CN217404208U

CN217404208U - Electric eddy current sensor circuit for in-pipeline detection

Info

Publication number: CN217404208U
Application number: CN202123331352.XU
Authority: CN
Inventors: 熊鑫; 郑莉; 李志华; 张广宇
Original assignee: Beijing Huahang Radio Measurement Research Institute
Current assignee: Beijing Huahang Radio Measurement Research Institute
Priority date: 2021-12-27
Filing date: 2021-12-27
Publication date: 2022-09-09
Anticipated expiration: 2031-12-27

Abstract

The utility model discloses an electric eddy current sensor circuit for detecting in a pipeline, which comprises an eddy current excitation circuit and a signal conditioning circuit; in the eddy current excitation circuit, an eddy current coil L is connected with a capacitor C in parallel and then is connected with a resistor R in series, and alternating current voltage with fixed amplitude and frequency f is applied; the signal conditioning circuit translates the eddy current excitation circuit high frequency ac signal IDOD1 to a lower frequency for sampling at a lower sampling frequency. The utility model discloses a can with pipeline magnetic leakage in check out test set's magnetic leakage sensor circuit integrated to a module in, only need a set of sensor probe, for two sets of sensor probe schemes, the length of equipment is shorter. The utility model discloses each passageway eddy current testing sensor only needs a coil, only needs to sample a voltage signal with lower frequency, need not to carry out digital signal processing, simple structure, easily integration after the sampling.

Description

Electric eddy current sensor circuit for in-pipeline detection

Technical Field

The utility model relates to a detect technical field in the pipeline, especially relate to an electric eddy current sensor circuit is used in detecting in pipeline.

Background

The CN107388048A pipeline magnetic leakage internal detection internal and external wall defect distinguishing sensor and the identification evaluation method adopt a Hall sensor and an eddy current sensor to distinguish internal and external defects, the method only needs one group of sensor probes, an eddy current signal processing circuit of the sensor probes comprises an electric bridge, a first-stage amplifying circuit, a phase sensitive detection circuit, a second-stage amplifying circuit and an analog-digital acquisition circuit which are sequentially connected in series, wherein the phase sensitive detection circuit is used for converting detected defect signals into amplitude signals, and in addition, an excitation frequency circuit is arranged, and the excitation frequency is 20 kHz-800 kHz; however, the scheme does not disclose specific parameters and specific implementation methods of an electric bridge, a primary amplification circuit, a phase-sensitive detection circuit, a secondary amplification circuit, an analog-digital acquisition circuit and an excitation frequency circuit, and the circuit is complex and is inconvenient to integrate.

CN110108788A is based on the pipeline magnetic leakage internal detection integrated probe and the detection method of the pulse eddy current, adopt the method that the pulse eddy current test unit combines with three-dimensional magnetic leakage test unit to distinguish the inner and outer wall defect, this method only needs a set of sensor probe, but need at least two sets of coils of measuring coil and measuring coil, and need to sample the differential voltage and the electric current of two sets of coils 3 at least signals, then carry out the comprehensive analysis and calculation, need to gather and handle a plurality of signals with higher sampling frequency, the structure is more complicated, it is not convenient for the integration.

SUMMERY OF THE UTILITY MODEL

The utility model provides an it uses eddy current sensor circuit to detect in pipeline for detect in the pipeline magnetic leakage and assist the position of distinguishing the defect in the pipeline, outer wall, and mechanical arm type pipeline geometric deformation interior check out test set's detection error compensation, simple structure, easily integration.

The technical scheme of the utility model:

an eddy current sensor circuit for in-pipeline detection comprises an eddy current excitation circuit and a signal conditioning circuit;

in the eddy current excitation circuit, an eddy current coil L is connected with a capacitor C in parallel and then is connected with a resistor R in series, and alternating current voltage with fixed amplitude and frequency f is applied;

the signal conditioning circuit shifts the eddy current exciter high frequency ac signal IDOD1 to a lower frequency for sampling at a lower sampling frequency.

Further, the eddy current coil L is an I-shaped inductance coil, the magnetic core is made of ferrite, and the winding wire is an enameled wire; and (4) packaging by adopting a non-ferromagnetic metal shell.

Further, the inductance value of the inductance coil is not less than 1 mH; the shell packaging material is selected from non-magnetic metal materials such as 316 stainless steel or titanium alloy, and the thickness of the shell packaging material is not more than 1.5 mm.

Further, the values of the eddy current coil L, the capacitor C and the frequency f satisfy:

further, the frequency f is not less than 30 kHz.

Furthermore, a sine wave generating circuit consisting of an integrated function signal chip MAX038 applies an alternating voltage with a fixed amplitude and frequency f.

Furthermore, the signal conditioning circuit comprises a circuit for converting alternating current signals into direct current signals and a signal amplifying circuit; the circuit for converting the alternating current signal into the direct current signal adopts an AD637 chip, and the signal amplifying circuit adopts an LMV324 amplifier chip.

Furthermore, the eddy current excitation circuit, the signal conditioning circuit and a magnetic leakage sensor circuit of the pipeline magnetic leakage internal detection device are integrated into a sensor probe module or a mechanical arm type detection module of the mechanical arm type pipeline geometric deformation internal detection device.

The utility model has the advantages that:

(1) the utility model discloses a technical scheme eddy current sensor circuit can with pipeline magnetic leakage in check out test set's magnetic leakage sensor circuit integrated to a module in, only need a set of sensor probe, for two sets of sensor probe schemes, the length of equipment is shorter. CN109900783A A recognition method for detecting defects of inner and outer walls in oil and gas pipeline magnetic leakage, the method of combining an internal magnetic leakage detection system and a weak magnetic detection system is adopted to distinguish the defects of the inner and outer walls, the internal magnetic leakage detection system and the weak magnetic detection system are separated, two groups of sensor probes are needed, and the whole length of the system is longer.

(2) The utility model discloses a technical scheme each passageway eddy current inspection sensor only need a coil, only need to sample a voltage signal with lower frequency (being far below frequency f), need not to carry out digital signal processing after the sampling, simple structure, easily integration, can integrate the eddy current inspection sensor circuit of more passageways as required to improve the accuracy and the resolution ratio that detect. CN110108788A pipeline magnetic leakage internal detection integrated probe and detection method based on pulse eddy current, each channel pulse eddy current detection in the technical scheme needs at least two sets of (two) coils, needs to gather two coil currents, two coil voltage difference 3 signals, needs to carry out data signal processing operation after the sampling, and sampling and processing speed is higher (higher than frequency f), and the structure is relatively complicated.

Drawings

FIG. 1 vortex excitation principle;

FIG. 2 is an eddy current excitation circuit;

fig. 3AD637 virtual value-to-dc conversion;

FIG. 4 is a signal amplification circuit;

FIG. 5 is a schematic block diagram of an eddy current test sensor circuit;

FIG. 6 is a circuit diagram of an eddy current test sensor.

Detailed Description

The utility model discloses the eddy current sensor circuit includes vortex excitation circuit and signal conditioning circuit, and the following vortex detection eddy current inspection sensor technical scheme carries out the detailed description.

1. Eddy current exciting circuit

As shown in fig. 1, an eddy current inductor L is connected in parallel with a capacitor C and then connected in series with a resistor R, and an ac voltage of a fixed amplitude and frequency f is applied.

When it satisfies

When the coil L resonates with the capacitor C, the impedance is minimum after L, C are connected in parallel, and the voltage U at two ends of the resistor R _R Therefore, the values of f, L and C satisfy the formula (1), and a good detection effect can be ensured.

The eddy current has a skin effect and the depth at which the eddy current density decays to its surface value of 1/e is called the standard penetration depth, denoted by the symbol δ in m (meters) and is calculated as follows:

wherein f is the frequency of eddy current (excitation signal frequency), mu is the magnetic conductivity of the conductor, and sigma is the electrical conductivity of the conductor material, for the actually detected pipelines, the materials are different, the thicknesses are different, and the proper excitation source frequency f is selected, so that the penetration depth is smaller than the wall thickness of the pipeline, and the frequency f is selected to be as high as possible. However, too high a frequency reduces the skin depth, which reduces the accuracy and the noise immunity, so that the frequency f should be selected in an appropriate range according to experiments. The experiment shows that the vortex penetration depth of the conventional pipe is about 3mm when the frequency is about 32kHz, and the vortex penetration depth is suitable for the conventional steel pipe with the wall thickness larger than 6 mm.

As shown in fig. 2, the ac excitation circuit is a sine wave generating circuit composed of an integrated function signal chip MAX038, and has stable output waveform, adjustable frequency, simple structure and small volume. A +5V, A-5V, AGND are respectively a power supply signal and a power ground signal of +/-5V; the PC22 values selected for different sinusoidal signal frequencies are also different, using a capacitance value of 1nF around 32 kHz; a 50 ohm resistor is added to the 19 pin output of the MAX038 circuit to prevent output short circuit and overlarge current; adjusting the resistance value between 1 and 10 pins of the MAX038 can play a role in adjusting the frequency, three resistors PR 11-PR 13 are reserved between the 1 and 10 pins in the scheme, and as the adjustment of the frequency, PR11 corresponding to the frequency 32kHz is 100k Ω, PR12 is 62k Ω, and PR13 is 0 Ω; the SINE-WAVE signal is an alternating current excitation signal, the eddy current coil is connected between IDODSig _1A and IDODSig _1B signal nodes, and the IDOD1 is a signal of original eddy current detection; AC12 is calculated according to equation (1) taking f-32 kHz and L-1.1 mH, resulting in AC 12-22 nF.

The eddy current coil adopts an I-shaped inductance coil, the inductance value is 1.1mH, the magnetic core material is ferrite with the diameter of 1.5mm, the winding adopts an enameled wire, the width of the winding is 2mm, the wire diameter is 0.06mm, and the number of turns is 2000. In actual use, the inductor coil can be protected only by the encapsulation of the shell. The non-ferromagnetic metal shell is adopted for packaging, the influence on eddy current detection is small, and on the premise of meeting the strength of the shell, the thinner the shell, the higher the sensitivity of the detector is, and the better the detection effect is. According to experimental experience, the shell packaging material is selected from non-magnetic metal materials such as 316 stainless steel or titanium alloy, and the thickness is not more than 1.5 mm.

2. Signal conditioning circuit

In fig. 2, the original eddy current detection signal IDOD1 is a high-frequency ac signal, and in order to reduce the difficulty of signal sampling and analysis, a signal conditioning circuit is required to process the signal IDOD1 so as to perform sampling at a lower sampling frequency.

(1) Circuit for converting alternating current signal into direct current signal

The effective value of the sine wave alternating current signal is 0.707 times of the maximum value of the sine wave alternating current signal, so that the effective value can represent the maximum value, and the signal processing circuit converts the alternating current signal into an effective value direct current signal in the first step, namely RMS-to-DC conversion, and is realized by AD 637; as shown in FIG. 3, A +5V, A-5V, AGND are the power supply and power ground signals of + -5V, respectively; the capacity value of C02 influences the speed of effective value conversion and the steady-state error, C02-0.01 uF is selected, the response time is 0.25ms according to an AD637 data manual, and the steady-state error is only 0.8% of the peak value; IDOD1 is the original eddy current test AC signal input, and IDOD _1 is the effective value DC voltage output.

(2) Signal amplifying circuit

The circuit for converting the ac signal into the dc signal outputs IDOD _1, which has less variation when defective and needs further amplification for detection and discrimination, uses an LMV324 amplifier chip for amplification, as shown in fig. 4. A +5V, AGND is +5V power supply and power ground signal respectively; the LMV324 is configured as a difference value amplifying circuit, and IDOD _1 is input to a positive phase input end of the amplifying circuit; the reference voltage offset _1 is generated by dividing AR11, AR18, AR12 and AR19 and is connected to the inverting input end of the amplifying circuit; the voltage difference between IDOD _1 and offset _1 is amplified to finally output IDODSig _1 to the acquisition circuit. And adjusting the resistance values of AR11, AR18, AR12 and AR19 and the resistance values of AR15, AR13, AR10 and AR17 according to the analog signal input range of the acquisition circuit and the expected defect signal variation. The tests show that AR11 is 12k Ω, AR18 is 9.1k Ω, AR12 is 1k Ω, AR191k Ω, AR15 is 100k Ω, AR13 is AR10 is 1k Ω, and IDODSig _1 is between 1.5V and 3.0V.

To sum up, the general schematic block diagram and schematic diagram of the eddy current inspection sensor circuit are respectively shown in fig. 5 and fig. 6, a +5V, A-5V, AGND are ± 5V power supply and power ground signals, an eddy current coil is connected between signal nodes of the IDODSig _1A and the IDODSig _1B, the IDODSig _1 is an eddy current signal which is conditioned and finally enters the acquisition circuit, the signal is an analog signal which changes corresponding to the change of the inner surface profile of the pipe wall, and the frequency of the analog signal is independent of the excitation frequency, so that sampling can be performed at a sampling frequency far lower than 32kHz, and the eddy current signal of the internal defect can be acquired at a sampling frequency f not less than 2V/l not less than 2kHz if the minimum length l of the internal defect is 5mm and the maximum inspection speed V is 5 m/s.

The scheme is that the eddy current sensor circuit with one channel can be configured with a plurality of eddy current sensor circuits according to requirements in practical application; the eddy current sensor circuit can be integrated into a sensor probe module together with a magnetic flux leakage sensor circuit of the detection equipment in the magnetic flux leakage of the pipeline, and can also be integrated into a mechanical arm type detection module of the detection equipment in the geometric deformation of the mechanical arm type pipeline.

The foregoing description of the preferred embodiments of the invention is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Therefore, the protection scope of the present invention is not limited to these solutions and details, and those skilled in the art can make modifications or equivalent substitutions to these solutions and details without departing from the basic principle of the present invention, and the modified or substituted embodiments will also fall within the protection scope of the present invention.

Claims

1. An eddy current sensor circuit for in-pipeline detection is characterized by comprising an eddy current excitation circuit and a signal conditioning circuit;

in the eddy current exciting circuit, an eddy current coil L is connected with a capacitor C in parallel and then is connected with a resistor R in series, and alternating voltage with fixed amplitude and frequency f is applied;

the signal conditioning circuit translates the eddy current excitation circuit high frequency ac signal IDOD1 to a lower frequency for sampling at a lower sampling frequency.

2. The eddy current sensor circuit for in-pipeline inspection according to claim 1, wherein the eddy current coil L is an i-shaped inductance coil, the magnetic core material is ferrite, and the winding is enameled wire; and (4) packaging by adopting a non-ferromagnetic metal shell.

3. The eddy current sensor circuit for in-pipe inspection as claimed in claim 2, wherein the inductance value of the inductor coil is not less than 1 mH; the shell packaging material is 316 stainless steel or titanium alloy, and the thickness is not more than 1.5 mm.

4. The eddy current sensor circuit for in-pipe inspection according to claim 1, wherein the values of the eddy current coil L, the capacitance C, and the frequency f satisfy:

5. the eddy current sensor circuit for in-pipe inspection as recited in claim 4, wherein the frequency f is not less than 30 kHz.

6. The eddy current sensor circuit for in-pipe inspection as claimed in claim 1, wherein the sine wave generating circuit composed of the integrated function annunciator chip MAX038 applies an ac voltage of fixed amplitude and frequency f.

7. The eddy current sensor circuit for in-pipe inspection according to claim 1, wherein the signal conditioning circuit comprises a circuit for converting an alternating current signal into a direct current signal and a signal amplifying circuit; the circuit for converting the alternating current signal into the direct current signal adopts an AD637 chip, and the signal amplifying circuit adopts an LMV324 amplifier chip.

8. The eddy current sensor circuit for in-pipe inspection as claimed in any one of claims 1 to 7, wherein the eddy current excitation circuit and the signal conditioning circuit are integrated into a sensor probe module with the leakage magnetic sensor circuit of the in-pipe inspection apparatus or into a mechanical arm inspection module of the in-pipe geometric deformation inspection apparatus.