Metal Detector Buying AdviceUnder different situations, to mention the
words metal detector, you will get completely different
reactions from different people. For example, some people
think of combing a cave in search of coins or buried treasure.
Other people think of airport security, or the handheld
scanners at a concert or sporting event. The truth is that all
of these scenarios could be real. Metal-detector technology is
a huge part of our lives, with a range of uses that spans from
leisure to work to safety. |
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The metal detectors in airports, office buildings, schools,
government agencies and prisons help ensure that no one is bringing
a weapon onto the premises. Consumer-oriented metal detectors
provide millions of people around the world with an opportunity to
discover hidden treasures around them.
The actual usage of
metal detectors is based upon the rules of electromagnetic
induction. Metal detectors contain one or more inductor coils that
are used to interact with metallic elements on the ground. The
single-coil detector illustrated below is a simplified version of
one used in a real metal detector. A pulsing current is applied to
the coil, which then induces a magnetic field. When the magnetic
field of the coil moves across metal, such as the coin in this
illustration, the field induces electric currents in the coin. The
eddy currents induce their own magnetic field, which generates an
opposite current in the coil, which induces a signal indicating the
presence of metal.
Most of the metal detectors use two
oscillators; each of them produces a radio frequency. One of these
oscillators uses a coil of wire that is called as the search loop.
The second oscillator uses a much smaller coil of wire, and is
usually inside the control box and is usually called the reference
oscillator. By adjusting the oscillators so their frequencies are
almost the same, the difference between them is made audible as a
beat note, this beat note changes slightly when the search loop is
moved over or near to a piece of metal. It has been found in
practice best to make the search oscillator fixed say at 100 kHz and
to arrange for the reference oscillator to be adjustable 100 kHz
plus or minus 250 Hz. This gives a beat note of 250 Hz to 0 to 250
Hz. The beat note disappears or nulls when the two oscillators are
about equal. This type of detector is most sensitive when the beat
note is close to zero, about 5 Hz (motor boating) any slight change
being noticeable.
Maybe you're close to the ocean or lakes,
and are thinking of jumping in the water with your metal detector to
find out what was lost there? If finding jewelry is your thing then
a waterproof detector is a must. Waterproof detectors could be still
functional even in deep water.
Buying Tips:
When
buying a metal detector for home security, make sure that you
determine where to put the metal detector. You don't want the metal
detector to go off everytime someone walks in the door with a belt
buckle. For the most part, you want to have your metal detector
protecting a room with your highly valued prized belongings. Most
metal detectors you buy are the ones to help you find items
containing metal on the ground. Those probably would not be useful
for home security. You want to the ones that can fit around a
doorway. It is best to ask a professional home security company to
determine if you even need metal detectors for your home.
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