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Fig. 1. Plot of a waveform and its first derivative from a Tektronix 1502C TDR cable tester set to begin at –0.5 m (inside the cable tester). The voltage step is shown to be injected just before the zero point (BNC connector on instrument front panel). At 3 m from the instrument, a TDR probe is connected to the cable. The relative voltage levels, VI, Vmin, Vo, and VF are used in calculations of the bulk electrical conductivity of the medium in which the probe is inserted and in determination of the probe characteristic impedance. Waveform positions for determining values of these parameters are described numerically in Evett (2000a)(2000c), where Vo here is denoted Vo2.
