Since 1931, when the first portable metal detector was patented, the growth in the use of metal detectors has steadily increased. Metal detectors are every where. There are both industrial, commercial and personal use of metal detectors. When most people think of metal detectors they think of the guy on the beach with a set of head phones swinging back and forth a funny looking stick. People that use metal detectors to look for lost relics or treasure are known as treasure hunters, or relic hunters.

How do metal detectors work? What wondrous magic do they use to see through the ground and point us to what we are looking for. The principles behind metal detectors are fairly simple. The first metal detector was invented by Alexander Graham Bell in 1881. Although the principles a simple their use in the invention were ingenious especially for the time.

Metal detectors can be used to find all sorts of metal in anything but other metal. There are metal detectors designed for specific terrain; for instance under water. The reason for this will become apparent when we talk about how they actually work.

Metal detectors are designed to detect shifts in electromagnetism in metal. This is accomplished by transmitting a magnetic field through the target surface. As the magnetic field passes over an area metal objects in the area will become magnetically charged. These changes in electromagnetism are detected in by a receiver attached to the metal detector in very much the same way radar detects aircraft in the sky. Once a shift in the magnetic field is detected then a signal is sent to a speaker to notify the operator that a piece of metal has been detected.

With older metal detectors different types of metal could not be differentiated between. But, today’s metal detectors can determine the difference between different types of metal and signal to the operator which type it is. Higher metal detectors can actual be programmed to only search for a specific type of metal.

The magnetic field of a metal detector can be generated in many different ways. But, there are three specific ways that modern metal detectors generate this field. First would be via a pulse and if there is an echo of the pulse detected then you have found some treasure. The second way is through what is known as beat frequency. With beat frequency two oscillators are used to create different but close frequencies. When an audible beat is detected between them then metal has been found.

The third and final detective device uses measuring sine waves. When there is no metal in the area the sine waves are flat like a lake on a windless day. When there is a shift in the magnetic field indicating a change in magnetism the sine waves bounce to indicate that metal has been found.

Although some of this really sounds very scientific, it really is not very difficult to understand. The basic mechanics behind a metal detector is that it plays on metals ability to become magnetized and then measures those changes to determine where the metal is and what type of metal it is.