Eddy current sensor response bandwidth testing device and method

Abstract

The invention discloses a device and method for testing the response bandwidth of an eddy current sensor. The device comprises a response bandwidth testing module, an eddy current sensor, a sensor driving and conditioning module, a power module, a signal generating module, and an output signal display module; the response bandwidth testing module consists of an analog switch, a coil frame and a metal coil, the metal coil is wound on the coil frame, and both ends of the metal coil are respectively connected to the analog switch; one end of the response bandwidth testing module is respectively connected to the power module and the signal generating module, wherein the power module is used to supply power to the response bandwidth testing module, and the signal generating module is used to provide a stable square wave signal to the response bandwidth testing module; the other end of the response bandwidth testing module is sequentially connected to the eddy current sensor, the sensor driving and conditioning module, and the output signal display module.

Description

Technical Field

[0001] The present invention relates to the field of sensor performance testing, and in particular to a device and method for testing the response bandwidth of an eddy current sensor. Background Art

[0002] Eddy current sensor is a sensor based on the principle of eddy current effect. It has the advantages of small size, compact and sturdy structure, corrosion resistance, moisture and heat resistance, good long-term working reliability, wide measurement range, high sensitivity, high resolution, fast response speed, strong anti-interference ability, and no influence from media such as oil pollution. It is increasingly widely used in many fields such as industrial automation, aerospace, military engineering, environmental monitoring, marine monitoring, petrochemical engineering, bioengineering, etc., especially in online status monitoring and fault diagnosis of large rotating machinery.

[0003] Rotating blades are the core working elements of large rotating machinery such as aircraft engines, steam turbines, gas turbines, flue gas turbines, and blowers. Their own working conditions directly determine the operating safety and efficiency of large rotating machinery. Currently, online status monitoring of rotating blades is the most effective means to prevent blade failures. In order to achieve online status monitoring of rotating blades, it is necessary to install a blade tip sensor for online status monitoring of rotating blades on the casing directly opposite the blade disk. When the blade passes the blade tip sensor, a blade tip sensor signal is generated. Subsequently, various blade status parameters such as blade tip clearance and blade tip arrival time can be obtained by analyzing and processing the blade tip sensor signal.

[0004] When the blade sweeps across the eddy current sensor probe, the magnetic field generated by the coil inside the probe will be partially offset by the magnetic field generated by the eddy current of the blade, causing the inductance, impedance and quality factor of the coil to change. This change is related to the geometric dimensions, electrical conductivity and magnetic permeability of the blade, as well as the geometric parameters of the coil, the frequency of the current and the distance between the coil and the blade.

[0005] When the eddy current sensor is used as a blade tip sensor, the blades of different equipment and different levels of blades of the same equipment have different lengths and rotation speeds, so there are different requirements for the response bandwidth of the eddy current sensor. At present, the 3dB response bandwidth is usually used as a test indicator to measure the response bandwidth of the eddy current sensor. b The rise time τ of the blade tip sensor signal r According to f b ≈0.35 / τ r Estimate, where τ r =d s / v,d sis the diameter of the eddy current sensor signal sensing area, and v is the blade tip linear velocity. Taking a steam turbine as an example, the radius of its last blade can reach 2m, and the rotation speed can reach 3000rpm, so its maximum blade tip linear velocity is 628m / s. Suppose the diameter of the eddy current sensor signal sensing area d is s is 5mm, then the 3dB response bandwidth of the eddy current sensor is f b Need to satisfy f b ≥230kHz. If the 3dB response bandwidth of the eddy current sensor is lower than the minimum required response bandwidth, when the blade rotates too fast, the blade tip sensing signal obtained will be distorted, which will affect the accuracy of the blade state parameter measurement and seriously affect the real-time monitoring of the blade state parameters.

[0006] However, since the mechanical simulated rotating test bench is difficult to reach the actual rotational speed frequency of large rotating machinery, it is difficult to test the response bandwidth of the eddy current sensor directly using the simulated turntable. In addition, the rotating blades vibrate when running at high speed, which will affect the quantitative test of the response bandwidth of the eddy current sensor. There is currently no quantitative test method for the response bandwidth of eddy current sensors. Therefore, it is an urgent problem to develop an eddy current response bandwidth test module with adjustable frequency and stable inductance modulation, simulate the inductance change of the eddy current sensor coil, replace the conductor to be tested, realize the test of the response bandwidth of the eddy current sensor, and obtain the 3dB response bandwidth range of the eddy current sensor. Summary of the invention

[0007] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an eddy current sensor response bandwidth test device and method, which utilizes a response bandwidth test module to generate an inductance modulation signal, changes the inductance modulation frequency through a signal generation module, and utilizes an output signal display module to detect the response of the eddy current sensor at different frequencies, thereby realizing the response bandwidth test of the eddy current sensor. The device and method can measure the 3dB response bandwidth of the eddy current sensor simply, quickly, intuitively, in real time, stably, and accurately, and can be used to determine the limit response speed of the eddy current sensor during the blade state parameter monitoring process, so as to avoid the sensor from working in a measurement environment that exceeds the limit response speed, thereby affecting the accuracy of the blade state parameter measurement.

[0008] The objective of the present invention is achieved through the following technical solutions:

[0009] An eddy current sensor response bandwidth test device comprises a response bandwidth test module, an eddy current sensor, a sensor drive and conditioning module, a power module, a signal generation module, and an output signal display module; the response bandwidth test module is composed of an analog switch, a coil frame and a metal coil, the metal coil is wound on the coil frame, and both ends of the metal coil are respectively connected to the analog switch;

[0010] One end of the response bandwidth test module is connected to the power supply module and the signal generating module respectively, wherein the power supply module is used to supply power to the response bandwidth test module, and the signal generating module is used to provide a stable square wave signal to the response bandwidth test module; the other end of the response bandwidth test module is connected to the eddy current sensor, the sensor driving and conditioning module, and the output signal display module in sequence; the eddy current sensor can generate inductance changes with the same frequency as the metal coil, and the sensor driving and conditioning module is used to drive the eddy current sensor and process the output signal; the output signal display module is used to display the real-time changes of the output signal of the eddy current sensor.

[0011] Furthermore, under the stimulation of the power module and the signal generating module, the analog switch produces on-off changes, causing the metal coil to produce inductance changes due to the magnetic effect of the current. The magnitude of the inductance change is controllable and is determined by the wire diameter, number of turns and coil frame size of the metal coil. The end face of the coil frame is in close contact with the end face of the eddy current sensor probe to ensure the stability of the inductance change received by the eddy current sensor. When the metal coil produces an inductance change, the alternating magnetic field of the eddy current sensor is modulated by the inductance change generated by the metal coil, generating an inductance change with the same frequency as the metal coil.

[0012] Furthermore, the signal generating module is any one of a signal generator, a function generator, a pulse generator, and an arbitrary waveform generator; and the output signal display module is any one of an oscilloscope, a waveform recorder, and a spectrum analyzer.

[0013] The present invention also provides a testing method based on the eddy current sensor response bandwidth testing device, comprising:

[0014] S1. Apply a test excitation signal; turn on the power module, signal generating module and output signal display module, adjust the power module to the analog switch operating voltage, set the input waveform type of the signal generating module to a square wave, set the peak-to-peak value of the signal generating module, and ensure that the output signal of the output signal display module is not saturated;

[0015] S2. Determine the center frequency f c ; Increase the input frequency of the signal generating module from 0, observe the output signal of the output signal display module, and record the input frequency of the signal generating module when the output signal amplitude is the largest. The input frequency of the signal generating module at this time is recorded as the center frequency f of the eddy current sensor. c , record the peak-to-peak value of the output signal of the output signal display module at this time as A;

[0016] S3. Perform response bandwidth test; adjust the signal generating module, increase the input frequency of the signal generating module from 0Hz, record the frequency and peak-to-peak value of the output signal of the output signal display module at each input frequency, and record the peak-to-peak value of the output signal at each input frequency as An , where n corresponds to each input frequency value;

[0017] S4. Determine the upper and lower limits of the 3dB response bandwidth; according to the definition of 3dB response bandwidth, when A n ≥0.707A, the frequency value n is considered to be within the 3dB response bandwidth; the peak-to-peak value A of the output signal at each input frequency recorded in step S3 is n With the center frequency f c Compare the peak-to-peak values ​​of the output signals A one by one; find A n = 0.707A, denoted as f1 and f2, where f1<f c <f2, then f1 and f2 are the upper and lower limits of the 3dB response bandwidth of the eddy current sensor;

[0018] S5. Determine the 3dB response bandwidth value; the upper and lower limits of the 3dB response bandwidth of the eddy current sensor obtained by step S4 are [f1, f2], then the 3dB response bandwidth value is f b =f2-f1.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] (1) The present invention proposes a method for testing the response bandwidth of an eddy current sensor, which can obtain the 3dB response bandwidth of the eddy current sensor, overcomes the limitation that it is difficult to test the response bandwidth of the eddy current sensor using a mechanical simulation turntable, and solves the problem that the existing method cannot quantitatively test the response bandwidth of the eddy current sensor.

[0021] (2) The measurement parameters required for the eddy current sensor response bandwidth test method proposed in the present invention are intuitive and easy to obtain, and no subsequent cumbersome algorithm processing is required. It can realize a fast, real-time and intuitive test of the 3dB response bandwidth of the eddy current sensor.

[0022] (3) The present invention designs a device for testing the response bandwidth of an eddy current sensor. The device has a simple structure, and the measuring instruments used are common and easily available and not easily affected by external interference. The device can realize a simple, stable and accurate test of the 3dB response bandwidth of the eddy current sensor.

[0023] (4) Through the testing device and method described in the present invention, the response bandwidth performance of the eddy current sensor can be effectively tested, and then the limit response speed of the eddy current sensor in the process of measuring the blade state parameters can be determined, so as to avoid the sensor working in a measurement environment that exceeds the limit response speed and affects the accuracy of the blade state parameter measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the testing device of the present invention.

[0025] Figure 2 The figure is a flow chart of the testing method of the present invention.

[0026] Figure 3 This is a diagram of the 3dB response bandwidth.

[0027] Figure numerals: 1-response bandwidth test module, 2-analog switch, 3-coil skeleton, 4-metal coil, 5-eddy current sensor, 6-sensor driving and conditioning module, 7-power supply module, 8-signal generating module, 9-output signal display module. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] The present invention provides a device for testing the response bandwidth of an eddy current sensor. Figure 1 , including a response bandwidth test module 1, an eddy current sensor 5, a sensor drive and conditioning module 6, a power module 7, a signal generation module 8, and an output signal display module 9. The response bandwidth test module 1 is composed of an analog switch 2, a coil skeleton 3, and a metal coil 4. The power module 7 can be a voltage-stabilized power supply, a battery, a switching power supply, etc., the signal generation module 8 can be a signal generator, a function generator, a pulse generator, an arbitrary waveform generator, etc., and the output signal display module 9 can be an oscilloscope, a waveform recorder, a spectrum analyzer, etc.

[0030] The response bandwidth test module 1 is connected to the power module 7 and the signal generating module 8 respectively, wherein the power module 7 is used to supply power to the response bandwidth test module 1, and the signal generating module 8 is used to provide a stable square wave signal to the response bandwidth test module 1. In the response bandwidth test module 1, the metal coil 4 is wound on the coil skeleton 3 and connected to the analog switch 2. Under the excitation of the power module 7 and the signal generating module 8, the analog switch 2 produces an on-off change, causing the metal coil 4 to produce an inductance change due to the magnetic effect of the current. The magnitude of the inductance change is controllable and is determined by the wire diameter, number of turns, and size of the coil skeleton. The end face of the coil skeleton 3 is in close contact with the end face of the probe of the eddy current sensor 5 to ensure the stability of the inductance change received by the eddy current sensor. When the metal coil 4 produces an inductance change, it can be known from the working principle of the eddy current sensor that the alternating magnetic field of the eddy current sensor 5 will be modulated by the inductance change generated by the metal coil 4, and an inductance change with the same frequency as the metal coil 4 will be produced. The sensor driving and conditioning module 6 is connected to the eddy current sensor 5, and is used to apply drive to the eddy current sensor 5 and process the output signal. The output signal display module 9 is connected to the sensor driving and conditioning module 6 to display the real-time changes of the output signal of the eddy current sensor 5. The specific steps of the eddy current sensor response bandwidth test method are as follows, and the flow chart is as follows: Figure 2As shown:

[0031] (1) Build the test equipment

[0032] The response bandwidth test module 1 is connected to the power supply module 7 and the signal generating module 8, the eddy current sensor 5 is connected to the sensor driving and conditioning module 6, the sensor driving and conditioning module 6 is connected to the output signal display module 9, and the end face of the coil skeleton 3 of the response bandwidth test module 1 is in close contact with the end face of the probe of the eddy current sensor 5.

[0033] (2) Apply test excitation signal

[0034] Turn on the power module 7, the signal generating module 8 and the output signal display module 9, adjust the power module 7 to the working voltage of the analog switch 1, set the input waveform type of the signal generating module 8 to a square wave, set the peak-to-peak value of the signal generating module 8, and ensure that the output signal of the output signal display module 9 is not saturated.

[0035] (3) Determine the center frequency f c

[0036] Increase the input frequency of the signal generating module 8 from 0, observe the output signal of the output signal display module 9, and record the input frequency of the signal generating module 8 when the output signal amplitude is the largest. The input frequency of the signal generating module 8 at this time is recorded as the center frequency f of the eddy current sensor 5. c , record the peak-to-peak value of the output signal of the output signal display module 9 as A.

[0037] (4) Perform response bandwidth test

[0038] Adjust the signal generating module 8, increase the input frequency of the signal generating module 8 from 0 Hz, record the frequency and peak-to-peak value of the output signal of the output signal display module 9 at each input frequency, and record the peak-to-peak value of the output signal at each input frequency as A n , where n corresponds to each input frequency value.

[0039] (5) Determine the upper and lower limits of the 3dB response bandwidth

[0040] like Figure 3 As shown, according to the 3dB response bandwidth definition, when A n ≥0.707A, the frequency value n is considered to be within the 3dB response bandwidth. The peak-to-peak value A of the output signal at each input frequency recorded in step (4) is n With the center frequency f c By comparing the peak-to-peak value A of the output signal one by one, we can find A n = 0.707A, denoted as f1 and f2, where f1<f c<f2, then f1 and f2 are the upper and lower limits of the 3dB response bandwidth of the eddy current sensor.

[0041] (6) Determine the 3dB response bandwidth value

[0042] The upper and lower limits of the 3dB response bandwidth of the eddy current sensor obtained by step (5) are [f1, f2], so the 3dB response bandwidth value is f b =f2-f1.

[0043] Finally, it should be pointed out that the above examples are only used to illustrate the calculation process of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above examples, a person skilled in the art should understand that the calculation process described in the above examples can still be modified, or some parameters can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding calculation method deviate from the spirit and scope of the calculation method of the present invention.

[0044] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solution of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, a person of ordinary skill in the art can also make many forms of specific changes under the guidance of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. An eddy current sensor response bandwidth test device, characterized in that: It includes a response bandwidth test module, an eddy current sensor, a sensor drive and conditioning module, a power module, a signal generation module, and an output signal display module; the response bandwidth test module is composed of an analog switch, a coil frame, and a metal coil, the metal coil is wound on the coil frame, and both ends of the metal coil are respectively connected to the analog switch; One end of the response bandwidth test module is connected to the power supply module and the signal generating module respectively, wherein the power supply module is used to supply power to the response bandwidth test module, and the signal generating module is used to provide a stable square wave signal to the response bandwidth test module; the other end of the response bandwidth test module is connected to the eddy current sensor, the sensor driving and conditioning module, and the output signal display module in sequence; the eddy current sensor can generate inductance changes with the same frequency as the metal coil, and the sensor driving and conditioning module is used to drive the eddy current sensor and process the output signal; the output signal display module is used to display the real-time changes of the output signal of the eddy current sensor.

2. The eddy current sensor response bandwidth test device according to claim 1, characterized in that: Under the stimulation of the power module and the signal generating module, the analog switch produces on-off changes, causing the metal coil to produce inductance changes due to the magnetic effect of the current. The magnitude of the inductance change is controllable and is determined by the wire diameter, number of turns and size of the coil skeleton of the metal coil. The end face of the coil skeleton is in close contact with the end face of the eddy current sensor probe to ensure the stability of the inductance change received by the eddy current sensor. When the metal coil produces an inductance change, the alternating magnetic field of the eddy current sensor is modulated by the inductance change generated by the metal coil, producing an inductance change with the same frequency as the metal coil.

3. The eddy current sensor response bandwidth test device according to claim 1, characterized in that: The signal generating module is any one of a signal generator, a function generator, a pulse generator, and an arbitrary waveform generator; the output signal display module is any one of an oscilloscope, a waveform recorder, and a spectrum analyzer.

4. A testing method based on the eddy current sensor response bandwidth testing device according to claim 1, characterized in that: include: S1. Apply a test excitation signal; Turn on the power module, signal generation module and output signal display module, adjust the power module to the analog switch working voltage, set the input waveform type of the signal generation module to square wave, set the peak-to-peak value of the signal generation module, and ensure that the output signal of the output signal display module is not saturated; S2. Determine the center frequency f c ; Increase the input frequency of the signal generating module from 0, observe the output signal of the output signal display module, and record the input frequency of the signal generating module when the output signal amplitude is the largest. The input frequency of the signal generating module at this time is recorded as the center frequency f of the eddy current sensor. c , record the peak-to-peak value of the output signal of the output signal display module at this time as A; S3. Perform response bandwidth test; adjust the signal generating module, increase the input frequency of the signal generating module from 0Hz, record the frequency and peak-to-peak value of the output signal of the output signal display module at each input frequency, and record the peak-to-peak value of the output signal at each input frequency as A n , where n corresponds to each input frequency value; S4. Determine the upper and lower limits of the 3dB response bandwidth; according to the definition of 3dB response bandwidth, when A n ≥0.707A, the frequency value n is considered to be within the 3dB response bandwidth; the peak-to-peak value A of the output signal at each input frequency recorded in step S3 is n With the center frequency f c Compare the peak-to-peak values ​​of the output signals A one by one; find A n = 0.707A, denoted as f1 and f2, where f1<f c <f2, then f1 and f2 are the upper and lower limits of the 3dB response bandwidth of the eddy current sensor; S5. Determine the 3dB response bandwidth value; the upper and lower limits of the 3dB response bandwidth of the eddy current sensor obtained by step S4 are [f1, f2], then the 3dB response bandwidth value is f b =f2-f1.

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