I am replying a bit late on this and couldn't read the other replies completely but I would suggest using a time-domain-reflectometer. This precisely fits your requirements, using a high speed capacitor with a PIC having CTMU, people have reported that they reach a resolution level of "less than 1ns". I am currently trying to achieve better, you might want to look into AN1375 and en542792.pdf. Good luck. On Tue, Nov 29, 2011 at 3:35 PM, Bob Ammerman wrote= : > I have a customer who wants to measure the characteristic impedance of a > length of coax. Actually, we know what it is supposed to be according to = the > manufacturer, but they want to verify it. > > Test equipment available: high accuracy multimeters (5-1/2 digit?), cheap > analog oscilloscope, relatively low frequency signal generator (sine, > square, triangle) (top end is maybe 1Mhz), frequency counter, bench suppl= y. > > Willing to buy high-precision R's or C's if needed. > > Accuracy required: hopefully a few percent, 10% is some help. > > I am really a digital guy, so this is a bit out of what I do. > > Any ideas? > > -- Bob Ammerman > RAm Systems > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .