Differential Capacitance. Basically 3 plates in a row hooked up to monostables. The difference in capacitance between the middle and outter plates is sensed and displayed. Stud finders also find patches in wallboard because the repair has a different dielectric constant than normal wall. Great invention. Can find pipes and wires too, if they're close enough to the wall. Zircon also has a micropower radar based unit for use in concrete. Has a PIC in it . Robert Tal Bejerano - AMC wrote: > > wood studs in wall? maybe plastic, then no coil help :-) > > -----Original Message----- > From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On > Behalf Of David Koski > Sent: Monday, February 18, 2002 10:06 PM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [OT]: How does a wall "Stud Finder" work? > > I can see how that would work for a steel stud. But wood? > > David > > On Mon, 18 Feb 2002 21:38:49 +0200 > Tal Bejerano - AMC wrote: > > > yeah coil and a very sensitive circuit.. > > this is the right and the only way > > > > Tal Tal, you didn't think it through very far, did you... -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.