This metal detector detects magnetic field values using the magnetic sensors that is built into the phone.
The magnetic field level(EMF) in nature is about 49μT(microtesla) or 490mG(milligauss); 1μT = 10mG.
As soon as your phone approaches a metal, you will see metal detector's signal increasing.
Lost anything metal?
Trying to search someone's body?
That's a great tool.
If this app does not work properly, it may mean that your phone's sensors are damaged, broken or non-existent. To initialize the sensors, point your phone up towards the sky and move it in a figure 8 pattern.
Sometimes a leather case with a magnetic "snap" can cause unwanted results. Remove the case to increase accuracy.