[time-nuts] Part 2: Atomic Clocks: It is important that they keep good time.
chris at elfpen.com
Fri Jan 4 21:59:30 EST 2019
You had me hooked at the part about a national standard being built on spare parts, returns and scounged units!
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On Jan 4, 2019, 18:07, at 18:07, "Rice, Hugh (IPH Writing Systems)" <hugh.rice at hp.com> wrote:
>HP's Santa Clara Division (SCD), in addition to building the Cesium
>Beam Frequency Standard Atomic Clocks, was an official time-keeper for
>the U.S. Naval Observatory, maintaining the west coast reference for
>Coordinated Universal Time. This was done in our standards lab where
>we kept a rack of several HP Cesium standards. Hopefully the attached
>picture of the lab comes through for some of you.
>A side note on the Cesium Standards in this lab. It was a collection
>of random instruments from over the years. The 5060 and 5061 family
>was reliable and easy to repair, especially with the factory was
>upstairs, and these were likely scrounged units of some kind.
>Customers also used to send Cesium Beam tubes to HP for disposal and
>end of life. These customer tubes were sometimes replaced on periodic
>maintenance schedules when used in critical applications, and often had
>a lot of good life left. The standards lab working with the CBT techs
>would pick through the returns, and select out the best tubes for the
>standards lab. As far as I know, the standards lab never had to
>purchase a new CBT. I'll bet there are a few on this list that would
>love to pick though the piles of old CBTs we had back in the day.
>In about 1987, Jim Horner, the general manager of SCD, said: "If we
>keep the official time for the US Naval Observatory, we should have a
>fancy display in the lobby showing exact time." This would allow us
>to showcase our technology to customers and dignitaries that would
>visit the site. But there was a catch: IT MUST ALWAYS HAVE THE
>CORRECT TIME. (Oh, and PFS engineering needed to find the money to
>pay for it. But it didn't wind up being all the expensive.)
>Some years prior, at HP headquarters (or maybe HP Labs?), they also had
>a "Lobby Clock" to show off HPs accurate time keeping technology to
>visitors. I never saw a picture of this it, but it was supposedly an
>elegant electro-mechanical clock, in a glass case so you could look in
>at the gold plated gears and such. On day, a visitor saw it and said:
>"I think your clock is slow." Impossible! It is connected to the
>house standard, and is *perfect*. But it was checked, and sure
>enough, the clock was slow by some embarrassing amount. The gold
>plating on the gears had gotten gummed up, and caused the clock to drag
>behind. Some senior executive (Packard, Hewlett, HP Labs director?)
>probably lost their temper, and had it quickly removed. HP didn't
>need an atomic clock in the lobby of the corporate headquarters with
>the incorrect time. (I think Lou Mueller told me this story, and
>most of this one is probably true. He was the lead CBT engineer, and
>his history with Cesium Standards went back to nearly the beginning of
>time. A wonderful guy that was always very kind to me, and told lots
>of great stories.)
>This was a after the 5061B project was complete, and I was now the
>production engineer on the 5061B. My follies as a clock designer had
>not been discovered yet, and PFS management asked me to design the
>Lobby Clock display, and figure out a way to make sure it was never
>wrong. I had learned a lot about turning a 1PPS signal into a
>HH:MM:SS format, and leveraged this new expertise into the new lobby
>The strategy was to have a small clock display in the standards lab,
>sitting on top of the rack of official Cesium Standards, where the
>tech's there could regularly confirm that it indeed had the correct
>time. A key feature of the design was to have the 6 digits of the
>clock display in BCD data format, which could be piped out to the lobby
>on a 24 connector data cable. (I got to learn about RS 422 line
>drivers, which I used to drive the data lines. The distance from the
>standards lab to the lobby was maybe 100 feet.) The clock display in
>the lobby would display the BCD data, and not have to be checked, as
>long as the standards lab guys kept their local display accurate. No
>gears to gum up. What could go wrong?
>The guys from the industrial design team designed a very elegant, very
>large black glass display for my electronics to hide behind. On the
>left side was an "analog clock" made of long narrow LED segments, and
>would progress around in a circular display with simulated hour,
>minutes and second hands. On the right side was a giant 7-segment, dot
>matrix like digital display for the time. The digits were maybe a foot
>tall. We had two giant PCBs laid out to hold the analog and digital
>clock LEDs, and all the electronics to control them. All mounted in a
>fancy aluminum box, with the enormous glass display over the top. It
>was at least 3 feet wide, and nearly as tall. And really heavy.
>Facilities pulled the 24 conductor cable through all the false ceilings
>and found AC power up there for me to plug into, and mounted the beast
>high on the wall in the lobby. We fired it all up, and it worked
>great. (Yes, I tested it extensively before we installed it.)
>SCD management scheduled a grand opening ceremony for the clock
>display, and invited Len Cutler down to do the official unveiling. A
>few quick speeches, and Len pulled off the black cloth hiding it until
>the big event. He appeared very pleased with the product. It
>remained in the SCD lobby for many years, and was still there the last
>time I visited in the late 1990s. As far as I know, it never had the
>wrong time. Or at least it always showed the same time as the little,
>reference clock in the standards lab.
>This was a really fun project, that was completed over a few months,
>and something that I was proud of for many years. I wonder if it is
>still on the wall of the lobby. Keysight technologies now occupies the
>building, but is no longer in the Cesium Standard business.
>Have any of you ever seen this clock in the old SCD lobby, on Stevens
>Creek Boulevard where it crosses Lawrence Expressway in Santa Clara?
>Anyone know how long it was there?
>Happy time keeping,
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