On Wednesday 16 April 2014 09:09:06 Simon Wise did opine: > On 16/04/14 17:19, david wrote: > > Interesting. What is the difference between speed of sound in air and > > the speed of electricity through a cable? > > sound is about 3ms per metre (330 m/s) in air > > ... in a room, talking about sound, there is no significant delay for > the signal in the cable ... from Sydney to Hawaii via copper or fibre > yes, considering phase differences for RGB video signals in a building > yes, talking about timing on a circuit board or a bus while syncing > gigahertz clocks yes, but for sound within a building the speed over > copper may as well be infinite. > > > I was shown a rather nice artwork that used high resolution radar > (resolutions around 1 centimetre I think) to get positions (it was made > in a university robotics department that had such things!). The way > those work is very interesting ... the frequencies are way to high to > digitise, so the electronics has to be all analogue ... the 'circuitry' > is basically plumbing ... gold lined tubes and chambers using > resonances and such to measure delays and phase differences. At those > frequencies the speed of light becomes a dominant consideration. > > > Simon We have a gismo thats basically much simpler than all that plumbing, to use when checking a cable for damage, called a Time Domain Reflectometer. The pro versions using a tunnel diode switch as a pulse generator, can tell you theres a bullethole in the line 883.6' out from where you are hooked up. I've made homemade versions using a pulse generator and a fast oscilloscope to measure the echo delay, punched some buttons on a good calculator and then told the tower crew where to open it up and replace a burned up connector bullet and/or the teflon disk holding it centered in the line. It got the job done so I figured it was good enough for the girls I go with. :) > _______________________________________________ > Linux-audio-user mailing list > Linux-audio-user@xxxxxxxxxxxxxxxxxxxx > http://lists.linuxaudio.org/listinfo/linux-audio-user Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
