Accurate Temperature Measurements Research Articles

Design and analysis of sensor structure based on ultrasonic temperature measurement

Abstract Based on the principle of ultrasonic temperature measurement, this paper designs the structure of a waveguide rod sensor with a reflective groove. Using multi-physics field simulation software to conduct acoustic thermal coupling parametric simulation analysis on six different high melting point materials, we obtain the curve functions of the relationship between sound velocity and temperature for the six materials and verify the feasibility of ultrasonic temperature measurement using waveguide rods. Analysis shows that the sensitivity of six alloys to temperature changes is as follows: Ti6Al4V titanium alloy > α-Al2O3 > Inconel693 nickel-based alloy > ThO2 > Tungsten-rhenium alloy > Ta8W2Hf. At the same time, three different shapes of waveguide rods were designed: single groove waveguide rod, multi-zone waveguide rod, and spiral waveguide rod to analyze the impact of temperature measurement accuracy. The research results have important theoretical guidance significance for solving the problem of temperature measurement in high-temperature environments.

Composite structures with embedded fiber optic sensors: A smart propellant tank for future spacecraft applications

Modern spacecraft and launch vehicle design is more oriented towards reducing system-level design and assembly complexities. In order to maintain high overall system performance while reducing these complexities, the use of smart materials and smart structural components is a well-known practice and is currently of rising interest to space systems' designers. The paper discusses a concept of smart space structures, in particular, a carbon fiber composites structure embedded with Optical Fiber Sensors (OFS) for spacecraft and launch vehicle applications. This study highlights the operational requirements for such tank and the smart features enabled by the optical fiber sensors. For the latter aspect, a quantitative comparison between Fiber Bragg Grating sensors (FBGs) and Distributed Optical Fiber Sensors (DOFS) based on Optical Frequency Domain Reflectometry (OFDR) is presented to state their core performance parameters, such as the sensitivity, sensing range, dynamic measurement capability, and spatial resolution. The increased performance and reliability in harsh environments associated with fiber optic sensors come with a reduction in size, mass, and power consumption compared to the conventional electronic sensors. Optical fiber sensors embedded in carbon fiber structures have proven their capability in providing accurate real-time measurements of temperature and monitoring structural integrity while detecting precisely possible points of rupture and failure as discussed and demonstrated in the literature review. The applications of fiber optic sensing in smart propellant tanks may extend to detecting fluid leakage, also providing increased precision in propellant gauging through temperature mapping, and can be used in on-ground qualification, pre-flight testing, as well as in-orbit operation, condition, and structural health monitoring. The article presents a statement for an optimal FOS embedding approach in composite pressure vessels and discusses the related placement and orientation method for the fiber optic sensors, coupled with a one component simplified analytical stress-strain transfer model deriving the stress component along the maximum principal direction (i.e., σMaxPrincipal). The novel approach is believed to serve the optimal employment of embedded FOS in composite structures, e.g., pressure vessels and light-weight structures in spacecraft, among other applications. The simplified model is believed to pave the way for effective data interpretation and processing, utilizing the available limited computational resources on-board the spacecraft.

Improvement of fiber optic sensor measurement methods for temperature and humidity measurement in microelectronic circuits

A wide range of applications such as healthcare, human comfort, agriculture, food processing and storage, and electronics manufacturing also require fast and accurate measurement of humidity and temperature. Optical fiber-based sensors have several advantages over electronic sensors, and much research has been conducted in this area in recent years. This paper describes the current trends in fiber optic temperature and humidity sensors. The evolution of optical structures aimed at humidity detection is presented, as well as a new design of an optical sensor used for this purpose. The main methods of humidity determination using fiber-optic laser reflection based on Optical fiber humidity sensor (FPI) were analyzed and experimental results were obtained. Based on temperature-sensitive strain variation, a method for temperature determination based on the specific spectral back-reflection effect of fiber Bragg gratings (FBGs) is considered. Experimental analyses were conducted on the light reflection of humidity-sensitive agarose using optical fibers based on the Fabry-Perot Interferometer (FPI). It exhibits a good linear response to relative humidity, ranging from 25 % to 95 %. During temperature measurement, the deformation changes of the Fiber Bragg Grating fibers showed excellent performance, ranging from –5 °C to 70 °C. New structures, such as resonators, are being explored to improve the resolution of fiber optic temperature and humidity sensors. In addition, recent studies on polymer optical fibers show that the sensitivity of this type of sensor has not yet been achieved. Thus, materials sensitive to humidity and temperature still need to be investigated to improve sensitivity and resolution

Advances in Femtosecond Coherent Anti-Stokes Raman Scattering for Thermometry

The combustion process is complex and harsh, and the supersonic combustion flow field is also characterized by short duration and supersonic speed, which makes the real-time diagnostic technology for the transient environment extremely demanding. It is of great significance to realize high time-resolved accurate measurement of temperature, component concentration, and other parametric information of the combustion field to study the transient chemical reaction dynamics of the combustion field. Femtosecond CARS spectroscopy can effectively avoid the collision effect between particles in the measurement process and reduce the influence of the non-resonant background to improve the measurement accuracy and realize the time-resolved measurement on a millisecond scale. This paper introduces the development history of femtosecond CARS spectroscopy, points out its advantages and disadvantages, and looks forward to the future development trend to carry out high time-resolved measurements, establish a database of temperature changes in various complex combustion fields, and provide support for the study of engine mechanisms.

Temperature-Dependent Luminescence of Nd3+-Doped Carbon Nanodots for Nanothermometry.

Noncontact optical nanothermometers operating within the biological transparency windows are required to study temperature-sensitive biological phenomena at the nanoscale. Nanoparticles containing rare-earth ions such as Nd3+ have been reported to be efficient luminescence-based ratiometric thermometers, however often limited by poor water solubility and concentration-related quenching effects. Herein, we introduce a new type of nanothermometer, obtained by employing low-dimensional carbon nanodots (CNDs) as matrices to host Nd3+ ions (NdCNDs). By means of a one-pot procedure, small (∼7-12 nm), water-soluble nanoparticles were obtained, with high (15 wt %) Nd3+ loading. This stable metal-CND system features temperature-dependent photoluminescence in the second biological window (BW II) upon irradiation at 808 nm, thereby allowing accurate and reversible (heating/cooling) temperature measurements with good sensitivity and thermal resolution. The system possesses remarkable biocompatibility in vitro and promising performance at a high penetration depth in tissue models.

Experimental Measurement of Emissivity of Polished Steel Strips from a Continuous Annealing Line.

The long-term use of steel strip in various industries makes it an important semi-finished product, which makes it necessary to improve its chemical composition and mechanical properties, reduce its thickness and weight, expand the range of new types of steel strip and increase its production. This entails a large number of technological operations dependent on precise temperature measurement and control. In some industrial plants, the steel strip is in continuous motion, which makes the use of contact measuring devices impossible. When using non-contact measuring devices such as pyrometers or thermal imaging cameras, the emissivity of the materials being measured is a problematic parameter, as setting an incorrect emissivity value to the measuring device results in inaccurate temperature readings. The essence of this research was to establish a measurement method and to perform experimental measurements of the emissivity of a polished steel strip used in a continuous annealing line, the subsequent processing of the data from these measurements and their evaluation. The emissivity measurements were carried out for 5 types of steel strip of different parameters, while the measurement itself was carried out in the long wavelength range of 7.5-14 µm and at strip temperatures of 100-300 °C. Depending on the type of steel strip, the mean emissivity values ranged from 0.0835- to 0.1143. The emissivity of the steel strip increased with increasing strip temperature, and it was not a linear dependence. The emissivity values determined in this research could be applied to measuring equipment in actual production, which could improve the accuracy of temperature measurement in the heat treatment of polished steel strip. Thermal camera measurements in the long wavelength range, taking thermal images and their processing and determining the emissivity value of polished steel strips are the parts of this research that make it different from other already published research.

Experimental Study on Spontaneous Combustion Monitoring in Coal Mine Airspace Based on Distributed Fiber Optic Temperature Measurement

ABSTRACT Spontaneous combustion fires in the mining airspace seriously affect safety at mines. It is crucial to accurately predict the location of fire sources and forecast spontaneous combustion disasters. This study, therefore, proposes an intuitive, accurate, and efficient distributed fiber optic temperature measurement technique for detecting spontaneous coal combustion. To overcome the limitations of using traditional optical fibers in the complex environment of the goaf, this study independently developed an enhanced armored distributed optical fiber for coal mines through experiments. Aiming at the possible influence of the armoring material on the accuracy of temperature measurement, the temperature of the armored distributed optical fiber was corrected through calibration experiments of the armored optical fiber and the heat transfer simulation study of the enhanced temperature measurement optical fiber, to improve the accuracy of the measurement. Based on COMSOL’s simulation study of the spontaneous combustion temperature field and fiber optic detection in the extraction zone, a method of laying optical fibers in parallel at 15-meter intervals to achieve accurate detection of the fire source location in the extraction zone. To explore the feasibility of this technology, a field test was carried out in the 22,117 working faces of Shanxi Lu’an Group Luning Coal Co. Ltd. in the hollow area. The temperature analysis results are consistent with the results of the beam pipe monitoring. The results show that the distributed fiber optic temperature measurement technology can produce a graded warning of spontaneous coal combustion and achieve an accurate detection of the fire source.

Normal spectral emissivity measurement study of high-temperature alloy (316L) at 673–1273 K with a thermal oxidation surface

One effective approach to better understanding the performance characteristics of high-temperature alloys is to study their thermal oxidation behavior, and to accurately determine their spectral emissivity is helpful for increasing the accuracy of temperature measurements. Using a self-developed high-temperature emissivity testing system, the normal spectral emissivity across the range 673–1273 K and a spectral band of 1–14 μm was measured relative to this background radiation. The normal spectral emissivity of 316L high-temperature alloy was investigated during the thermal oxidation process. The change in emissivity of 316L high-temperature alloy during thermal oxidation was observed. The emissivity of the 316L high-temperature alloy undergoes great changes during thermal oxidation; for example, at 1273 K it was 0.055 in its un-oxidized state but after 50 h’ thermal oxidation went up to 0.829. Below 1073 K the emissivity of 316L high-temperature alloy in 8–14 μm range showed little change, making it ideal for radiation thermometry. By fitting the measurement data, we derived that the emissivity of 316L high-temperature alloy has an exponential relationship with thermal oxidation temperature, and is a power function relationship with thermal oxidation time.

Assessment of alternative fluid calibration to estimate traceable liquefied hydrogen flow measurement uncertainty

The usage of liquefied hydrogen (LH2) is growing fast as the EU aims to be climate-neutral by 2050. Therefore, reliable and consistent measurements of LH2 amounts (as determined by flow meters) will become increasingly important for custody transfers. Reliability and consistency of measurements is established from calibration. Due to the lack of facilities being able to calibrate flow meters directly with LH2 as calibration fluid, the question arises whether the measurement error of the calibration performed on a different fluid and different process conditions are representative for the errors when measuring LH2. An on-site calibration of two turbine meters measuring LH2 flow was performed. A Coriolis mass flow meter calibrated on water was used as a reference in conjunction with a dedicated flow meter model, which was validated by a directly SI-traceable calibration on liquefied natural gas. LH2 flow rates were within 1000 kg/h and 3000 kg/h, which are relevant to hydrogen transport by LH2 trailers. The analysis of the measurement data reveal errors on totalized mass ranging from 2.0 % to 2.9 % with a total calibration uncertainty of 1.3 % (k=2), where the main uncertainty source was identified as the on-site density estimate necessary to convert the volume flow measurements into mass flow measurements. The results indicate the need for reliable and accurate temperature measurements (the latter allowing for an accurate density estimate), so that volume based and mass based amount measurements can be compared with smaller uncertainties.

Analiza porównawcza wybranych metod kalibracji kamery termowizyjnej z chłodzonym detektorem pracującym w zakresie MWIR

For accurate remote temperature measurement with a thermal imaging camera, it is necessary to perform radiometric calibration. This allows the radiative parameters of an object, and therefore its temperature, to be related to the response of the infrared detector observing it. The article presents the basic concepts related to radiometric calibration and various factors influencing its effectiveness. The most common calibration methods were also reviewed, and then two of them were implemented and compared on a specially constructed laboratory station, using proprietary software and equipped with a cooled infrared camera, operating in the MWIR range. The camera was calibrated in the temperature range from 20 °C to 50 ° C. The comparison of methods was carried out on the basis of a series of temperature measurements, analysis of absolute and relative errors, as well as analysis of the dispersion of the measured temperature values.

Metoda pomiaru temperatury ciała człowieka za pomocą kamery termowizyjnej

Measurement and monitoring of human physiological parameters play an important role in many applications such as health care, sports training and prevention of disease spread. Dynamic changes in physiological parameters can reveal not only changes in a patient’s physiological state and function, but also be used to assess a person’s activity status, fitness and fatigue. Body temperature is among the most important human physiological parameters for assessing basic vital functions, apart from heart rate, blood pressure and respiratory rate. In medical practice, various types of measuring instruments are used to measure temperature, such as liquid thermometers, electronic thermometers, non-contact ear thermometers, non-contact forehead thermometers. Liquid and electronic thermometers require the appropriate sensors to be connected to a person, which may be undesirable or impossible as, for example, in newborns or during sports training. Non-contact thermometers operate over short distances and often force a specific position of the person during the measurement. In addition, the above body temperature measurement techniques require direct supervision by medical personnel, which often reduces the effectiveness and efficiency of screening temperature measurement. In screening temperature measurements of a large number of people, especially those on the move, a measuring thermal imaging camera works well. The article presents a method for measuring human body temperature using a thermal imaging camera. The presented method is characterized by high accuracy of temperature measurement, which allows medical use of the obtained measurements. The measurement method has been tested on a test stand and for a selected test sample of people. The measurements and tests carried out confirmed the possibility of obtaining temperature measurement accuracy with an expanded uncertainty of less than 0.05 K with a resolution of less than 0.1 K.

Transient temperature measurement of silicon carbide Schottky barrier diode based on thermal reflection.

In this article, we present a transient temperature detection device for silicon carbide (SiC) Schottky barrier diodes (SBDs) based on thermal reflection theory. We constructed a thermal reflection temperature measurement device based on a 530-nm green laser. This device is more suitable for transient temperature measurement of SiC SBDs than previous thermal reflection equipment. The accuracy of temperature measurement by our device was confirmed by comparison with the results of infrared thermal imaging. The high temporal resolution characteristics of the thermal reflection technology allowed the detection of millisecond-level transient temperature changes in SiC SBDs. In addition, we investigated the complementarity of transient temperature change curves during heating and cooling processes, as well as the reasons for the differences between these curves. Finally, we used the structural function method combined with the Bayesian deconvolution algorithm to obtain the thermal resistance along the heat flow path of the device and validated the results using an established thermal resistance testing method.

Understanding the accuracy of body temperature measurements in patient triage during cancer treatment: a retrospective audit

Understanding the accuracy of body temperature measurements in patient triage during cancer treatment: a retrospective audit

Accurate Measurement of the Internal Temperature of 280 Ah Lithium-Ion Batteries by Means of Pre-Buried Thermocouples

Batteries with an energy storage capacity of 280 Ah play a crucial role in promoting the development of smart grids. However, the inhomogeneity of their internal temperature cannot be accurately measured at different constant charge and discharge power, affecting the efficiency and safety of the battery. This work adopts finite element analysis to determine the typical internal temperature of a single-cell model, which can guide the measuring position of the battery. Before the manufacturing process, a slim pre-buried sensor is utilized to reduce the negative impacts of different constant charge and discharge powers. The maximum internal temperature of the battery is up to 77 °C at a constant charge and discharge power of 896 W. The temperature difference between the two poles and the battery surface is as high as 26.2 °C, which is beyond the safety temperature (55 °C). This phenomenon will result in the degradation of the positive electrode through dQ/dV curves. These measurements of battery internal temperature can improve battery heat control and facilitate the development of energy storage technology.

Analysis of scuffing through temperature measurement experiment and numerical simulation for spiral bevel gears

Tooth surface scuffing failure, as one of the primary failure modes of gears, frequently occurs during the operation of gear mechanisms. Scuffing properties of spiral bevel gears were investigated through a numerical analysis and experimental study. A novel temperature model for a single tooth was proposed to predict scuffing temperatures on the tooth surface. The model allows the analysis of variations in tooth surface temperature, considering both operating conditions and tooth contact scenarios. Experiments were carried out to explore tooth surface adhesion of spiral bevel gears under precisely defined operating conditions. Measurement of tooth surface temperatures was conducted by combining non-contact infrared temperature sensors and temperature-measuring cameras. This experiment verifies temperature changes on the tooth surface adhesion of spiral bevel gears. The combination of two temperature measurement methods ensures accurate temperature measurements, with errors below 8%, and facilitates the swift opening of the end cover. Experimental validation of the scuffing prediction model yields a maximum temperature difference of 5.93%. The method establishes a theoretical foundation for evaluating tooth surface adhesion of spiral bevel gears.

Innovative Non-Invasive and Non-Intrusive Precision Thermometry in Stainless-Steel Tanks Using Ultrasound Transducers.

Measuring temperature inside chemical reactors is crucial to ensuring process control and safety. However, conventional methods face a number of limitations, such as the invasiveness and the restricted dynamic range. This paper presents a novel approach using ultrasound transducers to enable accurate temperature measurements. Our experiments, conducted within a temperature range of 28.8 to 83.8 °C, reveal a minimal temperature accuracy of 98.6% within the critical zone spanning between 70.5 and 75 °C, and an accuracy of over 99% outside this critical zone. The experiments focused on a homogeneous environment of distilled water within a stainless-steel tank. This approach will be extended in a future research in order to diversify the experimental media and non-uniform environments, while promising broader applications in chemical process monitoring and control.

High-Entropy CeNbO4+δ-Based Ceramics with Ultrahigh Comprehensive Thermosensitive Performances.

Next-generation advanced high-temperature sensors rely heavily on negative temperature coefficient thermosensitive ceramics with low cost, small volume, high sensitivity, and fast response. However, thus far, the enormous challenge of achieving ultrahigh stability and accuracy has become a critical bottleneck restricting the development of thermosensitive ceramics in high-temperature sensor applications. Here, we propose a high-entropy strategy to design a "cation valence self-equilibrium" system in CeNbO4+δ-based ceramics introducing redox couple compensation and ultrahigh density dislocations to solve the problem of temperature-dependent oxygen nonstoichiometry that restricts the performances of high-temperature thermosensitive ceramics. Ferroelastic domains are generated by enhancing the configurational entropy at both A and B sites, resulting in a dramatic increase of dislocation density to >1010 mm-2, which ultimately optimizes the thermosensitive performances. Extreme temperature measurement accuracy with R2 as high as 999.98‰ and RSS as low as 0.011 and high-temperature stability with ΔR/R0 as low as 0.23% after aging at 873 K for 1000 h are realized in high-entropy CeNbO4+δ-based ceramics, indicating a breakthrough in the comprehensive performances of thermosensitive ceramics. This work opens up an effective way to design thermosensitive materials with ultrahigh comprehensive performance to meet the requirements of advanced high-temperature sensors.

Design Implementation of a Logger-Based Digital Thermometer

LM35 temperature sensor is a widely used 3-terminal sensor known for its precise temperature measurement capabilities without the need for external calibration circuitry. With a sensitivity of 10mV/°C, it operates within a temperature range of -55°C to 150°C, with an error margin of 0.5°C. This paper presents the development and testing of a logger-based digital thermometer using LM35 sensor, integrated with a dsPIC30F4013 digital signal processing controller, an LCD, a real-time clock (DS1307), and other essential components. The methodology involves the analysis of the sensor's sensitivity and its response under both stress and non-stress temperature conditions. The findings indicate that the sensor's output closely follows the theoretical sensitivity, with a negligible offset, ensuring accurate temperature measurements. Comparative analysis with a standard laboratory thermometer suggests that the digital sensor provides superior precision, with an error margin of ±0.01°C. The results confirm LM35's suitability for accurate ambient temperature monitoring and validation of environmental temperature fluctuations.

Printed Thick Film Resistance Temperature Detector for Real-Time Tube Furnace Temperature Monitoring.

Accurately acquiring crucial data on tube furnaces and real-time temperature monitoring of different temperature zones is vital for material synthesis technology in production. However, it is difficult to achieve real-time monitoring of the temperature field of tube furnaces with existing technology. Here, we proposed a method to fabricate silver (Ag) resistance temperature detectors (RTDs) based on a blade-coating process directly on the surface of a quartz ring, which enables precise positioning and real-time temperature monitoring of tube furnaces within 100-600 °C range. The Ag RTDs exhibited outstanding electrical properties, featuring a temperature coefficient of resistance (TCR) of 2854 ppm/°C, an accuracy of 1.8% FS (full scale), and a resistance drift rate of 0.05%/h over 6 h at 600 °C. These features ensured accurate and stable temperature measurement at high temperatures. For demonstration purposes, an array comprising four Ag RTDs was installed in a tube furnace. The measured average temperature gradient in the central region of the tube furnace was 5.7 °C/mm. Furthermore, successful real-time monitoring of temperature during the alloy sintering process revealed approximately a 20-fold difference in resistivity for silver-palladium alloys sintered at various positions within the tubular furnace. The proposed strategy offers a promising approach for real-time temperature monitoring of tube furnaces.

Infrared photodetection in graphene-based heterostructures: bolometric and thermoelectric effects at the tunneling barrier

Graphene/hBN/graphene tunnel devices offer promise as sensitive mid-infrared photodetectors but the microscopic origin underlying the photoresponse in them remains elusive. In this work, we investigated the photocurrent generation in graphene/hBN/graphene tunnel structures with localized defect states under mid-IR illumination. We demonstrate that the photocurrent in these devices is proportional to the second derivative of the tunnel current with respect to the bias voltage, peaking during tunneling through the hBN impurity level. We revealed that the origin of the photocurrent generation lies in the change of the tunneling probability upon radiation-induced electron heating in graphene layers, in agreement with the theoretical model that we developed. Finally, we show that at a finite bias voltage, the photocurrent is proportional to either of the graphene layers heating under the illumination, while at zero bias, it is proportional to the heating difference. Thus, the photocurrent in such devices can be used for accurate measurements of the electronic temperature, providing a convenient alternative to Johnson noise thermometry.