[time-nuts] Measuring the accurcy of a wrist watch

[Chris Albertson]

On Fri, Apr 18, 2014 at 10:37 PM, DaveH <info at blackmountainforge.com> wrote:

> Hi Chris
>
> My concern was not the magnetization of the watch movement but the
> induction
> of eddy currents into the balance wheel which will cause drag.
>
> The act of moving the watch into the field of the pickup could cause the
> watch to start running more slowly. You will be getting a strong signal but
> it will be the wrong signal.
>

What is the magnitude of this effect?  Would anyone know the relationship
between field strength and watch speed.   For example the strength of the
Earth's  magnetic field changes over at least a factor of four in different
parts of the world.  Is this a seconds per day or seconds per decade kind
of problem?

But yes I agree forsaking serious measurements I'm make a purpose built
coil.  Or actually like I said two of them wires in anti-phase.

But even then, it can't measure a mechanical watch.   I think a microphone
would be best.





> Dave
>
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com
> > [mailto:time-nuts-bounces at febo.com] On Behalf Of Chris Albertson
> > Sent: Friday, April 18, 2014 08:44
> > To: Discussion of precise time and frequency measurement
> > Subject: Re: [time-nuts] Measuring the accurcy of a wrist watch
> >
> > On Thu, Apr 17, 2014 at 11:12 PM, Hal Murray
> > <hmurray at megapathdsl.net>wrote:
> >
> > >
> > >
> > > Steel makes very good springs.  Are there any non-magnetic
> > materials that
> > > are
> > > close?
> > >
> >
> > I think they can use some kind of non-magnetic stainless steel
> >
> > Also this might be a moot point because I got a good strong signal by
> > placing the watch on top of the guitar strings.  I did not
> > have to restring
> > the guitar.   The wall clock works even some inches away.
> > You don't have
> > to get really close to the magnets.   If you were building a
> > sensor, just
> > use a plain iron core and 1/4 pound of #40 wire
> >
> > >
> > >
> > --
> >
> > Chris Albertson
> > Redondo Beach, California
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-- 

Chris Albertson
Redondo Beach, California