How A Metal Detector Works

How Metal Detectors Work
by: Phil Morris


The first metal detector was created in 1881 by Alexander Graham Bell
to detect the bullet lodged in the body of President James Garfield when
he was assassinated. The first portable version was patented in 1931 by
Fischer. Since then, this instrument has become very common. Here are
some insights on the workings of metal detectors.

What is a metal detector? An electronic instrument that can find any
instance of metal from the ground, a human body or a parcel is called
metal detector. It has the ability to pass through the sand, soil, wood
and any other non-metallic items. It can track anything metallic.

How the metal detector is constructed? An elementary metal detector has
an electronic box along with a battery on one side, with a handle to
let the operator place his arm. It has a coil made of insulated wire
wrapped around the telescoping shaft and ends in a round plastic disk. The
disk is displaced from the shaft making an angle that helps it to
maintain parallel position to the floor. The operator holds the electronic
box and switches on the power to start sweeping the coil slowly on the
ground till there is an electronic signal. This signal shows the
presence of a metallic item underneath the area already swept by the coil.

How does a metal detector work? Metal detectors use the principal of
electromagnetism and the effect it exerts on metals. The metal coil
called the transmitter works on the battery power and generates a magnetic
field that works on the surroundings. When this field enters the ground,
any metallic item becomes magnetic. This generates the electronic
signal, which is detected by the receiver in the coil. Receiver in turn
dispatches a signal to the electronic box. The speaker makes this sound
louder, generating a beep for the operator. The electronic box consists of
microprocessors to measure the time lag between charging the area and
receiving the signal. This time lag is called the phase shift and lets
you know which metals are present. Using this principle, you can
configure the high-end metal detectors to look out for specific metals.

For more Information on how Metal Detectors work, follow this link:

http://electronics.howstuffworks.com/metal-detector.htm