Detectors are simple machines designed for identifying specific physical bodies that are not readily apparent. As an example, a metal detector is used for detecting the presence of metal under the surface. Here, you will learn the classification of detectors used for identification of under surface metals, more specifically precious metals like gold, uranium etc. This article will also provide tips for metal detector owners to cross check the efficiency of the machine.
Depending on the various mechanisms of action, the classification of detectors features three major types of metal detectors. BFO, TR and VLF are the three major types being used in different industries. Explore more about these popular detectors, how they work and their applications across various industries.
Beat Frequency Oscillation
This refers to the simplest metal detector mechanism. Here are its features.
- There is a simple two-button on/off and tuning system with a volume control in this machine. The machine sends beat radio frequency for detecting presence of metals under the surface. The strength and accuracy of this machine is satisfactory.
- It uses two different coils, one is larger and the other is smaller. Larger coil is installed in the head whereas smaller coil is inside the control box. The coils transmit sounds in two different frequencies that create a steady oscillatory beat. If there is a metal slab under the surface, the transmission is interrupted and the machine-holder can catch the offbeat. That is how the machine works.
These machines also consist of different coils for sending and receiving the sound. However, the coil sending sound has a known frequency. Here the receiving coil doesn’t produce sound. Rather, it receives the echo of the sound sent to the ground. If the sound received by the receiver has the same frequency, it signifies the fact that no metallic particle is present. And if the frequency changes, this signifies presence of metal.
Very Low Frequency Detectors
These detectors use a transmitting coil and a receiving coil. These VLF detectors have both the coils in their heads though in two different loops (outer and inner). The transmitting coil is present in the outer loop whereas inner loop contains the receiving coil. Here are the mechanisms on how this detector works.
- AC current is passed across the transmitting coil. The current creates a perpendicular magnetic field with the AC current direction.
- The field changes polarity with the change in the direction of the AC current.
- If the machine is parallel to the ground (i.e. the coil is parallel), the magnetic field will constantly change its direction up and down.
- However, any conductive material or metal slabs will interrupt the directional changes in the magnetic field. It is also possible to assume the depth and type of metal under the surface. That’s why these machines have more commercial involvement and an example of this is the Minelab metal detectors.
How to check if the metal detector is functioning or not
There are several methods to cross check the efficiency and functionality of these metal detectors. The classification of detectors here has explained the basic mechanism of action for all major types. The efficiency-test largely depends on their principle of action.
- First, switch on your metal detector and hold that close to any metal it is capable to detect. It may be a coin, bronze, metal door or anything made of metal. The positive signals will ensure that the coils are working properly.
- Next, find a neutral zone where no metal is nearby. Keep the machine switched on. Check if it gives false positive signals. This will ensure you from misidentification or confusions.
- Finally, preset a target metal under the soil, not to deep or not to superficial. Ideal depth is researched to be within the range of 60 centimeters and 120 centimeters. Try to detect the metal with your metal detector. If it can identify the metal, it’s fully functional and it’s time to start your adventure.
The classification of detectors discussed here are intended to educate enthusiastic users. Learn more about the products; compare prices and choose something that suits your budget and requirements.