tidsdomeneReflektrometri

Tidsdomene Reflektrometri, or TDR, is a non-destructive technique used to determine the electrical characteristics of transmission lines. It operates by sending a pulse of electrical energy down a transmission line and monitoring the reflections that return. These reflections are caused by impedance changes along the line. The time it takes for the pulse to travel down the line and back, along with the amplitude and shape of the reflected pulse, provide information about the line's length, characteristic impedance, and the location and nature of any discontinuities or faults.

The basic principle of TDR involves Ohm's Law and the concept of impedance matching. When a pulse encounters an impedance mismatch, a portion of the energy is reflected back towards the source. A TDR instrument, often called a reflectometer, includes a pulse generator and a high-speed oscilloscope or digitizer. The generator sends a fast-rising voltage step or pulse into the transmission line. The oscilloscope displays the outgoing pulse and any subsequent reflected pulses. By measuring the time difference between the outgoing pulse and a reflected pulse, and knowing the propagation velocity of the signal in the transmission line, the distance to the impedance discontinuity can be calculated.

TDR is widely used in various fields, including telecommunications for testing coaxial cables and twisted pairs, radar systems, and in the semiconductor industry for characterizing interconnects on integrated circuits. It is particularly effective at locating faults such as breaks, shorts, and crimps in cables. The analysis of the reflected waveform can also reveal details about the nature of the fault, such as whether it is an open circuit or a short circuit.