[time-nuts] They Look Like the Emperors’ Clocks. But Are They Real?

[Brooke Clarke]

Hi:

An interesting article with nice photos and short video clips.
https://www.nytimes.com/2018/12/21/arts/design/china-clocks-forbidden-city.html

--
Have Fun,

Brooke Clarke
https://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how 
well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.


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Re: [time-nuts] HP Cesium Standards in the International Atomic Time Scale, the legend of Felix Lazarus, and the "top cover

[Rice, Hugh (IPH Writing Systems)]

Hi Magnus –

To resolve the cliff hangers:  😊

There really wasn’t a way to “fix” the top cover effect.   Looking back now as 
a career engineer, rather than from my inexperienced view from 1986, what I 
realize is that in any precise application, there will always be something 
holding you a step away from perfection.You can’t tune this out in every 
individual product. One challenge with the 5061B is that it was a *primary* 
standard, meaning that it didn’t need calibration, by definition.   If you 
spent a bunch of effort calibrating a unit, is it still a primary standard? 
With careful enough measurements, you could detect that all were not identical. 
(We would do this by comparing the phase drift of the 10MHz signal against 
our house standard.  Over a few hours, an instrument would drift a few 
nano-seconds. That is, the unit under test was different than the house 
standard.

But it then begs the question, which one is right?   Time keeping labs, like 
the one with NBS in Colorado, or the west coast standard in our building in 
Santa Clara CA, or the one in Geneva, would determine the “best” time by 
averaging a bunch of primary standards.  The unit that was closest to the 
average would be declared the house standard. (At least that is how I remember 
it worked.)   Essentially establishing truth by taking a vote. (As many on 
this list know so well.)

For a specific instrument shipping to an isolated customer, where they didn’t 
have another standard to compare against, you had to take your cesium standard 
as perfect.  It was the primary standard after all.   As the instrument would 
get handled or power cycled, it could shift a touch each time.  And God forbid 
if you took the top cover off for some reason!   All of Felix’s fine tuning, 
screw by screw, would be lost.   (I don’t think he actually hand tuned each 
screw on every product.  More likely, he pointed out that if the screws were 
removed or tightened differently, the frequency offset would change.   Not an 
ideal behavior. )

From a practical “factory” approach to the 5061 products, we guaranteed that 
every cesium standard was within specs.   We couldn’t guarantee that they would 
be exactly centered (if we could, we would tighten up the specs), or would 
always remain centered (or even the same) if you messed around it with it.
Just comfortably within specs.

So, with no disrespect to Felix and his efforts to make things better, at some 
point, work to perfect each unit becomes silly.   You could fool yourself into 
thinking it was better, but then only if the instrument was never touched, 
moved, power cycled, etc.And even then, would it still be exactly the same 
months later?

Fortunately, the managers and senior engineers had a realistic perspective on 
how perfect was achievable.   Felix was good in that he kept us from being 
sloppy, and sometimes would find real things that we screwed up.But 
torqueing screws carefully (and uniquely for each product), or twisting cables 
left vs. right  was a step too far.  To really make the cesium standards 
better, they needed a better design.And that was what the 5071A was all 
about.   But that is a story for another day.

Hugh Rice



Date: Fri, 21 Dec 2018 08:22:05 +0100
From: Magnus Danielson 
mailto:mag...@rubidium.dyndns.org>>
To: time-nuts@lists.febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] HP Cesium Standards in the International
Atomic Time Scale, the legend of Felix Lazarus, and the "top cover
effect".
Message-ID: 
<6626d228-ec95-f4c6-a91e-73b37cee9...@rubidium.dyndns.org>
Content-Type: text/plain; charset=windows-1252

Dear Hugh,

I really enjoyed reading this! You have several cliff-hangers in there:
Did you (HP) fix/reduce the top cover issue? Did you alter the setup to
meet tighter specs? Did you fix the oven controller cable offset?
What else war-stories do you got?

It is by war-stories one shares knowledge, lessons learned is not
without its background and at least you have a great story.

Cheers,
Magnus

On 12/20/18 12:36 AM, Rice, Hugh (IPH Writing Systems) wrote:
> Hello Time Nuts,
> I found this HP Application note in my archives, and attached a scanned copy:
>
> Application Note 52-4. Contribution of HP clocks to the BIH's International 
> Atomic Time Scale (IATS).
> I also found a couple of archives for HP application notes for anyone who may 
> be interested:
> http://hparchive.com/appnotes
> https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=1127547&id=1127547&cmpid=zzfindclassic-app-notes
>
>
> It is an interesting snapshot at the method of keeping the official IATS 
> time, and how HP Cesium standards are a major part of it, published in

Re: [time-nuts] HP Cesium Standards in the International Atomic Time Scale, the legend of Felix Lazarus, and the "top cover

[Magnus Danielson]

Hi Hugh,

Many thanks.

Well, I do know about the 5071A, and well, for some reason a pair of
those found their ways to my lab.

I think I know a few things about references and such,
clocks/EAL/TAI/UTC isn't all that lost on me. NBS is NIST these days,
and I will visit them again in two weeks during my US tour.

The 5071A story would be nice to hear from you. We heard one part of it
from Rich, so it will be interesting to hear your take on it.

There is many aspects that goes into precision instruments like these,
and it is interesting to hear the war stories and thoughts that came up
along the way.

In my basement I find HP 5060, 5061, 5062, 5065, 5071 and various other
cesiums, rubidiums and what have you... the 5061 is the last in the HP
chain to be "analog" where as 5071 includes the more digital
interigation scheme that others used, one of several improvements.

Cheers,
Magnus

On 12/23/18 1:11 AM, Rice, Hugh (IPH Writing Systems) wrote:
> Hi Magnus –
> 
>  
> 
> To resolve the cliff hangers:  😊
> 
>  
> 
> There really wasn’t a way to “fix” the top cover effect.   Looking back
> now as a career engineer, rather than from my inexperienced view from
> 1986, what I realize is that in any precise application, there will
> always be something holding you a step away from perfection.    You
> can’t tune this out in every individual product.     One challenge with
> the 5061B is that it was a **primary** standard, meaning that it didn’t
> need calibration, by definition.   If you spent a bunch of effort
> calibrating a unit, is it still a primary standard?     With careful
> enough measurements, you could detect that all were not identical. 
>    (We would do this by comparing the phase drift of the 10MHz signal
> against our house standard.  Over a few hours, an instrument would drift
> a few nano-seconds.     That is, the unit under test was different than
> the house standard. 
> 
>  
> 
> But it then begs the question, which one is right?   Time keeping labs,
> like the one with NBS in Colorado, or the west coast standard in our
> building in Santa Clara CA, or the one in Geneva, would determine the
> “best” time by averaging a bunch of primary standards.  The unit that
> was closest to the average would be declared the house standard. (At
> least that is how I remember it worked.)   Essentially establishing
> truth by taking a vote.     (As many on this list know so well.)
> 
>  
> 
> For a specific instrument shipping to an isolated customer, where they
> didn’t have another standard to compare against, you had to take your
> cesium standard as perfect.  It was the primary standard after all.   As
> the instrument would get handled or power cycled, it could shift a touch
> each time.  And God forbid if you took the top cover off for some
> reason!   All of Felix’s fine tuning, screw by screw, would be lost.  
> (I don’t think he actually hand tuned each screw on every product.  More
> likely, he pointed out that if the screws were removed or tightened
> differently, the frequency offset would change.   Not an ideal behavior. )
> 
>  
> 
> From a practical “factory” approach to the 5061 products, we guaranteed
> that every cesium standard was within specs.   We couldn’t guarantee
> that they would be exactly centered (if we could, we would tighten up
> the specs), or would always remain centered (or even the same) if you
> messed around it with it.    Just comfortably within specs. 
> 
>  
> 
> So, with no disrespect to Felix and his efforts to make things better,
> at some point, work to perfect each unit becomes silly.   You could fool
> yourself into thinking it was better, but then only if the instrument
> was never touched, moved, power cycled, etc.    And even then, would it
> still be exactly the same months later?
> 
>  
> 
> Fortunately, the managers and senior engineers had a realistic
> perspective on how perfect was achievable.   Felix was good in that he
> kept us from being sloppy, and sometimes would find real things that we
> screwed up.    But torqueing screws carefully (and uniquely for each
> product), or twisting cables left vs. right  was a step too far.  To
> really make the cesium standards better, they needed a better design. 
>   And that was what the 5071A was all about.   But that is a story for
> another day. 
> 
>  
> 
> Hugh Rice
> 
>  
> 
>  
> 
> 
> Date: Fri, 21 Dec 2018 08:22:05 +0100
> From: Magnus Danielson  >
> To: time-nuts@lists.febo.com 
> Cc: mag...@rubidium.se 
> Subject: Re: [time-nuts] HP Cesium Standards in the International
> Atomic Time Scale, the legend of Felix Lazarus, and the "top cover
> effect".
> Message-ID: <6626d228-ec95-f4c6-a91e-73b37cee9...@rubidium.dyndns.org
> >
> Content-Type: text/plain; charset=windows-1252
> 
> Dear Hugh,
> 
> I really enjoyed reading this! You have several cliff-h