The velocity of propagation (also known as the Phase Velocity) test measures the speed of electrical signal transmission down a wire/cable. The velocity of signal propagation is typically represented as a fraction of the speed of light in a vacuum and is primarily impacted by the wire/cable dielectric.
This test may also be used as a means of assessing the symmetry of cable construction by comparing the speed of propagation simultaneously down two or more cable components. If a significant difference is measured, this can indicate poor cable construction, inconsistent dielectric material, and/or design flaws.
Perform visual examination of the specimen. Record any defects.
Cut specimen to specified length and attach both ends to impedance match terminations.
Attach to the specimen and calibrated cable to a waveform generator and to an oscilloscope.
Measure the time difference between the zero crossings between the specimen and calibrated cable.
Calculate the characteristic impedance of the specimen.
Report the specimen length, velocity of propagation, characteristic impedance, and test frequency.