Patent ID: 7977950

Claim:
A time domain reflectometer for testing an electrical cable, comprising: a test signal generator; at least one line feed resistor, connected between the test signal generator and a pair of terminals, for connection to the ends of an electrical cable under test; and a signal processor, connected to the terminals, to receive a line signal including a reflection of a test signal transmitted into the cable under test, wherein the signal processor is programmed to filter the line signal to enhance a portion of the signal indicative of any fault on the cable by balancing the signal according to the electrical characteristics of a normal cable of the same type as the cable under test, by applying a filter function: 1+Rf.Y(s) to the reflected signal, where Rf is the resistance of the feed resistor, and Y(s) is an estimate of the input admittance of the transmission line, s being the Laplace variable, and acquiring at least one estimate of Y(s) from known or estimated electrical characteristics of the cable under test selected from the variables: C, the distributed line capacitance per unit length L, the distributed line inductance per unit length R, the distributed line resistance per unit length and G, the distributed line conductance per unit length or functions of these variables, in the equation for input admittance in the Laplace domain: Y ( s )=√(( sC+G )/( sL+R )).