How It Works - UK (2020-05)

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TECHNOLOGY

M

etal detectors come in a range of shapes

and sizes, and though they all share the

same purpose of finding buried metal

objects, they can be used in many different ways.

You may see people patrolling with a metal

detector in hand and wonder how much fun it

could possibly be, but the main reward of this

hobby comes at rare and unexpected moments.

From the moment the metal detector is turned

on,thedetectoristwalksinanticipationofthe

From beachfront hobbies to savinglives,these

dev ices have many applications

How metal

detectors work

Words by Ailsa Harvey

Types of detector

All metal detectors use electricity-to-

magnetism conversions, but there are

three different types that use different

electromagnetic frequencies. Most

amateur metal detector users will use the

simplest type. These have a fixed low

frequency of less than 30 kHz and are

most commonly used for treasure hunts.

Higher frequency detectors, called

pulse induction (PI) detectors, use signals

in short pulses. These are better for

finding items deeper in the ground. The

third metal detector type is full-band

spectrum, or FBS. These use different

frequencies at the same time, so are able

to pick up a larger range of items from

different distances. Some advanced

detectors can differentiate between the

types of metal discovered and how far

away finds are.

Waterproofmetaldetectorsareusedtoexplore

thedepthsoftheocean

© Alamy

buzzing signal that tells them a metal object is

close by. Follow ing this, the peak of their

excitement – and often the cause of subsequent

disappointment – is the big reveal. Have they

stumbled across precious treasure? Or will they

just end up picking up someone else’s litter?

Either way, for many people metal detecting is

all about the search.

More expensive and sophisticated detectors

canbeused in safet y and securit y. Technolog y

found in handheld metal detectors can also be

utilised to monitor items people take abroad or

into protected buildings. The electronic

door ways you walk through in airport securit y

can reveal any prohibited items on your person,

while another detector scans your bags. While

these are much more high-tech, all metal

detectors use the core principles of

electromagnetism that were seen in Alexander

Graham Bell’s first metal detector in 1881.

Prepare for

rubbish

For every piece of treasure

you find you are likely to find

many more tin cans, bottle

tops or foil pieces.

Persistence is key.

Findthe

best spots

If you’re looking for items of

historic value, check with

historians – but don’t

forget to ask for permission

from the landowner!

Stayflat

When scanning the floor,

make sure the coils are

parallel to the ground. If part

of the detector is lifted too

high you could miss out on

potential treasure.

Go afterrainfall

When the ground is wet it

becomes a better conductor

of electricity. Not only will it

be easier to detect metal,

but also easier to recover

items from deep soil.

Sweepsurfaces

Sometimes tiny pieces of

rubbish or minerals can set

off the detector. Removing

any that could be lingering

above ground prevents

unnecessary digging.

Followsuccess

If you uncover something

impressive, don’t stop

looking. Often items are

found together, so make

sure you check the

surrounding area.

Tips for treasure hunters

© Getty