What is the technology VLF metal detector
Metal Detectors VLF (Very Low Frequency ) Is the most common and the perfect type of metal detector is being used to detect hidden coins , gold nuggets , military paraphernalia , or other metal objects. It is built on technology VLF most conventional and computerized devices of all known manufacturers.
After VLF detector based on the principle of inductive balance using very low frequency ( less than 20 kHz). Most devices have VLF range of operating frequencies from 2 to 20 kHz. This range of radiation is best for the detuning from the influence of the soil and the detection of small objects.
It is known that the different metals have different conductivity. VLF detector analyzes the phase difference between the signal from the transmitting and receiving coils . The phase shift varies depending on the conductivity of the metal. This makes it easy to distinguish black from colored metal and non-ferrous metals together ( silver, copper , bronze , lead) . Feature discrimination VLF metal detector is implemented well.
Depth detecting objects at different search conditions depends on the size of the object , the object orientation , the type of soil and its properties .
The principle of the VLF metal detector
Search head form a radiating and receiving coils arranged in a circular horizontal block . Alternating current flowing in the coils of the emitting coil creates an electromagnetic field . The emitted signal is a sine wave at a constant frequency and amplitude. Effects on soil scanned made constant electromagnetic field.
When the engine head near a metal object on the surface eddy currents, which produce their own magnetic field. This field triggers an alarm ( secondary electromagnetic field) in the receiving coil . The amplitude of the signal in the receiving coil is increased, and the phase shift varies with the conductivity of metals (ferrous or non-ferrous metals ) .
Operation VLF detector based on an analysis of the amplitude of the signal from the object in the receiving coil and search head of the phase shift between the emitted and received signal. If no search head near metallic objects in the amplitude of the receiver coil signal is minimal , and the phase shift of 0 or 90 degrees.
VLF technology allows selective discrimination of metals , ground balance and metal debris to determine the metal target, and even distinguish between non-ferrous metals .
VLF metal detector search coil require a very accurate production and customization. This is a prerequisite for the effective operation of the device .
Operating frequency VLF metal detector
Can be divided VLF frequency range of operation of devices on multiple ranges . Each of them will correspond to a specific group of objects to be detected.
Smaller effectively detected by the operating frequency range 5 … 15 kHz (such as coins , silver jewelry ) . Operating frequency range of 5 … 10 kHz is effective for finding all sorts of military paraphernalia ( bayonets , helmets , parts, weapons).
VLF metal detector to find gold using the operating frequency range of 10 … 30 kHz, and even outside the range of VLF ( maximum up to 100 kHz) . At these frequencies, improved sensitivity to very small objects, such as the gold nuggets , which generally have small sizes and weights .
There VLF devices simultaneously working on multiple frequencies. Multi-frequency search under certain conditions gives advantages. This greatly increases the efficiency of detection , and satisfies the desire to own a versatile instrument . But there are two important points.
A significant increase in the depth of discrimination in comparison with single-frequency devices is not achieved. In the case of complex shape their findings may be ” cut off .”