Metal Detector Sensor
Metal detector sensor is referring to a special sensor or tools used in metal detectors
that contains special designed circuits for detecting of metallic objects underground.
Metal detector sensor maybe a search coil as in electromagnetic metal detectors,
or refer to a special circuit contained in search probe in more complex metal detectors
devices like 3D imaging devices.
Here in this article will explain all details about metal detector sensor and its applications
in metal detectors plus a principle of metal detectors and its uses in treasure hunting
and other applications.
Metal detectors is an electronic device specially designed for detecting of buried underground
metal objects such as golden treasures, archeological treasures of ancient civilizations
and various kinds of precious and non-precious metals.
Metal detectors can be used by prospectors and treasure hunters.
They help detect any metal object under the ground for varying depths depending
on the device type and technology.
Metal Detector Principle
While explaining how metal detectors work can be complicated,
the principle behind their function is fairly simple:
metal detectors transmit an electromagnetic field toward the ground and then analyze
a reflected magnetic field – resulting from hitting a metal object like a coin
– as it is returned from the area that the signal was originally transmitted into (the ground).
In electromagnetic detectors for example there are two copper coils in the search
head [ search coil] of the metal detector. One coil act as a transmitter, and the other
coil acts as a receiver. The first one transmits a magnetic field that is generated
by electricity that moves through the coil. That magnetic field that is being transmitted
will cause electricity to flow into metal objects that it comes into contact with.
The second coil, the receiver, identifies the difference in the magnetic field that
is created as the buried metal absorbs it and the electricity begins to flow through it.
When the change is detected, the second coil sends the alert to the control box
through the attached cable, and you hear the signal from the speakers or your headphones.
The weaker the returning magnetic field the weaker the alert.
In other words: One coil sends, the other receives, detects changes and lets the control box
know and process the difference in signals and convert it to a digital signal that can be shown
as a number (Target ID) or as an audio tone
Find out more here : Metal Detector Principle
Uses of Metal Detector
- Find buried gold treasures such as: golden chests, ancient coins, golden jewellery
- Detection of Non-Ferrous metals such as silver, bronze, copper.
- Prospecting of natural gold objects such as gold nuggets, gold veins.
- Cavities detection (in some devices) like: tunnels, chambers, dugouts, bunkers
- Ferrous metal detection: iron, steel, iron alloys
Types of Metal Detectors
Metal detectors are very diverse. There are many types of metal detectors
which are classified according to different classifications.
Metal detectors can be classified according to their uses or according to the search system
and the technology in the device or according to other factors.
But the most commonly used classification is according to the search technology of the device,
where metal detectors are classified into several types will be reviewed by the following paragraph
Electromagnetic Metal Detectors
These devices have a limited scope of depth and relatively cheap prices and It is the most widespread
devices in the world because it is easy to manufacture and reliable for hobby and beginners.
Examples: Impact Pro
3D Imaging Metal Detectors
3D imaging detectors are characterized by high accuracy and coverage of a wide field of scan
and multiple features that ensure the accurate results for the prospector and professional searcher.
Examples: OKM EXP 6000
Long-Range Metal Detectors
The long-range metal detectors use search antennas to receive target signals buried underground remotely.
These devices are characterized by a very wide field of scan and huge search depths compared to other types of metal detectors
Examples: Mega Scan Pro
Multi – Systems Metal Detectors
There are some metal detectors devices that may contain more than one search system
that use different technologies within a single device and this gives the prospector
multiple search options that can be used for different applications or to confirm the results of other search systems.
Example: COBRA GX 8000
Metal detector can use what is called Inductive proximity sensors that can only detect metal targets.
They do not detect non-metal targets such as plastic, wood, paper, and ceramic.
Source : Here
Metal Detector Sensor Circuit Diagram
The electronic circuitry of a metal detector sensor can be very complex and consists of
dozens of electronic components that are usually available in the electronic circuits
of various electronic devices.
The following image shows the circuit diagram for do it yourself (DIY) metal detector circuit.
Through the electronic circuit diagram, it is possible to notice the availability of various electrical elements
such as resistors – capacitors – sensors – integrated circuits and others, which are designed according
to a specific circuit diagram to reach a working mechanism that ensures the generation and reception
of magnetic fields, signal processing and analysis.
Source : ElectronicsHub.org
Metal Detector Sensor Arduino
Arduino is an open-source hardware and software company, project and user community
that designs and manufactures single-board microcontrollers and microcontroller kits for building digital devices.
Arduino board designs use a variety of microprocessors and controllers.
The boards are equipped with sets of digital and analog input/output (I/O) pins that may be interfaced to various expansion
boards (‘shields’) or breadboards (for prototyping) and other circuits. The boards feature serial communications interfaces,
including Universal Serial Bus (USB) on some models, which are also used for loading programs from personal computers.
Arduino boards can be used in metal detector manufacturing projects where electronic
circuitry is used to process and interpret signals.
You can refer to the following article for a practical example of a metal detector that uses an Arduino circuit.
Metal Detector Sensitivity
Metal detector sensitivity is the measure of a metal detector’s ability to detect a specific type and size
of metal contaminant. The better the sensitivity of the metal detector, the smaller the pieces
of irregular-shaped metal it can detect. Performance is usually expressed in terms of the diameter of
a test sphere made from a specific type of metal, such as ferrous, non-ferrous, aluminum or stainless steel.
The higher the sensitivity of the metal detector, the smaller the pieces of metal it can detect.
It is a clear ideal, but one that is complicated by a number of factors.
Source : MT
Principle of Metal Detector Used in Pharma Industry
Metal detectors available for use in pharmaceutical industries are working in different principles for examples:
Balanced coil metal detector – Magnetic field metal detector – Pulse induction metal detector
The principle of operation for all these technologies used in the pharmaceutical industry is similar to the principle
of action of any metal detector that was previously explained with differences and additional working
mechanisms related to the pharmaceutical field.
You can refer to the following article for detailed information on the topic.
Source : Pharmabiz
For more read following article : Industrial Metal Detector