On Mon, October 29, 2018 6:57 am, Artek Manuals wrote: > The next flag for thought is your comment "assuming a velocity factor of > .7" What if the velocity factor is really .66 ? This would account for > almost half of the error.
Propagation velocity has an inverse dependence on permittivity, and permittivity changes with frequency. Electrical delay time will not be constant with frequency because of that. In addition to the fundamental physics at play, there are instrumentation difficulties. The rise time at low frequencies is long enough that any 50Hz/60Hz interference from power line related current flow can modify the trigger point and influence the measurement. The fast rise time signals proposed for evaluating the measurement setup get around that, but then of course you are measuring a wideband signal, which rather misses the point of the original goal of measuring vs. frequency, so at some point after verifying the setup basics you will have to go back to narrow band signals. A 5370 is a somewhat coarse instrument for this type of measurement, a VNA which has a suitable lower measurement frequency would probably be more suitable. -- Chris Caudle _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
