> >Michael Rigby-Jones wrote:
> >As an ultra cheap and nasty method, how about making the cable
> >the C part of a CR relaxation oscillator.  The PIC measures the frequency
> >and by having a set of fudge factors for different cable types, the
> length
> >could be calculated.  Granted it will never be as accurate as a
> commercial
> >instrucment but I think the idea is possibly workable.
> >
>
> -----Original Message-----
> From: j galt [SMTP:galt_57@HOTMAIL.COM]
> Sent: Thursday, February 20, 2003 11:24 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [PIC]: How would I build a reflectometer?
>
> There might be some way the pulse transit time on the cable might be made
> into a sort of oscillator circuit.
>
That's basicaly what Wagner suggested a few posts back.  I was thinking you
could perhaps do away with pulse reflections all together and just use cable
capacitance with some calibrations for cable type.  It might be able to be
made accurate enough for some applications, but TDR is the way to go for
real accuracy.

Mike

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