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

[paul swed]

Hugh,
Well I sure enjoyed the story and though I won't say I am scarred by
Cesiums, they have proven just how little I know more then a few times.
Like you it took some 3 years to get the monster working. Its called
Frankenstein. You guessed how its made.
Regards
Paul
WB8TSL

On Wed, Dec 19, 2018 at 8:07 PM Rice, Hugh (IPH Writing Systems) <
hugh.rice at hp.com> 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 1986.
>
> The author, Felix Lazarus, was a legendary Field Application Engineer (or
> something like that) for HP in Europe, based in Geneva Switzerland.   He
> was obsessively fussy, and insisted that any Cesium Standard shipped to key
> customers in Europe were first shipped to him, so he could verify
> acceptable performance before the customer received the instrument.
>
> He would fire up the product, re-tune and re-align all the settings, and
> then compare it to his house standard.  If it wasn't up to his exacting
> standards, he would keep tuning and testing until it was acceptable - to
> him.    He was looking for performance several times better than our
> published specifications, which were 5 x 10e-12.   He wasn't satisfied
> until is was less than 2, or something like that.    It drove us factory
> guys crazy.   He was a well-respected figure in the time keeping world, and
> would bash us for shipping product that were not beating the specs by
> enough margin.
>
> I think he is the one that discovered the "top cover effect".  If you
> removed the top sheet metal cover from the instrument, the offset would
> shift by a part in 10 to the 12th or so.   If you put the cover on, and
> changed how tight the screws were tightened, it would shift differently.
>  I recall he wanted us to fix this.
>
> I was the "Production Engineer" on the Cesium standards, a young BSEE
> college graduate.   I barely knew how a basic op-amp amplifier worked, and
> was completely overwhelmed by the complexity of the Cesium Standards.   "Go
> fix the problem on the most accurate commercial atomic standard for sale in
> the world, where if you change how tight a screw is, the performance shifts
> a touch."   It is safe to say that I didn't make this my highest priority.
>   There were theories that the root cause was subtle changes to the ground
> loops with a change like this.   The whole product used all the sheet metal
> as a common ground, meaning that the ground return paths were not designed
> at all, just left to chance.
>
> A related issue that I didn't work on was the "oven controller cable
> offset."   There was a big multi wire cable o the cesium oven heater
> controller, and if you twisted it left vs. right before plugging it in, the
> offset of the standard would change.
>
>
> Working on the 5061B destroyed my confidence in my engineering abilities.
>  I didn't think I could solve "real" engineering problems, because of
> issues like this.    After working on the 5061B product for several years,
> I applied for a job as an engineering manager over the frequency counter
> production product line.  During the interviews, my low technical
> self-confidence came through, and the R&D management partners to this
> position were worried I couldn't provide technical leadership to the other
> engineers.    So, in true HP fashion, my they sent me through the full
> scale HP R&D engineering interview -about a half dozen deep 1:1 technical
> interviews with EE experts in the lab.   Turns out that I wasn't a dunce
> after all, just scarred from my experience working on the cesium
> standards.   I got the job.
>
>
> I have a handful of other stories like this from my days inside HP
> frequency and time division.    Let me know if you want to hear more.
> Maybe Rick Karlquist will tell some stories of developing the 5071!
>
> Hugh Rice
>
>
>
>
>
>
>
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