Editing Time-domain reflectometer (section)

=== Method ===
The TDR analysis begins with the propagation of a [[Step function|step]] or impulse of [[energy]] into a [[system]] and the subsequent observation of the energy reflected by the system. By analyzing the magnitude, duration and shape of the reflected waveform, the nature of the impedance variation in the transmission system can be determined.

If a pure [[Resistor|resistive load]] is placed on the output of the reflectometer and a [[Step function|step signal]] is applied, a step signal is observed on the display, and its height is a function of the resistance. The magnitude of the step produced by the resistive load may be expressed as a fraction of the input signal as given by:

<math display="block">\rho = \frac{R_L - Z_0}{R_L + Z_0}</math>

where <math>Z_0</math> is the [[characteristic impedance]] of the [[transmission line]].