Working switch detection circuit and judgment method used in magnetic particle flaw detector

Abstract

The present invention discloses a working switch detection circuit and a judgment method thereof applied to a magnetic particle flaw detector, which belongs to the field of magnetic particle flaw detection technology, and solves the problem of poor contact and short service life of the working switch due to water ingress in the prior art. It mainly includes a single-chip microcomputer U1, which controls the yoke coil drive, and the single-chip microcomputer U1 and the yoke coil are both arranged inside the yoke probe. The single-chip microcomputer U1 is connected to a switch detection circuit, and the switch detection circuit includes a power chip U2, and the power chip U2 is connected to a current limiting resistor R2, and the current limiting resistor R2 is electrically connected to a working switch SW1 and a filter circuit respectively; the filter circuit is connected to an AD acquisition module KEY_AD of the single-chip microcomputer U1. The present invention can reduce the influence of water ingress on the working switch and extend the service life of the working switch; on the basis of this circuit, leakage detection can also be realized by software to improve the reliability and safety of the product.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic particle flaw detection, and more particularly to a working switch detection circuit and a judgment method thereof applied to a magnetic particle flaw detector. Background Art

[0002] The working switch is a control switch for starting and stopping magnetization of the magnetic yoke, and is generally assembled on the handle of the magnetic yoke of the magnetic particle flaw detector for easy operation. The working switch is an important accessory of the magnetic yoke and is also a vulnerable part of the magnetic yoke. The reason for being vulnerable is that magnetic suspension liquid is generally required in the process of magnetic particle flaw detection. The magnetic suspension liquid is a suspension liquid formed by mixing magnetic powder and a medium liquid in a certain proportion. Usually, the medium liquid is water or kerosene. Water can conduct electricity and affect the operation of the circuit. When the working switch gets wet, it may malfunction, and the inside of the switch is prone to rust after being soaked in water for a long time, ultimately resulting in the damage of the working switch. Even a switch with silver contacts cannot avoid being damaged. Through long-term test analysis, it is determined that the main reason for the damage of the working switch of the magnetic yoke is that after getting wet, the detection voltage applied to the working switch makes the contacts inside the switch become electrodes, and an electrochemical reaction occurs; the switch with silver contacts cannot resist the erosion of the electrochemical reaction, and even a switch with ordinary copper electrodes is not easily damaged when soaked in water for a long time in the non-powered state. According to the conclusion of the test research, reducing the detection voltage on the working switch of the magnetic yoke so that the electrode potential difference is lower than the decomposition voltage of electrolyte solutions such as magnetic suspension liquid, and the decomposition voltage is the minimum voltage required to decompose the electrolyte to generate electrolysis products on the electrode. Below the decomposition voltage, the electrolysis reaction can be avoided, and the rapid corrosion of the contacts of the switch after getting wet can be avoided. It is actually measured that when a voltage lower than 0.9V is used to detect the on-off state of the switch, the switch can still work normally for a long time when soaked in water. However, the usual switch detection voltage is 5V or 3.3V. After reducing the detection voltage, it cannot be directly used as a switch signal in the original circuit, and the lower voltage signal is more vulnerable to the interference of the operation of the magnetic yoke.

[0003] A multifunctional switch circuit, a switch switching method and a magnetic particle flaw detector disclosed in the application with the announcement number of CN110213867B simplify the mechanical structure of the magnetic particle flaw detector to improve the waterproof ability of the magnetic particle flaw detector. However, kerosene is still used in the commonly used magnetic suspension liquid for magnetic particle flaw detection. Kerosene has a certain solvent effect and will cause a swelling reaction with commonly used waterproof rubber parts materials such as silica gel. Swelling is a phenomenon in which the volume of a polymer swells in a solvent, which will damage the waterproof structure. In addition, organic solvents are sometimes used as cleaning agents to treat the flaw detection surface during magnetic particle flaw detection, which will also contaminate the magnetic yoke and have adverse effects such as damaging and unsealing the sealant of the housing. This is also one of the reasons for the magnetic yoke to get water. However, due to the limitation of the application of the magnetic yoke, the working switch needs to be together with the magnetic yoke for the convenience of the operator to use, which inevitably comes into contact with liquids such as water or kerosene. And there is no reliable source of supply for finished switches that are waterproof, oil-proof and solvent-proof for organic solvents for the time being, so the problem of easy damage of the magnetic yoke working switch has not been effectively solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a working switch detection circuit and a judgment method applied to a magnetic particle flaw detector to solve the problems of poor contact and short service life of the working switch caused by water ingress in the prior art.

[0005] The present invention is realized through the following technical solutions:

[0006] A working switch detection circuit applied to a magnetic particle flaw detector includes a single-chip microcomputer U1. The single-chip microcomputer U1 controls the driving of the magnetic yoke coil. The single-chip microcomputer U1 and the magnetic yoke coil are both arranged inside the magnetic yoke probe. The single-chip microcomputer U1 is connected with a switch detection circuit. The switch detection circuit includes a power supply chip U2. The power supply chip U2 is connected with a current-limiting resistor R2. The current-limiting resistor R2 is electrically connected to a working switch SW1 and a filtering circuit respectively. The filtering circuit is grounded, and the working switch SW1 is grounded. The filtering circuit is connected to the AD acquisition module KEY_AD of the single-chip microcomputer U1.

[0007] Further, the filtering circuit includes a filtering resistor R1 and a capacitor C1. One end of the filtering resistor R1 is electrically connected to the current-limiting resistor R2, and the other end is electrically connected to the capacitor C1. The current-limiting resistor R2 is also connected to the AD acquisition module KEY_AD of the single-chip microcomputer U1, and the capacitor C1 is grounded.

[0008] Further, a zener diode D1 is connected in parallel at both ends of the filtering circuit. By adding the zener diode D1 to the filtering circuit, the voltage fluctuation can be effectively clamped, ensuring the stability of the circuit operation. The zener diode D1 can be replaced by a TVS diode or an ESD diode.

[0009] Further, the single-chip microcomputer U1 is communicatively connected to a yoke drive power supply through a communication interface TX, and the yoke drive power supply controls the energization of the yoke coil.

[0010] A judgment method for a working switch detection circuit applied to a magnetic particle flaw detector. The judgment method steps for the opening of the working switch SW1 include:

[0011] S1. The single-chip microcomputer U1 outputs a detection signal KEY_V to the power supply chip U2;

[0012] S2. After receiving the detection signal KEY_V, the power supply chip U2 outputs a voltage VREF;

[0013] S3. The AD acquisition module KEY_AD of the single-chip microcomputer U1 detects the level KEY+ at the connection of the filter resistor R1 and the capacitor C1, and judges whether the ripple of the level KEY+ is stable, so as to determine whether the switch is in a steady state;

[0014] S4. Calculate the value at the working switch SW1 according to the value of the steady-state level KEY+, and then judge whether the working switch SW1 is closed.

[0015] Further, in the step S4, if the value of the on-resistance R_KEY is within the effective range of the software-set parameters, it is regarded as the switch closing effectively; if the value of the on-resistance R_KEY is outside the effective range of the software-set parameters, it is regarded as the working switch SW1 not being closed.

[0016] Further, when it is judged that the working switch SW1 is closed effectively, a start signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply starts the magnetization work of the yoke coil; when it is judged that the working switch SW1 is not closed, a stop signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply stops the magnetization work of the yoke coil.

[0017] Further, it also includes a judgment method for whether there is leakage inside the yoke probe. When KEY_V outputs a low level, the power supply chip U2 is turned off and its output is in a high-impedance state. The AD acquisition module KEY_AD still continuously detects the level KEY+. If the level KEY+ is greater than the software-set parameters, it can be determined that there is leakage in the yoke coil, and the single-chip microcomputer U1 turns off the yoke drive power supply and performs an alarm process. According to the level value of the level KEY+, it can be identified whether there is leakage.

[0018] Further, it also includes a method for judging whether water enters the yoke probe. When KEY_V outputs a low level, the power supply chip U2 is turned off and its output is in a high-impedance state. The AD acquisition module KEY_AD still continuously detects the level KEY+, and judges whether water enters according to the waveform of the level KEY+. Recognition is performed according to the waveform of the level KEY+. The degree of water ingress and whether there is leakage can be judged. Through the processing of the level KEY+ waveform recognition process, such as software filtering, the problem that low-voltage signals are vulnerable to interference can be effectively solved.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The working switch is a vulnerable part, and the switch life affects the service life of the yoke to a certain extent. After the working switch ages, poor contact is likely to occur. In this application, the switch quantity is converted into an analog quantity for processing. The AD acquisition module KEY_AD is used to detect the switch state, and the value of the conduction resistance R_KEY is calculated to judge whether the switch is closed. This method can provide more accurate switch action recognition, ensure the reliability of the working switch during the magnetic particle flaw detection process, and can extend the actual service life of the switch.

[0021] 2. The working switch detection circuit of this application can, while completing the switch detection work, also judge whether the magnetic particle flaw detector is flooded or detect leakage according to the waveform of the level KEY+ in the non-powered state. When an abnormal situation is detected, the single-chip microcomputer U1 will promptly turn off the yoke drive power supply and issue an alarm, which not only protects the equipment itself but also ensures the safety of the user. Description of the Drawings

[0022] Figure 1 is the circuit schematic diagram of the present invention;

[0023] Figure 2 is the analog diagram of the level KEY+ when there is a normal induced voltage in the present invention;

[0024] Figure 3 is the analog diagram of the level KEY+ when there is an induced voltage due to water ingress in the present invention;

[0025] Figure 4 is the analog diagram of the level KEY+ when there is slight leakage in the present invention;

[0026] Figure 5 is the analog diagram of the level KEY+ when there is severe leakage in the present invention. Detailed Embodiment

[0027] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Based on the embodiments in this application, other similar embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application. In addition, the directional terms mentioned in the following embodiments, such as "upper", "lower", "left", "right", etc. are only with reference to the directions of the accompanying drawings. Therefore, the directional terms used are for illustration rather than limitation of the present invention.

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] Embodiment 1: A working switch detection circuit applied to a magnetic particle flaw detector, as Figure 1 shown, includes a single-chip microcomputer U1. The single-chip microcomputer U1 controls the driving of the yoke coil. Both the single-chip microcomputer U1 and the yoke coil are arranged inside the yoke probe. The single-chip microcomputer U1 is connected with a switch detection circuit. The switch detection circuit includes a power supply chip U2. The power supply chip U2 is connected with a current-limiting resistor R2. The current-limiting resistor R2 is electrically connected to a working switch SW1 and a filtering circuit respectively. The filtering circuit is grounded. The working switch SW1 is grounded. The filtering circuit is connected to the AD acquisition module KEY_AD of the single-chip microcomputer U1.

[0030] The usage mode of the yoke flaw detector is generally to stop magnetization after magnetizing for 1 to 3 seconds, and then adjust the position of the yoke probe and magnetize again. The working switch is in a state of being frequently triggered. In magnetic particle flaw detection operations, the number of times the working switch is triggered per day can reach thousands of times. Even if a long-life working switch is used, aging is inevitable. Generally, the manifestations of switch aging and damage are that the conduction resistance R_KEY becomes larger. After the switch is closed, it cannot conduct effectively and the switch fails. This application uses analog quantity detection. The single-chip microcomputer U1 can calculate the conduction resistance R_KEY after the switch is closed. Even if the resistance value of the switch becomes larger due to aging, the state of the switch can be identified, which can greatly improve the service life of the switch.

[0031] A judgment method for a working switch detection circuit applied to a magnetic particle flaw detector. The steps for judging the opening of the working switch SW1 include:

[0032] S1. The single-chip microcomputer U1 outputs a detection signal KEY_V to the power supply chip U2;

[0033] S2. After the power supply chip U2 obtains the detection signal KEY_V, it outputs a voltage VREF;

[0034] S3. The AD acquisition module KEY_AD of the single-chip microcomputer U1 detects the level KEY+ at the connection of the filtering resistor R1 and the capacitor C1, and judges whether the ripple of the level KEY+ is stable, so as to determine whether the switch is in a steady state;

[0035] S4. Calculate the on-resistance R_KEY value at the working switch SW1 based on the steady-state level KEY+ and the numerical value, and then determine whether the working switch SW1 is closed. Based on the level KEY+ at steady state, the input voltage VREF, and the resistance value of the current-limiting resistor R2, the microcontroller U1 calculates the on-resistance R_KEY of the working switch SW1. If the on-resistance R_KEY value is within the effective range of the software-set parameters, it is determined that the working switch is closed, and the enabled state of the working switch SW1 is sent to the host through the communication interface TX; if the on-resistance R_KEY value is outside the effective range of the software-set parameters, it is determined that the working switch is not closed, and the released state of the working switch is sent to the host through the TX communication.

[0036] The detection signal KEY_V is the detection signal of the working switch SW1. Only when detecting the state of the working switch SW1, it outputs a high level to start the power supply chip U2 to output the voltage VREF, which is loaded on the working switch SW1 through the current-limiting resistor R2, minimizing the energized time of the working switch. The voltage VREF is a fixed value, and its range is greater than 0V and less than 1.2V.

[0037] When the working switch SW1 is not closed, the voltage of KEY+ > 0V; when the working switch SW1 is closed, there will be a certain on-resistance R_KEY. The actually detected level KEY+ is equivalent to the voltage division of the parallel combination of the on-resistance R_KEY and the current-limiting resistor R2 and the filtering resistor R1. The more severely the working switch SW1 ages, the larger the value of the on-resistance R_KEY will be.

[0038] By performing an aging test on the existing switch in the yoke flaw detector, it is measured that the contact resistance when the normal switch is closed is about 50mΩ. After the switch contacts age, it gradually increases to several Ω to several hundred Ω, but the contact resistance is basically stable each time it is closed. When the contact resistance is greater than 1kΩ, the contact resistance will change each time it is closed, showing an unstable state. Therefore, a certain margin can be left, and 500Ω is selected as the upper limit parameter of the effective range of the switch on-resistance R_KEY.

[0039] Embodiment 2. A working switch detection circuit applied to a magnetic particle flaw detector. The filtering circuit includes a filtering resistor R1 and a capacitor C1. One end of the filtering resistor R1 is electrically connected to the current-limiting resistor R2, and the other end is electrically connected to the capacitor C1. The current-limiting resistor R2 is also connected to the AD acquisition module KEY_AD of the microcontroller U1; a zener diode D1 is connected in parallel at both ends of the filtering circuit. By adding the zener diode D1 to the filtering circuit, the voltage fluctuation can be effectively clamped, ensuring the stability of the circuit operation. The zener diode D1 can be replaced by a TVS diode or an ESD diode; the microcontroller U1 is communicatively connected to a yoke drive power supply through the communication interface TX, and the yoke drive power supply controls the energization of the yoke coil.

[0040] In step S4, if the on-resistance R_KEY value is within the effective range of the software-set parameters in step S4, it is regarded as the switch being closed effectively; if the on-resistance R_KEY value is outside the effective range of the software-set parameters, it is regarded as the working switch SW1 not being closed. When it is determined that the working switch SW1 is closed effectively, a start signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply starts the magnetization work of the yoke coil; when it is determined that the working switch SW1 is not closed, a stop signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply stops the magnetization work of the yoke coil.

[0041] A method for judging whether there is internal leakage in the yoke probe. When KEY_V outputs a low level, the power supply chip U2 is turned off and its output is in a high-impedance state. The AD acquisition module KEY_AD still continuously detects the level KEY+. If the level KEY+ is greater than the software-set parameters, it can be determined that there is leakage in the yoke coil, and the single-chip microcomputer U1 turns off the yoke drive power supply and performs alarm processing. By identifying according to the level value of the level KEY+, it can be judged whether there is leakage.

[0042] A method for judging whether there is water ingress inside the yoke probe. When KEY_V outputs a low level, the power supply chip U2 is turned off and its output is in a high-impedance state. The AD acquisition module KEY_AD still continuously detects the level KEY+. Whether there is water ingress is judged according to the waveform of the level KEY+. By identifying according to the waveform of the level KEY+, the degree of water ingress and whether there is leakage can be judged. Through the processing of the waveform recognition process of the level KEY+, such as software filtering, the problem that low-voltage signals are easily interfered can be effectively solved.

[0043] Others are the same as in Embodiment 1.

[0044] The working switch SW1 is the position directly touched when holding the yoke flaw detector, and its assembly structure will directly penetrate the yoke housing. It is the main water ingress point on the yoke flaw detector housing and is close to the yoke coil. Therefore, it is basically reasonable to detect leakage through the circuit of the working switch here.

[0045] Since it is an induced voltage, the waveform is always fluctuating. When there is no water ingress inside the yoke, the amplitude of the level KEY+ is relatively low, as Figure 2 shown. After water enters the yoke housing, since the dielectric constant of water is higher than that of air, the induced voltage applied to the level KEY+ will also increase, as Figure 3 shown. When the device has slight leakage, the amplitude of the level KEY+ will be even higher, as Figure 4 shown; when the device has severe leakage, the amplitude of the level KEY+ is as Figure 5As shown. Specifically, the voltage waveform obtained by the KEY_AD of the single-chip microcomputer U1 AD acquisition module is also related to the waveform of the yoke drive voltage and the parameters of the filter circuit. The lower the cut-off frequency of the filter circuit, the flatter the waveform. The peak value of the acquired voltage waveform is related to the parameters of D1.

[0046] The present invention has been described in detail above. The above description is only a preferred embodiment of the present invention, and it cannot limit the scope of the present invention. That is, all equivalent changes and modifications made according to the scope of this application should still fall within the scope covered by the present invention.

Claims

1. A method for determining a working switch detection circuit for a magnetic particle flaw detector, comprising a working switch detection circuit for a magnetic particle flaw detector, wherein the working switch detection circuit for a magnetic particle flaw detector comprises a single-chip microcomputer U1, the single-chip microcomputer U1 controls the driving of a yoke coil, and the single-chip microcomputer U1 and the yoke coil are both arranged inside a yoke probe, characterized in that: The single-chip microcomputer U1 is connected to a switch detection circuit, and the switch detection circuit includes a power chip U2, and the power chip U2 is connected to a current limiting resistor R2, and the current limiting resistor R2 is electrically connected to a working switch SW1 and a filter circuit, respectively, and the working switch SW1 is grounded; the filter circuit is connected to an AD acquisition module KEY_AD of the single-chip microcomputer U1; The steps of the method for determining whether the working switch SW1 is turned on include: S1, single chip microcomputer U1 outputs detection signal KEY_V to power chip U2; S2, the power chip U2 outputs a voltage VREF after receiving the detection signal KEY_V, and the voltage VREF is a fixed value, and its range is greater than 0V and less than 1.2V; S3, the AD acquisition module KEY_AD of the single-chip computer U1 detects the level KEY+ at the connection of the filter circuit, and determines whether the ripple of the level KEY+ is stable, and then determines whether the switch is in a steady state; S4. Calculate the on-resistance R_KEY value at the working switch SW1 according to the steady-state level KEY+ value, and then determine whether the working switch SW1 is closed; if the on-resistance R_KEY value is within the valid range of the software setting parameters, it is considered that the switch is closed and valid; if the on-resistance R_KEY value is outside the valid range of the software setting parameters, it is considered that the working switch SW1 is not closed; It also includes a method for determining whether there is leakage inside the yoke probe. When KEY_V outputs a low level, the power chip U2 is turned off and its output is in a high-impedance state. The AD acquisition module KEY_AD continues to detect the level KEY+. If the level KEY+ is greater than the software setting parameters, it can be determined that the yoke coil is leaking. The microcontroller U1 turns off the yoke drive power supply and issues an alarm.

2. The judgment method for the working switch detection circuit of the magnetic particle flaw detector according to claim 1 is characterized in that: The filter circuit includes a filter resistor R1 and a capacitor C1. One end of the filter resistor R1 is electrically connected to the current limiting resistor R2, and the other end is electrically connected to the capacitor C1. The current limiting resistor R2 is also connected to the AD acquisition module KEY_AD of the single chip microcomputer U1.

3. The judgment method for the working switch detection circuit of the magnetic particle flaw detector according to claim 2 is characterized in that: A voltage stabilizing diode D1 is connected in parallel at both ends of the filter circuit.

4. The judgment method for the working switch detection circuit of the magnetic particle flaw detector according to claim 1 is characterized in that: The single chip microcomputer U1 is connected to a yoke driving power supply via a communication interface TX, and the yoke driving power supply controls the yoke coil to be energized.

5. The judgment method for the working switch detection circuit of the magnetic particle flaw detector according to claim 1 is characterized in that: When it is determined that the working switch SW1 is closed and valid, a start signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply starts the magnetization work of the yoke coil; when it is determined that the working switch SW1 is not closed, a stop signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply stops the magnetization work of the yoke coil.

6. The judgment method for the working switch detection circuit of the magnetic particle flaw detector according to claim 1 is characterized in that: It also includes a method for determining whether water has entered the yoke probe. When KEY_V outputs a low level, the power chip U2 is turned off and its output is in a high-impedance state. The AD acquisition module KEY_AD continues to detect the level KEY+, and determines whether water has entered based on the waveform of the level KEY+.

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