Metal detection device

Abstract

The application relates to a metal detection device, comprising a signal source, an induction unit and a processing unit, the signal source is used for outputting an alternating current input signal, the induction unit is used for receiving the alternating current input signal and outputting an alternating current output signal based on magnetic field changes in an induction area, the induction unit comprises at least one induction coil group, the induction coil group comprises a first induction coil and a second induction coil connected to each other; in the case that there is no metal in the induction area of the first induction coil and the induction area of the second induction coil, the induction electromotive force of the first induction coil and the second induction coil cancels out each other; the processing unit is used for determining a metal detection result in the induction area of the first induction coil and the induction area of the second induction coil according to the alternating current output signal corresponding to the induction coil group, realizing high signal-to-noise ratio detection of air gap equivalent permeability differences caused by metal, and determining position information of the metal.

Description

Technical Field

[0001] This application relates to the field of metal detection technology, and in particular to a metal detection device. Background Technology

[0002] Industries such as food, electronics, and medical often require strict control of trace metal contamination in materials or articles, necessitating the use of highly sensitive metal detection devices. However, for the detection of tiny metal particles and fragments, due to their weak primary capacitance and electromagnetic effects, simply increasing the signal gain of traditional detection circuits is insufficient for reliable detection. This is because the signal-to-noise ratio of the sensitive element itself is too low, and the effective signal is easily drowned out by power supply noise, electronic component and circuit noise, and electromagnetic interference noise during amplification.

[0003] Existing technologies include schemes that use a common transmitting coil and dual D-shaped or dual rectangular differential coils to detect tiny metal particles. However, differential coils are complex to manufacture, and when the transmitting coil is large, the sensitivity in the central area decreases significantly. In particular, existing detection methods can only distinguish the presence or absence of metal objects and cannot provide more detailed positional information within the effective range of the sensor, nor can they distinguish multiple metal objects within the effective range.

[0004] There is currently no effective solution to the problem that existing micro-metal detection methods can only distinguish whether there is a metal object in the sensing area, but cannot provide the location information of the metal object. Summary of the Invention

[0005] This embodiment provides a metal detection device to solve the problem in related technologies that cannot provide position information of metal objects.

[0006] In a first aspect, this embodiment provides a metal detection device, comprising: a signal source, a sensing unit, and a processing unit. The signal source is used to output an AC input signal, and the sensing unit is used to receive the AC input signal and output an AC output signal based on changes in the magnetic field within the sensing area. The device is characterized in that...

[0007] The sensing unit includes at least one induction coil group, which includes a first induction coil and a second induction coil connected to each other; when there is no metal in the sensing area of ​​the first induction coil and the sensing area of ​​the second induction coil, the induced electromotive forces of the first induction coil and the second induction coil cancel each other out.

[0008] The processing unit is used to determine the metal detection results in the sensing area of ​​the first induction coil and the sensing area of ​​the second induction coil based on the AC output signal corresponding to the induction coil group.

[0009] In some embodiments, the first induction coil includes an excitation coil and a sensing coil arranged vertically, and the second induction coil includes an excitation coil and a sensing coil arranged vertically; wherein, the same-name terminal of the excitation coil of the first induction coil is connected to the non-same-name terminal of the excitation coil of the second induction coil, and the same-name terminal of the sensing coil of the first induction coil is connected to the same-name terminal of the sensing coil of the second induction coil.

[0010] In some embodiments, the metal detection device further includes a phase detection unit connected to the sensing unit and the processing unit. The phase detection unit is used to rectify the AC output signal into a DC signal of corresponding polarity based on the phase information of the AC input signal. The processing unit is used to determine the metal detection result of the sensing area of ​​the first induction coil and the sensing area of ​​the second induction coil based on the polarity of the DC signal.

[0011] In some embodiments, the metal detection device further includes a zero-adjustment unit connected to the processing unit and the phase detection unit, the zero-adjustment unit being used to cancel the zero-adjustment signal sent by the processing unit with the DC signal, so that the DC signal voltage output is zero.

[0012] In some embodiments, the metal detection device further includes a bandpass filter unit connected to the sensing unit, the bandpass filter unit being used to filter the AC output signal with the frequency of the AC input signal as the center frequency.

[0013] In some embodiments, the metal detection device further includes a DC gain unit connected to the processing unit and the zeroing unit. The DC gain unit amplifies the DC signal and sends it to the processing unit. The processing unit determines the metal detection result of the corresponding sensing area of ​​the first induction coil and the sensing area of ​​the second induction coil based on the polarity and voltage value of the DC signal.

[0014] In some embodiments, the metal detection device further includes an AC gain unit connected to the sensing unit, the AC gain unit being used to amplify the AC output signal.

[0015] In some embodiments, the ratio of the number of turns of the sensing coil to the number of turns of the excitation coil is less than a certain threshold.

[0016] In some embodiments, the sensing coil and the excitation coil have the same cross-sectional shape and size and are placed close to each other.

[0017] In some embodiments, the metal detection device further includes an input display unit connected to the processing unit, the input display unit being used to input parameters of the AC input signal and display the metal detection result.

[0018] Compared with related technologies, the metal detection device provided in this embodiment, by setting at least one induction coil group in the sensing unit, the induction coil group includes a first induction coil and a second induction coil connected to each other, when an AC input signal is input to the induction coil group, the first induction coil and the second induction coil can generate corresponding induced electromotive forces; and when there is no metal in the sensing area of ​​the induction coil group, the induced electromotive forces generated by the first induction coil and the second induction coil can cancel each other out; the change in magnetic field in the sensing area of ​​the induction coil group is determined by the AC output signal. When metal is present in the sensing area, the magnetic flux is enhanced, the induced electromotive force of the corresponding induction coil increases, resulting in a positive or negative offset of the AC output signal; the sensing area corresponding to the induction coil where the metal is located is determined by the AC output signal, thereby achieving high signal-to-noise ratio detection of the difference in equivalent permeability of the air gap caused by the metal, and determining the location information of the metal.

[0019] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 This is a schematic diagram of the structure of a metal detection device according to an embodiment of this application;

[0022] Figure 2 This is a connection diagram of the metal detection device according to an embodiment of this application;

[0023] Figure 3 This is a schematic diagram of the structure of a metal detection device including a phase detection unit and a zero-adjustment unit according to an embodiment of this application;

[0024] Figure 4 This is a schematic diagram of the structure of a metal detection device according to a preferred embodiment of this application. Detailed Implementation

[0025] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0026] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning as understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these,” used in this application, do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to such processes, methods, products, or devices. The terms “connected,” “linked,” and “coupled,” used in this application, are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. The term “multiple” used in this application refers to two or more. The "and / or" operator describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: A alone, A and B simultaneously, and B alone. Typically, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," and "third," etc., used in this application are merely for distinguishing similar objects and do not represent a specific ordering of the objects.

[0027] Please see Figure 1 The diagram shown is a structural schematic of a metal detection device according to an embodiment of this application. This application provides a metal detection device, including a signal source 4, a sensing unit 13, and a processing unit 6. The signal source 4 is used to output an AC input signal, and the sensing unit 13 is used to receive the AC input signal and output an AC output signal based on changes in the magnetic field within the sensing area.

[0028] Specifically, the sensing unit 13 includes at least one induction coil group 14, which includes a first induction coil 15 and a second induction coil 16 connected to each other. When there is no metal in the sensing area of ​​the first induction coil 15 and the sensing area of ​​the second induction coil 16, the induced electromotive forces generated by the first induction coil 15 and the second induction coil 16 cancel each other out. The processing unit 6 is used to determine the metal detection result in the sensing area of ​​the first induction coil 15 and the sensing area of ​​the second induction coil 16 based on the AC output signal corresponding to the induction coil group 14. Those skilled in the art will understand that... Figure 1 The connections shown are for illustrative purposes only and do not limit the configuration of the metal detection device. For example, the induction coil assembly 14 may also include... Figure 1 The quantity shown is more or less, or has the same as Figure 1Different configurations and connection methods are shown. In this embodiment, the induced electromotive forces generated by the first induction coil 15 and the second induction coil 16 can cancel each other out. This embodiment does not limit the material, structural parameters, connection method, and placement of the first induction coil 15 and the second induction coil 16.

[0029] Specifically, the signal source 4, the induction coil group 14, and the processing unit 6 are connected sequentially. The signal source 4 is an AC signal source, which can provide the induction unit 13 with regular AC input signals such as sine and cosine signals. Multiple induction coil groups 14 can use the same AC input signal from the signal source 4, and the multiple induction coil groups 14 are connected in parallel. Under the excitation of the AC input signal, the induction coil group 14 in the induction unit 13 generates a corresponding induced electromotive force and outputs an AC output signal to the processing unit 6. The processing unit 6 processes the AC output signal, which may include amplification, rectification, analog-to-digital conversion, etc. The processing unit 6 can compare the processing result with a set threshold to determine whether there is metal in the corresponding induction coil group 14. If there is, it further determines whether the metal is located in the sensing area of ​​the first induction coil 15 or the second induction coil 16. The number of induction coil groups 14 can be set according to requirements. Each induction coil group 14 generates a corresponding AC output signal. The AC output signals generated by each induction coil group 14 are independent of each other. The number of signal processing channels of the processing unit 6 should meet the processing requirements of the AC output signals.

[0030] In the induction coil group 14, the first induction coil 15 and the second induction coil 16 generate corresponding induced electromotive forces based on changes in their respective magnetic fields. Since the output terminals of the first induction coil 15 and the second induction coil 16 are interconnected and jointly output an AC output signal, this AC output signal is the superposition of the induced signals output by the first induction coil 15 and the second induction coil 16 respectively. By designing the connection relationship between the first induction coil 15 and the second induction coil 16, the coil constituent materials, and the coil structural parameters, it is possible to make the induced electromotive forces generated by the first induction coil 15 and the second induction coil 16 have equal frequencies and approximately equal amplitudes, even when there is no metal present in the induction area of ​​the coil. This allows the fundamental frequency voltages of the AC output signals output by the two induction coils in series to cancel each other out, mainly containing spatial electromagnetic wave noise.

[0031] When metal is present in the sensing area of ​​the first induction coil 15 and / or the second induction coil 16, the metal is excited by the AC input signal to generate magnetic flux, the magnetic flux in the corresponding sensing area is enhanced, and the induced electromotive force increases, so that the AC output signal contains a significant fundamental frequency voltage component. The processing unit processes the AC output signal and determines whether there is a metal object in the corresponding induction coil group and which induction coil in the first induction coil 15 or the second induction coil 16 the metal object is located in based on the phase, amplitude and other information of the AC output signal.

[0032] The metal detection device provided in this embodiment, by setting at least one induction coil group in the induction unit, includes a first induction coil and a second induction coil connected to each other. When an AC input signal is input to the induction coil group, the first induction coil and the second induction coil can generate corresponding induced electromotive forces. When there is no metal in the sensing area of ​​the induction coil group, the induced electromotive forces generated by the first induction coil and the second induction coil can cancel each other out. The change in the magnetic field of the sensing area of ​​the induction coil group is determined by the AC output signal. When there is metal in the sensing area, the magnetic flux is enhanced, and the induced electromotive force of the corresponding induction coil increases, resulting in a positive or negative offset of the AC output signal. The sensing area corresponding to the induction coil where the metal is located is determined by the AC output signal, thereby achieving high signal-to-noise ratio detection of the difference in equivalent permeability of the air gap caused by the metal, and determining the location information of the metal.

[0033] In some embodiments, please refer to Figure 2 The diagram shown is a connection schematic of a metal detection device according to an embodiment of this application. Figure 2 The induction unit shown here is only one induction coil group 14 as a connection illustration. In actual use, the number of induction coil groups 14 can be set according to requirements. The first induction coil 15 in the induction coil group 14 includes a first excitation coil 31 and a first sensing coil 32 arranged vertically, and the second induction coil 16 includes a second excitation coil 33 and a second sensing coil 34 arranged vertically. The first excitation coil 31 and the first sensing coil 32 are coupled, and the second excitation coil 33 and the second sensing coil 34 are coupled. The vertical order of the excitation coils and sensing coils can be adjusted as needed.

[0034] The first induction coil 15 and the second induction coil 16 are made of the same material and have the same dimensions. The same-name terminal of the first excitation coil 31 of the first induction coil 15 is connected to the non-same-name terminal of the second excitation coil 33 of the second induction coil 16, and the same-name terminal of the first sensing coil 32 of the first induction coil 15 is connected to the same-name terminal of the second sensing coil 34 of the second induction coil 16. Figure 2The black dot at one end of the intermediate sensing coils 32 and 34 and the excitation coils 31 and 33 indicates the corresponding terminals of the coils. The non-corresponding terminal of the first excitation coil 31 and the corresponding terminal of the second excitation coil 33 are respectively connected to the two ends of the signal source 4. The non-corresponding terminals of the first sensing coil 32 and the second sensing coil 34 are interconnected and output an AC output signal.

[0035] The induced electromotive force (EMF) of sensing coils 32 and 34 is proportional to the alternating magnetic flux passing through them. This alternating magnetic flux is the result of the combined effect of the magnetomotive force of the coaxial excitation coil and the equivalent permeability of the air gap it surrounds. Since the tiny metal target is much smaller than the volume of the sensing area, the core material of excitation coils 31 and 33 can be considered as the air gap. Because the first induction coil 15 and the second induction coil 16 are made of the same material and have the same dimensions, and excitation coils 31 and 33 are connected in series, the excitation current and magnetomotive force of the two excitation coils are the same. The corresponding and non-corresponding terminals of the two excitation coils 31 and 33 are connected to each other, and the corresponding terminals of the two sensing coils 32 and 34 are connected to each other, causing the induced EMFs generated by the two sensing coils 32 and 34 to be in opposite directions. This constitutes a balanced excitation and differential induction detection method, achieving a good balance of the induced EMFs of the first induction coil 15 and the second induction coil 16 under air gap conditions.

[0036] The metal detection device provided in this embodiment achieves a good balance of induced electromotive force between the first and second induction coils under air gap conditions by setting the connection method, material, and size of the excitation coil and sensing coil in the first and second induction coils. Thus, in the absence of metal, the induced electromotive force generated by the first and second induction coils can cancel each other out, laying the foundation for high signal-to-noise ratio detection of the difference in equivalent permeability of the air gap between the first and second induction coils caused by metal targets.

[0037] Furthermore, the cross-sectional shape and size of the sensing coil and the excitation coil in the same induction coil can be set to be the same and placed close to each other to achieve coaxial tight fit, so as to maximize the magnetic flux of the sensing coil and the excitation coil, avoid leakage flux caused by mismatch between the sensing coil and the excitation coil, as well as the attenuation of induced electromotive force and external interference caused by leakage flux.

[0038] Since the core material of the excitation coil can be regarded as an air gap, the magnetic flux generated by the excitation coil is approximately the air gap magnetic flux, which is weak. The ratio of the number of turns of the sensing coil to the number of turns of the excitation coil can be set to be less than a specific threshold, such as 1:5, to reduce the cancellation effect of the sensing coil operating current on the air gap magnetic flux.

[0039] In practical applications, the first induction coil 15 and the second induction coil 16 in the induction coil group can be fixed by a wire groove. The center of the wire groove can be a through-hole structure, serving as the sensing area of ​​the induction coil, allowing the object to be detected to pass through. The first induction coil 15 and the second induction coil 16 can be embedded in the wire groove. Since the tiny metal target is much smaller than the volume of the hollow area in the wire groove, the core material of the excitation coils 31 and 33 can be regarded as an air gap, making the magnetic flux generated by the excitation coils 31 and 33 approximately the air gap magnetic flux, which is very weak and avoids interference with the detection results in the metal detection process.

[0040] When the target to be measured enters the sensing range of the wire groove, it can enter from different directions, such as passing laterally through the first induction coil 15 and / or the second induction coil 16, or approaching the hollow area of ​​the induction coils 15 and 16 from a distance; the closer the metal object is to the geometric center of the first excitation coil 31 or the second excitation coil 33, the greater the increase in magnetic flux in the excitation coil, and the greater the induced electromotive force of the corresponding first sensing coil 32 or the second sensing coil 34.

[0041] Furthermore, the wire groove can be fitted with the wire frame and connected to the wire frame via a support or handheld component. The wire frame can contain one or more induction coil groups 14 to achieve handheld or portable metal detection.

[0042] Before performing metal detection, the frequency of the AC input signal can be set according to the type of metal to be detected. This frequency is related to the type of metal. The frequency and amplitude commands of the AC input signal can be sent to the signal source 4 through the processing unit 6, or the signal source 4 can be directly controlled to send an AC input signal with a corresponding frequency and amplitude to excite the first excitation coil 31 and the second excitation coil 33 in the first induction coil 15 and the second induction coil 16, so as to improve the sensitivity of the corresponding type of metal detection.

[0043] In some embodiments, the metal detection device further includes a phase detection unit connected to the sensing unit and the processing unit. The phase detection unit is used to rectify the AC output signal into a DC signal of corresponding polarity based on the phase information of the AC input signal. The processing unit is used to determine the metal detection result of the sensing area of ​​the first induction coil and the sensing area of ​​the second induction coil based on the polarity of the DC signal.

[0044] The phase detection unit determines whether the DC signal is positive or negative based on the phase information of the AC input signal. In this embodiment, the phase information is sent to the phase detection unit via a processing unit, or it can be sent via a signal source. The phase detection unit determines the polarity of the rectified DC signal based on this phase information. The processing unit processes the DC signal and, based on the magnitude and polarity of the processed digital signal, determines whether metal exists in the corresponding induction coil group. If metal is present, it determines whether the metal is located in the sensing area of ​​the first or second induction coil.

[0045] When there are no metal objects within the sensing areas of the first and second induction coils, they operate in a pure air-gap state with minimal magnetic flux difference. The induced voltages of the two coils are in phase and approximately equal in amplitude. The AC output signals from these two coils cancel each other out in terms of fundamental frequency, primarily containing spatial electromagnetic noise. After passing through the phase detection unit, the output voltage of the resulting DC signal is approximately zero.

[0046] When the positions of the metal object and the metal detection device are relatively fixed, the voltage and polarity of the DC signal output by the phase detection unit can determine the sensing area where the metal is located. When the metal object and the metal detection device move relative to each other, the location of the metal can also be determined based on the dynamic changes in the DC signal voltage and polarity. For example, when the metal object enters the sensing range of the first induction coil, the magnetic flux of the first induction coil is enhanced, and the amplitude of the induced voltage of the corresponding sensing coil is significantly greater than that of the second induction coil. This causes the AC output signal to contain a significant fundamental frequency voltage component, resulting in the DC signal voltage output by the phase detection unit rising from approximately zero to a positive value. The closer the metal target is to the center of the first induction coil, the higher the output voltage. When the metal object enters the sensing range of the second induction coil, the magnetic flux of the second induction coil is enhanced, and the amplitude of the induced voltage of the corresponding sensing coil is significantly greater than that of the first induction coil. Similarly, this causes the AC output signal to contain a significant fundamental frequency voltage component, but the phase is opposite to that of the metal object in the first induction coil. This causes the DC signal voltage output by the phase detection unit to become negative, and the closer the metal target is to the center of the sensing coil, the greater the negative value.

[0047] When a metal particle moves from the sensing area of ​​the first induction coil to the sensing area of ​​the second induction coil, the induced electromotive force of the sensing coil of the first induction coil returns to its initial equilibrium state, the induced electromotive force of the sensing coil of the second induction coil increases, and the polarity of the DC signal output by the phase detection unit is reversed. The processing unit can determine the current position of the metal based on the change in the polarity of the DC signal.

[0048] When two or more metal particles enter the sensing area of ​​the same induction coil, the magnetic flux of that coil is enhanced. The effect on the sensing coil is similar to that of a single, larger metal object, and the processing unit identifies it as a single metal object. When two or more metal particles enter the sensing areas of the first and second induction coils respectively, the magnetic flux of both coils is simultaneously enhanced. If the electromagnetic effects of the two metal particles are the same, the resulting increases in the induced electromotive force of the first and second induction coils completely cancel each other out, and the processing unit cannot detect the metal target. If the electromagnetic effects of the two metal particles are different, the processing unit identifies the two metal objects as a single, smaller metal target.

[0049] Furthermore, to avoid the mutual cancellation problem caused by the first and second induction coils simultaneously sensing a metal target, two or more sets of induction coils can be set up. By changing the connection relationship between the two or more sets of induction coils and performing metal detection two or more times, the results of each metal detection can be used to comprehensively determine whether there is a metal object in the sensing area of ​​each induction coil.

[0050] Taking a four-quadrant metal detection device composed of two sets of induction coils as an example, a first induction coil set and a second induction coil set are set up. The first induction coil set includes a first induction coil and a second induction coil, and the second induction coil set includes a third induction coil and a fourth induction coil. Before the first metal detection, the same-name terminal of the excitation coil of the first induction coil is connected to the non-same-name terminal of the excitation coil of the second induction coil, and the same-name terminal of the sensing coil of the first induction coil is connected to the same-name terminal of the sensing coil of the second induction coil; the same-name terminal of the excitation coil of the fourth induction coil is connected to the non-same-name terminal of the excitation coil of the third induction coil, and the same-name terminal of the sensing coil of the fourth induction coil is connected to the same-name terminal of the sensing coil of the third induction coil. Then the first metal detection is performed.

[0051] Before the second metal detection, connect the same-name terminal of the excitation coil of the first induction coil to the non-same-name terminal of the excitation coil of the third induction coil, and connect the same-name terminal of the sensing coil of the first induction coil to the same-name terminal of the sensing coil of the third induction coil; connect the same-name terminal of the excitation coil of the fourth induction coil to the non-same-name terminal of the excitation coil of the second induction coil, and connect the same-name terminal of the sensing coil of the fourth induction coil to the same-name terminal of the sensing coil of the second induction coil. Then perform the second metal detection.

[0052] If the first and second metal detection results are the same, with no metal or all metal in the same sensing area, then there is no issue of the sensing areas canceling each other out, and the detection result is correct. If the first and second metal detection results are different, then it is determined whether there are multiple sensing areas containing metal based on the two detection results.

[0053] Furthermore, in some embodiments, please refer to Figure 3 The diagram shown is a schematic representation of a metal detection device comprising a phase detection unit 53 and a zero-adjustment unit 54 according to an embodiment of this application. The metal detection device further includes a zero-adjustment unit 54 connected to the processing unit 6 and the phase detection unit 53. The zero-adjustment unit 54 is used to cancel out the zero-adjustment signal sent by the processing unit 6 with the DC signal, so that the DC signal voltage output is zero.

[0054] Before metal detection, the DC signal can be zeroed using a zero-adjustment unit. Once it is determined that there are no metal objects or other objects that could cause electromagnetic induction within the sensing area of ​​the induction coil group, the processing unit sends a zero-adjustment signal to the zero-adjustment unit. This zero-adjustment signal is an adjustable DC signal. Based on the polarity and magnitude of the DC signal output by the phase detector unit, the polarity and magnitude of the zero-adjustment signal are adjusted until the zero-adjustment signal and the output of the phase detector unit cancel each other out, resulting in a zero output for the zero-adjustment unit.

[0055] The metal detection device provided in this embodiment, after the first and second induction coils of the induction coil group have achieved induced electromotive force balance, further balances the output voltage of the DC signal by setting a zero-adjustment unit, and performs zero-point calibration when there is no metal in the sensing area, thereby improving the accuracy of metal detection.

[0056] In some embodiments, the metal detection device further includes a bandpass filter unit connected to the sensing unit. The bandpass filter unit is used to filter the AC output signal using the frequency of the AC input signal as the center frequency. This can filter out interference signals from other spatial electromagnetic fields sensed by the sensing coil, avoiding signal-to-noise ratio loss in the AC output signal from the sensing coil.

[0057] In some embodiments, the metal detection device further includes a DC gain unit connected to the processing unit and the zeroing unit. The DC gain unit amplifies the DC signal output by the zeroing unit and sends it to the processing unit. The processing unit determines the metal detection result of the corresponding sensing area of ​​the first induction coil and the sensing area of ​​the second induction coil based on the polarity and voltage value of the DC signal. The processing unit can convert the DC signal output by the DC gain unit into a digital quantity and compare it with a set threshold to determine whether metal has been detected. Furthermore, it determines which induction coil's sensing area the metal location belongs to based on the polarity of the digital quantity. The amplified DC signal is more conducive to analog-to-digital signal conversion and threshold determination, reducing the probability of false detection.

[0058] In some embodiments, the metal detection device further includes an AC gain unit connected to the sensing unit, which amplifies the AC output signal. Since the AC output signal generated by tiny metal particles is relatively weak, it needs to be amplified and filtered to be converted into a DC signal; otherwise, it is easily confused with spatial electromagnetic noise, leading to misjudgment of the detection results.

[0059] In some embodiments, the metal detection device further includes an input display unit connected to the processing unit. The input display unit is used to input parameters of the AC input signal and display the metal detection result. The operator can set parameters such as the operating frequency and amplitude in the input display unit according to the type of metal to be detected. The processing unit then sends the corresponding AC input signal to the signal source based on these parameters. After metal detection is completed, the presence of metal in the sensing area, and the specific location information such as the induction coil group, the first induction coil, or the second induction coil where the metal is located, are displayed in the input display unit.

[0060] The present embodiment will now be described and illustrated through preferred embodiments.

[0061] Figure 4 This is a schematic diagram of the structure of the metal detection device according to a preferred embodiment.

[0062] The metal detection device includes a support rod 1, a wire frame 2, a first induction coil group, a second induction coil group, a third induction coil group, a fourth induction coil group, a sinusoidal signal source 4, a signal conditioning unit 5, a processing unit 6, an input display unit 7, and a power module 8. The signal conditioning unit 5 includes an AC gain unit 51, a bandpass filter unit 52, a phase detector unit 53, a zero-adjustment unit 54, and a DC gain unit 55. The end of the support rod 1 is connected to the wire frame 2. The wire frame 2 has four quadrant grooves arranged in a grid pattern, with a through-hole structure in the center of each groove to allow the object to be detected to pass through. The first induction coil group is embedded in the first quadrant groove 21, the second induction coil group is embedded in the second quadrant groove 22, the third induction coil group is embedded in the third quadrant groove 23, and the fourth induction coil group is embedded in the fourth quadrant groove 24. Each induction coil group includes an excitation coil and a sensing coil stacked vertically, with the same terminal of the first excitation coil 31 connected to the second excitation coil 34. The non-identical terminals of magnetic coil 33 are connected; the identical terminal of the fourth excitation coil 37 is connected to the non-identical terminal of the third excitation coil 35; the identical terminal of the first sensing coil 32 is connected to the identical terminal of the second sensing coil 34; and the identical terminal of the fourth sensing coil 38 is connected to the identical terminal of the third sensing coil 36. The sinusoidal signal source 4 is connected to the identical terminals of the second and third excitation coils 33 and 35, and the non-identical terminals of the first and fourth excitation coils 31 and 37, respectively. The input channel A of the AC gain unit 51 is connected to the non-identical terminals of the first and second sensing coils 32 and 34. Input channel B is connected to the non-identical terminals of the fourth and third sensing coils 38 and 36; input channels A and B of bandpass filter unit 52 are connected to output channels A and B of AC gain unit 51, respectively; input channels A and B of phase detector unit 53 are connected to output channels A and B of bandpass filter unit 52, respectively; input channels A and B of zeroing unit 54 are connected to output channels A and B of phase detector unit 53, respectively; input channels A and B of DC gain unit 55 are connected to output channels A and B of zeroing unit 54, respectively; positive The sinusoidal signal source 4, bandpass filter unit 52, phase detector unit 53, zeroing unit 54, DC gain unit 55, input display unit 7, and processing unit 6 are electrically connected. The input display unit 7 is used to display the metal detection status of the processing unit 6 and also to set the operating parameters of the sinusoidal signal source 4 and signal conditioning unit 5. The power supply module 8 supplies power to the sinusoidal signal source 4, AC gain unit 51, bandpass filter unit 52, phase detector unit 53, zeroing unit 54, DC gain unit 55, and processing unit 6.

[0063] Specifically, processing unit 6 sends an electrical signal to sinusoidal signal source 4, controlling sinusoidal signal source 4 to emit a sinusoidal voltage signal with a set frequency and amplitude to excite the excitation coil connected to it; processing unit 6 sends an electrical signal to bandpass filter unit 52, adjusting the center frequency of bandpass filter unit 52 to match the output frequency of sinusoidal signal source 4; processing unit 6 sends an electrical signal to phase detection unit 53, controlling phase detection unit 53 to convert the input AC voltage signal into a bipolar DC signal; processing unit 6 sends an electrical signal to zeroing unit 54, controlling zeroing unit 54 to adjust its output signal value to zero; processing unit 6 receives the output channel A signal of DC gain unit 55, and determines whether there are metal objects in the first and second quadrants based on the magnitude and polarity of the converted digital value; processing unit 6 receives the output channel B signal of DC gain unit 55, and determines whether there are metal objects in the fourth and third quadrants based on the magnitude and polarity of the converted digital value.

[0064] When there are no metal objects within the sensing range of slots 21 and 22, the first and second quadrants are in a pure air gap state with minimal magnetic flux difference. The induced voltages of the first sensing coil 32 and the second sensing coil 34 are in phase and approximately equal in amplitude. The sensing signals output by the two coils in series cancel each other out in terms of fundamental frequency voltage, mainly containing spatial electromagnetic noise. After being amplified by the AC gain unit 51, the sensing signal is processed sequentially by the bandpass filter unit 52, the phase detector unit 53, the zero-adjustment unit 54, and the DC gain unit 55, resulting in a DC output voltage that is approximately zero. When a metal object enters the sensing range of slot 21, the magnetic flux in the first quadrant is enhanced, and the amplitude of the induced voltage of the first sensing coil 32 increases. The value is significantly greater than that of the second sensing coil 34, causing the sensing signal to contain a significant fundamental frequency voltage component. This causes the output voltage of the DC gain unit 55 to rise from near zero to a positive value, and the closer the metal target is to the center of the first sensing coil 32, the higher the output voltage. When the metal object enters the sensing range of the slot 22, the magnetic flux in the second quadrant is enhanced, and the amplitude of the voltage induced by the second sensing coil 34 is significantly greater than that of the first sensing coil 32. This also causes the sensing signal to contain a significant fundamental frequency voltage component, but the phase is opposite to that of the metal object in the first quadrant. This causes the output voltage of the DC gain unit 55 to become negative, and the closer the metal target is to the center of the second sensing coil 34, the lower the negative value.

[0065] When metal objects A and B simultaneously enter the sensing range of slots 21 and 24, the magnetic flux in the first and fourth quadrants is enhanced. The induced voltage amplitudes of the first and fourth sensing coils 32 and 38 are greater than those of the second and third sensing coils 34 and 36, respectively. Correspondingly, after the signal conditioning unit 5 processes the sensing signals from channels A and B, the output channels A and B of the DC gain unit 55 are both positive voltages. When metal objects A and B simultaneously enter the sensing range of slots 22 and 23, the output channels A and B of the DC gain unit 55 are both negative voltages. When metal objects A and B simultaneously enter the sensing range of slots 21 and 23, the output channels A and B of the DC gain unit 55 are positive and negative voltages, respectively. When metal objects A and B simultaneously enter the sensing range of slots 22 and 24, the output channels A and B of the DC gain unit 55 are negative and positive voltages, respectively.

[0066] The metal detection device provided in this embodiment has a differential sensor consisting of coaxial induction coil groups in the first and second quadrants, whose sensing signals are processed by signal conditioning unit channel A; and a differential sensor consisting of coaxial induction coil groups in the fourth and third quadrants, whose sensing signals are processed by signal conditioning unit channel B. The signal conditioning unit channels A and B do not affect each other and can simultaneously detect metal objects within the sensing range of grooves 21, 22 and grooves 24, 23.

[0067] Furthermore, in addition to constructing four sensing areas with two sets of coaxial induction coils in the above embodiment, the number of coaxial induction coil sets can be further increased to construct a wire slot and coaxial induction coil array with more areas, stronger position resolution, and larger detection coverage; correspondingly, for each additional set of induction coils, the number of signal conditioning unit channels and microcontroller analog-to-digital conversion channels also needs to be increased.

[0068] Furthermore, in addition to the above embodiment where the coaxial induction coil groups in the first and second quadrants are connected in series and the coaxial induction coil groups in the fourth and third quadrants are connected in series, other pairwise combinations can also be used, such as the first and third in series, the second and fourth in series, etc. In addition, the coaxial induction coil groups can be connected in series in pairs using either a fixed wiring method or a dynamic switching method to achieve optimized detection results, such as avoiding the mutual cancellation effect of two quadrants simultaneously sensing metal targets when using a fixed wiring method.

[0069] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated in this embodiment.

[0070] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0071] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0072] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0073] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A metal detection apparatus comprising: The signal source is used for outputting an alternating current input signal, and the induction unit is used for receiving the alternating current input signal and outputting an alternating current output signal based on a magnetic field change in an induction area. The induction unit includes at least two induction coil groups, a first induction coil group includes a first induction coil and a second induction coil connected to each other, and a second induction coil group includes a third induction coil and a fourth induction coil. In the absence of metal in the induction area of the first induction coil and the induction area of the second induction coil, the induction electromotive force of the first induction coil and the second induction coil cancels each other out. Before the first metal detection, the same name end of the excitation coil of the first induction coil is connected to the non-same name end of the excitation coil of the second induction coil, and the same name end of the sensing coil of the first induction coil is connected to the same name end of the sensing coil of the second induction coil. The same name end of the excitation coil of the fourth induction coil is connected to the non-same name end of the excitation coil of the third induction coil, and the same name end of the sensing coil of the fourth induction coil is connected to the same name end of the sensing coil of the third induction coil. Before the second metal detection, the same name end of the excitation coil of the first induction coil is connected to the non-same name end of the excitation coil of the third induction coil, the same name end of the sensing coil of the first induction coil is connected to the same name end of the sensing coil of the third induction coil, the same name end of the excitation coil of the fourth induction coil is connected to the non-same name end of the excitation coil of the second induction coil, and the same name end of the sensing coil of the fourth induction coil is connected to the same name end of the sensing coil of the second induction coil. The processing unit is used to determine the first metal detection result and the second metal detection result according to the corresponding alternating current output signals of the induction coil groups. When the first metal detection result and the second metal detection result are the same, it is determined that there is no metal or all the metals are in the same induction area. When the first metal detection result and the second metal detection result are different, it is determined whether there are multiple induction areas with metal according to the first metal detection result and the second metal detection result.

2. The metal detection apparatus of claim 1, wherein The phase detection unit connected to the induction unit and the processing unit is also included. The phase detection unit is used to rectify the alternating current output signal into a direct current signal of a corresponding polarity according to the phase information of the alternating current input signal. The processing unit is used to determine the metal detection results of the induction areas of the first induction coil and the second induction coil according to the polarity of the direct current signal.

3. The metal detection apparatus of claim 2, wherein, The zero adjustment unit connected to the processing unit and the phase detection unit is also included. The zero adjustment unit is used to cancel out the zero adjustment signal sent by the processing unit and the direct current signal, so that the direct current signal voltage output is zero.

4. The metal detection apparatus of claim 1, wherein, The band pass filter unit connected to the induction unit is also included. The band pass filter unit is used to filter the alternating current output signal with the frequency of the alternating current input signal as the center frequency.

5. The metal detection apparatus of claim 3, wherein The DC gain unit is connected with the processing unit and the zero adjustment unit, and is used for amplifying the DC signal and sending the DC signal to the processing unit.

6. The metal detection apparatus of claim 1, wherein, The AC gain unit is connected with the induction unit, and is used for amplifying the AC output signal.

7. The metal detection apparatus of claim 1, wherein The ratio of the number of turns of the sensing coil to the number of turns of the excitation coil is less than a certain threshold.

8. The metal detection apparatus of claim 1, wherein, The cross-sectional shape and size of the sensing coil and the excitation coil are the same and are placed in close contact with each other.

9. The metal detection apparatus of claim 1, wherein, The input display unit is connected with the processing unit, and is used for inputting parameters of the AC input signal and displaying the metal detection result.

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