On Mon, 3 Apr 2017 15:05:55 +1200 (NZST) Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote:
> For even more fun you could try to detect the PTFE phase change at around > 20C using a cable with PTFE dielectric. This will require several 100 meters of cable to be measureable with the TICC. Modern cables are all <500ppm/K, good cables <10ppm/K, phase stable cables reach even <1ppm/K. Measuring a change of 10ppm with a resolution of 60ps means that the delay has to be in the order of 6µs, which is close to 1000m of cable. Even if dithering gives another facor of 10, this still means 100m of cable. For this level of comparison I would suggest to use a sinusoidal signal, instead of a pulse, and do phase comparison, which gives a resolution in the order of 1ps with very little effort, thus reducing the required cable length to 10-20 meters. Attila Kinali [1] "Temperature Stability of Coaxial Cables", Czuba and Sikora, 2011 http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.