Gap sensor for gap measurement based on eddy current principle

Abstract

The utility model relates to a gap sensor for measuring a gap by using an eddy current principle, which comprises a measuring head and a transmitter, the measuring head is connected to the transmitter through a coaxial cable, the transmitter outputs a measuring signal, the measuring head comprises a measuring main body and a shell wrapping the measuring main body, and the measuring main body is connected with the transmitter through a coaxial cable. A measuring head is installed at the end of the measuring body, an eddy current probe is further installed in a through hole formed in the measuring body, a measured object corresponding to the eddy current probe is installed on the measuring body, a spring is further installed in the middle of the measuring body, and an upper cover and a lower cover are arranged at the upper end and the lower end of the shell respectively. The upper cover and the lower cover are matched with the shell to package the measuring body, the measuring head penetrates out of the upper cover, and a wire outlet nut arranged at the lower end of the measuring body penetrates out of the lower cover and then is connected to a coaxial cable. The change frequency response range of gap measurement based on the eddy current principle is wider, and gap measurement is more reliable.

Description

Technical Field

[0001] The present application relates to the field of gap sensors, and in particular to a gap sensor that uses the eddy current principle to perform gap measurement. Background Art

[0002] Current gap sensors on the market include a measuring head, a transmitter connected to the measuring head, and a shielded cable connecting the measuring head and transmitter. The measuring head includes a housing, a compressible and resilient main body fixed within the housing, and a probe for contacting the object being measured, fixed to the main body and exposed through a hole in the housing. The measuring head also includes an LVDT measurement principle structure (consisting of a primary coil, two secondary coils, a coil bobbin, a housing, and a movable iron core within the coil bobbin). This structure is located within the main body. Although this gap sensor effectively solves the gap measurement problem, it has a low response frequency during dynamic measurements. Furthermore, due to the LVDT principle (a primary coil and two secondary coils are wound around a bobbin. When the iron core moves left and right within the coil, the two secondary coils generate a varying voltage. This varying voltage varies linearly with the displacement of the iron core, thus converting the non-electrical quantity (displacement) into voltage, completing the sensor's function), the production process is complex. The three coils and the iron core must be compressed to their maximum size and then placed within the limited space of the main body, which is not conducive to production debugging and long-range research and development. Therefore, it is urgent to solve the existing problems. Utility Model Content

[0003] The purpose of the embodiments of the present application is to provide a gap sensor that uses the eddy current principle to measure the gap, so as to solve the technical problems of low response frequency and being unfavorable for production debugging and long-range research and development.

[0004] To achieve the above objectives, this application provides the following technical solutions:

[0005] An embodiment of the present application provides a gap sensor that uses the eddy current principle to measure the gap, including a measuring head and a transmitter. The measuring head is connected to the transmitter via a coaxial cable, and the transmitter outputs a measurement signal. The measuring head includes a measuring body and a shell that wraps the measuring body. A probe is installed at the end of the measuring body, and an eddy current probe is also installed in a through hole opened on the measuring body. A measured object corresponding to the eddy current probe is installed on the measuring body, and a spring is also installed in the middle of the measuring body. The gap detected by the probe is measured by the cooperation of the eddy current probe, the measured object and the spring. The upper and lower ends of the shell are respectively provided with an upper cover and a lower cover, and the upper cover and the lower cover cooperate with the shell to encapsulate the measuring body. The probe passes through the upper cover, and the outlet nut provided at the lower end of the measuring body passes through the lower cover and is connected to the coaxial cable.

[0006] A groove for convenient installation of the measuring heads is provided at the end of the measuring body, and the two measuring heads are inserted into the groove and fixed by fixing screws.

[0007] The eddy current probe is covered with a shielding cover, and the eddy current probe and the object to be measured are fixedly installed in a through hole opened on the measuring body through machine screws.

[0008] The spring is installed in a cavity opened in the middle of the measuring body, and the spring is fixed by shielding wire compression nuts and spring adjustment nuts arranged on both sides of the measuring body.

[0009] Mounting holes are provided on both sides of the shell, and adjusting nut seats are installed in the mounting holes. Adjusting nuts are installed in the adjusting nut seats to adjust the probe spacing.

[0010] The lower cover is provided with an elliptical groove and 10 screw holes. The lower cover passes through the outlet nut and is fixed to the front end of the shell by 4 lower cover screws.

[0011] The upper cover is provided with an elliptical hole and four screw holes, and the upper cover passes through the measuring head and is fixed to the housing by four upper cover screws.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] Gap measurement utilizes the principle of eddy currents. When the probe contacts an object with a varying gap, the two probes drive the eddy current probes on their internal bodies and the metal conductor being measured, causing the distance between the probes and the object to change. By varying the distance between the probes and the object, the impedance of the probes varies, resulting in a linear change. The distance is calculated by reading the probe voltage signal. The high-frequency signal driven by the eddy current probe can reach over 1 MHz, while the frequency of the LVDT's primary coil is only 4-5 kHz. After system filtering, the eddy current's frequency response range can reach over 10 kHz, while the LVDT's sampling frequency is only 1 kHz. Therefore, using the eddy current principle to measure gap changes offers a wider frequency response range and more reliable gap measurements.

[0014] The eddy current probe coil has only one set of coils and the coil size can be made extremely small, with low production cost and high efficiency, easy installation and simple debugging, and more advantages in mass production.

[0015] The eddy current principle is used to expand the measuring range. Since it is a single set of coils and has a very small size, it has more advantages when the measuring head is required to be the same size. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present application;

[0018] Figure 2 This is a schematic diagram of the exploded view of the measuring head according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings. It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0020] The terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0021] The purpose of this application is to provide a gap sensor that uses the eddy current principle for gap measurement, addressing technical issues such as low response frequency and inconvenience in production debugging and long-range R&D. The eddy current measurement principle is a type of inductive measurement principle. The eddy current effect originates from the energy of an oscillating circuit. However, the eddy current effect can only occur within metallic conductors. By introducing an alternating current into the coil within the sensor probe, an alternating magnetic field is generated around the probe coil. If a metallic conductor is placed within this magnetic field, eddy currents are generated on the conductor's surface according to Faraday's law of electromagnetic induction. According to Lenz's law, the direction of the eddy current's magnetic field is opposite to the coil's magnetic field, which changes the impedance of the probe coil. This impedance change is directly related to the distance between the coil and the object being measured. After the sensor probe is connected to a transmitter, the transmitter can detect the change in voltage within the sensor probe and use this change to calculate the corresponding distance. The eddy current measurement principle can measure all metallic conductors. Because eddy currents can penetrate insulators, even metallic materials covered with insulating surfaces can serve as test objects for eddy current sensors. The unique coil winding design not only makes the sensor extremely compact, but also meets the requirements of operating in high-temperature measurement environments.

[0022] like Figure 1 and Figure 2 As shown, the embodiment of the present application provides a gap sensor for gap measurement using the eddy current principle, including a measuring head 100 and a transmitter 300. The measuring head 100 is connected to the transmitter 300 via a coaxial cable 200. The transmitter 300 outputs the measurement signal. After the transmitter 300 is powered on, a high-frequency signal is generated to drive the eddy current probe, and the electrical signal fed back by the probe is converted into various output signals we need. The measuring head 100 includes a measuring body 1 and a shell 14 that wraps the measuring body. A probe 2 is installed at the end of the measuring body 1. An eddy current probe 7 is also installed in the through hole opened on the body 1, and a measured object 9 corresponding to the eddy current probe 7 is installed on the measuring body 1. A spring 4 is also installed in the middle of the measuring body 1. The gap detected by the probe 2 is measured by the cooperation of the eddy current probe 7, the measured object 9 and the spring 4. The upper and lower ends of the shell 14 are respectively provided with an upper cover 18 and a lower cover 12. The upper cover 18 and the lower cover 12 cooperate with the shell 14 to encapsulate the measuring body 1. The probe 2 passes through the upper cover 18, and the wire nut 11 set at the lower end of the measuring body 1 passes through the lower cover 12 and is connected to the coaxial cable 200.

[0023] A groove is provided at the end of the measuring body 1 for convenient installation of the measuring heads 2 , and the two measuring heads 2 are inserted into the groove and fixed by fixing screws 3 .

[0024] The eddy current probe 7 is sleeved with a shielding cover 8, and the eddy current probe 7 and the measured object 9 are fixedly installed in the through hole of the measuring main body 1 through the machine screw 10. The eddy current probe is wound with a coil, and a magnetic field is generated after being powered on, so that the distance of the measured object can be measured; the shielding cover shields the interference signal, the eddy current probe is installed in the shielding cover and locked by the machine screw; the measured object induces the magnetic field generated by the eddy current probe and generates a vortex magnetic field on the surface thereof, when the distance between the probe and the measured object is changed, the difference generated by the mutual offset of the two magnetic fields will change with the change of the distance, and the difference is converted into various output signals which change linearly with the distance by the transmitter, and the measured object is installed in the through hole of the main body and fixed by the machine screw.

[0025] The spring 4 is installed in the cavity opened in the middle of the measuring main body 1, the middle part of the measuring main body 1 is hollowed out and cut at the rear end, so that it can be pressed like a spring and restored to the original position, and the spring 4 is fixed through the shielding wire pressing nut 5 and the spring adjusting nut 6 arranged on both sides of the measuring main body 1.

[0026] Both sides of the shell 14 are also provided with mounting holes, and an adjusting nut seat 16 is installed in the mounting hole, and an adjusting nut 17 is installed in the adjusting nut seat 16 for adjusting the distance between the measuring head 2.

[0027] The lower cover 12 is provided with an oval recess and 10 screw holes, the lower cover 12 passes through the wire outlet nut 11 and is fixed at the front end of the shell 14 through four lower cover screws 15, the wire outlet nut protects and fixes the connecting wire between the eddy current probe and the transmitter, and is provided with external threads, and the wire outlet nut is screwed into the thread in the front end of the main body.

[0028] The upper cover 18 is provided with an oval hole and four screw holes, and the upper cover 18 passes through the measuring head 2 and is fixed on the shell through four upper cover screws 19.

[0029] The sensor assembly process of the present application is as follows:

[0030] S1: Assembly of the measuring head 100: First, insert the measuring head 2 into the main body 1 and tighten the two measuring heads with the fixing screws 3. Then, put the spring 4 into the hollow inside the main body 1 and fix it in the center position of the main body 1 with the spring adjustment nut 6 and the shield wire compression nut 5. Secondly, install the eddy current probe into the shielding cover 8 and insert it into the through hole on the left side of the main body 1 and tighten it with the machine screw 10. Insert the object to be measured 9 into the through hole on the right side of the main body 1 and tighten it with the machine screw 10. Then put the lower cover 12 on the front end of the main body 1 and tighten it with the main body fixing screw 13 is locked, and at the same time, the outlet nut is passed through the hole on the lower cover and tightened on the main body 1, and the coaxial cable 22 on the eddy current probe 7 is passed through the outlet nut 11. Finally, the above assembled main body accessories are placed in the shell 14 and the lower cover is fixed with the lower cover fixing screws 15. Then, the adjusting nut seats 16 are respectively installed into the holes on the left and right sides of the shell 14 and the adjusting nuts 17 are respectively inserted. Then, the upper cover 18 is passed through the probe 2 and fits it with the front end of the shell, and the upper cover is locked with the upper cover fixing screws. At this point, the assembly of the measuring head 100 is completed.

[0031] S2: Installing the transmitter 300: Electrically connect the measuring head 100 to the transmitter 300 via the coaxial cable 200. Thus, the installation of the gap sensor is completed.

[0032] Working principle: When the probe 2 contacts the object to be measured with a changing gap, the two probes will drive the eddy current probe 7 and the object to be measured 9 on the internal body 1 to move as the gap changes, so that the distance between the eddy current probe 7 and the object to be measured 9 changes. By changing the distance between the probe 7 and the object to be measured 9, the impedance of the eddy current probe 7 changes, that is, it changes linearly. By reading the voltage signal of the eddy current probe 7, the distance is calculated to achieve the purpose of measuring the gap change between the two probes.

[0033] The above description is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, various modifications and variations of the present application are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A gap sensor for gap measurement using the eddy current principle, characterized in that: It includes a measuring head and a transmitter, which is connected to the transmitter through a coaxial cable. The transmitter outputs a measurement signal. The measuring head includes a measuring body and a shell that wraps the measuring body. A probe is installed at the end of the measuring body. An eddy current probe is also installed in a through hole opened on the measuring body. A measured object corresponding to the eddy current probe is installed on the measuring body. A spring is also installed in the middle of the measuring body. The gap detected by the probe is measured by the cooperation of the eddy current probe, the measured object and the spring. The upper and lower ends of the shell are respectively provided with an upper cover and a lower cover. The upper cover and the lower cover cooperate with the shell to encapsulate the measuring body. The probe passes through the upper cover, and the wire nut provided at the lower end of the measuring body passes through the lower cover and is connected to the coaxial cable.

2. The gap sensor for gap measurement using eddy current principle according to claim 1, characterized in that: A groove for convenient installation of the measuring heads is provided at the end of the measuring body, and the two measuring heads are inserted into the groove and fixed by fixing screws.

3. The gap sensor for gap measurement using eddy current principle according to claim 1, characterized in that: The eddy current probe is covered with a shielding cover, and the eddy current probe and the object to be measured are fixedly installed in a through hole opened on the measuring body through machine screws.

4. The gap sensor for gap measurement using eddy current principle according to claim 1, characterized in that: The spring is installed in a cavity opened in the middle of the measuring body, and the spring is fixed by shielding wire compression nuts and spring adjustment nuts arranged on both sides of the measuring body.

5. The gap sensor for gap measurement using eddy current principle according to claim 1, characterized in that: Mounting holes are provided on both sides of the shell, and adjusting nut seats are installed in the mounting holes. Adjusting nuts are installed in the adjusting nut seats to adjust the probe spacing.

6. The gap sensor for gap measurement using eddy current principle according to claim 1, characterized in that: The lower cover is provided with an elliptical groove and 10 screw holes. The lower cover passes through the outlet nut and is fixed to the front end of the shell by 4 lower cover screws.

7. The gap sensor for gap measurement using eddy current principle according to claim 1, characterized in that: The upper cover is provided with an elliptical hole and four screw holes, and the upper cover passes through the measuring head and is fixed to the housing by four upper cover screws.

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