A hand-held metal detector

Abstract

The utility model relates to a handheld metal detector, including the internal setting of control mainboard's casing with handle, the casing is provided with the same shape and partially overlapping transmitting coil and receiving coil side by side, transmitting coil and receiving coil are connected with control mainboard electricity respectively, the wire diameter of transmitting coil is greater than the wire diameter of receiving coil, still be provided with in the receiving coil and with receiving coil concentric sub -coil in the casing, the outer diameter of sub -coil is the outer diameter of receiving coil 1 / 5 1 / 3, and the ratio of the number of turns of sub -coil and receiving coil is 1:15 1:20. The utility model improves the sensitivity and anti -interference of detection.

Description

Technical Field

[0001] This utility model relates to metal detectors for security checks, and more particularly to a handheld metal detector. Background Technology

[0002] Handheld metal detectors contain a transmitting coil and a receiving coil. When metal approaches the detector, the eddy currents generated by the metal affect the magnetic field around the detector. This induces a current in the receiving coil, causing a change in the induced voltage. By detecting this change in voltage, the presence of metal can be determined. However, due to limited space inside handheld metal detectors for the transmitting and receiving coils, a compact arrangement can cause the strong magnetic field generated by the transmitting coil to couple directly to the receiving coil, generating interference and affecting detection sensitivity. Conversely, a larger space is needed to accommodate both coils, requiring them to be separated as much as possible or employing complex physical shielding structures. This increases the size, cost, and complexity of the device. Utility Model Content

[0003] To address the shortcomings of existing methods, this invention provides a handheld metal detector.

[0004] The technical solution adopted by this utility model to solve its technical problem is: a handheld metal detector, including a housing with a handle and an internal control main board, wherein a transmitting coil and a receiving coil of the same shape and partially overlapping are arranged side by side in the housing, the transmitting coil and the receiving coil are electrically connected to the control main board respectively, the wire diameter of the transmitting coil is larger than that of the receiving coil, and a sub-coil located in the receiving coil and concentric with the receiving coil is also arranged in the housing, the outer diameter of the sub-coil is 1 / 5 to 1 / 3 of the outer diameter of the receiving coil, and the ratio of the number of turns of the sub-coil to the number of turns of the receiving coil is 1:15 to 1:20.

[0005] Preferably, the control motherboard is provided with a power supply unit, a transmission drive unit, a signal processing unit, and a processor. The power supply unit is used to provide power to the detector. The transmission drive unit is used to regulate the current driving the transmission coil. The signal processing unit is used to process the signals detected by the receiving coil and the sub-coil and transmit the processed signals to the processor. The processor is used to control the operation of the transmission drive unit, process the signals transmitted by the signal processing unit, and output the detection results.

[0006] Preferably, the power supply unit includes a rechargeable battery and a charging circuit for charging the rechargeable battery. The rechargeable battery is electrically connected to the transmission drive unit and the signal processing unit, respectively. The housing is provided with a charging interface connected to the charging circuit.

[0007] Preferably, the transmitting drive unit includes a DC-DC converter, a digital signal generator, and a power drive module; the DC-DC converter is used to change the magnitude of the transmitting current of the transmitting coil; the digital signal generator receives the DC voltage output by the DC-DC converter and outputs a corresponding high-frequency signal to the power drive module; the power drive module amplifies the received signal and converts it into a high-frequency AC current to drive the transmitting coil.

[0008] Preferably, the signal processing unit includes a differential amplifier, a filter, a digital-to-analog converter, and a digital lock-in amplifier for sequentially processing the signals detected by the receiving coil and the sub-coil.

[0009] Preferably, the housing is provided with an alarm mechanism that is electrically connected to the control motherboard.

[0010] Preferably, the alarm mechanism is one or more of the following: sound alarm mechanism, vibration alarm mechanism, and light alarm mechanism.

[0011] Preferably, the housing is provided with a display screen that is electrically connected to the control motherboard.

[0012] Preferably, the housing is provided with a control switch that is electrically connected to the control motherboard.

[0013] Preferably, the housing is provided with an indicator light that is electrically connected to the control motherboard.

[0014] The beneficial effects of this utility model are as follows: the concentrically arranged sub-coils can effectively eliminate the direct coupling interference between the transmitting coil and the receiving coil, greatly suppress background noise, and make weak signals stand out, thereby significantly improving the signal-to-noise ratio of the received signal and the sensitivity of the system detection, improving the accuracy and stability of the measurement, and also allowing the transmitting coil and receiving coil to be better arranged in a limited space. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the internal structure of the shell according to an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of the detector structure according to an embodiment of the present invention;

[0017] Figure 3 This is a structural block diagram of the control motherboard according to an embodiment of the present invention;

[0018] Component names and serial numbers in the diagram: 1-House; 10-Handle; 2-Control Mainboard; 20-Power Supply Unit; 21-Transmitter Drive Unit; 22-Signal Processing Unit; 23-Processor; 200-Rechargeable Battery; 201-Charging Interface; 210-DC-DC Converter; 211-Digital Signal Generator; 212-Power Drive Module; 220-Differential Amplifier; 221-Filter; 222-Digital-to-Analog Converter; 223-Digital Lock-in Amplifier; 3-Transmitting Coil; 4-Receiving Coil; 5-Sub-coil; 6-Alarm Mechanism; 7-Display Screen; 8-Control Switch; 9-Indicator Light. Detailed Implementation

[0019] To more clearly illustrate the purpose, technical solution, and advantages of the embodiments of this utility model, the present utility model will be further described below in conjunction with the accompanying drawings and embodiments. A clear and complete description will be provided. Obviously, the described embodiments are some, but not all, embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the protection scope of this utility model.

[0020] Examples of embodiments of this utility model Figures 1 to 3As shown, a handheld metal detector includes a housing 1 with a handle 10 and a control main board 2 internally housed therein. The housing 1 has an accommodating cavity, within which the control main board 2 is housed. The handle 10 on the housing 1 facilitates gripping. Inside the housing 1, transmitting coils 3 and receiving coils 4 of identical shape and partially overlapping are arranged side-by-side. The transmitting coils 3 and receiving coils 4 are electrically connected to the control main board 2. This means that the transmitting coils 3 and receiving coils 4 have the same shape, allowing for the use of the same winding process and molds during production, simplifying manufacturing. For example, both could be designed with an elliptical structure. They are then arranged side-by-side, with some overlap between them, thus satisfying the layout requirements within a limited space. The wire diameter of the transmitting coil 3 is larger than that of the receiving coil 4. The use of a thicker wire diameter in the transmitting coil 3 means that it can carry a larger current, generate a stronger transmitting magnetic field, and is more conducive to improving the detection depth or signal-to-noise ratio. Inside the housing 1, there is also a sub-coil 5 located in the receiving coil 4 and concentric with the receiving coil 4. The outer diameter of the sub-coil 5 is 1 / 5 to 1 / 3 of the outer diameter of the receiving coil 4, and the ratio of the number of turns of the sub-coil 5 to the number of turns of the receiving coil 4 is 1: 15-1:20, sub-coil 5 is used to compensate for transmitting coil 3. At this time, sub-coil 5 and receiving coil 4 are in the same transmitting magnetic field environment, making the phase and waveform of the interference signal generated by transmitting coil 3 to receiving coil 4 synchronized. However, the number of turns of sub-coil 5 is much less than the number of turns of receiving coil 4, and the amplitude of the interference signal voltage induced by it is also much smaller than the interference signal voltage induced by receiving coil 4. Then, through differential amplification, the total output signal of receiving coil 4, including the target signal and the interference signal, is subtracted by a proportionally amplified output signal of sub-coil 5. This subtraction operation... It can effectively cancel out most of the direct coupling interference from the transmitting coil 3, greatly suppressing the background noise, that is, the crosstalk of the transmitting coil 3, so that the weak target signal can be highlighted, thereby significantly improving the signal-to-noise ratio of the received signal and the sensitivity of the system to detect weak changes; the compensated signal more realistically reflects the target information, and the compensation of the sub-coil 5 actively cancels the crosstalk of the transmitting coil 3, improving the measurement accuracy and stability while maintaining high transmission power, and also allowing for a more compact layout of the transmitting coil 3 and the receiving coil 4, which helps to achieve the miniaturization and weight reduction of the handheld metal detector.

[0021] Further improvements, such as Figure 3As shown, the control motherboard 2 is equipped with a power supply unit 20, a transmission drive unit 21, a signal processing unit 22, and a processor 23. The power supply unit 2 is used to provide power to the detector. The transmission drive unit 21 is used to regulate the current driving the transmission coil 3. The transmission drive unit 21 generates a high-frequency alternating current with a specific frequency and controllable amplitude to drive the transmission coil 3 to generate an alternating magnetic field. The signal processing unit 22 is used to process the signals detected by the receiving coil 4 and the sub-coil 5 and transmit the processed signals to the processor 23. The processor 23 is a microcontroller, which is used to control the operation of the transmission drive unit 21 and process the signals transmitted by the signal processing unit 22 and output the detection results.

[0022] For the power supply unit 20, the power supply unit 20 includes a rechargeable battery 200 and a charging circuit for charging the rechargeable battery 200. The rechargeable battery 200 is a rechargeable lithium-ion battery, and the charging circuit is an existing circuit for charging lithium-ion batteries. The rechargeable battery 200 is electrically connected to the transmission drive unit 21 and the signal processing unit 22 respectively. The rechargeable battery 200 provides power to the transmission drive unit 21 and the signal processing unit 22. The housing 1 is provided with a charging interface 201 connected to the charging circuit. The charging interface 201 is a USB interface.

[0023] For the transmission drive unit 21, the transmission drive unit 21 includes a DC-DC converter 210, a digital signal generator 211, and a power drive module 212. The DC-DC converter 210 is used to change the magnitude of the transmission current of the transmission coil 3. The processor 23 adjusts its output voltage by controlling the change of the duty cycle of the DC-DC converter 210, thereby indirectly changing the transmission current of the transmission coil 3, thus changing the detection sensitivity of the detector to meet different usage requirements. After receiving the DC voltage output by the DC-DC converter 210, the digital signal generator 211 outputs a corresponding high-frequency signal to the power drive module 212. The power drive module 212 amplifies the received signal and converts it into a high-frequency AC current to drive the transmission coil 3. The DC-DC converter 210, the digital signal generator 211, and the power drive module 212 are all existing technologies and will not be described in detail here.

[0024] For the signal processing unit 22, the signal processing unit 22 includes a differential amplifier 220, a filter 221, a digital-to-analog converter 222, and a digital lock-in amplifier 223 that sequentially process the signals detected by the receiving coil 4 and the sub-coil 5. Receiving coil 4 and sub-coil 5 sense changes in the magnetic field and generate tiny voltage signals containing the target signal and environmental interference. Differential amplifier 220 receives these signals and amplifies the difference between them. Differential amplifier 220 can better highlight the difference between the target metal and pure environmental interference and effectively suppress these common-mode interferences. Filter 221 receives the signal after preliminary amplification by differential amplifier 220 and filters out a large amount of broadband environmental noise and non-target frequency interference remaining after differential amplification, ensuring that only signals related to the frequency of the transmitting magnetic field enter the subsequent processing stage. Filter 221 selects a bandpass filter. Digital-to-analog converter 222 receives the filtered analog signal and converts it into a digital signal. Digital lock-in amplifier 223 receives the digital signal from the ADC and the digital reference signal of the same frequency and phase from digital signal generator 211, performs phase and amplitude detection, extracts the target signal buried in the noise, and transmits it to processor 23.

[0025] Further improvements, such as Figure 2 As shown, the housing 1 is equipped with an alarm mechanism 6 electrically connected to the control motherboard 2. When metal is detected, the alarm mechanism 6 will sound an alarm. The alarm mechanism 6 can be one or more of the following: a sound alarm mechanism, a vibration alarm mechanism, and a light alarm mechanism. The sound alarm mechanism is a speaker, the vibration alarm mechanism is a linear vibration motor, and the light alarm mechanism is an LED that can produce different colors.

[0026] Further improvements, such as Figure 2 As shown, the housing 1 is provided with a display screen 7 electrically connected to the control motherboard 2, which can display the detection results or detection sensitivity.

[0027] Further improvements, such as Figure 2 As shown, the housing 1 is provided with a control switch 8 that is electrically connected to the control motherboard 2. The control switch 8 includes a power switch for turning the power on or off, and an adjustment switch for adjusting the detection sensitivity.

[0028] Further improvements, such as Figure 2 As shown, the housing 1 is provided with an indicator light 9 that is electrically connected to the control main board 2. The indicator light 9 is used to indicate whether the detector is in the working state or the off state, and can be a different LED light than that in the light alarm mechanism.

[0029] Although the present invention has been described in detail above with general description and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A handheld metal detector, characterized in that, The device includes a housing with a handle and an internal control board. Inside the housing, there are parallel and partially overlapping transmitting and receiving coils of the same shape. The transmitting and receiving coils are electrically connected to the control board. The wire diameter of the transmitting coil is larger than that of the receiving coil. The housing also contains a sub-coil located within the receiving coil and concentric with it. The outer diameter of the sub-coil is 1 / 5 to 1 / 3 of the outer diameter of the receiving coil, and the ratio of the number of turns of the sub-coil to the number of turns of the receiving coil is 1:15 to 1:

20.

2. The handheld metal detector according to claim 1, characterized in that, The control motherboard is equipped with a power supply unit, a transmission drive unit, a signal processing unit, and a processor. The power supply unit provides power to the detector. The transmission drive unit regulates the current driving the transmission coil. The signal processing unit processes the signals detected by the receiving coil and the sub-coil and transmits the processed signals to the processor. The processor controls the operation of the transmission drive unit, processes the signals transmitted by the signal processing unit, and outputs the detection results.

3. The handheld metal detector according to claim 2, characterized in that, The power supply unit includes a rechargeable battery and a charging circuit for charging the rechargeable battery. The rechargeable battery is electrically connected to the transmission drive unit and the signal processing unit, respectively. The housing is provided with a charging interface connected to the charging circuit.

4. The handheld metal detector according to claim 2, characterized in that, The transmitting drive unit includes a DC-DC converter, a digital signal generator, and a power drive module. The DC-DC converter is used to change the magnitude of the transmitting current of the transmitting coil. The digital signal generator receives the DC voltage output by the DC-DC converter and outputs a corresponding high-frequency signal to the power drive module. The power drive module amplifies the received signal and converts it into a high-frequency AC current to drive the transmitting coil.

5. The handheld metal detector according to claim 2, characterized in that, The signal processing unit includes a differential amplifier, a filter, a digital-to-analog converter, and a digital lock-in amplifier that sequentially process the signals detected by the receiving coil and the sub-coil.

6. The handheld metal detector according to claim 1, characterized in that, The housing is equipped with an alarm mechanism that is electrically connected to the control motherboard.

7. The handheld metal detector according to claim 6, characterized in that, The alarm mechanism is one or more of the following: sound alarm mechanism, vibration alarm mechanism, and light alarm mechanism.

8. The handheld metal detector according to claim 1, characterized in that, The housing is equipped with a display screen that is electrically connected to the control motherboard.

9. The handheld metal detector according to claim 1, characterized in that, The housing is equipped with a control switch that is electrically connected to the control motherboard.

10. The handheld metal detector according to claim 1, characterized in that, The housing is equipped with indicator lights that are electrically connected to the control motherboard.

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