[time-nuts] Line Frequency

Tom Van Baak (lab) tvb at leapsecond.com
Mon Feb 10 17:37:39 EST 2014


Tim,

Perhaps a watchmaster G47? Very clever device, and yes, a fine mechanical example of a phase comparator. Google for it and see sites like:
http://myplace.frontier.com/~dritland/watchmaster/

/tvb (i5s)

> On Feb 10, 2014, at 12:01 PM, Tim Shoppa <tshoppa at gmail.com> wrote:
> 
> >  IIRC some watch or clock company had a patent on calibrating a wristwatch crystal against AC hum. I read it once but can't find it now. Can you hunt for it?
> 
> Tom - when I was a kid in the 1970's, before digital watches, the local jeweler had device with a table on which a watch or clock could be placed, the table must've been a microphone, and it had a pen recorder. It produced a chart that looks like the "phase data" charts on yours and other websites; the jeweler adjusted the clock so the recorded line had no slope. It had a selector for several common watch/clock gear ratios (don't think it did the tuning fork watches like the Accutron; I think there was a similar but different device for checking the tuning fork Accutrons, my dad was enough of a clock nut that he actually had a tuning fork Accutron, and he is a NAWCC member still!). Over the course of an hour the adjustment could be fine trimmed to the point where we knew the movement was good to a few minutes a month. Don't know if it was locked to mains frequency or had a crystal. Do you know what this was called?
> 
> Tim N3QE



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