I don't pretend to know everything, but a good probe has controlled impedance and capacitance, and a trimmer of some sort to they can be adjusted. the issue is with fast signals the impedance and capacitance of the probe lead will distort your signals. What you get on the scope isn't what's actually happening. Also probes are 1x 10x (I think 100X too). Using those modes places less loading on the circuit under test. Hook a 1x to a crystal oscillator on a PIC and the oscillator will likely stop (to much load), but a 10x won't (shouldn't?) cause that. Even higher end probes are available with things like differential inputs (not ground referenced) and built in FET amplifiers (extremely low circuit loading) probably other I don't know about too. -Denny ----- Original Message ----- From: "Hulatt, Jon" To: Sent: Friday, October 31, 2003 7:16 AM Subject: Re: [EE:] choosing a scope > What's with probes anyway? Evidently a probe is more than just a wire with a > spike on the end? Why are they sometimes so expensive/ > > Jon > > > 20Mhz dual trace analog for $70 USD a few months back. One > > thing to watch out for, if they don't include probes and > > manuals. I haven't been able to find a manual (if anybody has > > one, I'd like to here from you) , and although I recently > > found some less expensive probes, better probes can easily > > cost more than I paid for the scope. > > > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.