> > I didn't find a specification on the electrode size, but in the photo of > > a popular tester they look to be maybe 3 or 4 inches in diameter. For > > my test, the electrodes were two saucepans, each about 7 inches in > > diameter and weighted with 5 pounds
When measuring the resistance of a two-dimensional conductor (like a mat), the resistance can be measured with point contacts, such as ordinary test meter probes. One of the interesting properties of two-dimensional conductors is that the measured resistance is independent of the spacing between the probes. In other words, one will get the same measurement on an ohmmeter if the probes are one centimeter apart as if they are one meter apart, provided the mat is larger than the probe spacing. This result may seem counter-intuitive, but it makes sense if you think about the lines of electic current that flow between the probes. Widely spaced probes have more area for the current to flow into, thus compensating for the fact that the probes are far apart. Thus the resistance is an intrinsic property of the conductor and not of the geometry of the measuring setup. Interesting, no? 73, Jim W8ZR _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
