How do stud finders work?

stud finder
A stud finder is a valuable tool that makes the job of finding studs behind a wall very simple.

Whether you are hanging pictures, putting up a new set of shelves or getting ready to start an addition, knowing where the studs are in a wall can be extremely handy! Before there were stud finders, either you pounded a small nail into the wall until you hit a stud or you used a small pivoting magnet. The magnet would help you find nails that had been driven into a stud. The first technique works, but it damages the wall. The magnet technique is slow.

Electronic stud finders changed all that. They give you an amazingly accurate view into the wall and show you exactly where each stud is. In a way, these stud finders are like a touch switch on a touch-sensitive lamp. They are using changes in capacitance to sense where the stud is.


When the plate inside the stud finder is over wall board, it will sense one dielectric constant (sort of like an insulating value); but when it is over a stud, the dielectric constant is different. It works on a capacitance differential generated by density difference. The circuit in the stud finder can sense the change and reports it on its display. The second patent below shows you exactly how to build this sort of stud finder.

The latest technology in stud finders uses a very small radar system to detect the stud. Click here to learn about radar.


Originally Published: Apr 1, 2000

Stud Finder FAQ

How does an electronic stud finder work?
The electronic stud finder works using changes in capacitance generated by density difference to determine where the stud is. When the plate inside the stud finder is over the wall, it senses one dielectric constant, but when it is over a stud, the dielectric constant changes. The circuit in the stud finder senses the change and shows it on its display.
What is the most accurate stud finder?
While you can use a magnetic stud finder to determine where the stud is in the wall, an electronic stud finder is more precise. Magnetic models, however, tend to be cheaper. Both types have pros and cons.
Do magnetic stud finders work?
Yes, magnetic stud finders can help you find nails or screws that have been driven into a stud. The trick with magnetic ones, though, is that they can detect any metal in the wall, whether it's driven into a stud or not.
How do I find studs in my wall?
There are three ways to find studs in your wall: You can just pound a small nail into the wall until you hit a stud, use a small pivoting magnet or magnetic stud finder or use an electronic stud finder. Those latter two will probably be your best bets.

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More Great Links

  • Patent #3,845,384: Stud finder
  • Patent #4,099,118: Electronic wall stud sensor
  • Patent #5,774,091: Short range micro-power impulse radar with high resolution swept range gate with damped transmit and receive cavities