[time-nuts] position determination over short distance

phil fortime at bellsouth.net
Sun Nov 23 21:58:17 EST 2008

----- Original Message ----- 
From: "Rick Harold" <rickharold at gmail.com>
To: <time-nuts at febo.com>
Sent: Sunday, November 23, 2008 9:34 PM
Subject: [time-nuts] position determination over short distance

> All,
> I'm planning doing some experiments in distance measurement.  They don't
> deal with atomic time directly but with extreme short periods of time.
> I need to determine the position of a instrument with a 1mm accuracy or
> less.
> The instrument is not connected to a mechanical device but is separate &
> independent.
> The surface which the instrument is positioned on is close to the size of 
> a
> 11"x11" square.
> I thought of using 1 RF transmitters (not sure of freq) on bottom of the
> device near the surface.
> The surface would have RF receivers on 3 or 4 edges/corners to receive the
> signal.
> If each of the receivers positions are known and they then send a signal 
> to
> a central circuit (again known positions) how can I differentiate the time
> of arrival
> at the central location?  Does anybody know of a circuit/chip or system
> which would determine the time 'difference'.
> Obviously this is used to triangulate the position of the instrument.
> Light travels 1 mm in ~3.3 picoseconds so I would suspect the 
> differentiator
> would have to have that or better resolution.
> It could also use some proportional method to extrapolate the position 
> since
> the surface has a fixed size.
> Any ideas/thoughts?
> Thanks in advance.
> Rick Harold

Rather vague as to what you are doing.
Have you considered ultrasonics or even laser rather than RF?

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