Metal detectors is often a big long stick with some circular coils attached at one end and it beeps whenever it is places near some metal or other ferro-magnetic material. There are both the toy versions of metal detectors that people give to kids as gifts and the professional versions of metal detectors that can actually detect metals buried in the ground as deep as 1.5 meters or more. But if you have an Android smartphone then you do not have to buy any extra metal detector. You can turn your existing Android smartphone into a simple metal detector easily.
This can be achieved through the help of an app called “Metal Detector”. This app is available in two versions – free version and the pro version. The free version displays ads while the pro version does not. The only requirement for this app to work is that your Android smartphone should have a magnetic sensor. The program also makes use of the accelerometer sensor to find the orientation of the phone. The magnetic sensor is not available in all of the Android smartphones, so you should check the specifications of your smartphone before installing this app using CPU-Z.
After installing the Metal Detector app, you should remove all the back panels or flip covers that could have magnetic material in them and keep the smartphone away from devices that generate electromagnetic signals such as your TV, computers, other phones etc. Now when you move the phone closer to a metal or ferro-magnetic material, it will make an audible alert and show you the intensity of the magnetic field in micro-Tesla. But the app does not work with non-ferromagnentic metals like aluminum and works only upto a distance of 15 cm from any metallic materials.
You can get the Metal Detector app from https://play.google.com/store/apps/details?id=com.gamma.metaldetector.