CN115494554A - Metal detection device and security check door based on multistage alternating magnetic field - Google Patents

Metal detection device and security check door based on multistage alternating magnetic field Download PDF

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Publication number
CN115494554A
CN115494554A CN202211224909.6A CN202211224909A CN115494554A CN 115494554 A CN115494554 A CN 115494554A CN 202211224909 A CN202211224909 A CN 202211224909A CN 115494554 A CN115494554 A CN 115494554A
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transmitting
winding
coil
magnetic field
coils
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郭俐栅
王云灵
刘金雷
姬光
蒙移发
张金海
王辉
谢群
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BEIJING TELESOUND ELECTRONICS CO LTD
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BEIJING TELESOUND ELECTRONICS CO LTD
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    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils

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Abstract

The invention relates to the technical field of security and protection security check facilities, and discloses a metal detection device and a security check door based on a multistage alternating magnetic field, which are used for solving the problem that the security check door in the prior art is easy to miss check. The metal detection device comprises a transmitting winding, a receiving winding and a detection unit; the transmitting winding and the receiving winding are arranged at intervals along a first direction in a horizontal plane to form a detection area between the transmitting winding and the receiving winding; the transmitting winding comprises a plurality of transmitting coils, the plurality of transmitting coils are overlapped along a first direction and form a plurality of transmitting blocks, and the alternating magnetic field in each transmitting block is the sum of the alternating magnetic fields of the transmitting coils in the area corresponding to the transmitting block; the receiving winding is used for generating induction signals based on the change of the alternating magnetic field in the plurality of transmitting blocks; the detection unit is used for determining the metal object information in the detection area based on the change of the induction signal generated by the receiving winding.

Description

Metal detection device and security check door based on multistage alternating magnetic field
Technical Field
The invention relates to the technical field of security and protection security check facilities, in particular to a metal detection device and a security check door based on a multistage alternating magnetic field.
Background
The security inspection door is a detection device for detecting personnel to have or not to carry metal object, and the coil that traditional security inspection door set up usually is balanced type coil structure, and the coil structure in the door plant of both sides is the same promptly, all includes the transmitting coil who sets up at the outer lane and sets up the receiving coil at the inner circle, like the structure that CN201000486Y and CN204405864U disclose, the detection principle does: when a metal object passes through an electromagnetic field, the detection is realized by detecting an electric variable signal generated by the disturbance of the metal object to the electric field, but because the energy of the electric field is stronger, when a tiny metal object is detected, the disturbance quantity of the metal object to the electric field is very small, so that the generated electric variable signal is very weak, the signal is not easy to identify, the risk of missed detection is higher, and in the security and protection industry, the occurrence of missed detection accidents possibly causes more serious safety accidents.
Disclosure of Invention
The invention provides a metal detection device based on a multistage alternating magnetic field and a security inspection door, which are used for solving the problem that the security inspection door in the prior art has high risk of missing inspection when detecting a tiny metal object.
In a first aspect, an embodiment of the present invention provides a metal detection device based on a multi-stage alternating magnetic field, including a transmitting winding, a receiving winding, and a detection unit;
the transmitting winding and the receiving winding are arranged at intervals along a first direction in a horizontal plane to form a detection area between the transmitting winding and the receiving winding;
the transmitting winding comprises a plurality of transmitting coils which are overlapped along the first direction and form a plurality of transmitting blocks, and the alternating magnetic field in each transmitting block is the sum of the alternating magnetic fields of the transmitting coils in the area corresponding to the transmitting block;
the receiving winding is used for generating induction signals based on the change of alternating magnetic fields in a plurality of transmitting blocks;
the detection unit is used for determining the metal object information in the detection area based on the change of the induction signal generated by the receiving winding.
In the above embodiment, the transmitting winding and the receiving winding of the metal detection device are respectively disposed on two sides of the detection area, where the transmitting winding includes a plurality of transmitting coils, the plurality of transmitting coils are stacked to form a plurality of transmitting blocks, the alternating magnetic field in each transmitting block is the sum of the alternating magnetic fields of the transmitting coils in the areas corresponding to the transmitting blocks, after alternating current is introduced into the transmitting coils, the alternating magnetic fields in the plurality of transmitting blocks form a multi-level alternating magnetic field, the magnetic induction strength of each level of alternating magnetic field is enhanced, and the distribution of the alternating magnetic field in the entire detection area is relatively uniform.
Optionally, orthographic projections of the plurality of emission blocks in a reference plane perpendicular to the first direction form a matrix structure with multiple rows and multiple columns, and the matrix structure is symmetrically distributed on two sides of a central axis extending in the height direction in the reference plane.
In the above alternative embodiment, by arranging the orthogonal projections of the emission blocks in the reference plane in a matrix structure of a plurality of rows and a plurality of columns, the alternating magnetic fields from different emission blocks are distributed in the height direction of the detection area, and the alternating magnetic fields from different emission blocks are also distributed in the traveling direction of the detection area.
Optionally, the plurality of emission blocks includes a top emission block and a bottom emission block, and the magnetic field strength of the top emission block and the magnetic field strength of the bottom emission block are greater than the magnetic field strength of an intermediate emission block between the top emission block and the bottom emission block.
Optionally, the transmitting coil includes a wire, the wire is enclosed into one or more transmitting sub-blocks according to a preset winding manner, and any two transmitting sub-blocks in different transmitting coils are completely overlapped, not overlapped, or partially overlapped;
and a plurality of transmitting coils with the transmitting sub-blocks are superposed to form the transmitting blocks.
Optionally, the plurality of transmitting coils include one or more first transmitting coils, and the first transmitting coils cover the entire area of the detection area in the height direction;
the first radiation coil comprises a plurality of first radiation sub-blocks, and the first radiation sub-blocks are arranged along the height direction of the detection area.
In the above optional embodiment, by providing the first transmitting coil, the alternating magnetic field is uniformly distributed in the whole area of the detection area in the height direction, and in the first transmitting coil, a plurality of first transmitting sub-blocks are formed by winding a conducting wire, so that the magnetic field strength in each first transmitting sub-block is enhanced, and the magnetic field strength in the whole area is also enhanced and is distributed more uniformly.
Optionally, the plurality of transmitting coils include one or more second transmitting coils, and the second transmitting coils cover a local region of the detection region in the height direction;
the second transmit coil includes one or more second transmit sub-blocks.
In the above alternative embodiment, by providing the second transmitting coil, the alternating magnetic field in the local region of the detection region in the height direction can be further enhanced.
Optionally, at least one of the second transmitting coils covers a bottom region of the detection region in the height direction, and is in an 8-shaped structure.
Optionally, a third transmitting coil is included in the plurality of transmitting coils, the third transmitting coil covers the whole or a partial region of the detection region in the height direction, and the third transmitting coil includes at least one transmitting unit in a "∞" shaped structure, and the transmitting unit includes two third transmitting sub-blocks.
In the above alternative embodiment, the third transmitting coil is arranged so that when a metal object passes through the detection region in the traveling direction, the metal object may disturb the alternating magnetic field in the two transmitting sub-regions arranged in the traveling direction.
Optionally, the third transmitting coil includes a plurality of transmitting units arranged at intervals along the height direction, the plurality of transmitting units are located in the same plane perpendicular to the first direction, and the plurality of transmitting units are sequentially arranged in series;
or, the third transmitting coil includes a plurality of transmitting units, the plurality of transmitting units are located in different planes perpendicular to the first direction, and orthographic projections of the plurality of transmitting units along the first direction do not coincide.
In a second aspect, an embodiment of the present invention further provides a security door, where the security door includes a first door panel, a second door panel, and the metal detection device based on a multi-stage alternating magnetic field in any one of the above technical solutions;
a security inspection channel is formed between the first door plate and the second door plate, the transmitting winding is arranged on the first door plate, the receiving winding is arranged on the second door plate, and the detection area is located in the coverage range of the security inspection channel.
In the above embodiment, first door plant can be located to emission winding among the metal detection device, the second door plant can be located to the receiving winding, emission winding can arouse after the circular telegram and produce multistage alternating magnetic field, the magnetic induction strength of alternating magnetic field at different levels obtains the reinforcing, and make the distribution of alternating magnetic field more even in the whole detection area, when small metallics pass through, this metallics can produce stronger eddy current, the magnetic field that the eddy current arouses can produce great interference to the original magnetic field in the detection area, make the receiving winding the induced signal that produces around the alternating magnetic field in the detection area takes place the disturbance have great difference, thereby can obtain the induced signal variation volume that is convenient for monitor and signal intensity is great, and then be favorable to detecting small metallics, reduce the risk of undetected.
Drawings
FIG. 1 is a schematic diagram of a metal detection device according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an orthographic projection of a transmitting winding in a reference plane perpendicular to a first direction according to an embodiment of the present invention;
fig. 3 and 4 are schematic structural diagrams of orthographic projections of two first transmitting coils in a reference plane perpendicular to a first direction according to an embodiment of the invention;
fig. 5 is a schematic structural diagram of an orthographic projection of a second transmitting coil in a reference plane perpendicular to a first direction according to an embodiment of the present invention;
fig. 6 and 7 are schematic structural diagrams of orthographic projections of two third transmitting coils provided by the embodiment of the invention in a reference plane perpendicular to the first direction;
fig. 8 is a schematic structural diagram illustrating an orthographic projection of each transmitting coil in a transmitting winding in a reference plane perpendicular to a first direction according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of an orthographic projection of each transmitting coil in another transmitting winding in a reference plane perpendicular to the first direction according to the embodiment of the invention;
fig. 10 is a schematic structural diagram of an orthographic projection of a receiving winding in a reference plane perpendicular to a first direction according to an embodiment of the present invention;
fig. 11 is a schematic structural diagram illustrating orthographic projections of the position detection coils in the receiving windings in a reference plane perpendicular to the first direction according to the embodiment of the present invention;
fig. 12 is a schematic structural diagram illustrating an orthographic projection of each of the metal object detecting coils in the receiving winding in a reference plane perpendicular to the first direction according to the embodiment of the present invention;
fig. 13 is a graph showing the variation of the induced signal of the reference coil with time when the metal object passes through the middle position of the transmitting winding and the receiving winding along the first direction, the side close to the transmitting winding and the side close to the receiving winding respectively;
FIG. 14 is a graph showing the variation of the induced current generated by two coils with time when a metal object passes through a coil having a "∞" shape and a coil having an "o" shape according to an embodiment of the present invention;
FIG. 15 is a graph of induced current versus time in the receiving winding with and without a paperclip in the detection zone according to an embodiment of the present invention;
FIG. 16 is a schematic structural diagram of a security door according to an embodiment of the present invention;
fig. 17 is an exploded view of the security door shown in fig. 16.
Reference numerals:
10-a transmission winding; 11-a transmitting coil; 110-a transmission block; 110 a-top transmit block; 110 b-bottom transmit block; 111-a first transmitting coil; 1110-a first transmit subblock; 112-a second transmitting coil; 1120-a second transmit sub-block; 113-a third transmit coil; 1130-a third transmit sub-block; 1131 — a transmitting unit;
20-a receiving winding; 21-a receiving coil; 210-a sensing block; 211-position detection coil; 2110-position sensing block; 211 a-neutral detection coil; 211 b-end detection coil; 212-metal detection coil; 212 a-a first metal species detection coil; 212 b-a second metalliferous detection coil; 2121-a first sensor sub-block; 2122-a second sensor sub-block;
30-a detection unit; 40-a detection zone;
50-a first door panel; 51-a first plate body; 52-a first cover plate;
60-a second door panel; 61-a second plate body; 62-a second cover plate; 70-a security inspection channel;
80 a-a first electric field shielding mesh; 80 b-a second electric field shielding mesh;
80 c-a third electric field shielding mesh; 80 d-a fourth electric field shielding mesh;
90-beam.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a metal detection device based on a multistage alternating magnetic field, which is used for solving the problem that detection omission is easy to generate when a tiny metal object is detected by adopting an electric field disturbance principle in the prior art.
As shown in fig. 1 and 2, the metal detection device includes a transmitting winding 10, a receiving winding 20, and a detection unit 30, wherein: the transmitting winding 10 and the receiving winding 20 are arranged at intervals in a first direction in a horizontal plane to form a detection region 40 therebetween; the transmitting winding 10 includes a plurality of transmitting coils 11, the plurality of transmitting coils 11 are overlapped along a first direction and form a plurality of transmitting blocks 110, and the alternating magnetic field in the transmitting blocks 110 is the sum of the alternating magnetic fields of the respective transmitting coils 11 in the region corresponding to the transmitting blocks 110; the receiving winding 20 is configured to generate an induced signal based on a change of the alternating magnetic field in the plurality of transmitting blocks 110, where the induced signal may refer to an induced current or an induced voltage; the detection unit 30 is used for determining the metal object information in the detection area 40 based on the change of the induction signal generated by the receiving winding 20.
Specifically, in the metal detection device, as shown in fig. 1, the transmitting winding 10 and the receiving winding 20 are disposed facing each other and spaced apart from each other along a first direction, wherein the first direction is perpendicular to a plane where coils of the transmitting winding 10 and the receiving winding 20 are located, the first direction is an X-axis direction in fig. 1, a detection region 40 is formed in a region between the transmitting winding 10 and the receiving winding 20, and an alternating magnetic field generated by excitation of the transmitting winding 10 is detected by the alternating magnetic fieldThe area 40 is then transmitted to the receiving winding 20, and the receiving winding 20 generates an induction current I along with the change of the alternating magnetic field 0 When the alternating magnetic field in the detection region 40 is disturbed, the induced current generated by the reception winding 20 is also disturbed, and the induced current at this time is represented as I 1 Then, I 1 Is different from I 0 The detection unit 30 is based on I 1 And I 0 The induced current variation Δ I can be obtained, accordingly, the induced voltage generated by the receiving winding 20 also changes, and the induced voltage variation Δ U can be obtained, and the larger the induced current variation Δ I and the induced voltage variation Δ U are, the larger the intensity of the magnetic field disturbance is. When the metal detection apparatus is applied to a security door, the transmitting winding 10 may be provided on a first door panel 50 of the security door, and the receiving winding 20 may be provided on a second door panel 60 of the security door.
It should be noted that the transmitting winding 10 and the receiving winding 20 in fig. 1 are illustrated as rectangular solids having a flat structure, and the main purpose is to show the structure of the metal detector and the relative position relationship between the transmitting winding 10 and the receiving winding 20, but the structure of the transmitting winding 10 and the receiving winding 20 is not shown, and the structure of the transmitting winding 10 and the receiving winding 20 and the structure of each coil will be described in detail below.
As shown in fig. 3 to 7, the transmitting winding 10 includes a plurality of transmitting coils 11 stacked along a first direction, the transmitting coils 11 are independent of each other, each transmitting coil 11 is formed by winding a wire according to a predetermined winding manner, wherein a start point and an end point of the wire winding may be set at the same end, so as to be connected to an ac power supply, the wire is routed from the start point along a predetermined path and finally returned to the end point, the wire may surround one or more transmitting sub-blocks, the paths of the wire are different, the areas and the numbers of the formed transmitting sub-blocks are different, when an alternating current is introduced into the wire, the magnitude and the direction of the magnetic induction in each transmitting sub-block periodically change with time, and compared with a single large coil, under the condition of the same alternating current, the area of each transmitting sub-block is reduced, so that the generated magnetic induction is enhanced, and the distribution density of the magnetic induction lines is increased.
The solid black lines shown in fig. 3 to 7, 8 and 9 indicate the conductive lines, the arrows indicate the wiring direction of the conductive lines, and the arrows do not indicate the current direction.
The number of the transmitting coils 11 is not limited, and may be two, three, four, five or other numbers, the transmitting coils 11 are disposed in different planes perpendicular to the first direction, each transmitting coil 11 does not interfere, the transmitting coils 11 may cover the whole area of the detection area 40 in the height direction, or may cover a local area of the detection area 40 in the height direction, and the routing paths of the wires in each transmitting coil 11 may be the same or different, as shown in fig. 2, the transmitting coils 11 may form a plurality of transmitting blocks 110 after being superimposed in the first direction, the transmitting blocks 110 are surrounded by a plurality of wires, the alternating magnetic field in each transmitting block 110 is the sum of the alternating magnetic fields of each transmitting coil 11 in the area corresponding to the transmitting block 110, if the strength of the alternating magnetic field in each transmitting block 110 is measured by the magnitude of the magnetic flux, the magnetic flux in each transmitting block 110 is formed by superimposing the magnetic flux in the area of each transmitting coil 11 corresponding to the transmitting block 110, so that the relationship between the magnetic flux in each transmitting coil 110 and the frequency of the alternating current in each transmitting coil 11 can be known, for example, the magnetic flux of the first transmitting block 110 is calculated as a certain time:
Figure BDA0003879213250000081
in the above formula, μ is the permeability of air, m is the ordinal number of the transmitting coil 11, N i Is the number of turns of the ith transmitting coil 11 at the position of the nth transmitting block 110, I i (f i T) is the current value at time t calculated from the frequency f of the alternating current fed to the ith transmitter coil 11, S n Is the area of the nth transmission block 110.
It should be noted that, the magnetic flux is a scalar quantity, considering that directions of magnetic induction lines generated by different transmitting coils 11 at the same transmitting block 110 may be different, if the directions of the magnetic induction lines are opposite, the magnetic fluxes may be cancelled after the different transmitting coils 11 are superimposed, in the calculation process, the directions of the magnetic induction lines may be defined, for example, by taking "+" perpendicular to the paper surface outward and "-" perpendicular to the paper surface inward, at time t, the direction of the magnetic induction line of each transmitting coil 11 in the region corresponding to the transmitting block 110 is determined by the right-hand rule, and finally, the magnitude of the magnetic flux of each transmitting block 110 and the direction of the magnetic induction line at time t are calculated according to the above formula.
As can be seen from the above formula, the magnetic flux passing through each of the transmitting blocks 110 has a corresponding functional relationship with the frequency of the alternating current in the transmitting coil 11, and the magnitude and direction of the magnetic induction in each of the transmitting blocks 110 periodically change with time.
Among this metal detection device, each transmitting coil 11 is after letting in alternating current, can stimulate the multistage alternating magnetic field that magnetic induction is gradient steady change, the magnetic induction of each level alternating magnetic field obtains the reinforcing, and alternating magnetic field distributes more evenly in whole detection area 40, when small metallics pass through, small metallics also can produce stronger electric vortex, electric vortex then produces magnetic field and produces great interference to the original magnetic field in detection area 40, make the induction signal that receiving winding 20 produced before and after the alternating magnetic field in detection area 40 takes place the disturbance have great difference, thereby can obtain the induction signal variation volume of being convenient for monitor and signal intensity is great, and then be favorable to detecting small metallics, reduce the risk of lou examining.
In addition, in the metal detection device, the transmitting winding 10 and the receiving winding 20 are separately arranged and located at two sides of the detection region 40, the alternating magnetic field generated by excitation of the transmitting winding 10 passes through the detection region 40 and then is emitted to the receiving winding 20, the receiving winding 20 can sense the magnetic field change in the detection region 40, and by separately arranging the transmitting winding 10 and the receiving winding 20, the transmitting winding 10 and the receiving winding 20 can be ensured to have enough installation space, the coil density of the transmitting winding 10 and the receiving winding 20 can be increased, and the combination flexibility between different transmitting coils 11 and between different receiving coils 21 can be improved.
In the prior art, the transmitting winding 10 and the receiving winding 20 are arranged on the same side, the installation space of the transmitting winding 10 and the receiving winding 20 is smaller, the combination mode that the transmitting winding 10 is arranged on the outer ring and the receiving winding 20 is arranged on the inner ring is usually adopted, the combination between the coils is not flexible enough, the arrangement density of the coils is relatively smaller, the magnetic induction intensity generated after the transmitting winding 10 is electrified is not uniformly distributed, and the electromagnetic induction coil has the characteristics that the central area is strong and the magnetic induction intensity is continuously reduced from the central area to the periphery.
In some embodiments, the orthographic projection of the plurality of emission blocks 110 in the reference plane perpendicular to the first direction forms a matrix structure of a plurality of rows and a plurality of columns, and is symmetrically distributed on both sides of the central axis extending in the height direction in the reference plane.
As shown in fig. 2, the emission blocks 110 are arranged in close proximity to each other in the orthogonal projection in the reference plane and arranged in a plurality of rows and a plurality of columns, where a plurality of rows means at least two rows and a plurality of columns means at least two columns, so that the alternating magnetic fields from different emission blocks 110 are distributed in the height direction of the detection area 40, and the alternating magnetic fields from different emission blocks 110 are also distributed in the traveling direction of the detection area 40, and when a metal object passes through the detection area 40 from different heights, the metal object may disturb the alternating magnetic fields in the emission blocks 110 disposed at and near the corresponding height, and the metal object may also disturb the alternating magnetic fields in the plurality of emission blocks 110 disposed in the traveling direction.
If the first direction is defined as an X-axis direction, the height direction of the detection region 40 is defined as a Z-axis direction, and the traveling direction of the detection region 40 is defined as a Y-axis direction, the reference plane is a YZ plane, orthogonal projections of the plurality of emission blocks 110 in the reference plane are distributed in a matrix along the Z-axis direction and the Y-axis direction, the magnetic field distribution is uniform, and the intensity is enhanced.
With continued reference to fig. 2, the transmitting winding 10 includes 20 transmitting blocks 110, the orthogonal projection of the transmitting blocks 110 in the reference plane forms a matrix structure of ten rows and two columns, and the areas of the transmitting blocks 110 may be equal or different.
When a metal object in the floor or a metal object in an electronic component at the top of the security door vibrates in the vertical direction due to the passage of a human body, for example, the metal object enters the detection region 40 along with the vibration and generates eddy current, so that the original magnetic field in the detection region 40 is interfered, the receiving winding 20 generates a false-alarm induction signal variation, and the false-alarm phenomenon of the security door is called as an end effect, so that the detection accuracy of the security door at an end region is reduced.
In order to eliminate the end effect, optionally, the plurality of transmission blocks 110 includes a top transmission block 110a and a bottom transmission block 110b, and the magnetic field strength of the top transmission block 110a and the bottom transmission block 110b is greater than that of a middle transmission block 110 between the top transmission block 110a and the bottom transmission block 110b, according to the principle: the sensing signal variation generated in the receiving coil arranged in the corresponding area due to the vertical vibration of the metal object in the floor or the metal object at the top of the security inspection door is enhanced by utilizing the larger magnetic field intensity in the top emission block 110a and the bottom emission block 110b, and the related threshold value is set.
As can be seen from the above, in the metal detection device, the transmitting coil 11 includes a conducting wire, the conducting wire surrounds one or more transmitting sub-blocks according to a predetermined winding manner, the winding manner of the conducting wire is different, the areas and the numbers of the formed transmitting sub-blocks are different, orthogonal projections of any two transmitting sub-blocks in different transmitting coils 11 along the first direction may be completely overlapped, non-overlapped or partially overlapped, and a plurality of transmitting coils 11 having the transmitting sub-blocks may form a plurality of transmitting blocks 110 after being overlapped.
Specifically describing the structure of the transmitting coil 11, optionally, the plurality of transmitting coils 11 includes one or more first transmitting coils 111, and the first transmitting coils 111 cover the entire area of the detection area 40 in the height direction; the first radiation coil 111 includes a plurality of first radiation sub-blocks 1110, and the plurality of first radiation sub-blocks 1110 are arranged along the height direction of the detection area 40.
As shown in fig. 3 and 4, the first transmitting coil 111 includes a conducting wire, the starting point and the ending point of the conducting wire are both at the same end, for example, both are disposed at the top end, the conducting wire extends downward in a serpentine routing manner, turns back after reaching the far end of the starting point, and continues to extend upward in a serpentine routing manner and reach the ending point, so that the conducting wire defines a plurality of first transmitting sub-blocks 1110, the first transmitting sub-blocks 1110 are arranged along the height direction of the detection region 40, when an alternating current is introduced into the conducting wire, the magnitude and the direction of the magnetic induction intensity in each first transmitting sub-block 1110 periodically change with time, and compared with a single large coil, under the condition of the same alternating current, the area of each first transmitting sub-block 1110 is reduced, the generated magnetic induction intensity is enhanced, and the distribution density of the magnetic induction lines is increased.
The areas of the first transmitting sub-blocks 1110 may be equal or different.
The first transmitting coil 111 enables an alternating magnetic field to be distributed in the whole detection area 40 along the height direction, in addition, in the first transmitting coil 111, a plurality of first transmitting sub-blocks 1110 are formed by winding a conducting wire, the magnetic field intensity in each first transmitting sub-block 1110 is enhanced, the magnetic field intensity in the whole area is also enhanced, and the distribution is more uniform. The number of the first transmitting coils 111 may be one or multiple, and when the number of the first transmitting coils 111 is multiple, the routing paths of the wires may be the same or different, for example, as shown in fig. 3 and 4, two different routing paths are adopted for the wires of the two first transmitting coils 111.
As shown in fig. 8 and 9, the two layers of the transmitting coils 11 are the two types of the first transmitting coils 111 shown in fig. 3 and 4, respectively, and the two layers of the transmitting coils 11 are the two types of the first transmitting coils 111 shown in fig. 3 and 4, wherein in the fourth layer of the transmitting coils 11, the boundary between two adjacent first transmitting sub-blocks 1110 is located in one first transmitting sub-block 1110 in the fifth layer of the transmitting coils 11, and vice versa, that is, in the fifth layer of the transmitting coils 11, the boundary between two adjacent first transmitting sub-blocks 1110 is located in one first transmitting sub-block 1110 in the fourth layer of the transmitting coils 11, so that the forward projection of the fourth layer of the transmitting coils 11 and the fifth layer of the transmitting coils 11 in the reference plane after being superposed can form more transmitting sub-blocks.
It should be noted that, in the first radiation coil 111, the number of turns of the wire corresponding to the first radiation sub-block 1110 located at the top and the bottom may be more, that is, the wire may be wound several more turns when reaching the bottom, and then continuously routed upward.
For example, in the fifth layer transmitting coil 11, the number of turns of the conducting wire corresponding to the first transmitting sub-block 1110 located at the top and the bottom is large, and meanwhile, the area of the first transmitting sub-block 1110 located at the top and the bottom can be small, so that the excessive area of the detection region 40 along the height direction is avoided being occupied, and the normal detection of the metal object carried by the passer by the detection region 40 is not affected.
Of course, the number of turns of the wire corresponding to each first transmitting sub-block 1110 in the first transmitting coil 111 may also be set to be the same, and the second transmitting coil 112 is added, the second transmitting coil 112 only covers a local area of the detection area 40 in the height direction, such as a top area and a bottom area, for example, as shown in fig. 9, the sixth layer transmitting coil 11 belongs to the second transmitting coil 112, and the transmitting sub-blocks included in the sixth layer transmitting coil 11 cover the top area and the bottom area of the detection area 40 in the height direction.
The number of the second transmitting coils 112 is one or more, the second transmitting coil 112 includes one or more second transmitting sub-blocks 1120 surrounded by conducting wires, unlike the first transmitting coil 111, the second transmitting coil 112 only covers a local area of the detection region 40 in the height direction, the second transmitting coil 112 can further enhance the alternating magnetic field in the local area of the detection region 40 in the height direction, and after the first transmitting coil 111 and the second transmitting coil 112 are combined, the alternating magnetic field can be distributed in the whole area of the detection region 40 in the height direction, or the alternating magnetic field in the local area of the detection region 40 in the height direction can be further enhanced.
The structure, number and position of the second transmitting coils 112 are not limited, and optionally, at least one of the second transmitting coils 112 covers the bottom area of the detection region 40 in the height direction and has an "8" shaped structure. Fig. 5 shows a structure of the second transmitting coil 112 in an "8" shape, and the third layer of transmitting coil 11 in fig. 8 and 9 uses such a transmitting coil, which corresponds to the foot and lower leg area of the human body, and can strengthen the magnetic field strength in this part of the detection area 40, when a metal object is carried in the shoes and boots of the passer, the metal object can generate a large disturbance to the magnetic field in this part, so as to generate a significant change of the induction signal in the correspondingly arranged receiving coil 21, thereby detecting the metal object.
In addition to the first and second transmission coils 111, 112, a third transmission coil 113 may be included in the plurality of transmission coils 11, the third transmission coil 113 covers the entire region or a partial region of the detection region 40 in the height direction, and the third transmission coil 113 includes at least one transmission unit 1131 in an "∞" shaped structure, the transmission unit 1131 including two third transmission sub-blocks 1130.
Two kinds of the third transmission coils 113 as shown in fig. 6, 7, wherein the third transmission coil 113 shown in fig. 6 includes one transmission unit 1131, the transmission unit 1131 is wound by a wire into a "∞" shaped structure and covers the entire region of the detection region 40 in the height direction, the third transmission coil 113 shown in fig. 7 includes two transmission units 1131, each of the transmission units 1131 is wound by a wire into a "∞" shaped structure, and one of the two transmission units 1131 covers the top region of the detection region 40 in the height direction and the other covers the bottom region of the detection region 40 in the height direction.
As shown in fig. 8 and fig. 9, the second layer transmitting coil 11 adopts the coil structure shown in fig. 6, wherein two third transmitting sub-blocks 1130 included in the transmitting unit 1131 are sequentially arranged along the Y-axis direction and extend along the Z-axis direction, so that when a metal object passes through the detection region 40 from different heights, the alternating magnetic field in the two transmitting sub-blocks arranged along the Y-axis direction is disturbed.
Optionally, the third transmitting coil 113 includes a plurality of transmitting units 1131 arranged at intervals along the height direction, the plurality of transmitting units 1131 are located in the same plane perpendicular to the first direction, and the plurality of transmitting units 1131 are sequentially arranged in series; alternatively, the third transmitting coil 113 includes a plurality of transmitting units 1131, the plurality of transmitting units 1131 are located in different planes perpendicular to the first direction, and orthographic projections of the plurality of transmitting units 1131 along the first direction are not coincident.
With continued reference to fig. 8 and 9, the first-layer transmission coil 11 includes two transmission units 1131, the two transmission units 1131 respectively correspond to the top and the bottom of the detection region 40, are arranged in the same layer, and are connected in series, where "connected in series" means that the plurality of transmission units 1131 are formed by winding the same wire, and the two transmission units 1131 can enhance the magnetic field strength in the top region and the bottom region, on the one hand, and on the other hand, because the two transmission units 1131 are in a "∞" shape, when a metal object passes through the top and the bottom of the detection region 40, the alternating magnetic field in the two transmission sub-blocks arranged in the Y-axis direction will be disturbed.
It should be noted that, in the metal detection device, the number of the transmission coils 11 included in the transmission coil 10, the structure of the transmission coils 11, and the like are specifically described by taking fig. 8 and 9 as an example, and the transmission coil 10 is not limited to the above two arrangements, and other arrangements may be adopted.
In addition, in each layer structure, the number of turns of the wire winding is not fixed, for example, one turn, two turns, three turns, four turns, etc. may be wound according to the routing path shown by the arrow, and in each layer structure, each transmitting sub-block is a rectangular structure or a nearly rectangular structure, in fig. 8 and 9, in order to show the routing path of the wire clearly, part of the wires are arranged crosswise, and because the wires all have an insulating layer, the two crossed wires are insulated.
In the plurality of transmitting coils 11, the number of turns of the transmitting coil 11 with a large coverage area is smaller than the number of turns of the transmitting coil 11 with a small coverage area, for example, in fig. 8, the second layer transmitting coil 11, the fourth layer transmitting coil 11 and the fifth layer transmitting coil 11 are wound for 4-6 turns, and the first layer transmitting coil 11 and the third layer transmitting coil 11 are wound for 18 turns, so that in the transmitting blocks 110 formed by overlapping the transmitting coils 11, the total number of turns of the coils corresponding to the plurality of transmitting blocks 110 located at both ends is greater than the total number of turns of the coils corresponding to the plurality of transmitting blocks 110 located in the middle.
Among this metal detection device, the structure to transmitting winding 10 has improved, make transmitting winding 10 can arouse and produce multistage alternating magnetic field, and alternating magnetic field distribution is more even in the whole reference plane, when small metallics pass through, small metallics also can produce stronger electric eddy current, electric eddy current then produces magnetic field and produces great interference to the original magnetic field in surveying the region 40, so, the variation intensity of the induction signal in the receiving winding 20 is great, be convenient for monitor and analysis, and be favorable to detecting small metallics.
In the metal detection device, the structure of the receiving winding 20 is further improved, the receiving winding 20 includes a plurality of receiving coils 21, the plurality of receiving coils 21 are stacked along the first direction to form a plurality of sensing blocks 210, orthographic projections of the plurality of sensing blocks 210 in a reference plane perpendicular to the first direction are distributed in a matrix and are arranged in close proximity, each receiving coil 21 includes one or more sensing blocks 210, an alternating magnetic field in each receiving coil 21 is a sum of alternating magnetic fields in the included sensing blocks 210, and each receiving coil 21 generates a sensing signal based on a change of the alternating magnetic field in a corresponding region.
Specifically, as shown in fig. 10, 11, and 12, the receiving winding 20 includes a plurality of receiving coils 21, the receiving coils 21 are independent of each other, each receiving coil 21 is formed by winding a wire according to a predetermined winding manner, wherein a start point and an end point of the winding of the wire can be set at the same end, so as to facilitate connection with an external circuit, the wire is routed from the start point along a predetermined path, and finally returns to the end point, the wire can enclose one or more sensor sub-blocks, the paths of the wire are different, the areas and the number of the formed sensor sub-blocks are different, and the alternating magnetic field in each sensor sub-block changes with the change of the alternating magnetic field in a region corresponding to the sensor sub-block in the detection region 40.
In order to enhance the detection sensitivity at the boundary of the receiving coils 21, some of the receiving coils 21 may be set at different heights, and the orthographic projections along the first direction partially overlap, taking two receiving coils 21 as an example, the bottom boundary of one receiving coil 21 may fall inside the other receiving coil 21, and when a metal object passes through the detection area 40 from a position equal to the bottom boundary of the previous receiving coil 21, the passing height of the metal object is just within the height range of the upper and lower boundaries of the next receiving coil 21, so that the metal object can generate a large disturbance at least on the alternating magnetic field received by the next receiving coil 21.
The number of the receiving coils 21 is not limited, and may be two, three, four, five, or other numbers, the receiving coils 21 may be disposed in different planes perpendicular to the first direction, that is, the receiving coils 21 are disposed in layers, so that each receiving coil 21 does not interfere with each other, the receiving coils 21 may cover the entire area of the detection area 40 in the height direction, or may cover a local area of the detection area 40 in the height direction, the routing paths of the wires in each receiving coil 21 may be the same or different, and each receiving coil 21 is formed by winding the wires to form a plurality of inductor blocks, a plurality of receiving coils 21 may form a plurality of induction blocks 210 after being stacked in the first direction, the orthogonal projections of the induction blocks 210 in the reference plane perpendicular to the first direction are distributed in a matrix and are disposed in close proximity, no gap exists between two adjacent induction blocks 210, the magnetic field received by each induction block 210 depends on the excitation magnetic field formed by the transmitting winding 10 in the corresponding area, and the transmitting winding 10 may specifically generate a multi-stage alternating magnetic field by excitation and superposition of the plurality of transmitting coils 11, so that each induction block 210 may receive different alternating magnetic fields.
In combination with the above, the transmitting winding 10 includes a plurality of transmitting coils 11, the plurality of transmitting coils 11 are stacked in the first direction to form a plurality of transmitting blocks 110, the alternating magnetic field in each transmitting block 110 is the sum of the alternating magnetic fields of the transmitting coils 11 in the area corresponding to the transmitting block 110, the alternating magnetic fields in different transmitting blocks 110 may be different, the transmitting winding 10 may be excited to generate a multi-level alternating magnetic field after being energized with an alternating current, the sensing blocks 210 in the receiving winding 20 correspond to the transmitting blocks 110 one to one, that is, the number of the sensing blocks 210 is the same as that of the transmitting blocks 110, and the orthogonal projections in the first direction may be coincident, so that the alternating magnetic field in each sensing block 210 changes with the change of the alternating magnetic field in the transmitting block 110 corresponding to the sensing block, and the alternating magnetic fields in different sensing blocks 210 may be different.
Each receiving coil 21 may include one or more sensing blocks 210, the alternating magnetic field in each receiving coil 21 is the sum of the alternating magnetic fields in the included sensing blocks 210, each receiving coil 21 generates a sensing signal based on the change of the alternating magnetic field in the corresponding area, where the sensing signal may refer to a sensing current or a sensing voltage, and for example, the direction of the sensing current of each receiving coil 21 at time t depends on the direction and the change of the magnetic sensing lines superimposed in the corresponding area of each receiving coil 21.
As shown in fig. 10, the sensing blocks 210 are arranged in close proximity in the reference plane, and there is no gap between two adjacent sensing blocks 210, that is, the entire area of the detection area 40 in the height direction can be covered by the receiving coil 21, there is no uncovered area, the magnetic field in each sensing block 210 changes with the change of the magnetic field emitted by the emitting winding 10 to the corresponding area, so as to affect the magnitude and direction of the induced current generated in the receiving coil 21, when a metal object passes through the detection area 40 from different heights, the magnetic field in one or more receiving coils 21 with a height closer to the passing height of the metal object can be greatly disturbed, so as to generate a more obvious induced signal change, which is more beneficial to monitoring and identifying the signal, and the detection unit 30 can determine the metal object information in the detection area 40 based on the change of the induced signal generated by each receiving coil 21, thus reducing the risk of missed detection.
In some embodiments, as shown in fig. 11, a plurality of position detection coils 211 are included in the reception coil 21, each position detection coil 211 covers a local area of the detection area 40 in the height direction, and the plurality of position detection coils 211 are located at different height positions; the detection unit 30 includes a position detection unit (not shown) for determining position information of the metal object based on a change in the induction signal generated by each position detection coil 211.
The position detection coils 211 can be arranged in different planes perpendicular to the first direction, the heights of the position detection coils 211 are different, orthographic projections of any two position detection coils 211 along the first direction can be arranged in a close proximity mode, or the position detection coils are partially overlapped, or the position detection coils are arranged at intervals, under the combination of the position detection coils 211, the whole area of the detection area 40 along the height direction can be covered, so that when metal objects pass through the detection area 40 from different heights, the positions of the metal objects can be judged according to the change condition of induction signals generated by the position detection coils 211, orthographic projections of a part of the position detection coils 211 along the first direction can be partially overlapped, and therefore the detection sensitivity of the boundaries of the position detection coils 211 can be enhanced.
The detection unit 30 includes a position detection unit for determining position information of the metal object based on a change in the induction signal generated by each position detection coil 211. When a metal object passes through the detection area 40 from different heights, the magnetic field disturbance conditions sensed by the position detection coils 211 at different heights are different, and specifically, the position of the metal object can be judged according to the changes of the induction signals generated by the position detection coils 211 at different heights before and after the alternating magnetic field is disturbed, the larger the change of the induction signal is, the stronger the magnetic field disturbance sensed by the corresponding position detection coil 211 is, the closer the position of the metal object is to the position of the position detection coil 211, and conversely, the smaller the change of the induction signal is, the weaker the magnetic field disturbance sensed by the corresponding position detection coil 211 is, and the farther the position distance between the position of the metal object and the position detection coil 211 is.
Specifically, the position detection unit includes a first position detection unit, and the first position detection unit is used for determining the height range of the metal object, specifically includes:
determining an induction signal variation amount based on induction signals generated by the respective position detection coils 211 before and after the disturbance of the alternating magnetic field in the detection region 40;
acquiring one or more position detection coils 211 of which the peak-to-peak value of the induction signal variation is larger than a threshold value;
if the peak-to-peak value of the variation of the induction signal corresponding to one position detection coil 211 is greater than the threshold, determining the height range of the metal object according to the position of the position detection coil 211;
if the peak-to-peak values of the induced signal variation amounts corresponding to the position detection coils 211 are all larger than the threshold, the height range of the metal object is determined according to the positions of the same induction blocks 210 included in the position detection coils 211.
Specifically, the first position detection unit may determine an induced signal variation based on a difference between an induced signal generated by each position detection coil 211 before the alternating magnetic field is disturbed and an induced signal generated by each position detection coil 211 after the alternating magnetic field is disturbed, where the induced signal variation corresponds to the position detection coils 211 one to one, and the larger the peak value of the induced signal variation is, the stronger the magnetic field disturbance induced by the corresponding position detection coil 211 is, the closer the passing height of the metal object is to the height of the position detection coil 211, and conversely, the smaller the peak value of the induced signal variation is, the weaker the magnetic field disturbance induced by the corresponding position detection coil 211 is, and the farther the passing height of the metal object is from the height of the position detection coil 211.
It can be understood that the induced signal generated by the position detecting coil 211 is a time variation function before and after the alternating magnetic field in the detecting region 40 is disturbed, and accordingly, the induced signal variation is also a time variation function, and the peak-to-peak value of the induced signal variation refers to the difference between the peak and the trough in the waveform curve.
The first position detection unit may acquire one or more position detection coils 211 in which a peak-to-peak value of the variation amount of the induction signal is greater than a threshold value, the magnetic field disturbance induced in the one or more position detection coils 211 is strong, and the height of the metal object is more correlated with the height of the one or more position detection coils 211.
If the peak-to-peak value of the variation amount of the induction signal corresponding to only one position detection coil 211 is greater than the threshold, the height range of the metal object can be determined according to the position of the position detection coil 211, for example, if the center of the position detection coil 211 is at a height H 0 The top edge is at a height H 1 The bottom side is at a height H 2 Then the height of the metal object is H 0 Near and between H 1 And H 2 In the meantime.
If the peak-to-peak value of the variation of the induction signals corresponding to the position detection coils 211 is greater than the threshold, the height range of the metal object is determined according to the positions of the same induction blocks 210 included in the position detection coils 211.
For example, as shown in fig. 11, the 7 position detection coils 211 are sequentially marked as the first layer position detection coil 211 and the second layer position detection coil 211 … … and the seventh layer position detection coil 211 from right to left, and the induced voltages generated by the 7 position detection coils 211 before and after the disturbance of the alternating magnetic field in the detection region 40 (here, the induced voltages are used as the induced signals) are respectively collected, and the induced voltage variation Δ U is obtained, when the peak value Δ U of the induced voltage variation is obtained pp At (0, 10)]When the magnetic field induced by the corresponding position detection coil 211 is disturbed, the intensity of the disturbance is defined as weak, and the peak value Δ U of the induced voltage variation is defined as weak pp In (10, 20)]The intensity of the magnetic field disturbance induced by the corresponding position detection coil 211 is defined as medium, when the peak-to-peak value Δ U of the induced voltage variation is reached pp At (20, 50)]When the intensity of the magnetic field induced by the corresponding position detection coil 211 is defined as strong, the above mentioned threshold value is 20, and when the metal object R passes through the detection area 40 along the dotted line direction, from right to left, the intensity of the magnetic field induced by the 7 position detection coils 211 is: that is, the peak-to-peak values of the induced voltage variation amounts corresponding to the first-layer position detection coil 211 and the sixth-layer position detection coil 211 are greater than a threshold value (the threshold value is 20), the height of the metal object R is relatively related to the heights of the first-layer position detection coil 211 and the sixth-layer position detection coil 211, or the metal object R is relatively close to the first-layer position detection coil 211 and the sixth-layer position detection coil 211 in the height direction (Z-axis direction), and the first-layer position detection coil 211 and the sixth-layer position detection coil 211 are partially overlapped in the height direction and include the same induction blocks 210, such as two induction blocks 210 in the sixth row shown in fig. 10, the metal object R passes through the height ranges corresponding to the two induction blocks 210, and if the heights corresponding to the upper and lower boundaries of the two induction blocks 210 in the sixth row are H, respectively 3 、H 4 Then the height of the metal object R is between H 3 And H 4 In this way, the range of the height of the metal object R is further narrowed.
The position detection unit may determine that the metal object is closer to the receiving winding 20 or the transmitting winding 10, in addition to determining the height range of the metal object, and optionally, the position detection unit further includes a second position detection unit, and the second position detection unit is specifically configured to:
determining an induction signal variation amount based on induction signals generated before and after the alternating magnetic field in the detection region 40 is disturbed by each position detection coil 211;
acquiring a position detection coil 211 with the maximum peak-to-peak value of the induction signal variation as a reference coil, and acquiring an actual curve graph of the time variation of the induction signal variation corresponding to the reference coil;
acquiring a pre-stored reference curve graph of the variation of the induction signal corresponding to the reference coil along with the time variation;
judging the relative position relationship between the metal object and the median line extending along the height direction of the detection region 40 according to the phase difference between the actual curve graph and the reference curve graph;
the reference graph is a graph of the variation of the induction signal with time when the calibrated metal object passes through a position with the same height as the center of the reference coil and a middle position of the transmitting winding 10 and the receiving winding 20 along the first direction.
The position detection coil 211 having the largest peak-to-peak value of the amount of change in the induced signal has the largest intensity of magnetic field disturbance induced by the position detection coil 211, and the passing height of the metal object is closest to the height of the position detection coil 211, so that the position detection coil 211 can be determined as the reference coil.
If the metal object R is calibrated 0 Passing from a position having the same height as the center of the reference coil and from the middle position of the transmitting winding 10 and the receiving winding 20 in the first direction, a graph of the variation amount of the induction signal of the reference coil with time can be obtained, and the graph is defined as a reference graph, such as the graph P in fig. 13 0 As shown, when the actual metal object R passes through the side of the detection region 40 close to the transmitting winding 10 or the side close to the receiving winding 20, the actual curve graph of the variation of the induction signal with time is shown as the curve P in FIG. 13 1 、P 2 The actual profile is shown to be out of phase with the reference profile, the actual profile P 1 Relative to the reference profile P 0 The first peak in the detection zone 40, the metal object R passes through the side of the detection zone 40 close to the transmission winding 10, the actual curve P 2 Relative to the reference profile P 0 Lags behind the leading peak of the signal, the metal object passes from the side of the detection zone 40 close to the receiving winding 20.
As described above, the position detection coils 211 cover the local area of the detection area 40 in the height direction, and each position detection coil 211 is located at a different height position, and optionally, the position detection coils 211 include a first group and a second group, and the position detection coils 211 in the first group are arranged in close proximity in the height direction of the detection area 40; the position detection coils 211 in the second group cover the local reinforcing area in the height direction of the detection area 40, and are disposed to be stacked with the position detection coils 211 in the first group in the first direction.
In some embodiments, the receiving winding 20 includes seven position detection coils 211, the seven position detection coils 211 are stacked in the first direction, and are sequentially a first layer position detection coil 211, a second layer position detection coil 211 … …, and a seventh layer position detection coil 211, in fig. 11, the seven position detection coils 211 are sequentially arranged from right to left, so as to clearly show the structure of each position detection coil 211 and the relative position relationship between the different position detection coils 211, wherein the fourth layer position detection coil 211 to the seventh layer position detection coil 211 are a first group, the four position detection coils 211 are arranged in close proximity in the height direction of the detection area 40, and cover the entire area of the detection area 40 in the height direction; the first-tier position detection coil 211 to the third-tier position detection coil 211 are a second group, and the three position detection coils 211 each cover a partial region of the detection region 40 in the height direction, wherein the first-tier position detection coil 211 overlaps with an orthographic projection portion of the fourth-tier position detection coil 211 and the sixth-tier position detection coil 211 in the first direction, respectively, the second-tier position detection coil 211 overlaps with an orthographic projection portion of the seventh-tier position detection coil 211 in the first direction, and the third-tier position detection coil 211 overlaps with an orthographic projection portion of the fifth-tier position detection coil 211 in the first direction.
Each position detection coil 211 in the first group is formed by winding a wire to form an infinity-shaped structure, such as a fourth-layer position detection coil 211, a fifth-layer position detection coil 211, a sixth-layer position detection coil 211, and a seventh-layer position detection coil 211, and the several position detection coils 211 are stacked in the first direction to cover the entire height-wise area of the detection region 40, taking one of the position detection coils 211 as an example, when a metal object passes through the detection region 40, an eddy current effect generated by the metal object itself may disturb an alternating magnetic field received by the position detection coil 211 in the infinity-shaped structure, and an induced signal variation amount corresponding to the position detection coil 211 in the infinity-shaped structure is large, which is more favorable for signal detection.
As shown in fig. 14, two graphs (a) and (b) showing the change amount of the induced current with time for the coils of two different structures are shown, in which the graph (a) is a graph showing the change amount of the induced current with time for the coil having the "∞" structure, and the graph (b) is a graph showing the change amount of the induced current with time for the coil having the "o" structure, and in the case where the areas of the two coils are equal, when the metal object R is present in the same time T 1 When passing along the middle line of the two coils, the disturbance energy of the metal object R to the magnetic field is the same, and the curve (a) and the curve (b) can be understood as the area of the shaded part is the same, namely Y 1 ＝Y 2 It can be seen that the peak value of the induced current variation in the curve (a) is significantly greater than the peak value of the induced current variation in the curve (b), that is, the coil having the "∞" structure generates a stronger magnetic variable signal, which is more beneficial to signal detection, and moreover, the direction of the induced current variation in the curve (a) changes periodically, so that the advancing direction of the metal object R can be determined, and thus, the practicability of the metal detection device is further improved.
In some embodiments, the second group includes a middle position detection coil 211a, the middle position detection coil 211a corresponds to a middle region of the human body, and the middle position detection coil 211a overlaps with orthogonal projection portions of two position detection coils 211 arranged in close proximity in the first group along the first direction; and/or, the second group further comprises at least one end detection coil 211b, and the end detection coil 211b covers the end of the detection region 40 along the height direction.
The middle position detection coil 211a corresponds to a middle position area of the human body, that is, corresponds to the position of the waist and the hip of the human body, because the position of the waist and the hip of the human body is easy to carry metal objects, and the detection of this area can be enhanced by overlapping the middle position detection coil 211a with the orthographic projection portions of the two position detection coils 211 arranged in the first group in close proximity in the first direction. As shown in fig. 11, the first layer position detection coil 211 is a middle position detection coil 211a, the first layer position detection coil 211 is respectively overlapped with the orthographic projection portions of the fourth layer position detection coil 211 and the sixth layer position detection coil 211 along the first direction, and the orthographic projection portions of the fourth layer position detection coil 211 and the sixth layer position detection coil 211 along the first direction are arranged in close proximity, so that the bottom boundary of the fourth layer position detection coil 211 and the top boundary of the sixth layer position detection coil 211 can fall into the first layer position detection coil 211, and thus, when the metal object R passes through the detection area 40 from the above boundaries, at least a large disturbance can be generated to the alternating magnetic field received by the first layer position detection coil 211, thereby improving the detection sensitivity of the boundary positions.
The median detection coil 211a may have a "∞" shaped structure, so that when a metal object passes through the corresponding region, the median detection coil 211a can generate a stronger magneto-variable signal, facilitating signal detection.
The second layer position detection coil 211 and the third layer position detection coil 211 belong to the end detection coil 211b, wherein the second layer position detection coil 211 covers the bottom area of the detection area 40 in the height direction, the third layer position detection coil 211 covers the top area of the detection area 40 in the height direction, when a metal object in the floor or a metal object in an electronic component at the top of the security door vibrates in the vertical direction due to the passage of a human body, for example, the metal object enters the detection area 40 along with the vibration and generates an eddy current, thereby generating interference on the original magnetic field in the bottom area and the top area, at least the variation of the induction signals of the second layer position detection coil 211 and the third layer position detection coil 211 can be obtained, and by setting a relevant threshold value, in the practical application process, whether the interference is generated by the metal object in the floor or the metal object at the top of the security door can be judged according to the magnitude relation between the variation of the induction signals actually generated by the second layer position detection coil 211 and the third layer position detection coil 211 and the set relevant threshold value, if yes, the alarm is not performed, it is proved that the pedestrian is detected, thereby being beneficial to eliminate the alarm effect.
The end detection coil 211b may be embodied in an "8" configuration.
In some embodiments, the plurality of position detection coils 211 are stacked to form a plurality of position sensing areas 2110, and an orthographic projection of the plurality of position sensing areas 2110 in a reference plane perpendicular to the first direction forms a matrix structure having a plurality of rows and columns and is symmetrically distributed on both sides of a central axis extending in the height direction in the reference plane.
Here, the position sensing section 2110 is one of the sensing sections 210, and particularly refers to the sensing section 210 formed by stacking the position detection coils 211.
As shown in fig. 10, the orthogonal projections of the position sensing areas 2110 in the reference plane are arranged in close proximity and are arranged in a plurality of rows and a plurality of columns, where a plurality of rows refers to at least two rows and a plurality of columns refers to at least two columns, so that the position sensing areas 2110 may vary with the variation of the alternating magnetic field emitted by the emitting winding 10 into the corresponding area, when a metal object passes through the detection area 40 from different heights, the alternating magnetic field in the plurality of position sensing areas 2110 arranged in the height direction will be disturbed, and the alternating magnetic field in the plurality of position sensing areas 2110 arranged in the traveling direction of the metal object will also be disturbed, thereby affecting the magnitude and direction of the induced current in the corresponding receiving coil 21.
Referring to fig. 10 and 11 together, the position detection coil 211 forms 20 position sensing areas 2110 in total, and the orthogonal projection of the position sensing areas 2110 in the reference plane forms a matrix structure of ten rows and two columns, and the areas of the position sensing areas 2110 may be equal or different.
In the metal detection device, the receiving winding 20 further includes a plurality of metal object detection coils 212 arranged in a stacked manner, and the metal object detection coils 212 cover the entire area of the detection area 40 in the height direction, and the detection unit 30 further includes a metal object detection unit for determining whether a metal object passes through the detection area 40 based on a change in an induction signal generated by the metal object detection coils 212.
As can be seen from the above description, the position detection coil 211 covers a local area of the detection area 40 in the height direction, and the height of each position detection coil 211 is different, when a metal object passes through the detection area 40, the intensity of the magnetic field disturbance sensed by the position detection coils 211 at different heights is different, and has a difference in intensity, and the area of the position detection coil 211 is smaller, and only the local magnetic field disturbance can be sensed, while different from the position detection coil 211, the metal detection coil 212 can cover the whole area of the detection area 40 in the height direction, and the area of the metal detection coil 212 is larger, and when a metal object passes through the detection area 40, the metal detection coil 212 can sense the magnetic field disturbance at the height position of the metal object and in a larger area nearby, and the change of the sensing signal is obvious, so that when a metal object passes through the detection area 40, the detection is relatively sensitive.
In some embodiments, the metal species detection coil 212 includes at least a first metal species detection coil 212a and a second metal species detection coil 212b that are stacked in a first direction, wherein: the first metal object detecting coil 212a includes a plurality of first sensor sub-blocks 2121 formed by winding a conducting wire, and the plurality of first sensor sub-blocks 210 are arranged along the height direction of the detecting region 40; the second metal object detecting coil 212b includes a plurality of second inductor sub-blocks 2122 formed by winding a conductive wire, and the plurality of second inductor sub-blocks 2122 are arranged along the height direction of the detecting region 40; and, the orthographic projection of the boundary between two adjacent first sensor sub-blocks 2121 along the first direction is located within the orthographic projection of the second sensor sub-block 2122 along the first direction.
This is because, for example, for any one sensor sub-block, the magnetic field perturbation in the sensor sub-block is larger when the passing height of the metal object is closer to the central height of the sensor sub-block, and vice versa, the magnetic field perturbation in the sensor sub-block is smaller when the passing height of the metal object R is farther from the central height of the sensor sub-block, and as shown in fig. 12, the orthographic projection of the boundary between two adjacent first sensor sub-blocks 2121 along the first direction is located within the orthographic projection of the second sensor sub-block 2122 along the first direction, and similarly, the orthographic projection of the boundary between two adjacent second sensor sub-blocks 2122 along the first direction is located within the orthographic projection of the first sensor sub-blocks 2121 along the first direction, so that, when the metal object passes through the detection region 40 from a position equal to the height of the boundary of the first sensor sub-block 2121, the passing height of the metal object is located just within the height range of the upper and lower boundaries of one second sensor sub-block 2122, and therefore, at least the magnetic field perturbation in the second sensor sub-block 2122 is larger, thereby affecting the current detection coil 212 and vice versa.
In the metal detector, the number of the receiving coils 21 in the receiving coil 20, the structure of the receiving coils 21, and the like are specifically described by taking fig. 11 and 12 as examples, and the receiving coil 20 is not limited to the above-described arrangement, and other arrangements may be adopted.
In addition, the solid black lines shown in fig. 11 and 12 indicate the wires, the arrows indicate the wiring direction of the wires, and do not indicate the current direction, and the number of turns of the wire winding is not constant in each layer structure, for example, two, three, four, etc. turns may be wound according to the wiring path shown by the arrows, and meanwhile, in each layer structure, each sub-block is a rectangular structure or a nearly rectangular structure, in fig. 11 and 12, in order to show the wiring path of the wires clearly, part of the wires are crossed, and since the wires have insulating layers, the two crossed wires are insulated.
Among this metal detection device, can realize the detection to small metal object, when small metal object passes through detection zone 40, for alternating electric field, small metal object can produce more obvious disturbance to alternating magnetic field for receiving winding 20 and taking place the induction signal that produces before and after the disturbance at alternating magnetic field and have great difference, thereby can obtain the induction signal variation volume of being convenient for monitor and signal strength is great, and then be favorable to detecting small metal object, reduce the risk of lou examining. Taking a paper clip with a length of 2cm as an example, as shown in fig. 15, when the paper clip is placed in the detection region 40, the induced current generated by the receiving winding 20 is received over timeThe graph is shown as a solid line S in FIG. 15 1 As shown, when there is no paper clip in the detection region 40, the graph of the induced current generated by the receiving winding 20 with time is shown as a dotted line S in FIG. 15 0 As shown, the two curves have a significant difference, that is, the change of the induced current is easily detected and recognized, and thus, it is relatively easily detected when a passer-by carries a minute metal object such as a paper clip through the detection region 40.
Based on the same technical concept, an embodiment of the present invention further provides a security door, as shown in fig. 16 and 17, the security door includes a first door panel 50, a second door panel 60, and the metal detection device based on partition induction according to any one of the above technical solutions, wherein a security channel 70 is formed between the first door panel 50 and the second door panel 60, the transmitting winding 10 is disposed on the first door panel 50, the receiving winding 20 is disposed on the second door panel 60, and the detection region 40 is located within a coverage area of the security channel 70.
In this safety inspection door, the whole region of detection zone 40 on along the direction of height all can be covered by receiving coil 21, does not have the region that does not cover, when the metal object passes through detection zone 40 from different heights, sets up the magnetic field in the one or more receiving coil 21 that highly are close through of height and metal object and can appear great disturbance to produce more obvious inductive signal and change, be convenient for control and discernment, so, reduced the risk of missed checking.
According to the theory of max Wei Dianci, after the transmitting winding 10 is energized, an electromagnetic field is excited around the transmitting winding 10 to generate, where the electromagnetic field includes an electric field and a magnetic field that are related and dependent to each other, and in order to perform detection by using the magnetic field generated by excitation of the transmitting winding 10, the security inspection door is provided with a first electric field shielding net 80a, and the first electric field shielding net 80a and the transmitting winding 10 are provided on the same door panel and are located on one side of the transmitting winding 10 facing the receiving winding 20, so that the first electric field shielding net 80a can limit electric field lines generated by excitation of the transmitting winding 10 from entering the security inspection channel 70 to shield an alternating electric field in the security inspection channel 70, and also can enable an alternating magnetic field generated by excitation of the transmitting winding 10 to pass through, so that a relatively pure magnetic field can be obtained in the security inspection channel 70, and thus, when a small metal object passes through the security inspection channel 70, the small metal object can generate relatively obvious disturbance on the alternating magnetic field, so that an induced signal generated by the receiving winding 20 before and after the disturbance, has a relatively large difference, thereby facilitating detection of the small induced signal intensity, and reducing the risk of detection.
When the device is specifically arranged, the orthographic projection of the first electric field shielding net 80a along the first direction covers the orthographic projection of the emission winding 10 along the first direction, so that electric field lines generated by excitation of the emission winding 10 and emitted to the security inspection channel 70 can be shielded by the first electric field shielding net 80a to a large extent, and the interference of an electric field is reduced. In addition, the first electric field shielding mesh 80a may also be provided grounded, thereby providing a strong barrier to penetration of an electric field in any direction.
The first electric field shielding net 80a is a grid-shaped structure formed by metal wires, the metal wires can be made of at least one of gold, silver, copper and aluminum or other metal materials and alloy materials, and copper wires can be selected to prepare the first electric field shielding net 80a in consideration of low cost, high conductivity and long service life of copper; the cross-sectional area of the wire may be circular and the diameter may take any value of 0.07mm or more and 1.0mm or less, for example, the diameter of the wire may be 0.07mm, 0.08mm, 0.1mm, 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1.0mm.
Generally, the larger the mesh number of the shielding net, the finer the mesh size, the more the electric field is attenuated, and the mesh number of the first electric field shielding net 80a may be a value of 2 or more and 14 or less, for example, the mesh number of the first electric field shielding net 80a may be 2, 4, 6, 8, 10, 12, 14 or other values, in consideration of the magnetic field penetration rate.
The meshes of the first electric field shielding mesh 80a may be square or diamond.
In order to further reduce the influence of an electric field on metal detection, the security door further comprises a second electric field shielding net 80b, the second electric field shielding net 80b is arranged on the first door panel 50, at least part of the second electric field shielding net 80b is positioned on one side of the transmitting winding 10, which is far away from the receiving winding 20, and the second electric field shielding net 80b is used for shielding electric field lines which shoot to the receiving winding 20 and the security channel 70 in the external environment, so that the anti-interference performance of the security door in a complex environment is further improved.
As shown in fig. 17, a side of the transmitting winding 10 facing the receiving winding 20 and a side of the transmitting winding 10 facing away from the receiving winding 20 are respectively provided with a first electric field shielding net 80a and a second electric field shielding net 80b, and in some embodiments, the first electric field shielding net 80a and the second electric field shielding net 80b may be connected to and cover the transmitting winding 10, so as to form a stable shielding structure around the transmitting winding 10, and meanwhile, in a case that the first electric field shielding net 80a is grounded, the second electric field shielding net 80b may also be grounded, so as to better shield electric field lines.
In some embodiments, the security door further includes a third electric field shielding net 80c, the third electric field shielding net 80c is disposed on the second door panel 60, and the third electric field shielding net 80c is at least partially disposed on a side of the receiving winding 20 facing the transmitting winding 10, and the third electric field shielding net 80c is used for shielding electric field lines of the transmitting winding 10 and the external environment facing the receiving winding 20.
The third electric field shielding net 80c can prevent the external electric field from interfering the receiving winding 20, so that the anti-interference performance of the security inspection door in a complex environment is improved, a back-end system can detect a thinner and weaker signal change, and the sensitivity of metal detection is improved.
In addition, the security inspection door may further include a fourth electric field shielding net 80d, the fourth electric field shielding net 80d is disposed on the second door panel 60, and at least a portion of the fourth electric field shielding net 80d is located on a side of the receiving winding 20 away from the transmitting winding 10, and the fourth electric field shielding net 80d is used for shielding electric field lines emitted to the receiving winding 20 and the security inspection channel 70 in an external environment. The fourth electric field shielding net 80d can also prevent the external electric field from interfering the receiving winding 20, so that the anti-interference performance of the security inspection door in a complex environment is improved, a back-end system can detect a thinner and weaker signal change, and the sensitivity of metal detection is improved.
In a specific arrangement, the third electric field shielding net 80c and the fourth electric field shielding net 80d may be connected to and cover the receiving winding 20, so as to form a stable electric field shielding net around the receiving winding 20 to resist interference of the external environment to the receiving winding 20 in various directions.
The electric field shielding mainly considers reflection loss, each electric field shielding net can adopt a shielding material with high conductivity to attenuate an electric field signal, and copper is the best choice based on the consideration of various aspects such as cost, conductivity, service life and the like, wherein the shielding net woven by copper or tin-copper can pass through 90% of an incident magnetic field while attenuating the electric field, and has weaker attenuation to the magnetic field.
The mesh number of each electric field shielding net can be 10, and the diameter of each electric field shielding net is 0.5mm, so that a good shielding effect on an electric field is realized, and a magnetic field is allowed to penetrate to a large extent.
The degree of electric field decay is given by the following equation:
Figure BDA0003879213250000281
wherein: b is the mesh width of the shielding net; f is the frequency of the electric field (the frequency of the alternating current of the excitation field) in the electromagnetic field to be shielded, and f is less than f c ，f c For shielding the cut-off frequency of the net, f c ＝1.5×10 8 /b。
The maximum working frequency of the security inspection door is set to be 50KHz, so that when a copper mesh with the diameter of 0.5mm and the mesh of 10 meshes is selected as a shielding mesh, the shielding effect on an electric field can reach 120lg3db, about 57 db.
The shielding effect of the magnetic field under the same conditions is as follows:
SH＝10lg(H 0 /H i )≈20lg(1+μ r d/2b)
wherein, mu r Is the relative permeability of the shielding material; d is the thickness of the shielding layer, namely the diameter of the copper wire; b is the mesh width of the shielding mesh.
From the above formula, the shielding of the copper mesh with 10 mesh and 0.5mm diameter against the magnetic field is about 1db (mu) r Taken as 1.0), it can be seen that the copper mesh is substantially non-attenuating to the magnetic field.
Regarding the structure of the door panels, as shown in fig. 17, the first door panel 50 includes a first panel body 51 and a first cover plate 52, the first cover plate 52 is disposed toward the security inspection passage 70, the first panel body 51 and the first cover plate 52 cover to form an accommodating space, and the transmitting winding 10 and the first electric field shielding net 80a are disposed in the accommodating space. First apron 52 and first plate body 51 can be connected or the joint through the fastener, and like this, first apron 52 can be dismantled to, first apron 52 dismantles the back, can form great opening in one side towards security installations passageway 70, so, the maintenance of the inner assembly of being convenient for, first apron 52 closes the back in the lid, can encapsulate first electric field shielding net 80a and transmission winding 10 in the inner space, avoids first electric field shielding net 80a and transmission winding 10 to expose.
In the case where the first door panel 50 is further provided with the second electric field shielding net 80b, the second electric field shielding net 80b is also provided in the accommodating space formed by the first cover plate 52 and the first plate 51.
Similarly, as shown in fig. 17, the second door 60 includes a second plate 61 and a second cover plate 62, and the second cover plate 62 is disposed toward the security inspection channel 70, the second cover plate 62 and the second plate 61 cover to form an accommodation space, the receiving winding 20, the third electric field shielding net 80c and the fourth electric field shielding net 80d can be disposed in the accommodation space, and meanwhile, the second cover plate 62 also has the effects of facilitating the maintenance and avoiding the exposure of internal components.
In some embodiments, the first electric field shielding mesh 80a and/or the emission winding 10 are adhered to the first door panel 50 by glue, and the first electric field shielding mesh 80a and the emission winding 10 are arranged in a gap along the first direction.
The first door panel 50 is thin, the inner space is small, the first electric field shielding net 80a and/or the transmitting winding 10 are/is bonded to the first door panel 50 through glue, the narrow operation space can be adapted to, and the glue has insulating performance and can play an insulating role between the first electric field shielding net 80a and the first door panel 50 and between the transmitting winding 10 and the first door panel 50.
Meanwhile, the first electric field shielding net 80a and the transmitting winding 10 are arranged along the first direction at a gap, and the first electric field shielding net 80a and the transmitting winding 10 are not in contact with each other, because long-time contact friction between the transmitting coil 11 of the transmitting winding 10 and the first electric field shielding net 80a may cause abrasion of an insulating coating on the surface of the transmitting coil 11, so that a circuit is exposed, and further, electrical connection is easy to occur.
In addition, under the condition that the second electric field shielding net 80b is disposed in the first door panel 50, the second electric field shielding net 80b may also be adhered to the first door panel 50 by glue, and the second electric field shielding net 80b and the emission winding 10 are disposed at a gap along the first direction to avoid electrical connection therebetween.
Similarly, referring to the above arrangement, the third electric field shielding net 80c, the fourth electric field shielding net 80d, and the receiving winding 20 may be adhered to the second door panel 60 by glue, and the third electric field shielding net 80c and the receiving winding 20 are disposed in a gap, and the fourth electric field shielding net 80d and the receiving winding 20 are disposed in a gap.
As shown in fig. 16 and 17, the security door further includes a cross member 90, and the cross member 90 is disposed on top of the first door panel 50 and the second door panel 60 and encloses a door-shaped structure together with the first door panel 50 and the second door panel 60.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (10)

1. A metal detection device based on a multistage alternating magnetic field is characterized by comprising a transmitting winding, a receiving winding and a detection unit;
the transmitting winding and the receiving winding are arranged at intervals along a first direction in a horizontal plane to form a detection area between the transmitting winding and the receiving winding;
the transmitting winding comprises a plurality of transmitting coils which are overlapped along the first direction and form a plurality of transmitting blocks, and the alternating magnetic field in each transmitting block is the sum of the alternating magnetic fields of the transmitting coils in the area corresponding to the transmitting block;
the receiving winding is used for generating induction signals based on the change of alternating magnetic fields in a plurality of transmitting blocks;
the detection unit is used for determining the metal object information in the detection area based on the change of the induction signal generated by the receiving winding.
2. The multilevel alternating magnetic field-based metal detection device according to claim 1, wherein orthographic projections of the plurality of emission blocks in a reference plane perpendicular to the first direction form a matrix structure with a plurality of rows and a plurality of columns, and are symmetrically distributed on both sides of a central axis extending in a height direction in the reference plane.
3. The multistage alternating magnetic field based metal detection device according to claim 1 or 2, wherein the plurality of transmission blocks comprises a top transmission block and a bottom transmission block, and the magnetic field strength of the top transmission block and the magnetic field strength of the bottom transmission block are larger than that of a middle transmission block between the top transmission block and the bottom transmission block.
4. The metal detection device based on the multistage alternating magnetic field as claimed in claim 1 or 2, wherein the transmitting coil comprises a conducting wire, the conducting wire is surrounded into one or more transmitting sub-blocks in a preset winding manner, and any two transmitting sub-blocks in different transmitting coils are completely overlapped, non-overlapped or partially overlapped;
and a plurality of transmitting coils with the transmitting sub-blocks are superposed to form the transmitting blocks.
5. The multilevel alternating magnetic field-based metal detection device according to claim 4, wherein the plurality of the transmission coils includes a first transmission coil, the number of the first transmission coils is one or more, and the first transmission coil covers the entire area of the detection area in the height direction;
the first radiation coil comprises a plurality of first radiation sub-blocks, and the first radiation sub-blocks are arranged along the height direction of the detection area.
6. The multilevel alternating magnetic field-based metal detection device according to claim 4, wherein the plurality of the transmission coils includes a second transmission coil, the number of the second transmission coils is one or more, and the second transmission coil covers a local area of the detection area in a height direction;
the second transmit coil includes one or more second transmit sub-blocks.
7. The multilevel alternating magnetic field-based metal detection device according to claim 6, wherein at least one of the second transmitting coils covers a bottom area of the detection area in a height direction and has an "8" shaped structure.
8. The multilevel alternating magnetic field-based metal detection device according to claim 4, wherein a third transmission coil is included in the plurality of transmission coils, the third transmission coil covers an entire region or a partial region of the detection region in a height direction, and the third transmission coil includes at least one transmission unit in a "∞" structure, the transmission unit including two third transmission sub-blocks.
9. The multilevel alternating magnetic field-based metal detection device according to claim 8, wherein the third transmitting coil includes a plurality of transmitting units arranged at intervals in a height direction, the plurality of transmitting units are located in a same plane perpendicular to the first direction, and the plurality of transmitting units are arranged in series in sequence;
or, the third transmitting coil includes a plurality of transmitting units, the plurality of transmitting units are located in different planes perpendicular to the first direction, and orthographic projections of the plurality of transmitting units along the first direction do not coincide.
10. A security door, comprising a first door panel, a second door panel and a metal detection device based on a multistage alternating magnetic field according to any one of claims 1 to 9;
a security inspection channel is formed between the first door plate and the second door plate, the transmitting winding is arranged on the first door plate, the receiving winding is arranged on the second door plate, and the detection area is located in the coverage range of the security inspection channel.
CN202211224909.6A 2022-10-09 2022-10-09 Metal detection device and security check door based on multistage alternating magnetic field Pending CN115494554A (en)

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CN202211224909.6A CN115494554A (en) 2022-10-09 2022-10-09 Metal detection device and security check door based on multistage alternating magnetic field

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Application Number Priority Date Filing Date Title
CN202211224909.6A CN115494554A (en) 2022-10-09 2022-10-09 Metal detection device and security check door based on multistage alternating magnetic field

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