[time-nuts] HP 113BR (was Other HP 10x manuals)

Bill Hawkins bill at iaxs.net
Thu Sep 15 13:40:24 EDT 2005

David Forbes wrote, in part,

"113BR  mechanical clock (a rare bird and a fascinating manual)"

Rare? I have two of them, and a manual. If I thought they had
any value, I'd get them working again. One ran for two years
until the 103 gave out. The other didn't work, but I'd lost
interest in trying for <1 second per year so I didn't fix it.
All I had then was the 103AR and a selection of WWV receivers.

The 113 uses regenerative solid state dividers to take 100 KC
down to 1 KC, which goes through a servo resolver to drive a
stepping motor. Various gears run the analog clock face and two 
notched wheels that generate a one second tick pulse. The servo
resolver adjusts the phase of the tick. The clock hour and minute
can be adjusted independently of the second hand. The second hand
can also be adjusted independently. The 1 KC motor is not quiet
in one of them. Resolution of the tick phase adjustment is 10 uS,
but the dial is analog and can be set finer than that. 

The clock is inadequate for those who seek E-15 accuracy, but it is
an engineering marvel. I first saw one many years ago at an exhibit
of standard time in the Smithsonian.

Speaking of large exponents, if time were to run backwards until the
universe contracted to a point, it's temperature would only be E16.
Ah, that's assuming that entropy is not irreversible.

Bill Hawkins

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