Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!lll-winken!unixhub!slacvm!dbg
From: DBG@SLACVM.SLAC.STANFORD.EDU
Newsgroups: sci.electronics
Subject: Re: Electronic Stud Finders
Message-ID: <90304.114239DBG@SLACVM.SLAC.STANFORD.EDU>
Date: 31 Oct 90 19:42:39 GMT
References: <4110@radio.oakhill.UUCP> <1990Oct31.144258.9595@canterbury.ac.nz>
Organization: Stanford Linear Accelerator Center
Lines: 15

Several principles are used in various studfinders. The one I find most
effective is based on capacitance, determining the effective dielectric
constant of the wall. With wallboard made of gypsum and cardboard, this
locates the boundaries of wood studs and even shows where double or triple
ones have their edges, quite accurately. This type typically has a flat
body which is slid along the wall, an activating button on the side which
zero's the detector somewhere you hope has no stud, and several LEDs on
the face which form a bargraph. They sell in the US$10-20 range. They
don't work where the wall is filled with foil-backed insulation, as the
foil blocks the electric field effectively.
-- David B. Gustavson, Computation Research Group, SLAC, POB 4349 MS 88,
    Stanford, CA 94309   tel (415)926-2863  fax (415)961-3530
-- What the world needs next is a Scalable Coherent Interface!
-- Any opinions expressed are mine and not necessarily those
   of SLAC, Stanford University or the Department of Energy.