At 10:49 AM 2/19/2003 -0500, you wrote:
> > A pulse will travel in a wire around 1 foot/nanosecond.
>
>The speed of light is about 1 foot/nanosecond in vacuum.  However, it will
>be significantly less on a transmission line.  It depends on the impedence
>of course, but figure about half as a rough rule of thumb.
>
>Still, making reaonable distance measurments will required speeds many
>times faster than what a PIC can handle.

You can play tricks like clocking an HCMOS register from a delay line to get
resolution in the hundreds of picoseconds, and control the thing with a PIC
or whatever. I'm not sure if that's now commercial TDR meters do it.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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