An electromagnetic interference resistant high temperature monitoring method for an open sintering apparatus

Abstract

The application provides an electromagnetic interference resistant high-temperature monitoring method for an open sintering device, which comprises a pulsed light source, the pulsed light source is connected with the input end of a first optical fiber coupler through a single-mode optical fiber, the first output end of the first optical fiber coupler is connected with an optical fiber isolator through a single-mode optical fiber, the second output end of the first optical fiber coupler is connected with the first input end of a second optical fiber coupler through a single-mode optical fiber, the first output end of the second optical fiber coupler is connected with the input end of a first optical fiber temperature sensor through a single-mode optical fiber, the output end of the first optical fiber temperature sensor is connected with the second input end of the second optical fiber coupler through a single-mode optical fiber, the second output end of the second optical fiber coupler is connected with the input end of a photoelectric detector through a single-mode optical fiber, and the photoelectric detector is connected with a signal processing unit; the dynamic range of temperature measurement is improved by combining the optical fiber temperature sensor and the optical fiber ring mirror, so that the measurement of high temperature is realized.

Description

Technical Field

[0001] This invention relates to temperature monitoring technology for open sintering equipment, specifically to a method for high-temperature monitoring of open sintering equipment against electromagnetic interference. Background Technology

[0002] High-temperature monitoring of open-type sintering equipment is crucial for improving equipment maintenance quality. Because high-temperature furnaces utilize electromagnetic heating, most electronic sensors will melt and fail. Fiber optic temperature sensors offer advantages such as small size, light weight, resistance to electromagnetic interference, and ease of forming distributed sensor networks. Therefore, fiber optic temperature sensors are an excellent choice for high-temperature monitoring of medium-frequency induction heating furnaces. Currently popular fiber optic sensors for temperature measurement include fiber Bragg gratings, FP cavities, long-period gratings, Mazer interferometers, Michelson interferometers, and fiber Sachner interferometers. The analysis of these sensors primarily uses a spectrometer to extract characteristic wavelengths to characterize changes in external temperature. However, this demodulation method generally has a limited detection range, posing a challenge for high-temperature measurements up to 1000 degrees Celsius. Summary of the Invention

[0003] To address the problems in the prior art, this invention provides a method for high-temperature monitoring of open sintering equipment against electromagnetic interference, aiming to improve the dynamic range of temperature measurement and overcome the shortcomings of high-temperature measurement methods based on wavelength demodulation.

[0004] A method for high-temperature monitoring of an open-type sintering equipment against electromagnetic interference includes a pulsed light source. The pulsed light source is connected to the input end of a first fiber optic coupler via a single-mode fiber. The first output end of the first fiber optic coupler is connected to a fiber optic isolator via a single-mode fiber. The second output end of the first fiber optic coupler is connected to the first input end of a second fiber optic coupler via a single-mode fiber. The first output end of the second fiber optic coupler is connected to the input end of a first fiber optic temperature sensor via a single-mode fiber. The output end of the first fiber optic temperature sensor is connected to the second input end of the second fiber optic coupler via a single-mode fiber. The second output end of the second fiber optic coupler is connected to the input end of a photodetector via a single-mode fiber. The photodetector is connected to a signal processing unit to acquire the linear transmission region offset Δλ of the first fiber optic temperature sensor caused by temperature changes.

[0005] Δλ=[(∈+α)ΔT]λ (1)

[0006] Where ∈ represents the thermo-optic coefficient of the fiber core and cladding, α represents the effective thermal expansion coefficient of the optical fiber, and λ represents the free space wavelength;

[0007] The edge filtering effect of the first fiber optic temperature sensor is described as follows:

[0008] ΔP out =ΔλP inλ i (2)

[0009] Where, ΔP out P represents the change in optical power detected by the photodetector. in λ is the optical power output by the pulsed light source. i The center wavelength of the output light from the pulsed light source;

[0010] Combining equations (1) and (2), we get:

[0011]

[0012] ΔT is the temperature of the first fiber optic temperature sensor.

[0013] Furthermore, the coupling ratio of the second fiber coupler is 50:50.

[0014] Furthermore, the first optical fiber temperature sensor is composed of a single-mode fiber, a 6mm dispersion compensation fiber, and a single-mode fiber cascaded together. The core diameter of the dispersion compensation fiber is 5µm, the cladding diameter of the dispersion compensation fiber is 110µm, and both ends of the dispersion compensation fiber are coaxially fused with the single-mode fiber.

[0015] Further, the coupling ratio of the first fiber coupler is 95:5, wherein the output end with 95% pulse light energy is the first output end, and the output end with 5% pulse light energy is the second output end; the first output end of the first fiber coupler is connected to the fiber isolator through another first fiber coupler, and this other first fiber coupler is referred to as the third fiber coupler; the second output end of the third fiber coupler is connected to the first input end of another second fiber coupler, and this other second fiber coupler is referred to as the fourth fiber coupler; the first output end of the fourth fiber coupler is connected to the input end of another first fiber temperature sensor through a single-mode fiber, and this other first fiber temperature sensor is referred to as the second fiber temperature sensor; the output end of the second fiber temperature sensor is connected to the second input end of the fourth fiber coupler through a single-mode fiber; the second output end of the fourth fiber coupler is connected to the other input end of the photodetector through a single-mode fiber.

[0016] Furthermore, the pulsed light source has a center wavelength of 1550nm, a power of 50mW, a frequency of 1kHz, and a pulse width of 1200ns, and is used as the probe light output.

[0017] Furthermore, the signal processing unit includes an A / D converter, a digital signal processor, and a PC.

[0018] The beneficial effects of this invention are as follows: the use of fiber optic ring mirror and fiber optic temperature sensor structure improves the dynamic range of displacement measurement; the use of linear region shift of the transmission spectrum of fiber optic temperature sensor improves the temperature measurement range; and the use of fiber optic temperature sensor overcomes the electromagnetic interference problem of open sintering equipment. Attached Figure Description

[0019] Figure 1 This is a system diagram of the first embodiment of the present invention;

[0020] Figure 2 This is a system diagram of the second embodiment of the present invention. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings. Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The directional terms such as left, center, right, top, and bottom in the embodiments of the present invention are only relative concepts or referenced to the normal use state of the product, and should not be considered restrictive.

[0022] First embodiment:

[0023] A method for high-temperature monitoring of electromagnetic interference in open sintering equipment, such as... Figure 1 As shown, the system includes a pulsed light source 1, which is connected to the input of a first fiber optic coupler 2 via a single-mode fiber. The first output of the first fiber optic coupler 2 is connected to a fiber optic isolator 4 via a single-mode fiber. The second output of the first fiber optic coupler 2 is connected to the first input of a second fiber optic coupler 5 via a single-mode fiber. The first output of the second fiber optic coupler 5 is connected to the input of a first fiber optic temperature sensor 6 via a single-mode fiber. The output of the first fiber optic temperature sensor 6 is connected to the second input of the second fiber optic coupler 5 via a single-mode fiber. The second output of the second fiber optic coupler 7 is connected to the input of a photodetector via a single-mode fiber. The photodetector 7 is connected to a signal processing unit and acquires the linear transmission region offset Δλ of the first fiber optic temperature sensor 6 caused by temperature changes.

[0024] Δλ=[(∈α)ΔT]λ (1)

[0025] Where ∈ represents the thermo-optic coefficient of the fiber core and cladding, α represents the effective thermal expansion coefficient of the optical fiber, and λ represents the free space wavelength;

[0026] The edge filtering effect of the first fiber optic temperature sensor 6 is described as follows:

[0027] ΔP out=ΔλP in λ i (2)

[0028] Where, ΔP out P represents the change in optical power detected by photodetector 7. in λ is the optical power output by pulsed light source 1. i The center wavelength of the output light from pulse light source 1;

[0029] Combining equations (1) and (2), we get:

[0030]

[0031] ΔT is the temperature of the first fiber optic temperature sensor 6. Therefore, based on the edge filtering effect of the first fiber optic temperature sensor 6, we can characterize the temperature change as long as we measure the change in optical power detected by the photodetector 7.

[0032] The second fiber coupler 5 has a coupling ratio of 50:50. It forms a fiber ring mirror with a single-mode fiber and a fiber temperature sensor, and the fiber temperature sensor is connected in series to improve the dynamic range of temperature measurement. The first fiber temperature sensor 6 is composed of a single-mode fiber, a 6mm dispersion compensation fiber, and a cascaded single-mode fiber. The dispersion compensation fiber has a core diameter of 5µm and a cladding diameter of 110µm. Both ends of the dispersion compensation fiber are coaxially fused to the single-mode fiber. When the fundamental mode in the single-mode fiber is transmitted to the dispersion compensation fiber, it will cause mode mismatch and excite higher-order modes. The various modes will form mode interference in the dispersion compensation fiber and then be output from the single-mode fiber to form a fiber interferometer, which forms the edge filtering effect of the sensor. This type of sensor is formed by cascading standard fibers and has the advantage of low cost.

[0033] In addition, the pulsed light source 1 has a center wavelength of 1550nm, a power of 50mW, a frequency of 1kHz, and a pulse width of 1200ns, serving as the probe light output. The use of a high-power pulsed light source in conjunction with a fiber optic ring mirror maximizes the dynamic range of temperature measurement to meet the requirements of high-temperature measurement. Furthermore, the frequency and pulse width settings reduce the difficulty of subsequent signal acquisition, minimizing system noise and improving the system's signal-to-noise ratio. The signal processing unit includes an A / D converter 8, a digital signal processor 9, and a PC 10. The post-processing features further enhance the system's capabilities, enabling real-time display of the sensing effect and improving its advantages in high-temperature detection in open-type sintering equipment.

[0034] Second embodiment:

[0035] Other technical features are the same as in the first embodiment, such as... Figure 2As shown, the coupling ratio of the first fiber coupler 2 is 95:5, where the output end with 95% pulse light energy is the first output end, and the output end with 5% pulse light energy is the second output end. The first output end of the first fiber coupler 6 is connected to the fiber isolator 4 through another first fiber coupler, which is designated as the third fiber coupler 3. The second output end of the third fiber coupler 3 is connected to the first input end of another second fiber coupler, which is designated as the fourth fiber coupler 11. The first output end of the fourth fiber coupler 11 is connected to the input end of another first fiber temperature sensor via a single-mode fiber, which is designated as the second fiber temperature sensor 12. The output end of the second fiber temperature sensor 12 is connected to the second input end of the fourth fiber coupler 11 via a single-mode fiber. The second output end of the fourth fiber coupler 11 is connected to the other input end of the photodetector 7 via a single-mode fiber. Since each fiber temperature sensor only inputs 5% of the light energy, only two fiber temperature sensors are set up in this system diagram for demonstration. Theoretically, up to 20 fiber temperature sensors can be used for simultaneous measurement.

[0036] Compared with existing technologies:

[0037] In current technologies, high-temperature fiber optic measurements primarily rely on spectrometers to extract characteristic wavelengths to characterize changes in external physical quantities, which limits the detection range. This invention addresses the limitations of various fiber optic power demodulation schemes. Unlike wavelength-modulation-based sensing, we designed an anti-electromagnetic interference high-temperature detection device for open-type sintering equipment to overcome the shortcomings of wavelength-modulation-based measurement methods. A high-temperature fiber optic sensing system was designed, combining a fiber optic temperature sensor and a fiber optic ring mirror to improve the dynamic range of temperature measurement. Utilizing the edge filtering effect of the fiber optic temperature sensor, temperature changes cause a linear shift in the sensor's edge transmission spectrum. After linear filtering by the sensor, the power received from the narrowband light source also changes linearly, thus enabling high-temperature measurement.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for high-temperature monitoring of electromagnetic interference in an open sintering equipment, characterized in that: The system includes a pulsed light source (1), which is connected to the input of a first fiber coupler (2) via a single-mode fiber. The first output of the first fiber coupler (2) is connected to a fiber isolator (4) via a single-mode fiber. The second output of the first fiber coupler (2) is connected to the first input of a second fiber coupler (5) via a single-mode fiber. The first output of the second fiber coupler (5) is connected to the input of a first fiber temperature sensor (6) via a single-mode fiber. The output of the first fiber temperature sensor (6) is connected to the second input of the second fiber coupler (5) via a single-mode fiber. The second output of the second fiber coupler is connected to the input of a photodetector via a single-mode fiber. The photodetector (7) is connected to a signal processing unit and acquires the linear transmission region offset Δλ caused by temperature change in the first fiber temperature sensor (6). Δλ=[(∈+α)ΔT]λ (1) Where ∈ represents the thermo-optic coefficient of the fiber core and cladding, α represents the effective thermal expansion coefficient of the optical fiber, and λ represents the free space wavelength; The edge filtering effect of the first fiber optic temperature sensor (6) is described as follows: ΔP out =ΔλP in l i (2) Wherein, ΔP out P is the change in optical power detected by the photodetector (7). in λ is the optical power output by the pulsed light source (1). i The center wavelength of the output light from the pulsed light source (1); Combining equations (1) and (2), we get: ΔT is the temperature of the first fiber optic temperature sensor (6).

2. The method for high-temperature monitoring of electromagnetic interference in open sintering equipment according to claim 1, characterized in that: The coupling ratio of the second fiber coupler (5) is 50:

50.

3. The method for high-temperature monitoring of electromagnetic interference in open sintering equipment according to claim 1 or 2, characterized in that: The first optical fiber temperature sensor (6) is composed of a single-mode fiber, a 6mm dispersion compensation fiber, and a single-mode fiber cascaded together. The core diameter of the dispersion compensation fiber is 5um, the cladding diameter of the dispersion compensation fiber is 110um, and the two ends of the dispersion compensation fiber are coaxially fused with the single-mode fiber.

4. The method for high-temperature monitoring of electromagnetic interference in open sintering equipment according to claim 3, characterized in that: The coupling ratio of the first fiber coupler (2) is 95:5, wherein the output end with 95% pulse light energy is the first output end, and the output end with 5% pulse light energy is the second output end; the first output end of the first fiber coupler (2) is connected to the fiber isolator (4) through another first fiber coupler, and the other first fiber coupler is referred to as the third fiber coupler (3). The second output end of the third fiber coupler (3) is connected to the first input end of another second fiber coupler, and the other second fiber coupler is referred to as the fourth fiber coupler (11). The first output end of the fourth fiber coupler (11) is connected to the input end of another first fiber temperature sensor through a single-mode fiber, and the other first fiber temperature sensor is referred to as the second fiber temperature sensor (12). The output end of the second fiber temperature sensor (12) is connected to the second input end of the fourth fiber coupler (11) through a single-mode fiber. The second output end of the fourth fiber coupler (11) is connected to the other input end of the photodetector (7) through a single-mode fiber.

5. The method for high-temperature monitoring of electromagnetic interference in open sintering equipment according to claim 1, characterized in that: The pulsed light source (1) has a center wavelength of 1550nm, a power of 50mW, a frequency of 1Khz, and a pulse width of 1200ns, and is used as the probe light output.

6. The method for high-temperature monitoring of electromagnetic interference in open sintering equipment according to claim 1, characterized in that: The signal processing unit includes an A / D converter (8), a digital signal processor (9), and a PC (10).

Images