A stud finder (also stud detector or stud sensor) is a handheld device used to determine the location of wood and metal framing studs used in light-frame construction after the walling surface has been installed.
There are three main types of these devices:
- The first uses a small magnet to detect the nails or screws placed into studs during the manufacturing of the wall.
- The second type uses an internal capacitor plate to detect changes in the dielectric constant of the wall as the user moves the finder over the surface of the wall. A significant change in the dielectric constant indicates a dense object behind the wall, normally a framing stud. Internal capacitor stud finders are the most common.
- The third type uses a very small radar system to show exactly where the edges of a stud are behind the wallboard (drywall).
Internal capacitor stud finders are divided into two classes:
- Edge finders detect the edges of the stud or other target behind the wall. The sensor in an edge finder detects when it's directly over a change in density, such as the edge of a stud. Edge finders have to be moved from both right and left directions to find both edges so the center can be determined. The first internal capacitor stud finders were all edge finders, and most inexpensive models still are.
- Center finders detect the center of the stud. These tools register the wall’s dielectric constant from multiple sensors, and use the different readings to determine the location of the target center. Unlike edge finders, these stud finders need to be moved from only one direction to indicate the center of the stud. These kinds of stud finders are also called "one step" finders.
Internal capacitor stud finders also can come with other features that locate metal and live AC voltage.
The development of the internal capacitor stud finder Edit
The internal capacitor stud finder was first designed by Robert Franklin in 1977. After he had patented the device, he tried to sell the rights to produce it to several major tool companies, all of which turned down the idea. He took the design to Zircon Corporation, an electronics manufacturer in Campbell, California, who agreed to build and market the device. Zircon was the sole producer of internal capacitor stud finders until 1998, when the original patent expired, allowing other companies to manufacture it as well. Other developments and improvements in stud finders remain under patent protection.
- "Electronic wall stud sensor" at USPTO
- "Short range micro-power impulse radar with high resolution swept range gate"