Re: [time-nuts] HP 10811 Response I Replies

2011-09-24 Thread Rick Karlquist
WarrenS wrote:
> Does your Mode B 10811 use a different xtral or same xtral, different
> frequency?
> What does Mode B do better, ... and worse?
> Why was it not used in the 10811?

Mode B is the same crystal on a different frequency
(about 10.95 MHz).  It does not have a turnover and
the tempco is much higher than mode C.  It makes
a very sensitive thermometer and is therefore useful
for evaluating the oven.  The reason is not used in
a production 10811 is obviously that for timebase
use, you definitely don't want a high tempco.

Rick


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Re: [time-nuts] HP 10811 Response I Replies

2011-09-24 Thread WarrenS
Does your Mode B 10811 use a different xtral or same xtral, different 
frequency?

What does Mode B do better, ... and worse?
Why was it not used in the 10811?


When trouble shooting a freq stability problem, usually the more data the 
better.

What can really help to narrow down the cause or see the cause/effect,
is to study a High Speed (100+ sps), High Resolution (>1e-12) plot of the 
frequency change with time.
That way one can see if the freq change is instantaneous or happens in 
steps, is the change monotonic, if there is a time constant to the freq 
change what is the TC's value and shape, is the freq change in fixed values 
or random noisy steps and now and if the freq returns to the original value.
With a good freq plot, the source of the problem can often be narrow down to 
a single possible source.
And the best tool that I know of for making that kind of plot is a TPLL-2.0 
tester.


Here is a freq plot that has nothing to do with the existing problem,
It is just an example where a TPLL-1.0  freq plot is useful in identifying 
the source of some "noise".



and another example showing a plot of purposely induced "Noise" that only a 
few instruments could even measure:



ws

**


WarrenS wrote:


I have to wonder if the unit being tested had its high impedance oven
control points lifted off the PCB board and on Teflon standoffs like the
production units?

ws


It was a production unit, no modifications whatsoever.
The oven change is an interesting theory; I never thought of that.
I have a mode B 10811 on hand that I could use to test that theory.

Rick Karlquist N6RK







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Re: [time-nuts] HP 10811 Response I Replies

2011-09-23 Thread Magnus Danielson

On 23/09/11 23:25, Rick Karlquist wrote:

Magnus Danielson wrote:

On 23/09/11 05:40, Richard (Rick) Karlquist wrote:




Blowing on the case? Did you consider the increased cooling that higher
humidity provides?

Cheers,
Magnus



Against, the frequency change we saw was considerably more
than what we got from changing the temperature 50 degrees.


Which would not be well explained by that effect, true.

Cheers,
Magnus

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Re: [time-nuts] HP 10811 Response I Replies

2011-09-23 Thread J. Forster
Maybe you have a bad joint in the tuning circuit and the humidity makes
the actual tuning voltage vary.

-John

===


> Magnus Danielson wrote:
>> On 23/09/11 05:40, Richard (Rick) Karlquist wrote:
>
>>
>> Blowing on the case? Did you consider the increased cooling that higher
>> humidity provides?
>>
>> Cheers,
>> Magnus
>>
>
> Against, the frequency change we saw was considerably more
> than what we got from changing the temperature 50 degrees.
>
> rick
>
>
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Re: [time-nuts] HP 10811 Response I Replies

2011-09-23 Thread Rick Karlquist
Magnus Danielson wrote:
> On 23/09/11 05:40, Richard (Rick) Karlquist wrote:

>
> Blowing on the case? Did you consider the increased cooling that higher
> humidity provides?
>
> Cheers,
> Magnus
>

Against, the frequency change we saw was considerably more
than what we got from changing the temperature 50 degrees.

rick


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Re: [time-nuts] HP 10811 Response I Replies

2011-09-23 Thread Rick Karlquist
WarrenS wrote:
>
>
> I have to wonder if the unit being tested had its high impedance oven
> control points lifted off the PCB board and on Teflon standoffs like the
> production units?
>
> ws
>
It was a production unit, no modifications whatsoever.
The oven change is an interesting theory; I never thought of that.
I have a mode B 10811 on hand that I could use to test that theory.

Rick Karlquist N6RK


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Re: [time-nuts] HP 10811 Response I Replies

2011-09-23 Thread WarrenS


I have made plots of the effects of everything I can find that effects the 
freq of a HP10811.
Most things are much slower than minutes, more like an hour time constant, 
such as anything effecting the outside case's temperature
OR the effect is much faster than minutes, things such as voltage and load 
changes.
The only thing that I've seen that responds to instantaneous changes within 
"minutes" is the oven loop.


If  one assumed Rick's data is correct, then one likely cause of what was 
happing (not why it was happening)

is that the oven set point temperature was changed.
That is the ONLY thing I've seen that can cause that sort of freq change 
over that kind of time period.
It does not take much, a degree or so change in the oven's set point could 
do it.
If I saw a real plot of freq change with time, I could be more sure of the 
cause.


But even if the exact reason is not known, This string does show,
If you want the best from your 10811 then it is NOT a good idea to heat it 
up in an oven to near its limits and then dump in water.


I have to wonder if the unit being tested had its high impedance oven 
control points lifted off the PCB board and on Teflon standoffs like the 
production units?
If not just blowing with your mouth on theses sensitive points could cause 
this type of freq change.


ws

**



"Within minutes the frequency changed more than the spec"
Rick


For humidity to get thru something like that it takes weeks or more IF 
it does it at all.
That fast of reaction, Sure sounds like some other effect like blowing a 
little air on the case or loading the osc output with water in the 
output cable etc, etc.
I think it is safe to say the effect was not due to water inside, unless 
there was a hole.

ws

***


The effect we saw was like parts in 10^8 of something. Way too big
to be related to output loading or air on the case. In any event,
the air blowing on the case was constant during the test.
We saw that when we didn't even try to seal the 10811 and also
when we tried to seal it.
Richard (Rick) Karlquist

**


Blowing on the case? Did you consider the increased cooling that higher 
humidity provides?

Cheers,
Magnus





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Re: [time-nuts] HP 10811 Response I Replies

2011-09-23 Thread Magnus Danielson

On 23/09/11 05:40, Richard (Rick) Karlquist wrote:

On 9/22/2011 5:17 PM, ws at Yahoo wrote:

Within minutes the frequency changed more than the spec


For humidity to get thru something like that it takes weeks or more it
does it at all.
That fast of reaction, Sure sounds like some other effect like blowing a
little air on the case or loading the osc output with water in the
output cable etc, etc.
I think it is safe to say the effect was not due to water inside, unless
there was a hole.

ws


The effect we saw was like parts in 10^8 of something. Way too big
to be related to output loading or air on the case. In any event,
the air blowing on the case was constant during the test.
We saw that when we didn't even try to seal the 10811 and also
when we tried to seal it.


Blowing on the case? Did you consider the increased cooling that higher 
humidity provides?


Cheers,
Magnus

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Re: [time-nuts] HP 10811 Response I Replies

2011-09-22 Thread Richard (Rick) Karlquist

On 9/22/2011 5:17 PM, ws at Yahoo wrote:

Within minutes the frequency changed more than the spec


For humidity to get thru something like that it takes weeks or more it
does it at all.
That fast of reaction, Sure sounds like some other effect like blowing a
little air on the case or loading the osc output with water in the
output cable etc, etc.
I think it is safe to say the effect was not due to water inside, unless
there was a hole.

ws


The effect we saw was like parts in 10^8 of something.  Way too big
to be related to output loading or air on the case.  In any event,
the air blowing on the case was constant during the test.
We saw that when we didn't even try to seal the 10811 and also
when we tried to seal it.

Rick Karlquist

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Re: [time-nuts] HP 10811 Response I Replies

2011-09-22 Thread Richard (Rick) Karlquist



On 9/22/2011 4:17 PM, Chuck Harris wrote:

You had a leak. If epoxy was really as bad as you indicate,
it would not be usable for holding pressure, or mild vacuum,
and yet it is. Somehow, someway you left a big hole in the
bucket.

-Chuck Harris


Soda pop bottles hold pressure for years.  Vacuum packed
nuts hold vacuum for years.  I hope you're not going to
tell me that therefore those containers are hermetic.
Maybe we screwed up the epoxy somehow, although we tried
re-epoxying several times just in case of that.

In any event, an unsealed 10811 was humidity sensitive
according to our tests.

Rick

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Re: [time-nuts] HP 10811 Response I Replies

2011-09-22 Thread Neville Michie

Humidity is a confusing subject to many engineers and scientists.
Unlike most parameters it is a quantity with two input variables,
concentration and temperature. There are many ways to combine
these to give different units.
As a research scientist I spent most of my career working with
"composite materials" which exhibit great sensitivity to humidity.
Most composite materials respond to the Relative Humidity with
only a small temperature dependance. So 80% RH has the same
effect at any temperature. Note that the Absolute Humidity varies
exponentially with temperature.
For a fixed Absolute Humidity (say 10gms /m3) and at 70% RH the
relative humidity changes about 10% per degree celsius. So if you
have a sealed container with some water vapour in it the RH will vary
about 10% per C*.
If you have a fixed ambient humidity, a heated enclosure will have a
humidity that falls 10%/K as the temperature rises.
Now there are many grandiose "environmental chambers" sold to
scientists and engineers that perform poorly. They have internal
temperature gradients, so even if the concentration of water vapour
is uniform the distribution of relative humidity is not.
If a chamber set to 80% RH has a 2 degree gradient it could have  
internal

condensation.
The problems are made worse by the plethora of nearly useless humidity
probes made by manufacturers who are having a bidding war based on
claimed specs.
Since there are very few facilities to calibrate humidity sensors,  
and no
company can make a dollar by having their humidity measured more  
accurately,

there is no pressure to improve instrument quality and the situation
remains that there is a lot of misunderstanding about humidity.

The instruments I have built have an inaccuracy of less than 0.1% RH,
and I have built isothermal chambers that can be programmed to 0.1% RH.
They are based on calculable processes for calibration, and so have
absolute calibration.

In the case of quartz crystals in ovens, when the oven is 30K above  
ambient

the relative humidity is very low, so you would expect there to be very
little absorbed or adsorbed water to interfere with stability. The  
main effects are
surface leakage on hydrophilic surfaces and dielectric absorption in  
composite
material insulators. There is a second order effect that the  
dielectric constant
of air changes with absolute humidity. Humidity sensitivity would  
seem to me
to be a problem of the measurement system rather than the item being  
tested.


Cheers, Neville Michie





On 23/09/2011, at 9:07 AM, Rick Karlquist wrote:


Perry Sandeen wrote:

Wrote: Doing what you describe will result in a very sensitive  
humidity

sensor, having eliminated the thermometer effect.

I do not understand.  I believed that since the OCXO temperature  
will be
substationally higher than the surrounding temps, any residual  
moisture
would migrate to a lower temperature.  The fiberglass insulation  
inside


Heating up a space does not change the absolute humidity AFAIK.
It only changes the relative humidity.  We did tests where we
"sealed" a 10811 inside a box that was held together with so-called
"hermetic" epoxy.  We put it in an environmental chamber at a
constant temperature and constant low humidity and let it stabilize.
We then increased the humidity to something like 80%,
while holding the temperature constant.  Within
minutes the frequency changed more than the spec for the entire
temperature range.  Therefore, you should do your experiment with
the hermetic version of the 10811.  The hermetic version is soldered
shut, rather than using epoxy, which turns out not to be hermetic,
no matter what they claim.

Rick Karlquist


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Re: [time-nuts] HP 10811 Response I Replies

2011-09-22 Thread ws at Yahoo

Within minutes the frequency changed more than the spec


For humidity to get thru something like that it takes weeks or more it does 
it at all.
That fast of reaction, Sure sounds like some other effect like blowing a 
little air on the case or loading the osc output with water in the output 
cable etc, etc.
I think it is safe to say the effect was not due to water inside, unless 
there was a hole.


ws

*
Chuck Harris cfharris at erols.com

You had a leak.  If epoxy was really as bad as you indicate,
it would not be usable for holding pressure, or mild vacuum,
and yet it is.  Somehow, someway you left a big hole in the
bucket.

-Chuck Harris


Rick Karlquist wrote:

Perry Sandeen wrote:


Wrote: Doing what you describe will result in a very sensitive humidity
sensor, having eliminated the thermometer effect.

I do not understand.  I believed that since the OCXO temperature will be
substationally higher than the surrounding temps, any residual moisture
would migrate to a lower temperature.  The fiberglass insulation inside


Heating up a space does not change the absolute humidity AFAIK.
It only changes the relative humidity.  We did tests where we
"sealed" a 10811 inside a box that was held together with so-called
"hermetic" epoxy.  We put it in an environmental chamber at a
constant temperature and constant low humidity and let it stabilize.
We then increased the humidity to something like 80%,
while holding the temperature constant.  Within
minutes the frequency changed more than the spec for the entire
temperature range.  Therefore, you should do your experiment with
the hermetic version of the 10811.  The hermetic version is soldered
shut, rather than using epoxy, which turns out not to be hermetic,
no matter what they claim.

Rick Karlquist





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Re: [time-nuts] HP 10811 Response I Replies

2011-09-22 Thread ws at Yahoo
A problem I've seen when using the hermetic sealed soldered version of the 
10811 from a dual oven unit,
 is when the case is sealed the osc makes a good barometer because of changes 
in its case due to barometric changes.
A 1 inch difference (such as 30 to 29) caused something on the order of 1e-11 
freg change.
To see the effect just need to put a little pressure on  the case 
So now I'm trying to determine which is worse, leaving the freq adj screw tight 
and sealed or leaking a little, inside a box containing desiccant.

ws

**
> 
> Heating up a space does not change the absolute humidity AFAIK.
> It only changes the relative humidity.  We did tests where we
> "sealed" a 10811 inside a box that was held together with so-called
> "hermetic" epoxy.  We put it in an environmental chamber at a
> constant temperature and constant low humidity and let it stabilize.
> We then increased the humidity to something like 80%,
> while holding the temperature constant.  Within
> minutes the frequency changed more than the spec for the entire
> temperature range.  Therefore, you should do your experiment with
> the hermetic version of the 10811.  The hermetic version is soldered
> shut, rather than using epoxy, which turns out not to be hermetic,
> no matter what they claim.
> 
> Rick Karlquist
> 
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Re: [time-nuts] HP 10811 Response I Replies

2011-09-22 Thread Chuck Harris

You had a leak.  If epoxy was really as bad as you indicate,
it would not be usable for holding pressure, or mild vacuum,
and yet it is.  Somehow, someway you left a big hole in the
bucket.

-Chuck Harris

Rick Karlquist wrote:

Perry Sandeen wrote:


Wrote: Doing what you describe will result in a very sensitive humidity
sensor, having eliminated the thermometer effect.

I do not understand.  I believed that since the OCXO temperature will be
substationally higher than the surrounding temps, any residual moisture
would migrate to a lower temperature.  The fiberglass insulation inside


Heating up a space does not change the absolute humidity AFAIK.
It only changes the relative humidity.  We did tests where we
"sealed" a 10811 inside a box that was held together with so-called
"hermetic" epoxy.  We put it in an environmental chamber at a
constant temperature and constant low humidity and let it stabilize.
We then increased the humidity to something like 80%,
while holding the temperature constant.  Within
minutes the frequency changed more than the spec for the entire
temperature range.  Therefore, you should do your experiment with
the hermetic version of the 10811.  The hermetic version is soldered
shut, rather than using epoxy, which turns out not to be hermetic,
no matter what they claim.

Rick Karlquist


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Re: [time-nuts] HP 10811 Response I Replies

2011-09-22 Thread Rick Karlquist
Perry Sandeen wrote:

> Wrote: Doing what you describe will result in a very sensitive humidity
> sensor, having eliminated the thermometer effect.
>
> I do not understand.  I believed that since the OCXO temperature will be
> substationally higher than the surrounding temps, any residual moisture
> would migrate to a lower temperature.  The fiberglass insulation inside

Heating up a space does not change the absolute humidity AFAIK.
It only changes the relative humidity.  We did tests where we
"sealed" a 10811 inside a box that was held together with so-called
"hermetic" epoxy.  We put it in an environmental chamber at a
constant temperature and constant low humidity and let it stabilize.
We then increased the humidity to something like 80%,
while holding the temperature constant.  Within
minutes the frequency changed more than the spec for the entire
temperature range.  Therefore, you should do your experiment with
the hermetic version of the 10811.  The hermetic version is soldered
shut, rather than using epoxy, which turns out not to be hermetic,
no matter what they claim.

Rick Karlquist


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