Pipeline triaxial stress internal detection circuit and device based on tunnel magnetic resistance

Abstract

The invention relates to a pipeline triaxial stress internal detection circuit and device based on tunnel magnetoresistance, and the circuit comprises a square wave generation circuit, a first high-pass filter circuit, a first low-pass filter circuit, an excitation signal generation circuit, a reference signal generation circuit, and a tunnel magnetoresistive sensor detection circuit. Square waves generated by the square wave generation circuit are converted into sine waves through the first high-pass filter circuit and the first low-pass filter circuit in sequence, the sine waves are input into the excitation signal generation circuit, and the excitation signal generation circuit is connected with the reference signal generation circuit and the tunnel magnetoresistive sensor detection circuit. The tunnel magnetoresistive sensor detection circuit comprises phase-sensitive detection circuits, the output of the reference signal generation circuit is connected to the phase-sensitive detection circuits respectively, and the tunnel magnetoresistive sensor detection circuit is arranged in three directions to form a pipeline triaxial stress internal detection circuit. Compared with the prior art, the method has the advantages of high detection precision, high practicability and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of internal detection of oil and gas pipelines, and in particular to a pipeline triaxial stress internal detection circuit and device based on tunnel magnetoresistance. Background Art

[0002] Oil and gas pipelines are buried underground for a long time, and are subjected to the effects of soil, medium pressure and their own gravity to form stress concentration areas. In stress concentration areas, due to mechanical damage, corrosion and cracks of the pipeline body, stress corrosion cracking and yield failure are very likely to occur, posing a great risk to the inherent safety of the pipeline. Therefore, internal stress detection of buried pipelines is an important step in pipeline operation and maintenance.

[0003] The common medium for oil and gas pipelines is ferromagnetic materials. When this material undergoes processing such as smelting, forging and heat treatment, the magnetic domain organization inside the pipeline will be disintegrated and the magnetism will disappear. When the pipeline is buried underground, it will be subjected to stress loads in the geomagnetic environment, and the magnetic domain organization with magnetostrictive properties will be oriented and irreversibly reoriented inside. The weak geomagnetic field will form changes in the leakage magnetic field in the stress concentration area. By measuring the axial, radial and normal components of the leakage magnetic field on the surface of the ferromagnetic pipeline, the stress concentration area of ​​the oil and gas pipeline can be determined.

[0004] Therefore, how to measure the axial, radial and normal components of the leakage magnetic field on the surface of ferromagnetic pipelines is of great significance to improving the measurement accuracy of stress concentration areas in oil and gas pipelines. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a pipeline triaxial stress internal detection circuit and device based on tunnel magnetoresistance for measuring the anisotropic components of the leakage magnetic field on the surface of a ferromagnetic pipeline.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance comprises a square wave generating circuit, a first high-pass filtering circuit, a first low-pass filtering circuit, an excitation signal generating circuit, a reference signal generating circuit, an X-axis tunnel magnetoresistance sensor detection circuit, a Y-axis tunnel magnetoresistance sensor detection circuit and a Z-axis tunnel magnetoresistance sensor detection circuit. The square wave generated by the square wave generating circuit is sequentially converted into a sine wave through the first high-pass filtering circuit and the first low-pass filtering circuit. The sine wave is input into the excitation signal generating circuit. The excitation signal generating circuit is respectively connected to the reference signal generating circuit, the X-axis tunnel magnetoresistance sensor detection circuit, the Y-axis tunnel magnetoresistance sensor detection circuit and the Z-axis tunnel magnetoresistance sensor detection circuit. The X-axis tunnel magnetoresistance sensor detection circuit, the Y-axis tunnel magnetoresistance sensor detection circuit and the Z-axis tunnel magnetoresistance sensor detection circuit all comprise phase-sensitive detection circuits. The output of the reference signal generating circuit is respectively connected to each phase-sensitive detection circuit.

[0008] Furthermore, the output of the excitation signal generating circuit is a sinusoidal wave excitation signal, and the reference signal generating circuit converts the sinusoidal wave excitation signal into an inverse signal having the same frequency as the sinusoidal wave excitation signal and outputs the inverse signal.

[0009] Furthermore, the phase-sensitive detection circuit includes a multiplier and a second low-pass filter circuit connected in sequence, one input end of the multiplier is connected to the reference signal generating circuit, the other input end is connected to the excitation signal generating circuit through the pre-circuit, and the output end of the second low-pass filter circuit is connected to the post-circuit.

[0010] Furthermore, the front-end circuit includes a tunnel magnetoresistance sensor, an instrument amplifier circuit and a second high-pass filter circuit connected in sequence, the input end of the tunnel magnetoresistance sensor is connected to the excitation signal generating circuit, and the output end of the second high-pass filter circuit is connected to the multiplier.

[0011] Furthermore, the multiplier is a four-quadrant analog multiplier, the second low-pass filter circuit is composed of two first-order RC cascades, the input of the multiplier is the output signal of the second high-pass filter circuit and the reference signal of the reference signal generating circuit, and the output is a sum frequency signal and a difference frequency signal. The second low-pass filter circuit filters out the sum frequency signal and retains the difference frequency signal as the output signal of the phase-sensitive detection circuit.

[0012] Furthermore, the tunnel magnetoresistance sensor includes a first tunnel magnetoresistance element, a second tunnel magnetoresistance element, a third tunnel magnetoresistance element and a fourth tunnel magnetoresistance element, the first tunnel magnetoresistance element and the second tunnel magnetoresistance element are connected in series to form a first circuit, the third element tunnel magnetoresistance and the fourth element tunnel magnetoresistance are connected in series to form a second circuit, the first circuit and the second circuit are connected in parallel to obtain two parallel connection points, and the tunnel magnetoresistance sensor includes an input end and two output ends, the input end is connected to the excitation signal generating circuit, and the two output ends are respectively connected to the two parallel connection points.

[0013] Furthermore, the instrumentation amplifier amplifying circuit includes a first pin, a second pin, a third pin, a fourth pin and an output end, the input of the first pin is an output end signal of the tunnel magnetoresistance sensor, the input of the fourth pin is another output end signal of the tunnel magnetoresistance sensor, the second pin and the third pin are connected through a gain resistor, and the output end of the instrumentation amplifier amplifying circuit is connected to a second high-pass filter circuit.

[0014] Furthermore, the post-circuit includes a common-phase amplifier circuit.

[0015] Furthermore, the in-phase amplifier circuit includes an amplifier circuit and a third low-pass filter circuit. The input signal of the in-phase amplifier circuit passes through the amplifier circuit and then passes through the third low-pass filter circuit to obtain an output voltage signal.

[0016] According to a second aspect of the present invention, a pipeline three-axis stress internal detection device based on tunnel magnetoresistance includes a first magnetoresistance sensor, a second magnetoresistance sensor, a third magnetoresistance sensor, a first plane, a second plane, and a pipeline three-axis stress internal detection circuit based on tunnel magnetoresistance as described above, wherein the first plane and the second plane are perpendicular to each other, the first magnetoresistance sensor is arranged on the first plane and is perpendicular to the intersection line of the first plane and the second plane, the second magnetoresistance sensor is arranged on the second plane and is perpendicular to the intersection line of the first plane and the second plane, the third magnetoresistance sensor is arranged on the first plane and is perpendicular to the first magnetoresistance sensor, and the X-axis tunnel magnetoresistance sensor detection circuit, the Y-axis tunnel magnetoresistance sensor detection circuit, and the Z-axis tunnel magnetoresistance sensor detection circuit are respectively connected to the first magnetoresistance sensor, the second magnetoresistance sensor, and the third magnetoresistance sensor.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1) The present invention uses an excitation signal generating circuit as the excitation signal of the tunnel magnetoresistance sensor to obtain an output signal of the tunnel magnetoresistance sensor as an input signal of a phase-sensitive detection circuit. A reference signal generated based on the excitation signal is used as another input signal of the phase-sensitive detection circuit through a reference signal generating circuit. A DC detectable signal of the tunnel magnetoresistance sensor is obtained through the phase-sensitive detection circuit and used for subsequent instrument detection processes, thereby improving the output accuracy of the tunnel magnetoresistance sensor and improving the accuracy of measuring the anisotropic components of the leakage magnetic field on the surface of a ferromagnetic pipeline.

[0019] 2) The present invention also provides a measuring device based on the circuit of the present invention. By vertically arranging magnetoresistive sensors in pairs, a measuring device structure capable of detecting magnetic fields in three-dimensional space is formed to achieve a specific application form of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the circuit structure.

[0021] Figure 2 is a circuit diagram of a square wave generating circuit of Embodiment 1;

[0022] Figure 3 is a circuit diagram of a first high-pass filter circuit of Embodiment 1;

[0023] Figure 4 is a circuit diagram of a first low-pass filter circuit of Embodiment 1;

[0024] Figure 5 is a circuit diagram of an excitation signal generating circuit of Embodiment 1;

[0025] Figure 6 is a circuit diagram of a reference signal generating circuit of Embodiment 1;

[0026] Figure 7 is a circuit diagram of the tunnel magnetoresistive sensor of Example 1;

[0027] Figure 8 is a circuit diagram of an instrument amplifier circuit of Example 1;

[0028] Fig. 9 is a circuit diagram of a second high-pass filter circuit of Embodiment 1;

[0029] Fig.10 is a circuit diagram of a multiplier of Embodiment 1;

[0030] Fig.11 is a circuit diagram of a second low-pass filter circuit of Embodiment 1;

[0031] Fig.12 is a circuit diagram of the in-phase amplifier circuit of Example 1;

[0032] Fig.13 This is a layout diagram of a single triaxial stress internal detection probe in Example 2;

[0033] Fig.14 Schematic diagram of detector distribution of multiple triaxial stress internal detection probes in Example 3.

[0034] Markings in the figure: 1. Square wave generating circuit, 2. First high-pass filtering circuit, 3. First low-pass filtering circuit, 4. Excitation signal generating circuit, 5. Reference signal generating circuit, 6. Tunnel magnetoresistance sensor, 7. Instrument amplifier amplification circuit, 8. Second high-pass filtering circuit, 9. Multiplier, 10. Second low-pass filtering circuit, 11. Phase-sensitive detection circuit, 12. In-phase amplifier circuit, 13. X-axis tunnel magnetoresistance sensor detection circuit, 14. Y-axis tunnel magnetoresistance sensor detection circuit, 15. Z-axis tunnel Magnetoresistive sensor detection circuit, 20, first magnetoresistive sensor, 21, second magnetoresistive sensor, 22, third magnetoresistive sensor, 23, first plane, 24, second plane, 30, probe, 31, detector, U1, oscillator, U2A, first operational amplifier, U2B, second operational amplifier, U3, instrumentation amplifier, U4, multiplier, U5, third operational amplifier, R1, first resistor, R2, second resistor, R3, third resistor, R4, fourth resistor, R5, fifth resistor, R6, first Sixth resistor, R7, seventh resistor, R8, eighth resistor, R9, ninth resistor, R10, tenth resistor, R11, eleventh resistor, R12, twelfth resistor, R13, thirteenth resistor, R14, fourteenth resistor, R15, fifteenth resistor, R16, sixteenth resistor, R17, seventeenth resistor, R18, eighteenth resistor, C1, first capacitor, C2, second capacitor, C3, third capacitor, C4, fourth capacitor, C5, fifth capacitor, C6, sixth capacitor, C7, seventh capacitor , S1, Wheatstone bridge, CLK, square wave signal, CLK1, first high-pass filter circuit output signal, CLK2, sine wave signal, EXC, sine wave excitation signal, OUT1, tunnel magnetoresistance sensor first output signal, OUT2, tunnel magnetoresistance sensor first output signal, AMP, instrumentation amplifier output signal, SIG, second high-pass filter circuit output signal, REF, reference signal, MUL multiplier output signal, FIL, phase-sensitive detection output signal, VOUT, voltage signal. 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] Example 1

[0037] like Figure 1As shown, the present invention is a pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance, comprising a square wave generating circuit 1, a first high-pass filtering circuit 2, a first low-pass filtering circuit 3, an excitation signal generating circuit 4, a reference signal generating circuit 5, an X-axis tunnel magnetoresistance sensor detection circuit 13, a Y-axis tunnel magnetoresistance sensor detection circuit 14 and a Z-axis tunnel magnetoresistance sensor detection circuit 15. The square wave generated by the square wave generating circuit 1 is sequentially converted into a sine wave through the first high-pass filtering circuit 2 and the first low-pass filtering circuit 3, and the sine wave is input into the excitation signal generating circuit 4. The excitation signal generating circuit 4 is respectively connected to the reference signal generating circuit 5, the X-axis tunnel magnetoresistance sensor detection circuit 13, the Y-axis tunnel magnetoresistance sensor detection circuit 14 and the Z-axis tunnel magnetoresistance sensor detection circuit 15. The X-axis tunnel magnetoresistance sensor detection circuit 13, the Y-axis tunnel magnetoresistance sensor detection circuit 14 and the Z-axis tunnel magnetoresistance sensor detection circuit 15 all include a phase-sensitive detection circuit 11, and the output of the reference signal generating circuit 5 is respectively connected to each phase-sensitive detection circuit 11.

[0038] The phase-sensitive detection circuit 11 includes a multiplier 9 and a second low-pass filter circuit 10 connected in sequence, one input end of the multiplier 9 is connected to the reference signal generating circuit 5, and the other input end is connected to the excitation signal generating circuit 4 through the pre-circuit, and the output end of the second low-pass filter circuit 10 is connected to the post-circuit.

[0039] The preamplifier circuit includes a tunnel magnetoresistance sensor 6, an instrument amplifier circuit 7 and a second high-pass filter circuit 8 connected in sequence. The input end of the tunnel magnetoresistance sensor 6 is connected to the excitation signal generating circuit 4, and the output end of the second high-pass filter circuit 8 is connected to the multiplier 9.

[0040] The post-circuit includes a non-inverting amplifier circuit 12 .

[0041] In this embodiment, each circuit is specifically:

[0042] Square wave generating circuit 1: used to generate square wave signal CLK, which is modulated into a sine wave and then loaded into the excitation signal generating circuit 4. Here, the square wave frequency is set to 208kHz to avoid low frequency and power frequency interference.

[0043] like Figure 2As shown, the oscillator U1 of the square wave generating circuit 1 is preferably LTC6906. LTC6906 is an existing mature technology and is not limited here. LTC6906 is a SOT-23 packaged programmable silicon oscillator with micro-power and a resistor setting frequency range of 10kHz to 1MHz. A single resistor is responsible for setting the oscillator frequency within a range of 10:1, and the initial accuracy is better than 0.5%. The output frequency can be divided by 1, 3 or 10 to span a total frequency range of 100:1 (10kHz to 1MHz). The first resistor R1 is a 160Ω resistor, and the frequency of the CLK square wave signal output by the OUT pin is:

[0044]

[0045] First high-pass filter circuit 2: The first high-pass filter circuit is used to filter out power frequency and low-frequency noise interference signals to obtain a first high-pass filter circuit output signal CLK1.

[0046] The first high-pass filter circuit is composed of C2 and R2. The output signal of the high-pass filter circuit is CLK1. Figure 3 As shown in the figure, C2 is a 220nf capacitor and R2 is a 3.3kΩ resistor, so the high-pass filter corner frequency is 219Hz, which can filter out the power frequency 50Hz interference and low-frequency interference signals.

[0047] The first low-pass filter circuit 3: Filter out high-frequency harmonic components of 3 times the fundamental frequency and above in the square wave. According to the Fourier series expansion formula of the square wave signal, the square wave signal can be decomposed into sinusoidal signals of 1, 3, 5, ... (2n+1) times the square wave (fundamental) frequency (n is a constant). Therefore, as long as the sinusoidal harmonic signals of 3, 5, ... (2n+1) times the fundamental frequency are filtered out by the filter, the sinusoidal wave signal CLK2 with the same frequency as the square wave can be obtained.

[0048] The low-pass filter circuit is composed of R3 and C3, such as Figure 4 As shown. R3 is a 24kΩ resistor, C3 is a 22pf capacitor, and the low-pass filter frequency is 301kHz. Since the square wave fundamental frequency is 208kHz, 3 times the fundamental frequency is 624kHz. Setting the low-pass filter frequency to 301kHz can filter out signals above 3 times the fundamental frequency of 624kHz. Therefore, the CLK1 signal can pass through this circuit to obtain a 208kHz sine wave signal CLK2 with the same frequency as the square wave.

[0049] Excitation signal generating circuit 4: used to generate a sine wave excitation signal EXC for driving the tunnel magnetoresistive sensor. Figure 5As shown, the sine wave signal CLK2 passes through the second operational amplifier U2B follower circuit to improve the driving ability of the sine wave signal, the fourth resistor R4 is a 3.3 kΩ resistor, and the output sine wave excitation signal EXC is used as the excitation signal of the tunnel magnetoresistive sensor.

[0050] Reference signal generating circuit 5: Figure 6 As shown, the reference signal input is the sinusoidal excitation signal output by the excitation signal generating circuit 4, and the inverted signal with the same frequency but different amplitude as the sinusoidal excitation signal is obtained through the inverting proportional amplifier circuit as the reference signal REF and input to the phase-sensitive detection circuit 11.

[0051] The sinusoidal wave excitation signal EXC is applied to the inverting input terminal of the first operational amplifier U2A. U2A acts as an inverting amplifier with an amplification factor of:

[0052]

[0053] In the formula, R5 is the resistance value of the fifth resistor R5, and R6 is the resistance value of the sixth resistor R6.

[0054] The inverted amplified reference signal REF is obtained:

[0055]

[0056] Tunnel magnetoresistance sensor 6: Figure 7 As shown, it includes 4 high-sensitivity tunnel magnetoresistance sensor (TMR) elements, and the 4 TMR elements are divided into 2 groups, each group consists of 2 TMR elements connected in series, and the 2 groups are connected in parallel to form a push-pull Wheatstone full-bridge structure resistance bridge. The output of the Wheatstone bridge is measured between the two groups of parallel connection points, and changes linearly with the leakage magnetic field, and the first output signal OUT1 and the second output signal OUT2 of the tunnel magnetoresistance sensor are obtained, which is the working area of ​​the tunnel magnetoresistance sensor. The tunnel magnetoresistance sensor is preferably a TMR2901 linear sensor. TMR2901 is an existing mature technology and is not limited here.

[0057] Instrumentation amplifier circuit 7: used to amplify the differential signal output by the tunnel magnetoresistive sensor 6, and only follow the common-mode input signal, so that the common-mode rejection ratio of the tunnel magnetoresistive sensor 6 is improved to obtain the output signal AMP.

[0058] like Figure 8As shown, the instrumentation amplifier U3 is preferably AD8421. AD8421 is an existing mature technology and is not limited here. Its built-in resistor is 9.9kΩ. The 4th pin of AD8421 is connected to OUT1, and the 1st pin is connected to OUT2. Here, R10 is selected as 1.1kΩ, and the gain multiple G of AD8421 is:

[0059]

[0060] The output of AD8421 is expressed as:

[0061] AMP=G*(OUT1-OUT2)+V REF

[0062] The eighth resistor R8 and the ninth resistor R9 are grounded, V REF is 0. Therefore:

[0063] V OUT =10(OUT2-OUT1)

[0064] High-pass filter circuit 2 8: used to isolate DC and power frequency noise, amplify the effective AC signal, and obtain the output signal SIG of the second high-pass filter circuit.

[0065] The second high-pass filter circuit is composed of R11 and C4, such as Fig. 9 As shown in the figure, R11 is a 2.5kΩ resistor and C4 is a 220nF capacitor, so the filter frequency is 289Hz.

[0066] Multiplier 9: used for multiplying the output signal SIG of the tunnel magnetoresistive sensor and the reference signal REF.

[0067] The structure design of multiplier 9 is as follows Fig.10 As shown, the multiplier U4 is preferably AD835. AD835 is an existing mature technology and is not limited here. It is a four-quadrant analog multiplier. The output signal SIG of the tunnel magnetoresistive sensor can be expressed as:

[0068] SIG=V S sin(ω0t+θ)

[0069] Among them, V S is the amplitude, ω0 is the sine wave frequency, and θ is the phase.

[0070] The reference signal REF can be expressed as:

[0071] REF=V r sin(ω0t)

[0072] Among them, V r is the amplitude, ω0 is the frequency of the sine wave.

[0073] Then the signal after multiplication by the multiplier is:

[0074]

[0075] in, is the sum frequency signal component of the output signal of the tunnel magnetoresistance sensor and the reference signal, is the difference frequency signal component between the output signal of the tunnel magnetoresistance sensor and the reference signal, which is filtered by a low-pass filter circuit. By filtering out the sum frequency signal component, the difference frequency signal component can be obtained so that it can be detected by DC. At the same time, the environmental noise is filtered out.

[0076] The second low-pass filter circuit 10 is composed of two first-order RC cascades. Since the circuit does not use an active filter, the volume of the probe can be reduced.

[0077] The first RC cascade consists of R14 and C5, and the second RC cascade consists of R15 and C6, as shown in Fig.11 As shown. R14 is selected as 1kΩ, C5 is selected as 220nf, R15 is selected as 1kΩ, and C6 is selected as 220nf, then the low-pass filter cutoff frequency is 732Hz, and the difference frequency signal component between the output signal of the tunnel magnetoresistive sensor and the reference signal can be retained for DC detection.

[0078] Phase-sensitive detection circuit 11: It is composed of a multiplier 9 and a low-pass filter 10. The output signal of the tunnel magnetoresistance sensor 6 and the reference signal generated by the reference signal generating circuit 5 are multiplied by the multiplier 9 to obtain the sum frequency and difference frequency signal MUL of the output signal SIG of the tunnel magnetoresistance sensor and the reference signal REF. By filtering out the sum frequency signal component of the output signal of the tunnel magnetoresistance sensor and the reference signal with a low-pass filter, the difference frequency signal component FIL of the output signal of the tunnel magnetoresistance sensor and the reference signal can be obtained, and the signal can be detected by direct current. At the same time, the low-pass filter circuit can also filter out environmental noise.

[0079] In-phase amplifier circuit 12: amplifies the output signal FIL of the phase-sensitive detection so as to output the effective tunnel magnetoresistance signal VOUT after amplification, where VOUT is a voltage signal. Subsequent instruments can collect the voltage signal VOUT output by the three-axis stress internal detection probe through the analog output signal.

[0080] like Fig.12 As shown, the in-phase amplifier circuit is composed of a third operational amplifier U5 and resistors R16, R17, R18 and C7. The amplifier circuit composed of resistors R16 and R17 has an amplification ratio of 6 times, and resistors R18 and C7 constitute a third low-pass filter circuit to further filter out power frequency interference and circuit noise.

[0081] Through the above circuit setting, the circuit of the present invention can realize the extraction of the effective part of the output signal of the tunnel magnetoresistive sensor 6, which is convenient for the subsequent use of instruments to confirm the output results of the tunnel magnetoresistive sensor and realize the accurate calculation of the components of pipeline stress in the three directions of X, Y and Z.

[0082] Example 2

[0083] Based on Example 1 of the present invention, Fig.13 As shown, three single-axis tunnel magnetoresistive sensors are arranged along two planes to form a three-dimensional space magnetic field detection. Fig.13 In the embodiment, the first magnetoresistance sensor 20, the second magnetoresistance sensor 21, the third magnetoresistance sensor 22, the first plane 23 and the second plane 24 are perpendicular to each other, the first magnetoresistance sensor 20 is arranged on the first plane 23 and is perpendicular to the intersection line of the first plane 23 and the second plane 24, the second magnetoresistance sensor 21 is arranged on the second plane 24 and is perpendicular to the intersection line of the first plane 23 and the second plane 24, the third magnetoresistance sensor 22 is arranged on the first plane 23 and is perpendicular to the first magnetoresistance sensor 20, the first plane 23 and the second plane 24 are generally circuit board structures, connected by welding or connectors, and arranged with circuits designed based on embodiment 1, wherein the X-axis tunnel magnetoresistance sensor detection circuit 13, the Y-axis tunnel magnetoresistance sensor detection circuit 14 and the Z-axis tunnel magnetoresistance sensor detection circuit 15 are connected to the first magnetoresistance sensor 20, the second magnetoresistance sensor 21 and the third magnetoresistance sensor 22 respectively. Thus, a tunnel magnetoresistance-based pipeline three-axis stress internal detection device of the present invention is formed.

[0084] Example 3

[0085] On the basis of Example 2, Fig.14 As shown, multiple detection probes 30 of the triaxial stress internal detection device according to Embodiment 2 are arranged circumferentially around the side wall of the pipeline stress internal detector 31 to achieve all-round detection of pipeline internal stress.

[0086] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance, characterized in that: The invention comprises a square wave generating circuit (1), a first high-pass filtering circuit (2), a first low-pass filtering circuit (3), an excitation signal generating circuit (4), a reference signal generating circuit (5), an X-axis tunnel magnetoresistance sensor detection circuit (13), a Y-axis tunnel magnetoresistance sensor detection circuit (14) and a Z-axis tunnel magnetoresistance sensor detection circuit (15); the square wave generated by the square wave generating circuit (1) is sequentially converted into a sine wave through the first high-pass filtering circuit (2) and the first low-pass filtering circuit (3); the sine wave is input into the excitation signal generating circuit (4); The excitation signal generating circuit (4) is respectively connected to a reference signal generating circuit (5), an X-axis tunnel magnetoresistance sensor detection circuit (13), a Y-axis tunnel magnetoresistance sensor detection circuit (14) and a Z-axis tunnel magnetoresistance sensor detection circuit (15); the X-axis tunnel magnetoresistance sensor detection circuit (13), the Y-axis tunnel magnetoresistance sensor detection circuit (14) and the Z-axis tunnel magnetoresistance sensor detection circuit (15) all include a phase-sensitive detection circuit (11); and the output of the reference signal generating circuit (5) is respectively connected to each phase-sensitive detection circuit (11).

2. According to the tunnel magnetoresistance-based pipeline triaxial stress internal detection circuit of claim 1, it is characterized in that: The output of the excitation signal generating circuit (4) is a sinusoidal excitation signal, and the reference signal generating circuit (5) converts the sinusoidal excitation signal into an inverse signal having the same frequency as the sinusoidal excitation signal and outputs the inverse signal.

3. The pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance according to claim 1 is characterized in that: The phase-sensitive detection circuit (11) comprises a multiplier (9) and a second low-pass filter circuit (10) connected in sequence, one input end of the multiplier (9) is connected to a reference signal generating circuit (5), the other input end is connected to an excitation signal generating circuit (4) via a pre-circuit, and the output end of the second low-pass filter circuit (10) is connected to a post-circuit.

4. The pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance according to claim 3 is characterized in that: The preamplifier circuit comprises a tunnel magnetoresistance sensor (6), an instrumentation amplifier circuit (7) and a second high-pass filter circuit (8) which are connected in sequence, the input end of the tunnel magnetoresistance sensor (6) being connected to an excitation signal generating circuit (4), and the output end of the second high-pass filter circuit (8) being connected to a multiplier (9).

5. The pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance according to claim 4 is characterized in that: The multiplier (9) is a four-quadrant analog multiplier, the second low-pass filter circuit (10) is composed of two first-order RC cascades, the input of the multiplier (9) is the output signal of the second high-pass filter circuit (8) and the reference signal of the reference signal generating circuit (5), and the output is a sum frequency signal and a difference frequency signal, and the second low-pass filter circuit (10) filters out the sum frequency signal and retains the difference frequency signal as the output signal of the phase-sensitive detection circuit (11).

6. The pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance according to claim 4, characterized in that: The tunnel magnetoresistance sensor (6) comprises a first tunnel magnetoresistance element, a second tunnel magnetoresistance element, a third tunnel magnetoresistance element and a fourth tunnel magnetoresistance element, the first tunnel magnetoresistance element and the second tunnel magnetoresistance element are connected in series to form a first circuit, the third element tunnel magnetoresistance and the fourth element tunnel magnetoresistance are connected in series to form a second circuit, the first circuit and the second circuit are connected in parallel to obtain two parallel connection points, and the tunnel magnetoresistance sensor (6) comprises an input end and two output ends, the input end is connected to an excitation signal generating circuit (4), and the two output ends are respectively connected to two parallel connection points.

7. The pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance according to claim 6, characterized in that: The instrument amplifier amplifying circuit (7) comprises a first pin, a second pin, a third pin, a fourth pin and an output end, the first pin is inputted with an output end signal of a tunnel magnetoresistive sensor (6), the fourth pin is inputted with another output end signal of the tunnel magnetoresistive sensor (6), the second pin and the third pin are connected via a gain resistor, and the output end of the instrument amplifier amplifying circuit (7) is connected to a second high-pass filter circuit (8).

8. The pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance according to claim 2 is characterized in that: The post-circuit comprises a common-phase amplifier circuit (12).

9. The pipeline triaxial stress internal detection circuit based on tunnel magnetoresistance according to claim 8, characterized in that: The in-phase amplifier circuit (12) comprises an amplifier circuit and a third low-pass filter circuit. The input signal of the in-phase amplifier circuit (12) passes through the amplifier circuit and then passes through the third low-pass filter circuit to obtain an output voltage signal.

10. A pipeline triaxial stress internal detection device based on tunnel magnetoresistance, characterized in that: The invention comprises a first magnetoresistance sensor (20), a second magnetoresistance sensor (21), a third magnetoresistance sensor (22), a first plane (23), a second plane (24) and a pipeline three-axis stress internal detection circuit based on tunnel magnetoresistance as claimed in any one of claims 1 to 9, wherein the first plane (23) and the second plane (24) are perpendicular to each other, the first magnetoresistance sensor (20) is arranged on the first plane (23) and is perpendicular to the intersection line of the first plane (23) and the second plane (24), the second magnetoresistance sensor (21) is arranged on the second plane (24) and is perpendicular to the intersection line of the first plane (23) and the second plane (24), the third magnetoresistance sensor (22) is arranged on the first plane (23) and is perpendicular to the first magnetoresistance sensor (20), and the X-axis tunnel magnetoresistance sensor detection circuit (13), the Y-axis tunnel magnetoresistance sensor detection circuit (14) and the Z-axis tunnel magnetoresistance sensor detection circuit (15) are respectively connected to the first magnetoresistance sensor (20), the second magnetoresistance sensor (21) and the third magnetoresistance sensor (22).

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