A metal detector is an electronic device that is used to locate the presence of metal in any specific region. This instrument has been used worldwide for years to detect valuable relics, underground mines, and armed weapons buried inside the ground. It is also used for archaeology, security checks, geophysical prospecting, and detection of foreign bodies in the food or reinforcing bars for the in the walls and floor during construction.
The science behind a metal detector
The science behind a metal detector involves electromagnetism. Electromagnetism is a phenomenon of the interaction between electricity and magnetism. Magnetic forces are produced when there is a flow of moving charges, also known as electricity. The simplest metal detector consists of a coil wire through which a current of charged particles is passed to create a magnetic field around it. This magnetic field induces a charge in the metal object placed near it which in return produces its magnetic field. Which can then be then detected by the sensor, a magnetometer, in the device? This charge is induced because if placed in a magnetic field, the electrons in an atom of a metallic object start acting differently. The closer the found metal object is, the louder the sensor beeps.
Many of our daily use appliances function on the same principle — the electricity used by various methods, some renewable and others which are not. The idea of electromagnetism is used to produce electricity by rotating copper wires through a magnetic field at a very high speed. This induces a current in the wire which is then channeled to be used for other purposes. This electricity is used by various appliances to work the electric motor, which produces a magnetic field in the wires that pushes against the permanent magnet to make it spin the engine. This depicts that electricity is used to make magnetism and vice versa. To sum up the relationship between the two, a Scottish physicist, James Clerk Maxwell gave mathematical equations, also known as Maxwell Equations.
Some of the key concepts at play with metal detectors are:
- Frequency
- Ground Balance
- Discrimination
Frequency of a metal detector determines the ability of the device to detect the presence of targets. A high-frequency detector can locate smaller objects with ease, whereas low-frequency detectors are more sensitive to larger objects and greater depths.
Ground balance and all the related details
Ground balance determines the depths of the ground, which are mineralized. Such grounds contain minerals and salts that make detection difficult because they respond similarly to the magnetic field produced by the metal detector. Ground balance removes the effect of these minerals that try to mask the buried targets. There are three types of ground balance:
- Manual Ground Balance: This allows you to change the ground balance settings manually.
- Automatic Ground Balance: This detector determines the optimal settings for ground balance automatically. This is the most convenient way as Automatic ground balance is rarely wrong about the settings.
- Tracking Ground Balance: This particular detector adjusts the ground balance settings continuously as per change in the ground. The advanced technology of tracking ground balance cannot be matched by either one of the trackers, as mentioned earlier.
Discrimination is the ability to difference between various types of targets. It identifies the goals based on specific properties like ferrous and conductivity. This helps us save our time not digging up for junk objects. There are different types of discrimination:
- Iron Reject: This discrimination is used when the material being searched is gold. This is done to avoid any iron objects that can be considered junk.
- Notch Discrimination: This discrimination allows certain materials to be targeted, leaving out others.
- Variable Discrimination: The type enables you to change the level of bias using a control meter to adjust.
- Smartfind: It is the most advanced type of discrimination as it plots the targeted materials based on the ferrous and conductive properties. This two-dimensional display helps in filtering out the unwanted objects.
Different types of metal detectors
There are different types of detectors. Some come with a sensor unit in the handheld which is swept over the ground to detect the presence of any buried metallic object. As soon as the metal detector sweeps over the metal object, a needle in the sensor indicates it. A beeping sound is heard in the headphones attached to the sensor. Others are a stationary walk through metal detectors. These detectors are used for security screening at airports, prisons, and other buildings.
Another important aspect of metal detection is the depth factor. Does the question arise that what depth does a detector cover? The answer lies in the diameter of the coil. The larger the coil, the deeper its detection will be. However, there are a few factors that affect the detectability of the objects. Some of them are:
- Ground Mineralization: The lower the mineralization of the ground, the deeper the magnetic field will seep in. Ground mineralization affects detectability significantly.
- Target orientation: The orientation of an object means the angular position of an object. This is affected because flatter objects are more comfortable to detect.
- Target Size: The size of the target matter because larger objects are easier to locate than the smaller ones regardless of the depth of the ground
- Target Material: The main property at play here is the conductivity. High conductive metals are easily detected than the low conductive metal.
- Target Shape: Detection of circular objects is relatively easier than the detection of long thin objects.
Conclusion
Now that you are well aware of all the facts, you can invest in quality metal detectors if you are looking for one. You are now well equipped to find the most suitable device depending on the type of object being located or the nature of the ground being searched. In case of any unanswered queries, you can contact us.