It depends on what you want to “see” and how much you want to pay. To locate a stud, the old school technique of tapping a tool on the wall for acoustic differences used hearing rather than sight and it was free. Initially, battery-operated stud finders used magnets to find screws and nails and provided an audio signal when they were detected. Today, several sensing technologies are used in basic stud detectors to more advanced wall scanners. The results are provided on a visual display for the user to see behind drywall or other materials, including concrete.

Magnetometers detect nails, screws or the presence of metal behind the wall. Devices that use rare earth magnets can detect metal pipes and metal studs as well as nails and screws.

Rather than 1 or even 2 sensors, Franklin Sensors stud finders use up to 13 sensors operating simultaneously to detect studs. The company’s patented Multi-Sense Technology employs a capacitive sensing technique with up to 13 plates and a common plate. Arranged in a sensor array, triangulation results in a larger sensing area and deeper, more accurate stud detection.

Multi-Sense Technology. Image source: Franklin Sensors

The Bosch D-TECT 150 wall/floor scanner uses ultra-wide band (UWB) radar technology to see up to 6” width and depth. The scanner has seven detection modes: concrete, wet concrete, deep concrete, in-floor heating, drywall, metal and signal view. Depending on the conditions, it can detect ferrous and non-ferrous metals, wood, live wiring and plastic pipes, including metal detection in concrete up to 6” deep.

Vayyar Imaging’s Walabot DIY 2 wall scanner used with an iPhone or Android smartphone displays its results on the smartphone’s screen. Using radio frequency technology, the 3-D scanner can see inside walls to a depth of 4”. In addition to the usual suspects, it can also find fiberoptic and other cables. In the Images Mode, it can even detect mice, rats or termites inside the wall.

Smartphone display of scan. Image source: Vayyar Imaging.