Apparatus and method for improving a time domain reflectometer

摘要

A method for detecting impedance discontinuities in two-conductor cable includes the initial step of transmitting a pulse of energy onto the cable and receiving any reflected pulses at a base location. The distance to the discontinuity is calculated by measuring the elapsed time between the transmitted and received pulses. A waveform is created on a display screen to shown the transmitted and reflected pulses, by taking a plurality of horizontal samples along the cable, and calculating a vertical value for each horizontal sample taken. Each horizontal sample is then converted to digital form and displayed on the screen. Another step in the method includes determining the gauge of the cable and then subtracting the exponential decay of the transmitted pulse waveform based upon that determined cable gauge so as to create a modified transmitted pulse which is displayed on the screen. The method also includes the step of adjusting the calculation of the distance to the discontinuity so as to account for a decrease in the velocity of propagation of the transmitted and received pulses over the length of the cable. A method for detecting a bridge tap in a twisted pair cable includes the steps of transmitting a pulse of energy onto the cable and receiving any reflected energy pulses at a base location. The gauge of the cable is then determined and the phase of any reflected energy pulses are determined. The amplitude and distance from the base location is determined for each reflected pulse which is out of phase relative to the transmitted energy pulse, to create pulse values. These pulse values are then compared with predetermined pulse values for the particular cable gauge and type to identify the location of a pulse value which is within a predetermined range of pulse values for a bridge tap discontinuity.