So the cold ambient temperature was simulating the retuning of the oven
temperature as described here:
http://www.realhamradio.com/z3801a-turning-point.htm and the particular
unit graphed in the article happened to have the oven temperature a bit
high. Sounds like a sunny deck and a cooler of ice (plus your beverage
of choice, of course) would be useful test equipment to check your 10811
to see if retuning the oven is necessary.
Warren:
On your list of things to do, checking that the crystal inflection point
matches the oven temperature should probably come before adjusting the
thermal gain.
Ed
Bob Camp wrote:
Hi
The "best at tha cold end" was a function of where the oven was relative to the turn temperature of the crystal. There's actually a bit more to it than that, but that's the simple answer.
Bottom line - the temperature curve of *your* 10811 likely will be a bit different than what they show.
A cooler, a small bag of ice, a thermometer, and a sunny deck in the summer
will give you a temperature ramp. That and some patience will give you a pretty
good idea of what your oscillator actually looks like. Other techniques may
also work, most provide less of an excuse to drink beer during the
experiment.....
Bob
On Mar 28, 2010, at 4:20 PM, Ed Palmer wrote:
Have you considered putting the 10811 in a deep freeze? :-)
The March 1981 issue of the HP Journal includes an in-depth article on the
10811A/B. It talks about the heater, thermal gain, optimization, etc. Figure
5 on page 21 shows a graph of ambient temperature vs. frequency change. The
figure shows that the lowest frequency changes occur around an ambient
temperature of -20C! Maybe instead of an outer oven we need to use a Peltier
cooler.
http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1981-03.pdf
Ed
WarrenS wrote:
Richard wrote approx
... This is how the Thermal gain can be increase to eliminate temperature drift
over typical room variations.
Thank You
Great Idea. Wish I would of thought of that. But Yeah almost as good, Now I
know it, can take that away.
That is the type of useful and not obvious information that I was hoping for.
THANKS SO MUCH
That goes to the top of my list to find a procedure to do it.
You are a true Nut hero.
WS
********************
----- Original Message ----- From: "Richard H McCorkle" <mccor...@ptialaska.net>
To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com>
Sent: Sunday, March 28, 2010 11:32 AM
Subject: Re: [time-nuts] Making a HP 10811 better
Warren,
One thing Rick Karlquist pointed out is a higher thermal gain can be
realized to minimize temperature effects by optimizing the heater
transistor balance. The 10811A/B Quartz Crystal Oscillator Operating
& Service Manual describes the balance circuit in section 8-40. The
two heater transistors are not equally spaced with Q7 being closer
to the crystal so rather than 50% of the current flowing thru both
heater transistors the current in Q8 is set slightly higher at 57%
+/- 2% in a production unit to apply equal heat at the crystal.
The typical thermal gain on a production unit is on the order of
100 without optimization, but gains of 1000 or more are possible if
the heater transistor balance is optimized. I was fortunate enough
to obtain a set of single oven 10811-60158 units that had been
optimized by an HP engineer for different temperature sensitivities
and tagged as such. The unit optimized for maximum thermal gain is
virtually immune to typical room temperature variations. A second
unit optimized for double oven operation has much lower thermal
gain and makes a great unit for testing software temperature
compensation routines and outer oven designs.
Richard
Time to Push the "reset button"
I hope we can all agree what one is not going to find an axes that makes the
Frequency modulation that is caused by tapping on the Oscillator, or the
table or the airplane, or the boat, to go away, for whatever reasons.
Sorry, what I've been falsely referring to as the zero-G axes is actually
the "Zero Tilt" angle axes.
I have not had problems with My G changing short term, (BUT it would be
interesting to see if I can detect the moon overhead).
What I do have is some problems with the Osc tilt angle changing due to its
position changing a little.
It is the Zero-tilt angle axes that works over a very small change of a few
degrees at most.
On the other hand, the Zero tilt axes is in fact the Max G sensitivity axes.
If you want the Min G sensitivity axes, so that there is no change when
turning the Osc over, That is 90 deg from the zero tilt axes, which is also
how you make the Osc into its best Tilt angle meter.
What happens at any G value that is between +1 and -1, or is greater than +1
or -1, I have not tested for, so I'm not qualified to speculate.
I am only stating that there is an axes where the Oscillator frequency is
exactly the same when you turn it exactly over.
AND this is NOT the axes you want to have, If it is going to be tilted even
a sub sub fraction of a deg.
Now can we get back to making the 10811 Osc better?
ws
**********************
*************************
From: "Bob Camp" <li...@rtty.us>
Hi
If your zero g axis only works over a 1/100 G range, you are looking at
something other than acceleration. If you have found an axis with a zero, it
should be a just as much a null at 1 mG as at 1 G as at 10 G's. It's also
possible that your "zero" is actually a minimum below your test resolution
and higher G's bring it up to the point you can measure it. There's no
guarantee of a zero being there.
Hitting the oscillator makes it vibrate in all three axis, that's not going
to be suppressed regardless of which way you have it mounted.
Bob
*********************
On Mar 28, 2010, at 12:42 AM, WarrenS wrote:
Humm,
Have to admit, I did not consider that as a possibility before.
Maybe when I tap on it, its not microphonics after all that cause the freq
to modulate, but the vibration of the inside stuff that is warming it up.
For every action there is a reaction and for every nut there is a
wing-it-nut.
ws
*****************
Hi
If that's the result you are getting, you are measuring something other
than G sensitivity. Temperature effects possibly.
Bob
****************
On Mar 27, 2010, at 11:02 PM, WarrenS wrote:
Just a friendly comment about the Zero G turn over point and Vibration
Like Zero temp turn over, Special orientation of the OSC ONLY works good
over a VERY SMALL range, (maybe a 1/100 of G change)
It would not help vibration and has no effect on microphonics which are
likely a bigger problem anyway.
Try taping you Osc, It's freq will go crazy if monitoring it at high
resolutions and bandwidths
ws
************************
Hi
The concrete basement floor is your friend.
Stay as far away from the blower on the furnace as you can. If you have a
drop forge in the basement avoid it as well :)....
You will indeed have a seismograph, but not a very useful one. There's
not a lot of G's at seismic frequencies unless you live in an active
earthquake region. The fundamentals of G's and displacement vs frequency
are in your favor in that respect.
Bob
On Mar 27, 2010, at 12:42 PM, Stanley Reynolds wrote:
Is the source of the vibration important ? I'm thinking that any
vibration that is not on the same axis as gravity. Walking across the
lab vs a fan that is out of balance close by. Would a suspended mass
mounting help with vibration isolation and damping with rubber pads and
springs or would that just make a seismograph ?
Stanley
----- Original Message ----
From: Peter Vince <pvince at theiet.org>
To: Discussion of precise time and frequency measurement <time-nuts at
febo.com>
Sent: Sat, March 27, 2010 10:51:07 AM
Subject: Re: [time-nuts] Making a HP 10811 better
Warren,
If you turn over an oscillator, is the frequency change
completely reversible (to your "under 1e-12 resolution") when it is
restored? Thinking aloud, if an hour-glass is turned over twice, the
final level will be the same, but the grains will be mixed. A quartz
crystal, however, is solid, so hopefully nothing actually moves.
Presumably the zero-G axis is with the axis of oscillation at 90
degrees to gravity?
Peter (the "other" one :-)
Another thing I use it for is to test high resolution Freq meters.
Using a calibrated wedge that I can then slide under one edge of the
zero-G
Osc box, I can
make small, variable, repeatable, freq changes of under 1e-12
resolution,
something pretty hard to do otherwise.
If I want to make BIG changes like 1e-10, I can rotate the box on any
of its
sides and still use the wedge,
and for a quick check of new equipment, I just turn the box over which
then
gives a couple of parts in 1e-9 freq change.
It makes a weird but simple and indispensable variable freq source that
is
useful for many things, such as checking the LOOP TC of a TBolt.
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