Mohr CT100B Series, Operator'S Manual

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5. TDR Measurement Theory
Figure 5.4.
Normal SMA female barrel interconnect measuring 52.1 ohms.
Figure 5.5.
Comparison of typical SMA (red trace, bottom) and BNC (black trace, top)
coaxial cable interconnects.
velocity of propagation. The accuracy of the Distance-to-Fault measurement of a fault that
appears beyond another fault is reduced.
5.4. Velocity of Propagation (VoP, Vp)
As mentioned in previous sections, a transmission line, such as a cable, has uniform geometry
with a characteristic signal propagation velocity. This velocity of propagation (Vp, VoP, or VP),
sometimes also called the velocity factor (VF) or wave propagation speed, is the measure of the
velocity of an electrical signal within a cable expressed as a fraction of the speed of light in a
vacuum. With the CT100B, Vp can be set between 0.250000 and 1.000000.
Nominal Vp values for most types of cable can be found in the manufacturer’s data sheet, and
Appendix E: V
p
of Common Cables
contains nominal values for a variety of commonly used cable
types. These values can be a good start for basic cable Distance-to-Fault measurements, however
70 CT100B TDR Cable Analyzers Operator’s Manual