Metal detectors

Modern metal detectors came about by somewhat of an accident. A man named Gerhard Fisher was trying to develop a form of radio direction-finding that would make navigation more accurate. He soon found, however, that rocks with heavy ore content would distort the radio signals–which led to the prospect of being able to locate metal hidden in other materials. In 1937, Fisher received the first patent for a metal detector.

Fisher’s invention was first put to practical use as metal detectors during World War II. These contraptions were large, heavy and required separate battery packs–but they proved useful enough to retain popularity even after the war. The surplus of metal detectors was bought up by treasure hunters–thereby turning metal detecting into a recreational sport.

There are many types of metal detection, but they all share various similarities. All detectors rely on a basic system called beat frequency oscillation (BFO). This system involves two coils of wire, which are connected to an oscillator that produces thousands of pulses per second. When the pulses travel the length of the wire, they create radio waves.

A tiny receiver located on the metal detector will pick up these radio waves and transmit them into an audible series of beeps–usually based on the difference between the frequencies. When the coils pass over a metal object, the current passing through the coils creates a magnetic field around the object. This newly-created field interferes with the frequency from the initial coils, thereby changing the frequency of oscillation in the metal detector. The resulting radio waves change the duration and tone of the beeps, and that’s why hand held metal detectors will beep more rapidly when passed over metal objects.

Although they have become popular on countless beaches across the world, metal detecting has become crucial in the safety/security field. We’ve all experienced the relentless (see: irritating) safety measures set up at the airports that culminate in walking through a detector, and the lucky ones get to be frisked by a security wand for good measure.

Security wands have also found a niche on the consumer market and anyone can order one from the comfort of their homes. Companies like White, Garrett, and THD offer wands with advanced features. For example, Garrett’s SuperWand offers utmost sensitivity with automatic retuning, which means that it never needs to be adjusted. It also claims to be able to accurately differentiate between ferrous (containing iron) and non-ferrous materials, stainless steel and other dangerous contraband. Walk-through metal detectors can note a presence of metal, but wands can pinpoint the exact location of weapons on a perpetrator.

Many have found security wands useful in not just airport security, but any occasion where crowd safety is necessary. Sporting events, political rallies and even some public schools have utilized the effectiveness of security wands.

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