A metal detection circuit and device for multi-frequency detection

Abstract

The present invention relates to a metal detection circuit and device for multi-frequency detection, wherein the detection circuit includes a transmitting circuit, a receiving circuit and a controller, the controller is connected to the transmitting circuit and the receiving circuit respectively, the transmitting circuit is a dual-frequency transmitting circuit, and the receiving circuit includes: a receiving coil group, at least two groups are provided, and the two receiving coils of each receiving coil group are symmetrically arranged on both sides of the transmitting coil; a plurality of receiving demodulation circuits, the number of receiving demodulation circuits is consistent with the number of receiving coil groups, each receiving demodulation circuit is respectively connected to the corresponding receiving coil group, and each receiving demodulation circuit outputs a signal of a different frequency. Compared with the prior art, the present invention sets a plurality of receiving coil groups and corresponding receiving demodulation circuits in a multi-frequency metal detector, so that different frequencies are received by different receiving coil groups and receiving demodulation circuits, which reduces interference, improves the accuracy of the signal, and improves the detection efficiency under the premise of ensuring the accuracy of the signal.

Description

Technical Field

[0001] The present invention relates to the field of metal detection, and in particular to a metal detection circuit and device for multi-frequency detection. Background Art

[0002] As we all know, in the field of metal detection, high-frequency carrier signals are beneficial to the detection of metal interference, but are not conducive to suppressing product effects when the product effect is large. At this time, lower frequency signals are generally selected.

[0003] In the prior art, in order to improve the detection efficiency and test accuracy and suppress the product effect, a multi-frequency synchronous demodulation circuit is used to make the high and low frequency signals work simultaneously. This method only requires the installation of one set of coils, so the installation is relatively easy and the size can be kept small. However, the prior art still has some defects. For example, in the case of time division multiplexing, the upper limit of the detection speed is not high. If a dual-path filtering detection method is adopted, there will be a problem of low upper limit of detection accuracy. Summary of the invention

[0004] The purpose of the present invention is to provide a metal detection circuit and device for multi-frequency detection. In the multi-frequency metal detector, multiple receiving coil groups and corresponding receiving demodulation circuits are set, so that different frequencies are received by different receiving coil groups and receiving demodulation circuits, which reduces interference, improves signal accuracy and improves detection efficiency while ensuring signal accuracy.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A metal detection circuit for multi-frequency detection includes a transmitting circuit, a receiving circuit and a controller, wherein the controller is connected to the transmitting circuit and the receiving circuit respectively, the transmitting circuit is a dual-frequency transmitting circuit, and the receiving circuit includes:

[0007] There are at least two receiving coil groups, and the two receiving coils of each receiving coil group are symmetrically arranged on both sides of the transmitting coil;

[0008] Receiving and demodulating circuits corresponding to each receiving coil group, the number of receiving and demodulating circuits is consistent with the number of receiving coil groups, each receiving and demodulating circuit is connected to the corresponding receiving coil group, and each receiving and demodulating circuit outputs a signal of a different frequency;

[0009] Wherein, the receiving demodulation circuit comprises:

[0010] There are two tuning filter modules, and the input ends are connected to the two receiving coils of the corresponding receiving coil group.

[0011] The differential amplifier has its input connected to the output of the two tuned filter modules.

[0012] The input of the multiplier is connected to the output of the differential amplifier and the carrier generator respectively.

[0013] The filter amplifier module has an input end connected to the output end of the multiplier and an output end connected to the controller.

[0014] The tuning and filtering module includes a first transformer and a first filtering circuit which are connected in sequence.

[0015] The filtering and amplifying module comprises a second filtering circuit and an integrating amplifier which are connected in sequence.

[0016] The transmitting circuit includes a high-frequency signal generator, a low-frequency signal generator, an adding circuit, a bandpass filter, a power amplifier, a second transformer and a transmitting coil. The high-frequency signal generator and the low-frequency signal generator are both connected to the adding circuit, and the adding circuit, the bandpass filter, the power amplifier, the second transformer and the transmitting coil are connected in sequence.

[0017] There are two receiving coil groups in total.

[0018] A dual-frequency metal detection device comprises a host computer and a metal detection circuit connected to the host computer, wherein the metal detection circuit comprises a transmitting circuit, a receiving circuit and a controller, wherein the controller is respectively connected to the transmitting circuit and the receiving circuit, wherein the transmitting circuit is a dual-frequency transmitting circuit, and the receiving circuit comprises:

[0019] There are at least two receiving coil groups, and the two receiving coils of each receiving coil group are symmetrically arranged on both sides of the transmitting coil;

[0020] Receiving and demodulating circuits corresponding to each receiving coil group, the number of receiving and demodulating circuits is consistent with the number of receiving coil groups, each receiving and demodulating circuit is connected to the corresponding receiving coil group, and each receiving and demodulating circuit outputs a signal of a different frequency;

[0021] Wherein, the receiving demodulation circuit comprises:

[0022] There are two tuning filter modules, and the input ends are connected to the two receiving coils of the corresponding receiving coil group.

[0023] The differential amplifier has its input connected to the output of the two tuned filter modules.

[0024] The input of the multiplier is connected to the output of the differential amplifier and the carrier generator respectively.

[0025] The filter amplifier module has an input end connected to the output end of the multiplier and an output end connected to the controller.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. In the multi-frequency metal detector, multiple receiving coil groups and corresponding receiving demodulation circuits are set, so that different frequencies are received by different receiving coil groups and receiving demodulation circuits, which reduces interference, improves signal accuracy and improves detection efficiency while ensuring signal accuracy.

[0028] 2. The designed receiving demodulation circuit can output clearer signals.

[0029] 3. The designed transmitting circuit can output more stable multi-frequency signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the present invention;

[0031] Figure 2 is a schematic diagram of a receiving demodulation circuit;

[0032] Figure 3 is a schematic diagram of a transmitting circuit;

[0033] Figure 4 Schematic diagram of the distribution of the transmitting coil and the receiving coil;

[0034] Wherein: 1. transmitting circuit, 2. receiving circuit, 3. controller, 21. first transformer, 22. first filtering circuit, 23. differential amplifier, 24. multiplier, 25. carrier generator, 26. second filtering circuit, 27. integrating amplifier, 28. output end, 11. high frequency signal generator, 12. low frequency signal generator, 13. adding circuit, 14. band pass filter, 15. power amplifier, 16. second transformer, 17. transmitting coil, 201. receiving coil, 202. receiving coil. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0036] A metal detection circuit with multi-frequency detection, such as Figure 1 As shown, the metal detection circuit is applied to a metal detection device, including a transmitting circuit 1, a receiving circuit 2 and a controller 3, wherein the controller 3 is connected to the transmitting circuit 1 and the receiving circuit 2 respectively, the transmitting circuit 1 is a dual-frequency transmitting circuit 1, and the receiving circuit 2 includes:

[0037] There are at least two receiving coil groups, and the two receiving coils of each receiving coil group are symmetrically arranged on both sides of the transmitting coil 17. Figure 4As shown, in this embodiment, there are two receiving coil groups, 201 are two first receiving coil groups, and 202 are two second receiving coil groups;

[0038] The receiving and demodulating circuits corresponding to each receiving coil group, the number of the receiving and demodulating circuits is consistent with the number of the receiving coil groups, each receiving and demodulating circuit is connected to the corresponding receiving coil group, and each receiving and demodulating circuit outputs a signal of a different frequency, so that high-frequency signals and low-frequency signals can be detected at the same time, thereby improving the detection accuracy of the machine;

[0039] In a multi-frequency metal detector, multiple receiving coil groups and corresponding receiving demodulation circuits are provided, so that different frequencies are received by different receiving coil groups and receiving demodulation circuits. Although the length of the entire metal detector is increased and the installation workload is increased, interference is reduced, the accuracy of the signal is improved, and the detection efficiency is improved while ensuring the signal accuracy.

[0040] like Figure 2 As shown, the receiving demodulation circuit includes:

[0041] There are two tuning filter modules, and the input ends are connected to the two receiving coils of the corresponding receiving coil group.

[0042] The input end of the differential amplifier 23 is connected to the output ends 28 of the two tuning filter modules respectively.

[0043] The multiplier 24 has its input terminals connected to the output terminal 28 of the differential amplifier 23 and the carrier generator 25,

[0044] The filter amplification module has an input end connected to the output end 28 of the multiplier 24 , and an output end 28 connected to the controller 3 .

[0045] The tuning and filtering module includes a first transformer 21 and a first filtering circuit 22 which are connected in sequence.

[0046] The filtering and amplifying module comprises a second filtering circuit 26 and an integrating amplifier 27 which are connected in sequence.

[0047] The receiving and demodulating circuits are respectively passed through a transformer with capacitors (tuning) and filters with the same filtering parameters, so that the same group of receiving coils receives the transmitted high-frequency (or low-frequency) signal, and the other group of receiving coils receives the transmitted low-frequency (or high-frequency) signal, so that the two groups of coils work in different frequency states, and after the difference is multiplied with the carrier signal, the response signal of the corresponding frequency can be obtained through the filtering and amplifying circuit, thereby achieving the purpose of synchronous detection of the two frequencies.

[0048] like Figure 3As shown, the transmitting circuit 1 includes a high-frequency signal generator 11, a low-frequency signal generator 12, an adding circuit 13, a bandpass filter 14, a power amplifier 15, a second transformer 16 and a transmitting coil 17. The high-frequency signal generator 11 and the low-frequency signal generator 12 are both connected to the adding circuit 13. The adding circuit 13, the bandpass filter, the power amplifier 15, the second transformer 16 and the transmitting coil 17 are connected in sequence. The high-frequency and low-frequency signals are mixed through the adding circuit, and the signal is made purer through the bandpass filter 14 to reduce the interference signals of the high and low frequencies. The high-frequency cutoff frequency of the bandpass filter 14 should be greater than the frequency of the high-frequency signal, and the low-frequency cutoff frequency should be less than the frequency of the low-frequency signal. The mixed signal is amplified and loaded into the transmitting coil 17 through the second transformer 16.

[0049] In actual use, a switching circuit can also be set to select high or low frequency signals to be loaded onto the first group of receiving coils or onto the second group of receiving coils. The specific implementation method is to control the multi-way switch through the host computer to switch the resistors and capacitors to access the filter circuit, thereby changing the cutoff frequency of the filter circuit and realizing the selection of loading high or low frequency signals on the coils.

[0050] By controlling the high and low frequency signals to be loaded on different coils, dual-frequency synchronous detection is achieved and the product effect can be suppressed to a certain extent.

Claims

1. A metal detection circuit for multi-frequency detection, comprising a transmitting circuit, a receiving circuit and a controller, wherein the controller is connected to the transmitting circuit and the receiving circuit respectively, and the transmitting circuit is a dual-frequency transmitting circuit, characterized in that: The receiving circuit comprises: There are at least two receiving coil groups, and the two receiving coils of each receiving coil group are symmetrically arranged on both sides of the transmitting coil; Receiving and demodulating circuits corresponding to each receiving coil group, the number of receiving and demodulating circuits is consistent with the number of receiving coil groups, each receiving and demodulating circuit is connected to the corresponding receiving coil group, and each receiving and demodulating circuit outputs a signal of a different frequency; A plurality of receiving coil groups and corresponding receiving demodulation circuits are provided, and different frequencies are received by different receiving coil groups and receiving demodulation circuits.

2. A metal detection circuit with multi-frequency detection according to claim 1, characterized in that: The receiving demodulation circuit comprises: There are two tuning filter modules, and the input ends are connected to the two receiving coils of the corresponding receiving coil group. The differential amplifier has its input connected to the output of the two tuned filter modules. The input of the multiplier is connected to the output of the differential amplifier and the carrier generator respectively. The filter amplifier module has an input end connected to the output end of the multiplier and an output end connected to the controller.

3. A metal detection circuit with multi-frequency detection according to claim 2, characterized in that: The tuning and filtering module includes a first transformer and a first filtering circuit which are connected in sequence.

4. The metal detection circuit with multi-frequency detection according to claim 3, characterized in that: The filtering and amplifying module comprises a second filtering circuit and an integrating amplifier which are connected in sequence.

5. The metal detection circuit with multi-frequency detection according to claim 1, characterized in that: The transmitting circuit includes a high-frequency signal generator, a low-frequency signal generator, an adding circuit, a bandpass filter, a power amplifier, a second transformer and a transmitting coil. The high-frequency signal generator and the low-frequency signal generator are both connected to the adding circuit, and the adding circuit, the bandpass filter, the power amplifier, the second transformer and the transmitting coil are connected in sequence.

6. A dual-frequency metal detection device, comprising a host computer and a metal detection circuit connected to the host computer, wherein the metal detection circuit comprises a transmitting circuit, a receiving circuit and a controller, wherein the controller is connected to the transmitting circuit and the receiving circuit respectively, characterized in that: The transmitting circuit is a dual-frequency transmitting circuit, and the receiving circuit includes: There are at least two receiving coil groups, and the two receiving coils of each receiving coil group are symmetrically arranged on both sides of the transmitting coil; Receiving and demodulating circuits corresponding to each receiving coil group, the number of receiving and demodulating circuits is consistent with the number of receiving coil groups, each receiving and demodulating circuit is connected to the corresponding receiving coil group, and each receiving and demodulating circuit outputs a signal of a different frequency; A plurality of receiving coil groups and corresponding receiving demodulation circuits are provided, and different frequencies are received by different receiving coil groups and receiving demodulation circuits.

7. A dual-frequency metal detection device according to claim 6, characterized in that: The receiving demodulation circuit comprises: There are two tuning filter modules, and the input ends are connected to the two receiving coils of the corresponding receiving coil group. The differential amplifier has its input connected to the output of the two tuned filter modules. The input of the multiplier is connected to the output of the differential amplifier and the carrier generator respectively. The filter amplifier module has an input end connected to the output end of the multiplier and an output end connected to the controller.

8. A dual-frequency metal detection device according to claim 7, characterized in that: The tuning and filtering module includes a first transformer and a first filtering circuit which are connected in sequence.

9. A dual-frequency metal detection device according to claim 8, characterized in that: The filtering and amplifying module comprises a second filtering circuit and an integrating amplifier which are connected in sequence.

10. A dual-frequency metal detection device according to claim 6, characterized in that: The transmitting circuit includes a high-frequency signal generator, a low-frequency signal generator, an adding circuit, a bandpass filter, a power amplifier, a second transformer and a transmitting coil. The high-frequency signal generator and the low-frequency signal generator are both connected to the adding circuit, and the adding circuit, the bandpass filter, the power amplifier, the second transformer and the transmitting coil are connected in sequence.

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