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Detection Technology of Metal Detection
2017-10-27 17:30:17
The digital pulse signal reception and transfer of the metal detection gate is generated by the DDS (Direct Digital Synthesizer) and is implemented by an FPGA (Programmable Device Integrated Circuit). The pulse signal can control the discovery of the coil and activate a pulsed magnetic field. If there is no metal through, in the field of detection coil magnetic field is zero; when there is a metal object in the past, it will re-disrupt the original magnetic field distribution, this time, the device detection coil will be extremely sensitive to check this Change, produce the corresponding electrical signal, and then enter the equipment system to analyze the background, and then through the alarm signal, and from the top of the door to the digital tube to detect the location of the object to complete the detection process.  
(A) to improve the detection function strength
In order to be able to make the detection performance of the class well, in the design of technical thinking point of view, should consider the detection of metal detection gate area of ​​the magnetic field part of the uniform situation. Typically, the detection of metal door frame inside the edge of the winding turns, usually set a 2200mm × 500mm around the rectangular coil, winding the same direction, and the internal two-coil interface to be able to achieve interconnection, and thus can make two The coil between the composition of a large coil; corner is usually set into a circular arc, the angle should be noted that can not be set too small to prevent the local magnetic field is too strong. When the excitation signal is introduced from the interface, the internal flow of the coil will produce the same current, the same size of the current, making the magnetic field gradually strengthened with each other, thus forming a highly efficient detection area, to achieve uniform distribution of the magnetic field to ensure the stability of the basic performance.
(B) to improve the detection sensitivity
In order to enhance the sensitivity of the metal detection door system and avoid the defects caused by the traditional detection method, the technical requirements in the area of ​​the metal detection gate should be combined with the area of ​​the detection coil to cancel the change of the source magnetic field generated by the transmitting coil Set the technical parameters. For this reason, around any of the probing coils should be wound around a thin copper wire around the launch coil into a reverse direction and follow the path of the detection coil. The purpose of this is to enable the opposite direction of the coil to be opposite to the direction of the magnetic field of the transmitting coil so that the number of turns of the response coil can be set to ensure that the magnetic field in the detection coil region is zero. However, the result of the cancellation can not guarantee that the magnetic field in the detection coil is equal and zero, for which the coil is also wound around the area. Zeroing the coil is also around the launch coil with thin copper wire wound, according to the "8" shape in the detection area around a few back and forth. By adjusting the size of each small closed area of ​​"8" and the number of turns of the coil to enhance or attenuate the intensity of the co-directional or reverse magnetic field, it is ensured that the magnetic field strength of the detection area is the same and zero.