Review on 🔍 Sperry Instruments PD6902: 5-in-1 Multi-Scanner & Electrical Tester Kit - Find Studs, Metal Objects, and Test Voltage & GFCI; Audio & Visual Indicators; 120V AC, Non-Contact Detection; 2-Pc. Set by Dylan Deng

The device is calibrated every time you want to use the device and press a button. You can't test anything without spending a few seconds calibrating it first. As soon as you accidentally or intentionally take your finger off the button, it needs to be recalibrated. It works fine, just don't measure with a metal rod right in front of it. I have successfully found several electrical wires between 0.5 and 4 inches long in a (dry)wall. I've also successfully found nails or screws in the walls, 0.5 to 2 inches. I didn't try to look for studs. lets you know if something is wrong with the wiring in the outlet or if the ground connection is working properly.