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What is TDR?




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Time Domain Reflectometry or TDR, is a remote sensing electrical measurement technique that has been used for many years to determine the spatial location and nature of various objects. An early form of TDR, dating from the 1930's, which most people are familiar with is RADAR. Radar consists of a radio transmitter which emits a short pulse of microwave energy, a directional antenna, and a sensitive radio receiver. After the transmitter has radiated the pulse, the receiver then listens for an echo to return from a distant object, such as an airplane or ship. By measuring the time from the transmission of the pulse until the echo returns and knowing the speed of light, the distance to the reflecting object may be easily calculated. Detailed analysis of the echo can reveal additional details of the reflecting object which helps in identifying. The same principles hold for radar, lidar, coax TDR, optical fiber OTDR and broadband impulse radars.

[O'Connor, Kevin M. and Charles H. Dowding. Geomeasurements by Pulsing TDR Cables and Probes. Place: Boca Raton: CRC Press, 1999.]