Level of magnetic field in state of nature is about 48μT and it will be increase if there is metal or magnetic substance around the smartphone.
This app measures nearby electromagnetic fields using the phone's built-in magnetometer compass.
If there is any metal in the area, the strength of the magnetic field should increase, It is possible to detect the metal in such principles.
When metal is detected, it notifies by sound and vibration.
Try Metal Sensor App!! Detect hidden camera, Detect Spycam, Detect coins, Detect treasure, Detect lost electric products. It will let you detect the metal.
(Gold and Copper coins(Nonferrous metal) cannot be detected accurately)
* Metal Sensor App. cannot be operated if your smartphone does not have magnetic sensor.
Do not rotate or tilt your phone. This can cause false readings and need of recalibration.
If you put your smartphone vertically, it will recalibrate.