A metal detector is an electronic device designed to detect the presence of metal objects. It functions based on the principles of electromagnetism. When a metal object comes within the detector's magnetic field, it causes a disturbance that the detector can sense and signal to the user. These devices are used in a wide range of applications, from security screening at airports and public events to treasure hunting and industrial quality control.
The history of metal detectors dates back to the late 19th century. The first metal detectors were developed to assist in surgical procedures, helping to locate bullets and other metal fragments in the body. As technology advanced, their applications expanded. During World War I and World War II, metal detectors were used to detect landmines and other buried metallic objects. In the post - war era, they found their way into security and industrial settings. The development of more sensitive and portable detectors continued over the years, leading to the wide variety of metal detectors we have today.
Pulse Induction (PI): Pulse induction metal detectors work by generating short, powerful magnetic pulses. When a metal object is in the vicinity of the detector, the magnetic field induces eddy currents in the metal. These eddy currents then create a secondary magnetic field that the detector can sense. The detector measures the time it takes for the secondary magnetic field to decay, which is related to the size and conductivity of the metal object.
Very Low - Frequency (VLF): VLF metal detectors operate using two coils - a transmitter coil and a receiver coil. The transmitter coil generates a low - frequency magnetic field. When a metal object enters this field, it distorts the field. The receiver coil detects this distortion and sends a signal to the detector's electronics. The phase and amplitude of the received signal provide information about the type and location of the metal object.