brkblbn:
My supervisor did not like the method he told me to do with TDR(Time Domain Reflectometry) so my new concern is:
TDR doesn't measure the cable capacitance, it measures its length (assuming the dielectric constant
is known, or vice versa).
You measure the cable's characteristic impedance, but that depends on the capacitance and
inductance per unit length.
I need a send a pulse to a cable(coax or simple copper wire) either sin/cos wawe or square.
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Rectangular pulse with very fast edges, the rise and falltimes limit the resolution.Then that signal goes to end of the cable and reflected back to first position. After I understand the
exact(disconnection) open circuit location of the cable. For generating the signal can my oscillator in
arduino generate that kind of signal or I need to buy a new oscillator? And can I see the reflected signal
waweform from arduino software without an oscilloscope.
The fastest edges an Arduino generate is perhaps 3 to 5ns risetime, good enough for a resolution of
a few feet, but it has no way to measure arrival time to better than the system clock period, and the
complication is that the return voltage can be 0V, 5V or 10V for a 5V pulse going in.A TDR needs some high speed auxiliary circuitry, these days most 'scopes are fast enough to do the
measurement.
Normally you can just look up the cable capacitance in the specs for the cable...