CN111043946B - Magnetic field interference noise test system for eddy current displacement sensor - Google Patents

Magnetic field interference noise test system for eddy current displacement sensor Download PDF

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CN111043946B
CN111043946B CN202010022211.0A CN202010022211A CN111043946B CN 111043946 B CN111043946 B CN 111043946B CN 202010022211 A CN202010022211 A CN 202010022211A CN 111043946 B CN111043946 B CN 111043946B
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signal
magnetic
interference
eddy current
sensor
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CN111043946A (en
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潘成亮
任淑鹏
杨飞
戴天亮
石超
丰安辉
胡民港
张宵媛
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Hefei University of Technology
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Hefei University of Technology
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00Measuring arrangements characterised by the use of electric or magnetic means
    • G01B7/02Measuring arrangements characterised by the use of electric or magnetic means for measuring length, width or thickness

Abstract

The invention discloses a magnetic field interference noise test system of an eddy current displacement sensor, wherein a reference signal of a signal generator drives an exciting coil to simulate magnetic field interference through a power amplifier, an instrument amplifier is used for extracting voltage signals at two ends of a detection coil, the voltage signals and the reference signal are locked and amplified through a low-pass filter to obtain a magnetic field interference intensity signal, and a displacement signal and the reference signal of a sensor circuit are locked and amplified to obtain a noise level signal of the magnetic field interference. According to the invention, the in-situ measurement of the magnetic field interference strength can be realized without additionally arranging an additional magnetic field sensor, the noise level of the output displacement signal of the eddy current displacement sensor related to the magnetic field interference is obtained, and the system can provide analysis data for the product test of the eddy current displacement sensor for industrial environment and the research and development of a novel strong magnetic field interference resistant eddy current displacement sensor.

Description

Magnetic field interference noise test system for eddy current displacement sensor
The technical field is as follows:
the invention relates to the field of noise analysis of eddy current sensors, in particular to a magnetic field interference noise testing system of an eddy current displacement sensor.
Background art:
along with the development of ultra-precision manufacturing technology, the performance requirements on instruments and meters in the processes of processing, assembling, detecting and the like are higher and higher, the precision of displacement measurement is improved from micron level to nanometer level, and the eddy current displacement sensor is widely applied to the industrial field of equipment manufacturing due to the advantages of high sensitivity, non-contact measurement, high response speed, no influence of oil-water media and the like. The basic principle of the eddy current displacement sensor is electromagnetic induction, that is, the eddy current characteristic formed on the surface of a target conductor by a high-frequency magnetic field generated by a detection coil is utilized to realize micro-displacement measurement, so that magnetic field interference widely existing in an industrial environment can be coupled to the detection coil, the noise level of an output displacement signal is further increased, and the measurement accuracy of the sensor is reduced.
At present, the eddy current displacement sensor mainly adopts an electromagnetic shielding measure to avoid the influence of external magnetic field interference, and patent applications CN104729544A, CN109668504A and the like also propose to improve the capability of resisting strong magnetic field interference through probe and circuit design. However, currently, there is no matched test system for performing comprehensive and quantitative test analysis on the influence of magnetic field interference on the displacement signal output by the eddy current displacement sensor.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a magnetic field interference noise testing system of an eddy current displacement sensor, which adopts a simple, low-cost and high-efficiency testing mode to realize high-precision testing of the magnetic field interference on the noise correlation of the displacement signal output by the eddy current displacement sensor, thereby providing analysis data for the product testing of the eddy current displacement sensor in industrial environment and the research and development of a novel strong magnetic field interference resistant eddy current displacement sensor.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a magnetic field interference noise test system of an eddy current displacement sensor comprises a signal generator, a power amplifier, an exciting coil, a sensor probe, a detecting coil, a target conductor, a coaxial cable, a sensor circuit, an instrument amplifier, a low-pass filter, a lock-in amplifier A, a lock-in amplifier B and a computer;
the signal generator outputs a reference signal, and the exciting coil is driven by the power amplifier to generate simulated magnetic field interference;
the sensor probe penetrates through the exciting coil and is coaxially fixed with the exciting coil, a detection coil is arranged on the upper end face of the sensor probe, the detection coil is parallel to the exciting coil, a target conductor is arranged on the upper portion of the detection coil in parallel, and a lead of the detection coil is connected with a sensor circuit through a coaxial cable to output a displacement signal;
voltage signals at two ends of the detection coil are connected with an instrument amplifier through a coaxial cable, input into a locking amplifier A after passing through a low-pass filter, and are locked and amplified with a reference signal to output a magnetic field interference intensity signal;
the displacement signal of the sensor circuit is locked and amplified with a reference signal through a lock-in amplifier B, and a noise level signal of magnetic field interference is output;
and the reference signal, the displacement signal, the magnetic field interference intensity signal and the noise level signal are subjected to data acquisition and processing by a computer.
The further technology of the invention is as follows:
the reference signal output by the signal generator is a single-frequency sine wave signal, and the frequency of the reference signal is lower than the working frequency of the eddy current displacement sensor.
The signal generator changes the frequency and the amplitude of the reference signal, so that the relevant noise level of the displacement signal of the eddy current displacement sensor under the interference of magnetic fields with different frequencies and different strengths is tested.
In the invention, the detection coil of the eddy current displacement sensor is used for measuring displacement and magnetic field interference. After the detection coil is calibrated by a standard magnetic field, the in-situ measurement of the external magnetic field intensity at the detection coil position can be realized; the voltage signals at two ends of the detection coil are extracted by using the instrument amplifier, and the instrument amplifier has extremely high input impedance, so that the measurement of the magnetic field interference cannot influence the measurement of the eddy current displacement sensor.
In the invention, the lock-in amplifier is adopted to directly obtain the signal components related to the reference signal frequency of the signal regenerator, thereby eliminating the influence of other irrelevant interferences and noises and improving the accuracy of the test. Voltage signals at two ends of the detection coil contain magnetic field interference voltage, and after low-pass filtering, the voltage signals are locked and amplified by using a locking amplifier A and a reference signal, so that the magnetic field interference intensity under the frequency of the reference signal can be directly obtained; the displacement signal output by the sensor circuit contains magnetic field interference noise, and the noise level of the magnetic field interference can be directly obtained by utilizing the locking amplifier B to carry out locking amplification with the reference signal.
Compared with the prior art, the invention has the advantages that:
the invention can realize the in-situ measurement of the magnetic field interference intensity without additionally arranging an additional magnetic field sensor, thereby reducing the complexity of the system and improving the test precision;
2 the invention adopts the lock-in amplifier to directly obtain the magnetic field interference intensity of single frequency and the noise level of the displacement signal, and combines with computer equipment, thus realizing the rapid measurement and analysis of the noise level related to the displacement signal of the eddy current displacement sensor under the magnetic field interference of different frequencies and different intensities.
Description of the drawings:
in order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts;
FIG. 1 is a schematic diagram of a test system of the present invention;
FIG. 2 is a diagram showing voltage signals at two ends of a detection coil without magnetic field interference according to the present invention;
FIG. 3 is a graph of voltage signals across a detection coil in the presence of magnetic field interference in accordance with the present invention;
FIG. 4 is a diagram showing the noise of the displacement signal without magnetic field interference according to the present invention;
FIG. 5 is a diagram illustrating the noise of displacement signals under magnetic field interference according to the present invention.
The specific implementation structure is as follows:
the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
As shown in fig. 1, a system for testing magnetic field interference noise of an eddy current displacement sensor comprises a signal generator, a power amplifier, an exciting coil 1, a sensor probe 2, a detecting coil 3, a target conductor 4, a coaxial cable 5, a sensor circuit, an instrument amplifier, a low-pass filter, a lock-in amplifier a, a lock-in amplifier B and a computer; the signal generator outputs a reference signal, and the exciting coil 1 is driven by the power amplifier to generate simulated magnetic field interference; the sensor probe 2 penetrates through the exciting coil 1 and is coaxially fixed with the exciting coil 1, a detection coil 3 is arranged on the upper end face of the sensor probe 2, the detection coil 3 is parallel to the exciting coil 1, a target conductor 4 is arranged on the upper portion of the detection coil 3 in parallel, and a lead of the detection coil 3 is connected with a sensor circuit through a coaxial cable 5 to output a displacement signal; signals at two ends of the detection coil 3 are connected with an instrument amplifier through a coaxial cable 5, input into a locking amplifier A after passing through a low-pass filter, and are locked and amplified with a reference signal to output a magnetic field interference intensity signal; the displacement signal of the sensor circuit is locked and amplified with a reference signal through a lock-in amplifier B, and a noise level signal of magnetic field interference is output; and the reference signal, the displacement signal, the magnetic field interference intensity signal and the noise level signal are subjected to data acquisition and processing by a computer.
The reference signal output by the signal generator is a single-frequency sine wave signal, and the frequency of the reference signal is lower than the working frequency of the eddy current displacement sensor.
The signal generator changes the frequency and the amplitude of the reference signal, so that the relevant noise level of the displacement signal of the eddy current displacement sensor under the interference of magnetic fields with different frequencies and different strengths is tested.
The specific working process is as follows:
the basic principle of the eddy current displacement sensor is electromagnetic induction, micro-displacement measurement is realized by using the eddy current characteristic formed on the surface of a target conductor 4 by a high-frequency magnetic field generated by a detection coil 3, namely, the equivalent impedance of the detection coil 3 changes along with the change of the distance between the detection coil 3 and the target conductor 4, and the change of the distance between the detection coil 3 and the target conductor 4 is obtained by detecting the change of the equivalent impedance of the detection coil 3. The detection circuit of the current vortex displacement sensor comprises a modulation and demodulation circuit based on the principles of frequency modulation detection, amplitude modulation detection, phase modulation detection, alternating current bridge method and the like. No matter which eddy current displacement sensor detection circuit is adopted, the detection coil 3 on the upper end face of the sensor probe 2 needs to be connected with the sensor circuit through the coaxial cable 5, high-frequency modulation voltage is applied to the detection coil 3 and is generally larger than 100kHz for generating a high-frequency magnetic field, the equivalent impedance of the detection coil 3 is changed by eddy current formed by the high-frequency magnetic field on the surface of the target conductor 4, and when the detection coil 3 approaches the target conductor 4 and enters a measurement range, the sensor circuit demodulates the variation of the equivalent impedance, so that a displacement signal is output.
Under the condition of no magnetic field interference, the voltage signals at the two ends of the detection coil 3 are high-frequency modulation voltages, as shown in fig. 2, if the distance between the detection coil 3 and the target conductor 4 is kept unchanged, the frequency and amplitude of the voltage signals at the two ends of the detection coil 3 are kept unchanged. Under the magnetic field interference, the two ends of the detection coil 3 will generate induced electromotive force due to the electromagnetic induction principle, that is, the voltage signal will superpose the magnetic field interference voltage related to the magnetic field interference on the basis of the high-frequency modulation voltage.
In the present invention, the reference signal output by the signal generator is a single-frequency sine wave signal, the frequency of the reference signal is lower than the operating frequency of the eddy current displacement sensor, the reference signal drives the exciting coil 1 through the power amplifier to generate a simulated magnetic field interference, as shown in fig. 3, the voltage signals at the two ends of the detecting coil 3 will be superimposed with the magnetic field interference voltage of the reference signal frequency on the basis of the high-frequency modulation voltage. The detection coil 3 is connected with an instrument amplifier through a coaxial cable 5, signals extracted by the instrument amplifier comprise high-frequency modulation voltage and magnetic field interference voltage, high-frequency modulation voltage components are filtered out after the signals pass through a low-pass filter, the residual magnetic field interference voltage is input into a locking amplifier A and is locked and amplified with a reference signal, and output signals are direct-current voltage signals related to the strength of the magnetic field interference. The detection coil 3 is calibrated by a standard magnetic field, and the output of the lock-up amplifier A is a magnetic field interference intensity signal.
Under the condition of no magnetic field interference, the displacement signal output by the sensor circuit changes along with the change of the distance between the detection coil 3 and the target conductor 4, as shown in fig. 4, if the distance between the detection coil 3 and the target conductor 4 is kept unchanged, the displacement signal is a direct current voltage signal containing noise, and the main component of the noise is white noise in the measurement bandwidth of the sensor. In the present invention, a single-frequency sine wave signal is used to generate a simulated magnetic field interference, and a voltage signal at both ends of the detection coil 3 is superimposed with a magnetic field interference voltage at a reference signal frequency on the basis of a high-frequency modulation voltage, as shown in fig. 5, noise of a displacement signal output by the sensor circuit is also superimposed with a magnetic field interference noise at the reference signal frequency on the basis of white noise. The displacement signal of the sensor circuit is locked and amplified with the reference signal through the lock-in amplifier B, and then the output signal is a direct current voltage signal related to the magnetic field interference noise, namely a noise level signal of the magnetic field interference.
Through the process, the reference signal, the displacement signal, the magnetic field interference strength signal and the noise level signal are subjected to data acquisition and processing by a computer, and the noise level of the magnetic field interference of the eddy current displacement sensor under the magnetic field interference of certain frequency and strength can be obtained. The frequency and the amplitude of the reference signal are changed by utilizing the computer to control the signal generator, and the reference signal, the displacement signal, the magnetic field interference intensity signal and the noise level signal are synchronously acquired, so that the related noise level of the displacement signal of the eddy current displacement sensor under the magnetic field interference of different frequencies and different intensities is obtained, and the analysis data is provided for the product test of the eddy current displacement sensor for industrial environment and the research and development of a novel strong magnetic field interference resistant eddy current displacement sensor.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (3)

1. The utility model provides an electric eddy current displacement sensor magnetic field interference noise test system which characterized in that: the device comprises a signal generator, a power amplifier, an exciting coil, a sensor probe, a detecting coil, a target conductor, a coaxial cable, a sensor circuit, an instrument amplifier, a low-pass filter, a lock-in amplifier A, a lock-in amplifier B and a computer;
the signal generator outputs a reference signal, and the exciting coil is driven by the power amplifier to generate simulated magnetic field interference;
the sensor probe penetrates through the exciting coil and is coaxially fixed with the exciting coil, a detection coil is arranged on the upper end face of the sensor probe, the detection coil is parallel to the exciting coil, a target conductor is arranged on the upper portion of the detection coil in parallel, and a lead of the detection coil is connected with a sensor circuit through a coaxial cable to output a displacement signal;
voltage signals at two ends of the detection coil are connected with an instrument amplifier through a coaxial cable, input into a locking amplifier A after passing through a low-pass filter, and are locked and amplified with a reference signal to output a magnetic field interference intensity signal;
the displacement signal of the sensor circuit is locked and amplified with a reference signal through a lock-in amplifier B, and a noise level signal of magnetic field interference is output;
and the reference signal, the displacement signal, the magnetic field interference intensity signal and the noise level signal are subjected to data acquisition and processing by a computer.
2. The system of claim 1, wherein the eddy current displacement sensor magnetic field interference noise test system comprises: the reference signal output by the signal generator is a single-frequency sine wave signal, and the frequency of the reference signal is lower than the working frequency of the eddy current displacement sensor.
3. The system of claim 1, wherein the eddy current displacement sensor magnetic field interference noise test system comprises: the signal generator changes the frequency and the amplitude of the reference signal, so that the relevant noise level of the displacement signal of the eddy current displacement sensor under the interference of magnetic fields with different frequencies and different strengths is tested.
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CN112179259A (en) * 2020-09-21 2021-01-05 合肥工业大学 Method for eliminating interference magnetic field noise of eddy current displacement sensor

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