How Detectors Work
Metal detectors create an electromagnetic field which penetrates the ground. Metal
objects cause a change to this field because they conduct electricity. The detector senses
this change and sends a signal back to the control unit, alerting the operator.
1. Battery (Inside handle)
The battery provides power to the detector.
2. Control Unit
This is where the transmit signal is
generated and the receive signal is
processed and converted into a target
response.
3. Search Coil
The detector’s search coil transmits the
electromagnetic field into the ground and
receives the return electromagnetic field
from a target.
4. Transmit Electromagnetic Field (blue)
The transmit (Tx) electromagnetic field
energises targets to enable them to be
detected.
5. Target
A target is any metal object that can
be detected by a metal detector. In this
example the detected target is treasure,
which is a good (accepted) target.
6. Unwanted Targets
Unwanted targets can be ferrous (iron),
such as nails, and can also be non-ferrous,
such as pull-tabs. If the metal detector is
set to reject unwanted targets then a target
response will not be produced for those
targets.
7. Receive Electromagnetic Field
(yellow)
The receive (Rx) electromagnetic field is
generated from energised targets and is
received by the search coil.
8. Target Response (green)
When a good (accepted) target is detected
the metal detector will produce an audible
response, such as a beep or a change
in tone, and a visual display of target
information will be shown on the screen.
Basic Principles
Metal detectors work by transmitting an electromagnetic field from the search coil into
the ground. Any metal objects (targets) within this electromagnetic field will become
energised, creating their own circular electric currents (eddy currents) and transmit an
electromagnetic field of their own. The detector’s search coil senses this receive signal and
alerts the user by producing a target response. Minelab metal detectors are also capable of
discriminating (or differentiating) between different target types and can be set to ignore
unwanted targets.
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How Detectors Work | 14Contents
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