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WRT: The following statement which was recently posted:
> As I understand telephone cable fault finding, the rise times of the
> voltage pulses are normally long to allow large propagation distances.
TDR refers to a signal processing technique which relys on detection of
instaneous disturbances
in electromagnetic energy along a conductor rather than an "averaged energy"
technique. As such,
the important features for such a system focus on first establishing a
disturbance and then measuring the time
between the initial disturbance and a subsequent disturbance caused by a
discontinuity in the
conductor. The quality of measurement depends on the precision available
for determining the elapsed time.
Fast rising waveforms generally provide better measurements of instaneous
disturbances. Sine wave signals
are generally used for "averaged energy" signal processing. Other factors
have little direct bearing
other than for a specific implementation method to overcome losses and
distortion--i.e., a narrow pulse will
work as well as a long pulse if discernable at the initiating end.
M. G.
Marty Grogan, BSAE, MSEE
Grogan Engineering Services
1328 Rathwood Ave.
Richland, WA 99352
(509)627-3083 (voice and FAX)
ges@oneworld.owt.com
Specializing in Systems Integration Services for Agriculture: Automation,
Telemetry, Programming, Maintenence, Remote Sensing and Project Delivery.
GES--The technology buckstopper.