Stud finder

Stationary magnet stud detectors use a small stationary magnet to detect the nails or screws placed into studs while putting up the walling material. The user must move the magnet around the wall until feeling the pull of magnetic attraction, and move in the direction of attraction. Since stationary magnetic stud detectors rely on the user to feel the attraction they can be unreliable, especially when the metal fasteners are located more deeply in the walling, which decreases the overall attraction. When fasteners are deep or buried under thicker walling material (as in most plaster walls) the effectiveness of stationary magnets is considerably lower.

Moving magnet stud detectors use a neodymium magnet that is suspended in an enclosure and free to move in response to hidden metal. The strength of this rare earth magnet and the easy movement of the magnet allow moving magnetic stud detectors to work on a broad range of construction types. The magnet is suspended in such a way that it always sits in its "home" position until it is moved directly over a metal fastener or metal stud. On walls with shallow fasteners, the magnet moves towards the wall with such velocity that it makes a distinct thud sound when it hits the wall. Because a moving magnet is not dependent on the operator to feel the attraction to the metal, fasteners buried more deeply under plaster or tile can be located with this detector. For deeper fasteners, the sound is softer since the speed of movement is slower.

Edge finders are the most basic internal capacitor detectors. Edge finders detect the edges of the stud or other material behind the walling. This finder must first be calibrated over an empty section of the wall, and then it can be moved along the wall until it senses a change in density - such as the edge of a stud. Edge finders should be moved from both directions to find both edges of the stud. The single sensor in edge finders can be prone to error, sometimes indicating a spot an inch or more from the stud’s edge. Once both edges have been marked, the user must determine the location of the stud’s center.

Center stud finders detect the center of the stud by using two sensors that register separate readings of the wall’s dielectric constant. When the two readings match, the finder indicates that it is centered on a stud. The several readings are used to determine the target center. Center finders only need to be moved from one direction. Like edge finders, center finders require calibration. Wall texturing can cause bumpy movement across the wall impairing the calibration readings.

Instant stud finders are a more recent development. Instant stud finders have multiple sensor plates, and do not need to be moved across the wall to detect a stud, overcoming the effects of bumpy wall texture. They use an algorithm to analyze the readings from the multiple sensor plates for a quicker, more accurate indication. Instant stud finders sense multiple regions of a wall simultaneously including the center of a stud, edges of the stud, and regions without studs. Instant stud finders will indicate varied widths of studs and the location of multiple studs at the same time.

Because the instant stud finders use multiple readings to determine the location of studs they are also less vulnerable to construction anomalies (such as uneven paint, wall textures, wallpaper, uneven plaster, etc.) that can disorient center and edge finders.