[time-nuts] position determination over short distance

[Jean-Louis Oneto]

Hi,
A graphic tablet (11" square is a common size) should give you about 120 
positions/mm for something like a hundred bucks.
That's not very different from the "mouse" solution, but give you absolute 
position rather than relative.
Regards,
Jean-Louis Oneto

----- Original Message ----- 
From: "Rick Harold" <rickharold at gmail.com>
To: <time-nuts at febo.com>
Sent: Monday, November 24, 2008 2:34 AM
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
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