Keep the object to be measured at a distance, turn on the knob switch and adjust slowly until the device is in a state with no sound and no light to detect metal. When the detector's metal detection head (METAL) is moved parallel to the surface of the object, and a voltage loop is detected, the detector will respond. The detection part (VOLTAGE) moves parallel to the surface of the object. When the detector is near a metal object or a voltage circuit, it will emit light and sound. When there is no metal object or voltage circuit nearby, there will be no light or sound. After testing, please turn off the power. The detector cannot test AC voltage inside metal pipes, metal walls, or deep areas. Power supply: 6F22 type 9V battery (battery not included) Product size: 150x78x24mm Standard configuration: bare device (no battery), English manual Product advantages: suitable for use in interior decoration structures; it can detect the position of metal and wires in walls. When metal or voltage is sensed, the instrument will emit light and sound. Product technical features: Voltage test: AC 100V and above, depth up to 30mm Color: black Material: plastic Package Contents: 1 * metal detector (without battery) 1 * English manual Only the above package content is included; other items are not included. Note: Lighting and different displays may cause the color of the item in the picture to differ slightly from the actual product. Measurement error allowance is +/- 1-3cm.