How a Metal Detector Works

by : Jessica Deets

The metal detector, as the name suggests, is a tool to detect the presence of metal.

The most often used place for metal detectors is at the airports for check-ins and in high security areas.

Whether you are carrying metallic object in your shirt or in a bag, the metal detector is going to detect it. Even when the metallic objects are lying on the ground, metal detectors can detect those too.

Metal detectors can see through non-metallic surfaces. No wonder, it can see inside your bag, and detect the metallic piece instantly.

Metal detectors don't only find applications in security areas, but are abundantly used in treasure hunting as well and for finding lost items that consist of metal.

This wonderful application of science was invented by none other than the legendary Alexander Graham Bell. That was more than 125 years back in the year 1881. Fischer came out with a portable metal detector in the year 1931.

There have been many more modifications on the first portable detector made by Fischer. Hans Oersted was responsible for discovering electromagnetism. This happened in the year 1820.

Metal detectors work on the principle of electromagnetism. Electromagnetism is the science of studying two forces: those of electricity and magnetic in tandem with each other.

Metal detectors are supposed to be very good conductors of electricity and magnetism. Therefore it is but natural that the metal detector is affected by electromagnetism in the surrounding.

A high-powered coil generates magnetic effect with the help of power generated by the attached battery. When this electromagnetic field penetrates the ground the metals tend to get charged with magnetism.

The coil detects the electromagnetic behaviour and a signal is sent to the electronic box. The speaker attached to the electronic box beeps and the operator immediately becomes aware of the presence of metal.

Modern metal detectors work on the similar principle with more electronics added. Now you'll find microprocessors attached inside the box. These microprocessors can indicate the presence of a metal type. It can measure the time between charging of metal and the receiving the beep that concludes the type of metal and this length of time is known as phase shift.

There are adjustments in the device when searching for a particular kind of metal. Some detectors can even tell you on a viewscreen what it is that they found.

Metal detectors have electronic boxes with a battery case on one end and a handle for the operative's arm on the other. It has a coil made of insulated wire wound around a telescoping shaft that is inside a plastic disk. The device is held parallel to the ground due to the angle at which the disk comes out of the shaft. The electronic box is held in the hand, the power is put on and the coil end is slowly swept over the ground.

If the trace of metal is there on or buried in the ground, an electronic beep is heard when the device sweeps the ground.

Working with a metal detector is easy. With just a few hours of training a person can become very good at the skill of properly using a metal detector.