חיישני טמפרטורה של סיבים אופטיים INNO ,מערכות ניטור טמפרטורה.
חיישן טמפרטורה בסיב אופטי, מערכת ניטור חכמה, יצרנית סיבים אופטיים מבוזרת בסין
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1、 Types of Fiber Optic Temperature Sensors
There are various types of fiber optic temperature sensors based on different classification standards.
Component type and transmission type
Component type fiber optic temperature sensor:
This type of sensor uses optical fibers as sensitive components. לדוגמה, using a sensor that changes the amplitude of light with temperature, the principle is that the core diameter and refractive index of the optical fiber change with temperature, causing the light propagating in the fiber to scatter outward due to uneven paths, resulting in changes in light amplitude; There are also sensors that utilize the rotation of the polarization surface of light. The polarization surface of single-mode optical fibers rotates with temperature changes, and this rotation is detected by a polarizer to obtain amplitude changes; בנוסף, using sensors that detect changes in optical phase, the length, refractive index, and core diameter of single-mode optical fibers vary with temperature, causing phase changes in the light propagating in the fiber. This phase change is obtained through an interferometer to measure the amplitude change. The layout requirements for interferometers in component type fiber optic temperature sensors are very strict, and one of the difficulties is that the polarization plane of the light scatters after passing through the fiber optic, and interference fringes may not be observed due to the orthogonal polarization of the reference beam and signal beam. עם זאת, if the reference optical path is stable, it can measure changes in temperature by a fraction of a Celsius.
Transmission type fiber optic temperature sensor:
Transmission type fiber optic temperature sensors use optical fibers as transmission lines. One type is a fiber optic temperature sensor that combines a thermal sensor, LED, and optical fiber; Another method is to install sensitive components that convert temperature into light transmittance and reflectance on the fiber optic end face to form a fiber optic temperature sensor. לדוגמה, a fiber optic temperature sensor with a liquid crystal panel installed on the fiber optic end face can mix three types of liquid crystals in proportion into the liquid crystal panel. At 10-45 ° C, the color changes from green to deep red, and the reflectance of light changes accordingly. Transmission type sensors can obtain a lot of light flux in optical fibers, so multimode optical fibers are commonly used with an accuracy of about 0.1 ° C.
Other classifications based on working principles
Radiation (infrared) type fiber optic temperature sensor:
Composed of an optocoupler, transmission fiber, and optoelectronic converter. Mainly utilizing the coupling and transmission characteristics of optical fibers, the surface radiation energy of the measured object (which is related to the surface temperature of the measured object) is conducted to the photodetector and converted into electrical output. The optocoupler is the main component that determines the sensitivity of sensors, and its coupling efficiency is directly related to the numerical aperture of the optical fiber. To improve the sensitivity of sensors, optical fibers with larger numerical apertures should be used, but this will also affect the performance indicators of the sensor’s distance coefficient, which needs to be comprehensively considered. The main parameter of transmission optical fiber is transmittance. To improve transmittance, when the material is fixed, methods such as increasing the fiber diameter and shortening the fiber length can be adopted. Optoelectronic conversion elements generally use silicon photovoltaic cells, PbS or other detectors. When the optical fiber is directly coupled with the detector, the efficiency can reach over 85%. In addition to direct coupling, modulation disc coupling can also be used.
Semiconductor absorption type fiber optic temperature sensor:
A cut optical fiber is installed inside a thin steel pipe, with a semiconductor temperature sensing thin film (such as GaAs or InP) sandwiched between the two ends of the fiber. The transmitted light intensity of this semiconductor temperature sensing thin film varies with the measured temperature. When a constant light intensity is input at one end of the optical fiber, the transmission ability of the semiconductor temperature sensing thin film changes with temperature, and the light intensity received by the receiving element at the other end of the optical fiber also changes with the measured temperature. By measuring the voltage output of the receiving element, the temperature at the sensor position can be remotely measured.
Fiber optic fluorescence temperature sensor:
By coating the end of the optical fiber with fluorescent material and measuring the decay time of fluorescence energy, the temperature value of the measured point can be obtained by utilizing the intrinsic afterglow time temperature correlation of the fluorescent material. Applicable temperature range -50-200 ° C, with an accuracy of approximately ± 1 ° C. Currently, it is mainly used for temperature measurement inside electrical equipment. It has the characteristics of small size, easy integration, reliable performance, אנטי הפרעות אלקטרומגנטיות, good insulation performance, convenient installation, and flexible networking.
חיישן טמפרטורה Fiber Bragg Grating:
Utilizing the unique temperature sensitivity of gratings to monitor temperature changes, with small size, מהירות תגובה מהירה, high stability, דיוק גבוה, and easy networking for multi-point monitoring. The monitoring installation is convenient and can be installed on the surface or embedded in the structure to be tested for internal temperature monitoring. Suitable for long-term temperature monitoring in power plants, railways, and oil tanks, as well as temperature measurement in fields such as electricity, military, אווירונאוטיקה, וכו. לדוגמה, the ADCD03-51-0001 high-temperature resistant fiber Bragg grating temperature sensor has an outer diameter of no more than 5mm. Multiple sensors are connected in series on one fiber without any fusion points in between, and can measure temperatures ranging from -40 ° C to 300 ° C. The length of each sensor’s sensing part does not exceed the sensor’s length, diameter, number of sensors, sensing points, and their distance from each other can be set according to user needs.
Distributed fiber optic temperature sensor:
By using optical fibers as sensing and signal transmission media, the signal of specific scattered light in the fiber (כגון פיזור ריילי, Raman scattering, and Brillouin scattering) can be measured to reflect changes in strain or temperature of the fiber itself or the environment it is in. One fiber can achieve simultaneous measurement of hundreds or thousands of sensing points.
2、 Comparison of Fluorescent Fiber, Fiber Bragg Grating, and Distributed Fiber
Principle aspect
Fluorescent fiber:
Fluorescent fiber is composed of fluorescent substances and certain rare elements doped into the core and cladding. Fluorescent substances can absorb light within a specific wavelength range, excite themselves, and emit fluorescence in various directions. Fluorescence that satisfies the total reflection condition of the fiber core cladding interface in the radiation direction will be transmitted along the fiber axis. The temperature measurement is obtained by measuring the decay time of fluorescence energy and utilizing the temperature correlation of the intrinsic afterglow time of the fluorescent substance to determine the temperature value of the measured point.
Fiber Bragg Grating:
Fiber Bragg Grating (פ.ב.ג.) utilizes the temperature sensitive properties of the grating structure in optical fibers. When the temperature changes, the refractive index and grating period of the optical fiber will change, resulting in a change in the wavelength of light reflected or transmitted by the grating. Determine temperature changes by detecting changes in this wavelength. לדוגמה, when the temperature changes, the Bragg wavelength of the Bragg fiber grating will drift. By monitoring this drift, temperature change information can be obtained.
Distributed optical fiber:
Based on scattering effects in optical fibers, כגון פיזור ריילי, Raman scattering, and Brillouin scattering. Taking Raman scattering as an example, when light is transmitted in an optical fiber, Raman scattering occurs, and the intensity of Raman scattering light is related to temperature. By measuring the intensity distribution of Raman scattering light along the fiber, temperature information at different positions along the fiber can be obtained. Different scattering mechanisms have different characteristics and applicable ranges when measuring temperature. Brillouin scattering is sensitive to both temperature and strain, and it is necessary to distinguish or compensate for strain when measuring temperature; The Rayleigh scattering intensity is relatively weak, but it can provide information on fiber loss and can also be used as a reference for temperature measurement.
In terms of performance characteristics
Fluorescent fiber:
Temperature measurement range and accuracy: applicable temperature range -50-200 ° C, with an accuracy of approximately ± 1 ° C. This temperature range can meet the internal temperature measurement needs of many conventional industrial and electrical equipment. לדוגמה, in some temperature monitoring scenarios inside switchgear and transformers, its accuracy can also meet the requirements for normal operation monitoring of equipment.
Anti interference ability: It has strong anti electromagnetic interference ability because its measurement principle is based on fluorescence characteristics and is independent of electromagnetic signals. In some strong electromagnetic environments such as substations and near large motors, it can work stably without being affected by electromagnetic interference and affecting measurement results.
Insulation performance: Due to the fact that optical fibers are non-metallic materials and the combination of fluorescent substances and optical fibers, they exhibit excellent insulation performance. In temperature monitoring of high-voltage equipment, there is no need to worry about insulation issues, and temperature measurement can be safely carried out.
Volume and Integration: Small in size, easy to integrate. This makes it easy to install inside devices with limited space or in narrow spaces, such as temperature measurement scenarios in small micro environments that are not easily accessible, such as micro pipes and narrow slits.
Fiber Bragg Grating:
Temperature measurement range and accuracy: לדוגמה, the ADCD03-51-0001 high-temperature resistant fiber Bragg grating temperature sensor can measure temperatures ranging from -40 ° C to 300 ° C, and has good adaptability in some high or low temperature environments. It has high accuracy and can meet the needs of scenarios that are sensitive to temperature changes, such as long-term temperature monitoring scenarios in power plants, railways, and oil tanks. It can accurately monitor temperature changes and timely detect potential safety hazards.
Stability and reliability: It has high stability and can work stably for a long time in complex industrial environments. לדוגמה, in temperature monitoring of railway tracks, it is possible to provide stable and accurate temperature measurement data in the face of frequent train vibrations and temperature changes in different seasons.
Networking capability: It facilitates multi-point monitoring of networking, allowing multiple sensors to be connected in series on a single fiber optic cable without any fusion points in between. This facilitates temperature monitoring of large areas or structures, such as temperature monitoring of different locations inside large building structures. Through networking, a comprehensive understanding of the temperature distribution of the entire structure can be achieved.
Distributed optical fiber:
Measurement range and resolution: A single optical fiber can achieve simultaneous measurement of hundreds or thousands of sensing points, with a large measurement range that can monitor temperature over long fiber optic lines or large areas. עם זאת, its temperature resolution may be slightly lower for measuring individual points, but it is very suitable for monitoring the overall temperature distribution trend in some scenarios, such as monitoring the temperature distribution along long-distance oil pipelines, which can quickly detect whether there are local temperature abnormal areas.
Spatial resolution: It can achieve distributed measurement along optical fibers and determine the specific location of temperature changes. In temperature monitoring of some large-scale infrastructure such as bridges and tunnels, it is possible to accurately locate the location of temperature anomalies, which helps to timely detect structural safety hazards.
In terms of application scenarios
Fluorescent fiber:
Mainly used for temperature measurement inside electrical equipment, such as switch cabinets, transformers, וכו. In these scenarios, due to the limited internal space of the equipment, strong electromagnetic interference exists, and insulation performance is required. The small size, אנטי הפרעות אלקטרומגנטיות, and good insulation properties of fluorescent optical fibers make them an ideal temperature measurement tool.
Fiber Bragg Grating:
Suitable for long-term temperature monitoring in power plants, railways, and oil tanks, as well as temperature measurement in fields such as electricity, military, אווירונאוטיקה, וכו. Temperature monitoring can be carried out on key parts of the generator set in the power station to ensure the safe operation of the power generation equipment; Temperature monitoring can be carried out on railway tracks, switches, and other parts to prevent problems such as rail deformation caused by temperature changes; In oil tank monitoring, abnormal changes in oil temperature can be detected in a timely manner to avoid safety accidents.
Distributed optical fiber:
Widely used for temperature monitoring in large structures such as bridges and tunnels, as well as long-distance pipelines such as oil and gas pipelines. For bridges, temperature distribution of bridge structures can be monitored under different seasons and weather conditions, providing data support for bridge maintenance and safety assessment; For long-distance pipelines, the temperature along the pipeline can be monitored in real-time to prevent problems such as pipeline deformation and leakage caused by temperature changes.
3、 Advantages of Fluorescent Fiber
Strong anti-interference ability
Fluorescent fiber optic sensors measure temperature based on the temperature dependence of the afterglow time of fluorescent substances, and their working principle is independent of electromagnetic signals. In today’s complex electromagnetic environment, such as near substations, ציוד מיתוג מתח גבוה, and other places with strong electromagnetic fields in the power system, traditional temperature sensors based on electrical principles may be subject to electromagnetic interference, resulting in inaccurate measurement results. Fluorescent fiber optic sensors can work stably and will not be affected by external electromagnetic field interference to accurately measure temperature. This characteristic gives it unique advantages in temperature measurement in strong electromagnetic environments such as inside electrical equipment.
Good insulation performance
Fluorescent fiber optic sensors are mainly composed of optical fibers and fluorescent substances. The optical fibers themselves are non-metallic materials, and the addition of fluorescent substances makes the entire sensor have good insulation performance. In high-voltage equipment such as transformers, ציוד מיתוג מתח גבוה, וכו., insulation performance is very important. If metal temperature sensors are used, there may be insulation hazards and safety issues such as short circuits. Fluorescent fiber optic sensors can be directly installed inside these high-voltage devices for temperature measurement, without worrying about insulation issues, ensuring the safety of equipment and personnel.
Small size and easy integration
The structure of fluorescent fiber optic sensors is relatively simple and compact in size. In some limited space application scenarios, such as micro pipes, narrow slits, and other small and micro environments that are not easily accessible, it can be easily installed and used for temperature measurement. Moreover, it is easy to integrate and can be well integrated with other devices or systems without taking up too much space. It performs well in temperature measurement inside some devices that require strict space requirements. לדוגמה, in temperature monitoring scenarios inside some miniaturized electronic devices or precision instruments, the small size and easy integration of fluorescent fiber optic sensors are very practical.
Reliable Performance
Fluorescent fiber optic sensors can operate stably within the applicable temperature range of -50-200 ° C, with an accuracy of approximately ± 1 ° C. The measurement principle is based on the inherent characteristics of fluorescent substances, and as long as the performance of the fluorescent substance itself is stable, reliable temperature measurement results can be provided. In scenarios where electrical equipment operates for a long time and requires high temperature monitoring, fluorescent fiber optic sensors can continuously and stably provide accurate temperature data, which helps to timely detect temperature anomalies inside the equipment and ensure its normal operation.
Easy installation and flexible networking
In terms of installation, fluorescent fiber optic sensors, due to their small size and other characteristics, can be easily installed inside various devices or at locations where temperature measurement is required. In terms of networking, it can flexibly construct a temperature measurement network according to actual needs. לדוגמה, in a large electrical equipment room, if temperature monitoring is required for multiple devices or multiple locations inside the devices, multiple fluorescent fiber optic sensors can be conveniently networked to achieve temperature monitoring of the entire area, timely grasp the temperature distribution situation, and facilitate equipment maintenance and management.
4、 Which type of fiber optic temperature sensor is the best
Although each type of fiber optic temperature sensor has its own advantages and strengths in different application scenarios, when considering multiple factors, fluorescent fiber optic sensors exhibit unique advantages in many aspects and can be considered as an excellent fiber optic temperature sensor in specific scenarios.
5、 Why is fluorescent fiber the best
Unique anti-interference and insulation performance
In modern industrial environments, electromagnetic interference is ubiquitous, especially in places with dense electrical equipment such as substations and distribution rooms. Fluorescent fiber optic sensors have a natural immunity to electromagnetic interference based on their special measurement principles. This is because it determines temperature by measuring the decay time of fluorescence energy, which is unrelated to electromagnetic signals. Compared to other types of fiber optic temperature sensors, although they also have some anti-interference ability, they may still be affected to some extent in strong electromagnetic environments. לדוגמה, fiber Bragg grating sensors, although they have good stability themselves, may experience some interference in signal transmission and processing when facing extremely strong electromagnetic interference. In some complex electromagnetic interference environments, the signal detection based on scattering principle of distributed fiber optic sensors may also experience fluctuations.
The insulation performance of fluorescent fiber optic sensors is also a major advantage. In high voltage environments, such as inside transformers and high-voltage switchgear, good insulation performance is the key to ensuring the safe operation and accurate measurement of sensors. The non-metallic material and structural characteristics of fluorescent fiber optic sensors make them excellent in insulation performance. Other fiber optic temperature sensors may not be comparable in insulation performance to fluorescent fiber optic sensors. לדוגמה, some fiber optic temperature sensors with metal components or relatively complex structures may require additional insulation measures in high voltage environments, increasing costs and installation complexity.
Adapt to special measurement environments
The small size and easy integration of fluorescent fiber optic sensors enable them to adapt to some special measurement environments. Traditional temperature sensors may not be able to be installed in small spaces such as microchannels and narrow slits, or their installation may affect the normal operation of the equipment. Fluorescent fiber optic sensors can be easily installed in these locations and accurately measure temperature. In some electrical equipment with strict spatial layout requirements, such as small relays, precision electronic instruments, וכו., fluorescent fiber optic sensors can be used for temperature monitoring without affecting the structure and performance of the equipment. In contrast, although fiber Bragg grating sensors also have the characteristic of small size, fluorescent fiber optic sensors have higher flexibility in some ultra small spaces or special shaped measurement environments. Distributed fiber optic sensors do not have advantages in these extremely small space measurement scenarios because they are usually based on measuring the entire fiber optic cable.
Reliability and cost-effectiveness
Fluorescent fiber optic sensors have an accuracy of approximately ± 1 ° C within their applicable temperature range of 50-200 ° C, providing stable and reliable temperature measurements. The measurement principle is based on the intrinsic characteristics of fluorescent substances, and as long as the performance of the fluorescent substance is stable, it can work stably for a long time. In the temperature monitoring scenario inside electrical equipment, its reliability can meet the monitoring requirements for long-term operation of the equipment. Moreover, from a cost-benefit perspective, fluorescent fiber optic sensors may have better cost-effectiveness compared to other fiber optic temperature sensors in meeting specific scenarios such as temperature measurement inside electrical equipment. לדוגמה, in some scenarios that do not require ultra wide temperature measurement ranges or ultra long distance distributed measurements, the cost of fluorescent fiber optic sensors may be lower, and installation and maintenance may be easier, while fiber optic grating sensors may have higher costs in some high-precision, wide temperature range measurement scenarios. Distributed fiber optic sensors also have relatively higher equipment and installation costs when long-distance distributed measurements are required.
