Broken needle detection circuit and method

Abstract

This invention provides a broken needle detection circuit and method. The broken needle detection circuit includes: a detection coil for detecting a broken needle and generating a corresponding detection pulse, the size of which is set such that the pulse width of the broken needle detection pulse is greater than the pulse width of an interference signal; a first low-frequency amplifier for amplifying the output signal of the detection coil; a filtering module for filtering the output signal of the first low-frequency amplifier; a second low-frequency amplifier for amplifying the output signal of the filtering module; a sampling module for sampling the output signal of the second low-frequency amplifier; a pulse width measurement module for measuring the pulse width of the sampled pulse signal and outputting a pulse width measurement signal; and a processing module for filtering out interference signals with pulse widths smaller than a preset pulse width and generating a detection signal based on the amplitude of pulse signals with pulse widths greater than the preset pulse width. The broken needle detection circuit and method of this invention can effectively reduce interference in broken needle detection and improve detection accuracy; at the same time, it is highly flexible and has a wide range of applications.

Description

Technical Field

[0001] This invention relates to the field of metal detection, and in particular to a broken needle detection circuit and method. Background Technology

[0002] Textile products such as clothing and underwear often contain broken needles, requiring the use of ferromagnetic coil needle detectors for inspection. However, these detectors are significantly affected by various external magnetic fields and voltages during actual production. Motor starting, walkie-talkie conversations, soldering iron insertions and removals, and sudden changes in the power grid can all interfere with the detector, causing malfunctions and affecting detection accuracy. Furthermore, some small accessories on clothing, even after demagnetization, can generate trigger signals, leading to false detections.

[0003] Currently, shielding or improving the magnetic circuit are used to mitigate these problems, but because the coil itself is highly sensitive to magnetic fields, these methods rarely achieve satisfactory results. Therefore, how to effectively reduce interference and improve the detection accuracy of needle detectors has become one of the urgent problems to be solved by those skilled in the art.

[0004] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a broken needle detection circuit and method to solve the problem of false detection caused by the influence of external magnetic fields and voltage in the prior art.

[0006] To achieve the above and other related objectives, the present invention provides a broken needle detection circuit, the broken needle detection circuit comprising at least:

[0007] The system includes a detection coil, a first low-frequency amplifier, a filtering module, a second low-frequency amplifier, a sampling module, a pulse width measurement module, and a processing module.

[0008] The detection coil is used to detect the broken needle and generate a corresponding detection pulse, wherein the size of the detection coil is set such that the pulse width of the detection pulse for the broken needle is greater than the pulse width of the interference signal.

[0009] The first low-frequency amplifier is connected to the output terminal of the detection coil and is used to amplify the output signal of the detection coil;

[0010] The filtering module is connected to the output terminal of the first low-frequency amplifier and is used to filter the output signal of the first low-frequency amplifier.

[0011] The second low-frequency amplifier is connected to the output terminal of the filter module and is used to amplify the output signal of the filter module;

[0012] The sampling module is connected to the output terminal of the second low-frequency amplifier and is used to sample the output signal of the second low-frequency amplifier;

[0013] The pulse width measurement module is connected to the output terminal of the sampling module and is used to measure the pulse width of the sampled pulse signal and output the pulse width measurement signal.

[0014] The processing module is connected to the output of the pulse width measurement module, filters out interference signals with pulse widths smaller than the preset pulse width, and generates a detection signal based on the amplitude of pulse signals with pulse widths greater than the preset pulse width.

[0015] Optionally, the detection coil is a circular ring structure with a diameter of not less than 80 mm.

[0016] Optionally, the filtering module includes a 50Hz notch filter unit and a high-frequency filter unit, wherein the 50Hz notch filter unit and the high-frequency filter unit are cascaded in sequence at the output end of the detection coil; the 50Hz notch filter unit is used to filter out 50Hz power frequency interference; and the high-frequency filter unit is used to filter out high-frequency interference.

[0017] Alternatively, the high-frequency filtering unit includes a first operational amplifier, a first resistor, a first capacitor, and a second capacitor; one end of the first resistor serves as the input terminal of the high-frequency filtering unit, and the other end is connected to the non-inverting input terminal of the first operational amplifier; one end of the first capacitor is connected to the input terminal of the high-frequency filtering unit, and the other end is connected to the inverting input terminal and the output terminal of the first operational amplifier; one end of the second capacitor is connected to the non-inverting input terminal of the first operational amplifier, and the other end is grounded.

[0018] Optionally, the sampling module and the pulse width measurement module are implemented based on the same circuit, including a second resistor, a third resistor, a fourth resistor, a fifth resistor, a third capacitor, a fourth capacitor, and a fifth capacitor; the first end of the second resistor is connected to the output terminal of the preceding circuit, and the second end is connected to the first end of the third resistor; the second end of the third resistor outputs the pulse width measurement signal; the third capacitor and the fourth capacitor are connected in series between the first end of the second resistor and the second end of the third resistor; one end of the fifth capacitor is connected to the connection node of the second resistor and the third resistor, and the other end is grounded; the fourth resistor and the fifth resistor are connected in series between the connection node of the third capacitor and the fourth capacitor and ground.

[0019] Alternatively, the second low-frequency amplifier includes a second operational amplifier, a sixth capacitor, a seventh capacitor, an eighth capacitor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a first diode, and a second diode;

[0020] The sixth resistor and the seventh resistor are connected in series between the inverting input terminal of the second operational amplifier and ground; one end of the sixth capacitor serves as the input terminal of the second low-frequency amplifier, and the other end is connected between the connection node of the sixth resistor and the seventh resistor.

[0021] One end of the eighth resistor is connected to the non-inverting input terminal of the second operational amplifier, and the other end is grounded;

[0022] The ninth resistor is connected between the output terminal and the inverting input terminal of the second operational amplifier;

[0023] The seventh capacitor is connected in parallel across the ninth resistor;

[0024] The anode of the first diode is connected to the inverting input terminal of the second operational amplifier, and the cathode is connected to the cathode of the second diode; the anode of the second diode is connected to the output terminal of the second operational amplifier.

[0025] One end of the eighth capacitor is connected to the output of the second operational amplifier, and the other end is grounded.

[0026] To achieve the above and other related objectives, the present invention provides a broken needle detection method, implemented based on the aforementioned broken needle detection circuit, wherein the broken needle detection method includes at least:

[0027] The probe coil scans the object under test and generates corresponding probe pulses;

[0028] The detection pulses are filtered to remove interference;

[0029] The detection pulses after interference filtering are sampled, and the pulse width of the sampled pulse signal is measured. Pulse signals with a pulse width smaller than the preset pulse width are filtered out.

[0030] The amplitude of a pulse signal with a pulse width greater than the preset pulse width is measured. When the amplitude of the pulse signal is greater than the set value, it is determined that a broken needle has been detected and a detection signal is output. When the amplitude of the pulse signal is less than the set value, it is determined that no broken needle has been detected.

[0031] Optionally, the pulse width of the detection pulse when the detection coil detects a broken needle can be adjusted by controlling the scanning speed.

[0032] Alternatively, the scanning speed is set to 20 m / min to 50 m / min.

[0033] Optionally, the interference is power supply interference and / or high-frequency interference.

[0034] Optionally, the preset pulse width is set to 0.1s~0.15s.

[0035] As described above, the broken needle detection circuit and method of the present invention have the following beneficial effects:

[0036] The broken needle detection circuit and method of the present invention utilize the narrow pulse width of the interference signal by setting a detection coil with a larger size than the existing coil to increase the pulse width generated when the broken needle passes through the detection coil, thereby distinguishing the broken needle detection pulse from the interference signal. Combined with subsequent filtering of the interference signal, the interference of broken needle detection is effectively reduced and the detection accuracy is improved.

[0037] The broken needle detection method of the present invention further adjusts the pulse width of the broken needle detection pulse by adjusting the scanning speed, so as to adapt to different application occasions without changing the broken needle detection circuit, thereby improving flexibility and expanding the scope of application. Attached Figure Description

[0038] Figure 1 The diagram shown is a schematic representation of the broken needle detection circuit of the present invention.

[0039] Figure 2 The diagram shown is a structural schematic of the filtering module of the present invention.

[0040] Figure 3 The diagram shown is a schematic diagram of the circuit structure of the high-frequency filtering unit of the present invention.

[0041] Figure 4 The diagram shown is a schematic diagram of the circuit structure of the second low-frequency amplifier of the present invention.

[0042] Figure 5 The diagram shows the circuit structure of the sampling module, pulse width measurement module, and voltage follower module of this invention.

[0043] Figure 6 The diagram shown is a flowchart of the broken needle detection method of the present invention.

[0044] Component designation explanation

[0045] 1-Broken needle detection circuit; 11-Detection coil; 12-First low-frequency amplifier; 13-Filtering module; 131-50Hz notch filter unit; 132-High-frequency filter unit; 13a-First operational amplifier; 14-Second low-frequency amplifier; 14a-Second operational amplifier; 15-Sampling module; 16-Pulse width measurement module; 17-Processing module; 18-Voltage follower module; 18a-Third operational amplifier. Detailed Implementation

[0046] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0047] Please see Figures 1-6 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0048] The various interference signals received by a needle detector include, but are not limited to: a) power supply interference and motor switching. Sudden power supply changes and load fluctuations generate interference through the power supply, accounting for the majority of interference received by the needle detector. These interference pulses are characterized by narrow width and a 50Hz carrier signal. b) Inverters, walkie-talkies, etc., generate interference to the coil through electromagnetic fields. These interferences are characterized by a specific frequency band, but also appear as a series of continuous narrow pulses. c) Undemagnetized small accessories also produce narrow signal pulses. d) Large metal objects around the probe head. The movement of these large metal objects can affect the probe, but these effects are relatively easy to eliminate by changing the surrounding environment.

[0049] To effectively reduce the interference caused by points a, b, and c above, this invention proposes a broken needle detection circuit 1, as follows: Figure 1 As shown, the broken needle detection circuit 1 includes:

[0050] The system includes a detection coil 11, a first low-frequency amplifier 12, a filtering module 13, a second low-frequency amplifier 14, a sampling module 15, a pulse width measurement module 16, and a processing module 17.

[0051] like Figure 1 As shown, the detection coil 11 is used to detect the broken needle and generate a corresponding detection pulse; wherein, the size of the detection coil 11 is set such that the pulse width of the detection pulse of the broken needle is greater than the pulse width of the interference signal.

[0052] Specifically, in this embodiment, the detection coil 11 is a ferromagnetic coil with a high relative permeability (typically a high relative permeability). The magnetic permeability is much greater than that of air. The core of the ferromagnetic coil is made of ferromagnetic materials, including but not limited to silicon steel sheets, ferrite, and permalloy. In practical applications, any coil type and core material that can achieve broken needle detection is applicable to this invention and is not limited to this embodiment.

[0053] Specifically, the size of the detection coil 11 of the present invention is larger than that of the detection coil of the existing needle detector, thereby obtaining a broken needle detection pulse with a pulse width greater than that of the interference signal. As an example, the detection coil 11 is configured as a ring structure with a diameter of not less than 80 mm. For example, the diameter of the detection coil 11 is set to 85 mm, 88 mm, 90 mm, 95 mm, 100 mm, 110 mm, etc., which are not listed here. In actual use, the shape of the detection coil 11 can be set according to actual needs, as long as it can obtain a broken needle detection pulse with a pulse width greater than that of the interference signal. Because the size of the detection coil 11 of the present invention is increased, the pulse width of the detected broken needle detection pulse increases during relative movement with the broken needle, while the pulse widths of various interference signals remain unchanged.

[0054] like Figure 1 As shown, the first low-frequency amplifier 12 is connected to the output terminal of the detection coil 11 and is used to amplify the output signal of the detection coil 11.

[0055] Specifically, the output signal amplitude of the detection coil 11 is usually relatively small, and the first low-frequency amplifier 12 can amplify the output signal amplitude of the detection coil 11. Any circuit structure that can realize low-frequency amplification is applicable to the first low-frequency amplifier 12 of the present invention, and will not be described in detail here.

[0056] like Figure 1 As shown, the filter module 13 is connected to the output terminal of the first low-frequency amplifier 12 and is used to filter the output signal of the first low-frequency amplifier 12.

[0057] Specifically, in this embodiment, the filtering module 13 is used to filter out power supply interference, such as... Figure 2 As shown, the filtering module 13 includes a 50Hz notch filter unit 131 and a high-frequency filter unit 132. The 50Hz notch filter unit 131 and the high-frequency filter unit 132 are cascaded at the output of the first low-frequency amplifier 12. In this example, the 50Hz notch filter unit 131 is placed before the high-frequency filter unit 132. In actual use, the 50Hz notch filter unit 131 can also be placed after the high-frequency filter unit 132. The 50Hz notch filter unit 131 is used to filter out 50Hz power frequency interference (electromagnetic interference related to the power grid frequency). The high-frequency filter unit 132 is used to filter out high-frequency interference. As an example, this high-frequency interference is electromagnetic interference in the range of kHz to GHz. In actual use, the filtering module 13 can filter out unwanted components according to actual needs and set up corresponding filter units, which is not limited to this embodiment.

[0058] More specifically, as an example, the high-frequency filtering unit 132 includes a first operational amplifier 13a, a first resistor R1, a first capacitor C1, and a second capacitor C2. For example... Figure 3As shown, one end of the first resistor R1 serves as the input terminal IN1 of the high-frequency filter unit 132, and the other end is connected to the non-inverting input terminal of the first operational amplifier 13a; one end of the first capacitor C1 is connected to the input terminal IN1 of the high-frequency filter unit 132, and the other end is connected to the inverting input terminal and output terminal (also the output terminal OUT1 of the high-frequency filter unit 132) of the first operational amplifier 13a; one end of the second capacitor C2 is connected to the non-inverting input terminal of the first operational amplifier 13a, and the other end is grounded to GND. As another example, the high-frequency filter unit 132 also includes a tenth resistor R10, an eleventh resistor R11, a ninth capacitor C9, a tenth capacitor C10, an eleventh capacitor C11, and a twelfth capacitor C12. In this circuit, one end of the tenth resistor R10 is connected to the positive power supply VCC (e.g., +12V), and the other end is connected to the positive power supply terminal of the first operational amplifier 13a. The ninth capacitor C9 and the tenth capacitor C10 are connected in parallel, with one end connected to the positive power supply terminal of the first operational amplifier 13a and the other end grounded (GND). One end of the eleventh resistor R11 is connected to the negative power supply terminal of the first operational amplifier 13a, and the other end is connected to the negative power supply VEE (e.g., -12V). One end of the eleventh capacitor C11 and the twelfth capacitor C12 are connected together and grounded (GND), and the other ends are both connected to the negative power supply terminal of the first operational amplifier 13a. Further, in this example, the ninth capacitor C9 and the eleventh capacitor C11 are electrolytic capacitors, and the other capacitors are non-polarized capacitors. In practical applications, any circuit structure capable of high-frequency filtering is applicable to the high-frequency filtering unit 132 of this invention, and will not be elaborated upon here.

[0059] like Figure 1 As shown, the second low-frequency amplifier 14 is connected to the output terminal of the filter module 13 and is used to amplify the output signal of the filter module 13.

[0060] Specifically, the output signal amplitude of the filter module 13 is usually small, and the output signal amplitude of the filter module 13 can be amplified by the second low-frequency amplifier 14.

[0061] Specifically, such as Figure 4As shown, in this embodiment, the second low-frequency amplifier 14 includes a second operational amplifier 14a, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a first diode D1, and a second diode D2. In this configuration, the sixth resistor R6 and the seventh resistor R7 are connected in series between the inverting input terminal of the second operational amplifier 14a and ground GND; one end of the sixth capacitor C6 serves as the input terminal IN3 of the second low-frequency amplifier 14, and the other end is connected between the connection node of the sixth resistor R6 and the seventh resistor R7; one end of the eighth resistor R8 is connected to the non-inverting input terminal of the second operational amplifier 14a, and the other end is ground GND; the ninth resistor R9 is connected between the output terminal (i.e., the output terminal OUT3 of the second low-frequency amplifier 14) and the inverting input terminal of the second operational amplifier 14a; the seventh capacitor C7 is connected in parallel across the ninth resistor R9; the anode of the first diode D1 is connected to the inverting input terminal of the second operational amplifier 14a, and the cathode is connected to the cathode of the second diode D2; the anode of the second diode D2 is connected to the output terminal of the second operational amplifier 14a; one end of the eighth capacitor C8 is connected to the output terminal of the second operational amplifier 14a, and the other end is ground GND. As another example, the second low-frequency amplifier 14 also includes a twelfth resistor R12, a thirteenth resistor R13, a thirteenth capacitor C13, a fourteenth capacitor C14, a fifteenth capacitor C15, and a sixteenth capacitor C16. One end of the twelfth resistor R12 is connected to the positive power supply VCC (e.g., +12V), and the other end is connected to the positive power supply terminal of the second operational amplifier 14a. The thirteenth capacitor C13 is connected in parallel with the fourteenth capacitor C14, with one end connected to the positive power supply terminal of the second operational amplifier 14a and the other end grounded (GND). One end of the thirteenth resistor R13 is connected to the negative power supply terminal of the second operational amplifier 14a, and the other end is connected to the negative power supply VEE (e.g., -12V). One end of the fifteenth capacitor C15 and the sixteenth capacitor C16 are connected together and grounded (GND), and the other ends are both connected to the negative power supply terminal of the second operational amplifier 14a. Furthermore, in this example, the sixth capacitor C6, the thirteenth capacitor C13, and the fifteenth capacitor C15 are electrolytic capacitors, the other capacitors are non-polarized capacitors, and the first diode D1 and the second diode D2 are Zener diodes. In practical applications, any circuit structure capable of achieving low-frequency amplification is applicable to the second low-frequency amplifier 14 of this invention, and will not be elaborated upon here.

[0062] like Figure 1 As shown, the sampling module 15 is connected to the output terminal of the second low-frequency amplifier 14 and is used to sample the output signal of the second low-frequency amplifier 14.

[0063] like Figure 1 As shown, the pulse width measurement module 16 is connected to the output terminal of the sampling module 15 and is used to measure the pulse width of the sampled pulse signal and output the pulse width measurement signal.

[0064] Specifically, the sampling module 15 and the pulse width measurement module 16 sample and measure the pulse width of the output signal of the second low-frequency amplifier 14 to obtain the pulse width of each pulse signal. In this embodiment, the sampling module 15 and the pulse width measurement module 16 are implemented in the same circuit, such as... Figure 5 As shown, the circuit includes a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a third capacitor C3, a fourth capacitor C4, and a fifth capacitor C5. The first terminal of the second resistor R2 serves as the input terminal IN2, connected to the output terminal of the preceding circuit, and the second terminal is connected to the first terminal of the third resistor R3. The second terminal of the third resistor R3 serves as the output terminal OUT2, outputting the pulse width measurement signal. The third capacitor C3 and the fourth capacitor C4 are connected in series between the first terminal of the second resistor R2 and the second terminal of the third resistor R3 (i.e., between IN2 and OUT2). One end of the fifth capacitor C5 is connected to the connection point of the second resistor R2 and the third resistor R3, and the other end is grounded (GND). The fourth resistor R4 and the fifth resistor R5 are connected in series between the connection point of the third capacitor C3 and the fourth capacitor C4 and grounded (GND). Further, in this example, the third capacitor C3, the fourth capacitor C4, and the fifth capacitor C5 are non-polarized capacitors. In practical use, any circuit structure that can realize sampling and pulse width measurement is applicable to the present invention and is not limited to this embodiment; in addition, the sampling module 15 and the pulse width measurement module 16 can be implemented based on two separate independent circuits, which will not be described in detail here.

[0065] like Figure 5 As shown, in another implementation of the present invention, the broken needle detection circuit 1 further includes a voltage follower module 18. The voltage follower module 18 is connected to the output terminal of the pulse width measurement module 16 and is used to achieve signal isolation and impedance matching. In this example, the voltage follower module 18 is implemented using a third operational amplifier 18a; the non-inverting input terminal of the third operational amplifier 18a serves as the input terminal IN3 of the voltage follower module 18, and the inverting input terminal and output terminal are connected together and serve as the output terminal OUT3 of the voltage follower module 18.

[0066] like Figure 1 As shown, the processing module 17 is connected to the output terminal of the pulse width measurement module 16, filters out interference signals with pulse widths smaller than the preset pulse width, and generates a detection signal based on the amplitude of the pulse signal with a pulse width greater than the preset pulse width.

[0067] Specifically, in this embodiment, the processing module 17 is implemented using a DSP (Digital Signal Processing). In practical use, any device or structure capable of achieving the above functions is applicable to this invention.

[0068] Specifically, because the size of the detection coil 11 of this invention is larger than that of existing detection coils, the pulse width of the broken needle detection pulse detected by this invention is greater than the pulse width of the interference signal. The broken needle detection pulse and the interference signal can be identified by their pulse widths. This invention compares the pulse width of each pulse signal with a preset pulse width. Signals with pulse widths greater than the preset pulse width are identified as broken needle detection pulses, and signals with pulse widths less than the preset pulse width are identified as interference signals. For example, the pulse width of the broken needle detection pulse is between 0.2s and 0.5s, the pulse width of the interference signal is between 0.05s and 0.1s, and the preset pulse width is set to 0.1s to 0.15s. In actual use, these settings can be adjusted according to the specific application environment and are not limited to this embodiment.

[0069] Specifically, the amplitude of the broken needle detection pulse is detected. If the amplitude is greater than a set value, a broken needle is detected, and a detection signal is output to implement an alarm function based on the detection signal. If the amplitude is less than the set value, no broken needle is detected, and no alarm operation is performed. As an example, the set value is set to 1V; in actual use, this set value should be set according to the specific application environment.

[0070] like Figure 6 As shown, the present invention also provides a broken needle detection method, implemented using the broken needle detection circuit 1 of the present invention. This broken needle detection method includes:

[0071] S1) The detection coil 11 scans the object to be tested and generates a corresponding detection pulse;

[0072] S2) Filter the probe pulse to remove interference;

[0073] S3) Sample the detection pulse after filtering out interference, measure the pulse width of the sampled pulse signal, and filter out pulse signals with a pulse width smaller than the preset pulse width.

[0074] S4) Measure the amplitude of the pulse signal with a pulse width greater than the preset pulse width. When the amplitude of the pulse signal is greater than the set value, it is determined that a broken needle has been detected and a detection signal is output. When the amplitude of the pulse signal is less than the set value, it is determined that no broken needle has been detected.

[0075] Specifically, such as Figure 6As shown, in this embodiment, a preset pulse width is first set, and then detection is initiated. Subsequently, pulse signals are acquired, specifically including: obtaining a detection signal using a detection coil 11, which includes interference signals and a broken needle detection pulse (if a broken needle is detected); amplifying the output signal of the detection coil 11 using a first low-frequency amplifier 12; filtering out power supply interference and / or high-frequency interference in the output signal of the first low-frequency amplifier 12 using a filtering module 13; amplifying the output signal of the filtering module 13 using a second low-frequency amplifier 14; and sampling the filtered signal using a sampling module 15. Next, the pulse width of the acquired pulse signals is measured using a pulse width measurement module 16 to obtain the pulse width of each pulse. Finally, the pulse width of each pulse is compared and filtered using a processing module 17, filtering out pulse signals with pulse widths less than the preset pulse width as interference signals; the amplitude of the retained pulse signals with pulse widths greater than the preset pulse width is detected. If the amplitude is greater than a set value, a broken needle is considered detected, and an alarm can be issued subsequently; if the amplitude is less than the set value, a broken needle is not detected, and no alarm is issued.

[0076] It should be noted that before each signal processing step, an amplifier can be set to amplify the signal as needed to meet the processing requirements of subsequent circuits; however, this will not be elaborated upon here.

[0077] As another implementation of the present invention, by controlling the scanning speed, the pulse width of the detection pulse when the detection coil 11 detects a broken needle is adjusted to improve flexibility and expand the applicability of the same set of equipment.

[0078] Specifically, the detection coil 11 moves relative to the object to be tested to achieve scanning. In one example, the object to be tested (relative to the ground) remains relatively stationary. The detection coil 11 is placed on the moving device, and the scanning is achieved by moving the detection coil 11 through the moving device. In another example, the detection coil 11 (relative to the ground) remains relatively stationary. The object to be tested is placed on the moving device, and the scanning is achieved by moving the object to be tested through the moving device.

[0079] Specifically, the scanning speed also affects the pulse width of the broken needle detection pulse. This invention can further adjust the pulse width of the broken needle detection pulse by adjusting the scanning speed; a slower scanning speed results in a larger pulse width (but lower detection efficiency), and vice versa. In this embodiment, the moving speed of the mobile device is adjusted (e.g., changing the belt speed of the mobile device) to change the pulse width of the broken needle detection pulse. In this example, to balance pulse width and detection efficiency, the scanning speed is set to 20m / min~50m / min, including but not limited to 25m / min, 30m / min, 33m / min, 35m / min, 40m / min, and 45m / min; in actual use, the scanning speed can be set according to the specific application environment and is not limited to this embodiment.

[0080] This invention employs a detection coil larger than existing coils to increase the pulse width generated when a broken needle passes through it. It utilizes hardware circuitry and / or software algorithms to measure the width of various signal pulses. When the width of a signal pulse is less than a preset pulse width, it is identified as an interference signal, and no alarm is triggered regardless of its amplitude. Conversely, when the width of a signal pulse exceeds the preset pulse width, an alarm is triggered if its amplitude exceeds a set value. This invention also uses a filtering module to filter 50Hz notch filters and high-frequency signals, reducing power supply interference and high-frequency interference.

[0081] In summary, this invention provides a broken needle detection circuit and method. The broken needle detection circuit includes: a detection coil, a first low-frequency amplifier, a filtering module, a second low-frequency amplifier, a sampling module, a pulse width measurement module, and a processing module. The detection coil is used to detect broken needles and generate corresponding detection pulses. The size of the detection coil is set such that the pulse width of the broken needle detection pulse is greater than the pulse width of the interference signal. The first low-frequency amplifier is connected to the output terminal of the detection coil and is used to amplify the output signal of the detection coil. The filtering module is connected to the output terminal of the first low-frequency amplifier and is used to filter the output signal of the first low-frequency amplifier. The second low-frequency amplifier is connected to the output terminal of the filtering module and is used to amplify the output signal of the filtering module. The sampling module is connected to the output terminal of the second low-frequency amplifier and is used to sample the output signal of the second low-frequency amplifier. The pulse width measurement module is connected to the output terminal of the sampling module and is used to measure the pulse width of the sampled pulse signal and output a pulse width measurement signal. The processing module is connected to the output terminal of the pulse width measurement module, filters out interference signals with pulse widths smaller than a preset pulse width, and generates a detection signal based on the amplitude of pulse signals with pulse widths greater than the preset pulse width. The broken needle detection circuit and method of this invention can effectively reduce interference in broken needle detection and improve detection accuracy; at the same time, it is highly flexible and has a wide range of applications. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0082] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A broken needle detection circuit, characterized in that, The broken needle detection circuit includes at least: The system includes a detection coil, a first low-frequency amplifier, a filtering module, a second low-frequency amplifier, a sampling module, a pulse width measurement module, and a processing module. The detection coil is used to detect the broken needle and generate a corresponding detection pulse, wherein the size of the detection coil is set such that the pulse width of the detection pulse for the broken needle is greater than the pulse width of the interference signal. The first low-frequency amplifier is connected to the output terminal of the detection coil and is used to amplify the output signal of the detection coil; The filtering module is connected to the output terminal of the first low-frequency amplifier and is used to filter the output signal of the first low-frequency amplifier. The second low-frequency amplifier is connected to the output terminal of the filter module and is used to amplify the output signal of the filter module; The sampling module is connected to the output terminal of the second low-frequency amplifier and is used to sample the output signal of the second low-frequency amplifier. The pulse width measurement module is connected to the output terminal of the sampling module and is used to measure the pulse width of the sampled pulse signal and output the pulse width measurement signal. The processing module is connected to the output of the pulse width measurement module, filters out interference signals with pulse widths smaller than the preset pulse width, and generates a detection signal based on the amplitude of pulse signals with pulse widths greater than the preset pulse width.

2. The broken needle detection circuit according to claim 1, characterized in that: The detection coil has a circular ring structure with a diameter of not less than 80 mm.

3. The broken needle detection circuit according to claim 1, characterized in that: The filtering module includes a 50Hz notch filter unit and a high-frequency filter unit, which are cascaded in sequence at the output end of the detection coil. The 50Hz notch filter unit is used to filter out 50Hz power frequency interference, and the high-frequency filter unit is used to filter out high-frequency interference.

4. The broken needle detection circuit according to claim 3, characterized in that: The high-frequency filtering unit includes a first operational amplifier, a first resistor, a first capacitor, and a second capacitor; one end of the first resistor serves as the input terminal of the high-frequency filtering unit, and the other end is connected to the non-inverting input terminal of the first operational amplifier; one end of the first capacitor is connected to the input terminal of the high-frequency filtering unit, and the other end is connected to the inverting input terminal and the output terminal of the first operational amplifier; one end of the second capacitor is connected to the non-inverting input terminal of the first operational amplifier, and the other end is grounded.

5. The broken needle detection circuit according to claim 1, characterized in that: The sampling module and the pulse width measurement module are implemented based on the same circuit, including a second resistor, a third resistor, a fourth resistor, a fifth resistor, a third capacitor, a fourth capacitor, and a fifth capacitor; the first end of the second resistor is connected to the output terminal of the preceding circuit, and the second end is connected to the first end of the third resistor; the second end of the third resistor outputs the pulse width measurement signal; the third capacitor and the fourth capacitor are connected in series between the first end of the second resistor and the second end of the third resistor; one end of the fifth capacitor is connected to the connection node of the second resistor and the third resistor, and the other end is grounded; the fourth resistor and the fifth resistor are connected in series between the connection node of the third capacitor and the fourth capacitor and ground.

6. The broken needle detection circuit according to claim 1, characterized in that: The second low-frequency amplifier includes a second operational amplifier, a sixth capacitor, a seventh capacitor, an eighth capacitor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a first diode, and a second diode; The sixth resistor and the seventh resistor are connected in series between the inverting input terminal of the second operational amplifier and ground; one end of the sixth capacitor serves as the input terminal of the second low-frequency amplifier, and the other end is connected between the connection node of the sixth resistor and the seventh resistor. One end of the eighth resistor is connected to the non-inverting input terminal of the second operational amplifier, and the other end is grounded; The ninth resistor is connected between the output terminal and the inverting input terminal of the second operational amplifier; The seventh capacitor is connected in parallel across the ninth resistor; The anode of the first diode is connected to the inverting input terminal of the second operational amplifier, and the cathode is connected to the cathode of the second diode; the anode of the second diode is connected to the output terminal of the second operational amplifier. One end of the eighth capacitor is connected to the output of the second operational amplifier, and the other end is grounded.

7. A method for detecting broken needles, implemented based on the broken needle detection circuit as described in any one of claims 1-6, characterized in that, The broken needle detection method includes at least the following: The probe coil scans the object under test and generates corresponding probe pulses; The detection pulses are filtered to remove interference; The detection pulses after interference filtering are sampled, and the pulse width of the sampled pulse signal is measured. Pulse signals with a pulse width smaller than the preset pulse width are filtered out. The amplitude of a pulse signal with a pulse width greater than the preset pulse width is measured. When the amplitude of the pulse signal is greater than the set value, it is determined that a broken needle has been detected and a detection signal is output. When the amplitude of the pulse signal is less than the set value, it is determined that no broken needle has been detected.

8. The needle breakage detection method according to claim 7, characterized in that: By controlling the scanning speed, the pulse width of the detection pulse when the detection coil detects a broken needle is adjusted.

9. The needle breakage detection method according to claim 8, characterized in that: The scanning speed is set to 20m / min~50m / min.

10. The needle breakage detection method according to claim 7, characterized in that: The interference is power supply interference and / or high-frequency interference.

11. The needle breakage detection method according to claim 7, characterized in that: The preset pulse width is set to 0.1s~0.15s.

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