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

[Magnus Danielson]

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 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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