TDR Testing
The TDR sends electrical pulses down a cable. Some of the pulse energy is reflected by connectors, cable imperfections and terminations. This reflected energy is measured by the TDR and displayed in graphical form.
Cable have TWO important characteristics for TDR measurements.
Impedance is a measure of the AC resistance of the cable, whereas Velocity of propagation is a measure of the speed at which signals travel down the cable, relative to the speed of light.
Impedance is important for determing cable imperfections and bad connections and terminations. A cable which is unterminated will reflect all the transmitted energy back to the TDR, whereas a correctly terminated cable will reflect none. The amplitude (strength) of the reflected energy (how much of the original pulse) determines the severity of the fault.
© Copyright Brian Brown, 1988-2000. All rights reserved.