Answer: The detection depth of underground metal detectors is related to the metal material and shape of the objects being detected and the soil quality of the detection site. The detection depth of the same detector in different regions is completely different, because underground metal detectors are designed based on geological characteristics. , so the detection depth of the underground metal detector cannot be detected in the air (that is, suspended in the air). The best detection effect can only be achieved when the metal detector and the earth have a magnetic induction balance. If it is suspended in the air, the magnetic induction balance cannot be achieved! For example, if a silver dollar can be detected 20 centimeters in the air, then if the silver dollar is buried underground, the detection depth will be greatly increased, and the longer it is buried, the easier it will be to detect, because the metal is buried for a long time. The ground will gradually oxidize, producing metal rust that spreads around and reacts with the surrounding soil, generating a strong magnetic field, increasing the area of the metal and increasing the signal strength.