 10 s, 1E-11 at 100 s and 1E-12 at 1000 s. You see very clearly when
the linear slope ends and "lands" in the noise, at which time the noise
becomes dominant and is giving you the interesting reading. The 5370A is
20 ps single-shot resolution, giving you a whopping 2E-11 at 1 s, 2E-12
at 10 s, 2E-13 at 100 s and 2E-14 at 1000 s. It's some serious
improvement. You are more likely to be limited by your oscillators as
ref and under test at 1000 s with that one, than the instrument itself.

I think you have contributed by asking some really good questions.

A setup I use a lot is this:

1. Connect a reference oscillator to produce a 1 Hz or 10 Hz signal and
   feed into a counter Channel A/TI-start channel. For PPS signals, I make
   sure to trigger a but up on the rising edge not to false-trigger. For
   some counters this means turning of automatic trigger and set it to 1 V
   manually. It is important that no false triggers occurs.

2. Connect a signal under test to Channel B/TI-stop. Adjust trigger to
   through-zero or up on the edge as suitable.

3. TI-mode, continuous trigger

4. Collect data in TimeLab, give TimeLab the frequency of the signal on
   B-channel, give it the time-base of the period on the A-channel.

5. Look at data as it comes in. Look at phase view, frequency view,
   wrapped phase. Look at the ADEV, how the upper end flaps with data, but
   how the same tau becomes more and more stable as it comes in.

Using even old counters this setup have helped a lot for many measures.
It is simple and sturdy for many measures. Remember to save traces, to
annotate it carefully so one can understand afterwards what one did.

Using this setup, I swapped a HP53132A (150 ps) for a HP5335A (1 ns) and
then PM6853A (2 ns) to show that a particular problem did not needed the
best counter in the house to be well characterized.

Almost. It's a good start. The first slope for lower taus is due to the
instrument for sure. If you look carefully you will notice that the
actual performance shifts around, because it is more complex than just
being instrument limit, but it is the right ball-park for that part of
the plots. For the upper end, you can be limited by your device under
test drift. This can be handled by simply letting them be turned on
longer. Sub-sequent measurement will have that rising slope move more
and more towards higher taus and thus becomming less like a limit-issue
for a certain tau.

Good spirit. DMTD takes some care, but once you learned it, it can be a
magnificent tool.

Cheers,
Magnus

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Hi Taka,

On 2020-02-22 04:55, Taka Kamiya via time-nuts wrote:

Hmm, not exactly what I had hoped for as your experience... whatever,
hope it is worth it.

OK. Good question.

The instrument noise in itself can be while phase noise and flicker
phase noise. The resolution limit will be a systematic disturbance. All
these three has the same 1/tau slope so from these three, nothing
happens as tau increases. At some point naturally will thermal
instability come in, but that will be another systematic, but it will be
hard to cancel. So that is the limit of the instrument.

However, the noise of the reference and DUT will dominate for larger
taus, and thus it will be good enough to measure that noise. Besides,
length of measurement becomes a limit.

There are ways to get around it.

Now, what you can do is to do a three-cornered hat measurement.
Essentially you measure three sources at once as three pair-wise
measurements. You calculate your ADEV of each pair. Now, as you have the
noises n1, n2 and n3 of each source, measurement m1 = n1+n2, m2 = n1+n3
and m3 = n2+n3. This equation problem can be solved to bring out n1, n2
and n3 separate. The trouble is, this does not always work out as
precisely as one would like, because the measurements isn't precise and
well converged. Therefore it is a bit of sensitive process, but if one
gets it working, you can achieve the separation.

So far, you ask relevant questions that can be given an answer. Being a
curious person myself, I've digged down.

Cheers,
Magnus

As I understand, 3 cornered hat is nothing more than system of equations where you have 3 variables and 3 equations, that allows for solving for each.  I'm going to hold off on that one.  I forgot about thermal and equipment's internal noise.  It all makes sense.  I hope to be doing some measuring this weekend if all works as planned (hope, hope, hope....)
I mentioned earlier, I have various standards.  I also have TAPR's board to create 1 pps from any standards I have.  To start and follow your last example on how-to, what would you recommend for DUT and the standard?  I'd like to do one that I can show you, and immediately say if it's what you'd expect or not.
I have newly repaired HP105B, PRS10, Efratom FRK-c?, LPRO-101, and various GPSDO including T-bolt proper.  For the counter, I think I'll use the old HP interval counter, rather than 50132A.  The latter is all menu driven.  It's so easy to mis-set or otherwise screw it up and not notice it.  HP5370A is all switches and knobs.  How long of measurement?  In my experience, 2 days will show the inflection point. 

(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG

On Saturday, February 22, 2020, 3:03:37 AM EST, Magnus Danielson via time-nuts <time-nuts@lists.febo.com> wrote:  

Hi Taka,

On 2020-02-22 04:55, Taka Kamiya via time-nuts wrote:

Hmm, not exactly what I had hoped for as your experience... whatever,
hope it is worth it.

OK. Good question.

The instrument noise in itself can be while phase noise and flicker
phase noise. The resolution limit will be a systematic disturbance. All
these three has the same 1/tau slope so from these three, nothing
happens as tau increases. At some point naturally will thermal
instability come in, but that will be another systematic, but it will be
hard to cancel. So that is the limit of the instrument.

However, the noise of the reference and DUT will dominate for larger
taus, and thus it will be good enough to measure that noise. Besides,
length of measurement becomes a limit.

There are ways to get around it.

Now, what you can do is to do a three-cornered hat measurement.
Essentially you measure three sources at once as three pair-wise
measurements. You calculate your ADEV of each pair. Now, as you have the
noises n1, n2 and n3 of each source, measurement m1 = n1+n2, m2 = n1+n3
and m3 = n2+n3. This equation problem can be solved to bring out n1, n2
and n3 separate. The trouble is, this does not always work out as
precisely as one would like, because the measurements isn't precise and
well converged. Therefore it is a bit of sensitive process, but if one
gets it working, you can achieve the separation.

So far, you ask relevant questions that can be given an answer. Being a
curious person myself, I've digged down.

Cheers,
Magnus

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Hi Taka,

On 2020-02-22 16:08, Taka Kamiya via time-nuts wrote:

Good. As you get measures, more and more of this will sink in as you see
them.

I would start doing a few 1 hour measurements. Only when the measurement
makes sense you extend it.

The HP53132A requires you to set trigger to manual and then adjust
trigger level manually. A little painful in the beginning, but you learn
to do it. In the beginning it can be good to use an oscilloscope to
learn where a good trigger point is.

HP5370 will work. Use PPS from one of your GPSDOs for start. Use any
oscillator of choice as DUT. Once the measurement on one makes sense,
keep that and go to the next.

Mistakes in setup causes huge face-jumps, which is why wrapped phase
(w), phase (p) and frequency (f) is useful as one learns. After learning
to set things up, one end up not using wrapped phase anymore, one sees
the error and just fixes it. Use the 10 MHz output of a counter with no
external clock attached as a clock with worse perfromance than rubidiums.

Cheers,
Magnus

One question for Magnus.

Ch A start - pps (standard)Ch B stop - DUT
On item 4, you said "frequency of the signal on time B".  That much is obvious.  But then you said: "give it the time-base of the period on the A-channel".  Will you explain this?
Say I give 1 Hz, period is 1s.  Say I give 10Hz, period is 0.1s.  Is this what you mean?
I'm using HP5370A.  This instruction is valid on this TI counter, correct??

A request for everyone:
I am conducting an one hour measurement on HP105B.  Does anyone have 1 hour plot of this signal generator handy?  If so, will you DM me a copy?  For some reason, I cannot find one on the great Internet.

------------------- clip from Magnus's previous email------------------
A setup I use a lot is this:

1. Connect a reference oscillator to produce a 1 Hz or 10 Hz signal and
   feed into a counter Channel A/TI-start channel. For PPS signals, I make
   sure to trigger a but up on the rising edge not to false-trigger. For
   some counters this means turning of automatic trigger and set it to 1 V
   manually. It is important that no false triggers occurs.

2. Connect a signal under test to Channel B/TI-stop. Adjust trigger to
   through-zero or up on the edge as suitable.

3. TI-mode, continuous trigger

4. Collect data in TimeLab, give TimeLab the frequency of the signal on
   B-channel, give it the time-base of the period on the A-channel.

5. Look at data as it comes in. Look at phase view, frequency view,
   wrapped phase. Look at the ADEV, how the upper end flaps with data, but
   how the same tau becomes more and more stable as it comes in.---------------------

(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG

On Friday, February 21, 2020, 9:26:47 PM EST, Magnus Danielson via time-nuts <time-nuts@lists.febo.com> wrote:  

Hi Taka,

On 2020-02-21 23:26, Taka Kamiya via time-nuts wrote:

No problem. No worries. I hope you end up reading these and the other
replies again and acquire good knowledge. I know it's like drinking from
a fire-hoze, but you did ask some very relevant and fair questions.

ADEV is about the frequency stability. ADEV can be calculated using
phase or frequency measures. We tend to prefer using phase measures from
Time-Interval Counters for these things.

OK, so let's say that we want to output a counter which provides output
of frequency estimates but for a time-base which is longer than 1 s,
even if we output results every 1 s?

Classically counters could not do that. You acquired a start-value,
waited the time-base, acquired a stop-value, calculated a result to
display and then arm to get a new start-value for the next result. Such
counters will have a limit that the rate of readings will be limited by
the time-base, so if it is set to 10 s, only every 10 s and output is
produced.

To tackle this, one needs a counter that can interleave frequency
measurements, so that it generates new start-points at the update rate
even if the stop-point has not occurred. So, for a time-base of 10 s and
an update rate of 1 s, then every 1 s a new start-trigger is produced,
and then remembered until a stop trigger can be produced, at which time
the start-trigger 10 s back is used to estimate the frequency. In fact,
for this to work, the stop trigger time-stamp is also the start trigger
time-stamp for a new measurement. You can do this with any time-base
really, and the degree of interleaving only depends on the number of
start-points one can keep in memory.

There is benefits in time-measures over frequency measures when one
monitors long-term properties. Also, as one tries to create a
phase-curve from frequency estimates, any rounding off errors show in an
slope, as there is a tiny average frequency offset from round-offs. Only
really good such setups does not have significant slope.

The resolution of your counter tells you about where your 1/tau curve
will cut tau = 1 s, and it goes from there. There is a slight scaling
factor, but if we assume it is 1 for now, it is pretty simple. Your
5335A has 1 ns single-shot resolution, this gives 1E-9 at 1 s, but 1E-10
at 10 s, 1E-11 at 100 s and 1E-12 at 1000 s. You see very clearly when
the linear slope ends and "lands" in the noise, at which time the noise
becomes dominant and is giving you the interesting reading. The 5370A is
20 ps single-shot resolution, giving you a whopping 2E-11 at 1 s, 2E-12
at 10 s, 2E-13 at 100 s and 2E-14 at 1000 s. It's some serious
improvement. You are more likely to be limited by your oscillators as
ref and under test at 1000 s with that one, than the instrument itself.

I think you have contributed by asking some really good questions.

A setup I use a lot is this:

1. Connect a reference oscillator to produce a 1 Hz or 10 Hz signal and
   feed into a counter Channel A/TI-start channel. For PPS signals, I make
   sure to trigger a but up on the rising edge not to false-trigger. For
   some counters this means turning of automatic trigger and set it to 1 V
   manually. It is important that no false triggers occurs.

2. Connect a signal under test to Channel B/TI-stop. Adjust trigger to
   through-zero or up on the edge as suitable.

3. TI-mode, continuous trigger

4. Collect data in TimeLab, give TimeLab the frequency of the signal on
   B-channel, give it the time-base of the period on the A-channel.

5. Look at data as it comes in. Look at phase view, frequency view,
   wrapped phase. Look at the ADEV, how the upper end flaps with data, but
   how the same tau becomes more and more stable as it comes in.

Using even old counters this setup have helped a lot for many measures.
It is simple and sturdy for many measures. Remember to save traces, to
annotate it carefully so one can understand afterwards what one did.

Using this setup, I swapped a HP53132A (150 ps) for a HP5335A (1 ns) and
then PM6853A (2 ns) to show that a particular problem did not needed the
best counter in the house to be well characterized.

Almost. It's a good start. The first slope for lower taus is due to the
instrument for sure. If you look carefully you will notice that the
actual performance shifts around, because it is more complex than just
being instrument limit, but it is the right ball-park for that part of
the plots. For the upper end, you can be limited by your device under
test drift. This can be handled by simply letting them be turned on
longer. Sub-sequent measurement will have that rising slope move more
and more towards higher taus and thus becomming less like a limit-issue
for a certain tau.

Good spirit. DMTD takes some care, but once you learned it, it can be a
magnificent tool.

Cheers,
Magnus

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Hi,

On 2020-02-29 23:10, Taka Kamiya via time-nuts wrote:

Yes. Exactly.

Yes. It will work.

I have one of the 00105 oscillator ,as mounted and free-running in a
HP5065A, against hydrogen maser at hand. I can locate that and send you
if you wish. It's longer than 1 hour, but you get additional precision
from this.

Cheers,
Magnus

YES, please.  tkamiya9@yahoo.com.
So far, I've taken HP105B and did adev frequency reading based, T.I. based adev, and while at it, I am doing PRS-10 T.I. based.
I have a question.  My 1 second reference for channel A is coming from GPS based 1 second.  I understand it's only 10E-8 precision on second to second basis?  Is this sufficient for OCXO and Rb based oscillators?

(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG

On Saturday, February 29, 2020, 7:21:28 PM EST, Magnus Danielson <magnus@rubidium.se> wrote:  

Hi,

On 2020-02-29 23:10, Taka Kamiya via time-nuts wrote:

Yes. Exactly.

Yes. It will work.

I have one of the 00105 oscillator ,as mounted and free-running in a
HP5065A, against hydrogen maser at hand. I can locate that and send you
if you wish. It's longer than 1 hour, but you get additional precision
from this.

Cheers,
Magnus

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.