Metal detectors are an electronic device used to detect the presence of metal objects, such as the one used as a portable sweeping unit or one installed in an airport terminal archway to detect concealed explosives, weapons, and so on.
Principal of Metal Detectors
Metal detectors work on transmitting a magnetic field and analyzing the return signal from the target and environment—the transmitted magnetic field changes over time, typically at the rate of relatively high-pitched audio signals. The magnetic transmitter supplies electrons in the transmitting coil, and the current varies in the loop. The receiver is made up of a receive coil that is linked to receive and signal processing electronics. Sometimes the transmit coil and receive coil are the same coil. The coils are contained within a coil housing, which is commonly known as “the coil,” and all of the electronics are contained within an electronics housing, which is connected to the coil via an electric cable and commonly called the “control box.”
Working of Metal Detectors
Metal detectors work simply by transmitting an electromagnetic field into the ground from the search coil. Any metal objects (targets) within the electromagnetic field will become energized and retransmit their electromagnetic field. The search coil of the detector receives the retransmitted field and alerts the user with a target response. Mine metal detectors are capable of ignoring unwanted targets and can discriminate between different types of targets. Let’s discuss the working of Metal Detectors.
- Control Box
The control box contains all of the electronics of the Metal Detector. This is where the transmit signal is produced, and the received signal is processed and converted into a target response.
- Search Coil
Search Coil is responsible for transmitting the electromagnetic field into the ground and then receiving the target’s return electromagnetic field.
- Transmit Electromagnetic Field
Targets are energized by the transmit electromagnetic field, allowing them to be detected.
- Target
A target may be any metal object that the metal detector can detect.
- Unwanted Target
Unwanted targets are usually ferrous (attracted to a magnet), like nails, although they can also be non-ferrous, like bottle caps. A target response will not be created for undesirable targets if the metal detector is programmed to reject them.
- Receive Electromagnetic Field
The search coil receives the receiving electromagnetic field, which is generated by energized objects.
- Target Response
When a good (approved) target is discovered, the metal detector will produce an audible response, such as a beep or a change in tone, when a good (approved) target is found. A visual display of target information, such as an ID number or a two-dimensional array, is available on several Mine lab detectors.
Key Detecting Concepts
Following are some key detecting concepts of metal detectors
Frequency
One of the primary characteristics of a metal detector is frequency, which impacts how efficiently targets may be detected is the frequency of a metal detector. A single frequency detector transmitting at a high frequency is more sensitive to small objects, while a single frequency detector transmitting at low frequencies provides more depth on large targets. VLF and VFLEX are Minilab’s single frequency technologies.
Minilab’s world-leading BBS, FBS, MPS, and new groundbreaking Multi-IQ technologies transmit numerous frequencies simultaneously, making them sensitive to both small and large targets.
Ground Balance
Ground Balance is a variable that enhances the depth of detection in mineralized ground. As in wet beach sand, salts, or small iron particles, as in red soil, may be present in this ground. These minerals react to the transmit field of a detector in the same manner as a target does.
The effect of mineralization can easily mask small targets due to the earth’s significantly larger mass than a buried target. The Ground Balance setting corrects this by removing responsive ground signals, allowing you to hear target signals without being distracted by background noise.
Three main types of Ground Balance are as follows:
- Manual Ground Balance
Adjust the Ground Balance setting manually to ensure that only the smallest amount of ground signal is detected.
- Automatic Ground Balance
The optimal Ground Balance setting is determined automatically by the detector. This is faster, easier, and more precise than manually setting Ground Balance.
- Tracking Ground Balance
While detecting, the detector adjusts the Ground Balance setting on the fly. This guarantees that the Ground Balance setting is correct at all times.
No other detector can match Mine lab detectors. Exclusive, sophisticated technology is used to provide more outstanding ground balancing capabilities.
Discrimination
The capacity of a metal detector to distinguish buried targets based on their conductive and ferrous properties is known as discrimination. You can select whether to dig up a buried target or disregard it and continue searching after accurately identifying it. Mine lab detectors can detect target identification (Target ID) numbers and Target Tones.
Four main types of discrimination in Mine lab detectors are as follows;
- Variable discrimination
The most basic form of discrimination is which a control knob controls the level of discriminating.
- Iron Mask/Iron Reject
It’s usually used with gold prospecting detectors; ignore iron junk.
- Notch discrimination
Allows you to accept or reject particular target kinds.
- Smart find
Discrimination at its most extreme level. Target IDs are plotted based on ferrous and conductive qualities on a two-dimensional (2D) display. Unwanted targets can be rejected by shading individual segments or larger sections of the show.
Uses of Metal Detector
Since 1881, metal detectors have been used for diagnostic purposes. They have been used to locate many foreign objects, such as intraocular metallic fragments, bullets, swallowed coins, and other foreign bodies and medical devices. Rapid detection of metallic objects may help in diagnosis or treatment.
