Radiometric Temperature Measurements Research Articles

Performance of adjustable multilayer film based on radiation cooling and electrochromism

Energy and environmental challenges caused by the excessive consumption of fossil fuels are major concerns worldwide, and the use of automotive air conditioning can increase total fuel consumption by 10% to 30%, thereby exacerbating these problems. To reduce the energy consumption for automotive air conditioning, a multilayer-film design based on radiative cooling and electrochromic modulation is proposed for regulating the temperature inside vehicles. The designed multilayer-film not only passively realizes temperature drop but also actively regulates the entry of solar radiation, which can help the vehicle air conditioning system to adjust the interior temperature autonomously. To verify its effectiveness, a film-applied empty box device is designed for radiometric temperature measurement. Experimental results indicate that the maximum interior temperature drop of the multilayer film increases by approximately 9.8 ℃ compared with that of single-layer films in the sunlight irradiation, and dynamic temperature regulation of about 4.6 ℃ can be achieved by adjusting the transmittance of the multilayer film. To study the environmental adaptability of the multilayer film, experiments are conducted on an outdoor film-applied device during the summer and winter in Shenyang, China (<inline-formula><tex-math id="Z-20241025175516">\begin{document}$\rm 41^\circ44'N, 123^\circ39'E$\end{document}</tex-math></inline-formula>), the place which is characterized by a typical temperate continental climate. Results indicate that under high temperature conditions of 30–40 ℃ in summer, the maximum internal temperature drop of the multilayer film reaches 12.9 ℃; while under low temperature conditions of 0–15 ℃ in autumn and winter, the maximum internal temperature drop is only 1.9 ℃, preventing the interior temperature from being too low. In addition, the maximum interior temperature drop increases with the solar radiation intensity and ambient temperature increasing. Therefore, the proposed multilayer-film design, with its potential for temperature self-regulation, provides a promising solution for reducing energy consumption and improving passenger comfort.

Generalized inverse matrix-graphic deep learning algorithm for multispectral pyrometer temperature inversion.

The multispectral radiometric temperature measurement technique is affected by the unknown emissivity, and there is no multispectral radiometric temperature inversion algorithm applicable to any scene or target. To address the above problems, this paper converts the multispectral radiometric temperature inversion problem into an image recognition problem containing the temperature information to be measured, and proposes a graphical multispectral radiometric temperature adaptive inversion algorithm. In this paper, we use the difference between spectral channels to convert the one-dimensional radiation data into a two-dimensional radiation map; use the generalized inverse to obtain the spectral emissivity distribution features, fuse them with the two-dimensional radiation map, and use an improved deep learning network to achieve adaptive temperature inversion. It is experimentally verified that the algorithm proposed in this paper can achieve simultaneous inversion of temperature and emissivity for any scene or target with sufficient data set.

Graphical multispectral radiation temperature inversion algorithm based on deep learning.

Neural networks are the most promising tool to solve the problem that an assumed emissivity model is needed in the field of multispectral radiometric temperature measurement. Existing neural network multispectral radiometric temperature measurement algorithms have been investigating the problems of network selection, network porting, and parameter optimization. The inversion accuracy and adaptability of the algorithms have been unsatisfactory. In view of the great success of deep learning in the field of image processing, this Letter proposes the idea of converting one-dimensional multispectral radiometric temperature data into two-dimensional image data for data processing to improve the accuracy and adaptability of multispectral radiometric temperature measurement by deep learning algorithms. Simulation and experimental validation are carried out. In the simulation, the error is less than 0.71% without noise and 1.80% with 5% random noise, which improves the accuracy by more than 1.55% and 2.66% compared with the classical BP (backpropagation) algorithm, and 0.94% and 0.96% compared with the GIM-LSTM (generalized inverse matrix-long short-term memory) algorithm. In the experiment, the error is less than 0.83%. This indicates that the method has high research value and is expected to lead multispectral radiometric temperature measurement technology to a new level.

Radiometric Temperature Measurement of Copper Concentrates in Flash Smelting Conditions Simulated at Laboratory Scale Coupled With a Macroscopic Chemical Reaction Model and Automated Mineralogical Characterization

Radiometric Temperature Measurement of Copper Concentrates in Flash Smelting Conditions Simulated at Laboratory Scale Coupled With a Macroscopic Chemical Reaction Model and Automated Mineralogical Characterization

Multispectral radiometric temperature measurement algorithm for turbine blades based on moving narrow-band spectral windows.

This paper addresses the problem of inaccurate emissivity presets for multispectral temperature measurements of aero-engine turbine blades and proposes a narrow-band spectral window moving temperature inversion algorithm that does not rely on an assumed emissivity model. As the emissivity of the measured object changes slowly over the narrow spectral window, the temperature corresponding to the normalized spectral radiation intensity for each window in the set temperature range is calculated using the Mahalanobis distance coefficient. The temperature error is less than 1.33% relative to thermocouple measurements when using this algorithm to perform temperature inversion on the experimental spectrum curves for different types of alloy samples. Furthermore, a two-dimensional spectral temperature field measurement platform was built, and the surface temperature fields of alloy samples were reconstructed using the narrow-band spectral window moving algorithm. The proposed algorithm is shown to provide high-precision inversion of the temperature field without presetting the emissivity model, which gives a new processing concept for the application of infrared spectral temperature measurements.

Radiometric temperature measurement by incoherent digital holography.

This study aims to demonstrate radiometric temperature measurement using incoherent digital holography. Since in-focus images of thermal radiations can be reconstructed at any distance, three-dimensional radiometric temperature can be measured. This requires an optical configuration with a fixed magnification to record an incoherent hologram that contains information about the spectral radiance of an object. The derivation of spectral radiance from the intensity signal of a reconstructed image is described, in addition to calibration procedures correlating the holographic signal to radiation temperature. The experimental results and possible sources of uncertainty are discussed.

Assessment of Double Modulation Pyrometry as a diagnostic tool for use in concentrated solar facilities

Double modulation pyrometry (DMP) is a pyrometric method developed to enable radiometric temperature measurements in solar simulators, where solar blind pyrometry cannot be applied due to the continuous spectrum of the artificial light source. Sofar, DMP has been characterized in two solar simulator facilities, but no direct comparison to a reference pyrometer has been performed until now due to the limitations of applying pyrometry in solar simulators. Here, a series of experiments is reported that were conducted in concentrated natural sunlight where reference pyrometers are available. They demonstrate the performance enhancement gained by utilizing the inherent advantages of DMP, i.e. the in-situ reflectance measurement and the freedom to select the operation wavelength.

Double Modulation Pyrometry Applied to Radiatively Heated Surfaces With Dynamic Optical Properties

The accuracy of radiometric temperature measurement in radiatively heated environments is severely limited by the combined effects of intense reflected radiation and unknown, dynamically changing emissivity, which induces two correlated and variable error terms. While the recently demonstrated double modulation pyrometry (DMP) eliminates the contribution of reflected radiation, it still suffers from the shortcomings of single-waveband pyrometry: it requires knowledge of the emissivity to retrieve the true temperature from the thermal signal. Here, we demonstrate an improvement of DMP incorporating the in situ measurement of reflectance. The method is implemented at Paul Scherrer Institute (PSI) in its 50 kW high-flux solar simulator and used to measure the temperature of ceramic foams (SiSiC, ZrO2, and Al2O3) during fast heat-up. The enhancement allows DMP to determine the true temperature despite a dynamically changing emissivity and to identify well-documented signature changes in ZrO2 and Al2O3. The method also allows us to study the two dominant error sources by separately tracking the evolution of two error components during heat-up. Furthermore, we obtain measurements from a solar receiver, where the cavity reflection error limits measurement accuracy. DMP can be used as an accurate radiometric thermometer in the adverse conditions of concentrated radiation, and as a diagnostic tool to characterize materials with dynamic optical properties. Its simple design and ability to correct for both errors makes it a useful tool not only in solar simulators but also in concentrated solar facilities.

Atacama Field Campaign: laboratory and in-situ measurements for remote sensing applications

ABSTRACTThis work presents the preliminary results of the first field calibration campaign performed in the Atacama Desert, Chile, between the 18 and 22 August 2014, called the Atacama Field Campaign (ATAFIC 2014). In situ measurements were performed in order to spectrally characterize the surface reflectance spectra between 0.3 and 2.5 µm, radiometric temperature (8.0–14.0 µm) and atmospheric measurements. A soil sample was collected and analyzed using Fourier Transform Infrared Spectroscopy and X-Ray Diffraction techniques to characterize the surface reflectance spectra and mineralogical composition, respectively. ASTER land surface emissivity in addition to GOES, MODIS and Landsat-8 land surface temperature (LST) were also used. Results showed that the spectral features of the Atacama soil and the characteristics of this geographical zone, which is featured as the most hyper-arid and cloudless place in the world, make this area a potential target for surface reflectance characterization. Day and night LST comparison between field and remote sensing data are lower than 2 K and the Root Mean Square Error for land surface emissivity is close to 2%. This work opens the possibilities to consider the Atacama Desert as a reference target for calibration and validation activities for earth observation missions’ purposes.

Spectral-brightness pyrometry: Radiometric measurements of non-uniform temperature distributions

The paper proposes spectral-brightness pyrometry (SBP) as a new approach to measure the temperature field dynamics on the emitting body surface. The brief review of modern methods of pyrometry – radiometric temperature measurements – is presented. Their properties are analyzed in the Wien’s approximation. The SBP combines the high resolution on temperature, time, and space typical for the brightness pyrometry instruments, and small methodical error of temperature measurements of materials with unknown emissivity intrinsic for spectral pyrometers. The peculiarity of this method is calibration of the brightness pyrometer – thermal vision camera – directly during the measurement process using the integral thermal radiation spectrum of the object. The mathematical model of the SBP measurement system is proposed, the technique of data processing based on this model is verified. The examples of practical implementation of the SBP method for the determination of temperature field dynamics of objects with unknown emissivity are presented.

Ice detection using thermal infrared radiometry on wind turbine blades

Abstract Wind farms are located in areas with a high probability of ice occurrence. Icing involves problems such as energy losses, mechanical failures and downtimes. The priority is to detect icing in order to avoid these problems. Icing detection is a complex procedure for example, low temperatures are not a guaranty of ice formation, and other variables may affect. Different techniques have been recently proposed to detect ice in wind turbine blades. They are mainly based on damping of ultrasonic waves on the blade surface, or measuring the resonant frequency of a probe. But these methods have some drawbacks that may cause the system to fail, e.g. the behaviour of ultrasonic waves in composite materials is difficult to predict due to different fibre orientations, and the ice detection by changes in the resonance frequency could lead to false alarms due to variations in working conditions. This paper takes advantage of the remote sensing techniques to propose a novel approach for icing detection without physical contact. The approach is based on the drastic emissivity change that it is produced over a surface characterized with a low emissivity value when ice appears. An experiment was conducted using a broad-band thermal radiometer and a section of a wind turbine blade. Radiometric temperature measurements were collected over the blade with and without an aluminium foil patch. The piece of blade was cooled down and different scenarios were considered, including frozen with and without ice. This study was completed with a sensitivity analysis of the approach to dust accumulation, accounting for real operation conditions. Results show the feasibility of this technique to detect ice formation and discern between frozen and icing conditions.

Radiometric temperature measurement with Si and InGaAs single-photon avalanche photodiode.

We experimentally demonstrate the use of single-photon avalanche photodiode (SPAD) for radiometric temperature measurement. The low dark count rate CMOS SPAD and a commercial InGaAs/InP SPAD can detect the thermal radiation from a blackbody down to the temperatures of 510 and 405 K, respectively. Our work shows that current SPADs are cost-effective thermal sensors for various applications.

Continuous Temperature Measurement of Liquid Iron and Slag Tapped from a Blast Furnace

Temperature measurements of liquid pig iron coming out of a blast furnace are essential for estimating the thermal condition in the hearth. The temperature is generally monitored by a disposable thermocouple on a runner. This paper proposes radiometric temperature measurement that targets an iron-slag-mixed stream in front of a taphole. It enables non-contact continuous thermometry. Liquid iron and slag are spatially separated on a thermal image obtained by a CCD camera with a high-speed electronic shutter. Molten iron temperature is calculated from the iron radiance detected automatically by means of histogram processing of the thermal image. Regarding optically semitransparent molten slag, its radiance varies as a function of the thickness. Slag temperature is determined from the highest radiance, presuming that the emittance of sufficiently thick slag converges on a constant. The authors performed an on-site test at a blast furnace in ordinary operation. It was confirmed that both iron and slag temperatures were continuously monitored. The temperature data obtained from the test showed findings such as unsteady temperature difference between the two liquids and discontinuous temperature fluctuation. This imaging thermometry technique is expected to be used in a new sensor for blast furnace operation.

Microwave Radiometric Remote Sensing of Volcanic Ash Clouds From Space: Model and Data Analysis

The potential of satellite passive microwave sensors to provide quantitative information about near-source volcanic ash cloud parameters is assessed. To this aim, ground-based microwave weather radar and spaceborne microwave radiometer observations are used together with forward-model simulations. The latter are based on 2-D simulations with the numerical plume model Active Tracer High-Resolution Atmospheric Model (ATHAM), in conjunction with the radiative transfer model Satellite Data Simulator Unit (SDSU) that is based on the deltaEddington approximation and includes Mie scattering. The study area is the Icelandic subglacial volcanic region. The analyzed case study is that of the Grimsvotn eruption in May 2011. ATHAM input parameters are adjusted using available ground data, and sensitivity tests are conducted to investigate the observed brightness temperatures and their variance. The tests are based on the variation of environmental conditions like the terrain emissivity, water vapor, and ice in the volcanic plume. Quantitative correlation analysis between ATHAM/SDSU forward-model columnar content simulations and available microwave radiometric brightness temperature measurements, derived from the Special Sensor Microwave Imager/Sounder (SSMIS), are encouraging in terms of both dynamic range and correlation coefficient. The correlation coefficients are found to vary from -0.37 to -0.63 for SSMIS channels from 91 to 183 ± 1 GHz, respectively. The larger sensitivity of the brightness temperature at 183 ± 1 GHz to the columnar content, with respect to other channels, allowed us to consider this channel as the basis for a model-based polynomial relationship of volcanic plume height as a function of the measured SSMIS brightness temperature.

Short wavelength thermography: Theoretical and experimental estimation of the optimal working wavelength

Radiometric temperature measurement methods, such as thermography, use mainly radiation in the infrared spectrum. In this wavelength range, applications are limited by the diffraction to macroscopic devices. The empirical optical resolution limit is given by the Rayleigh criterion. Given the interest in the study of thermal microsystems, we propose an optimization criterion taking into account both the thermal sensitivity and the signal to noise ratio of the considered radiometric methods. The optimization analysis results highlight the opportunity to reduce the working wavelength of thermography applications and, thus, improving the spatial resolution limit of the radiometric method used. This theoretical approach for wavelengths optimization of the radiometric methods is experimentally validated by a phase transition temperature measurement of a fused aluminium bath in both visible and near infrared spectral ranges.

Experimental Study of a Hybrid Microwave Radiometry—Hyperthermia Apparatus With the Use of an Anatomical Head Phantom

This paper presents the latest progress made concerning a hybrid diagnostic and therapeutic system able to provide focused microwave radiometric temperature and/or conductivity variation measurements and hyperthermia treatment. Previous experimental studies of our group have demonstrated the system performance and focusing properties in phantom as well as human experiments. The system is able to detect temperature and conductivity variations with frequency-dependent detection depth and spatial sensitivity. Numerous studies have also demonstrated the improvement of the system focusing properties attributed to the use of dielectric and left handed matching layers. In this study, similar experimental procedures are performed but this time using an anatomical head model as phantom aiming to achieve a more accurate modeling of the system's future real function. This way, another step is made toward the deeper understanding of the system's capabilities, with the view to further use it in experimental procedures with laboratory animals and human volunteers.

Improved Radiometric Performance Attained by an Elliptical Microwave Antenna With Suction

We present a new way to securely mount a medical microwave antenna onto the human body for improved in vivo temperature measurements by microwave radiometry. A low cost and simple vacuum pressure source is used to provide suction (negative pressure) on the aperture of an elliptical antenna with vacuum chamber cavity backing. The concept offers improved electromechanical coupling between the antenna surface and the skin of the body. The proposed solution is evaluated experimentally to test repeatability of radiometric temperature measurements by remounting the antenna many times in one sequence on a given anatomical location. Four representative locations (hand, belly, hip, and chest) were used to test the suction antenna concept against anatomical curvature and load variations. Statistical analysis shows a marked decrease in the standard deviation of measured temperatures with the use of suction compared to conventional manual fixation. At repeated measurements, the vacuum antenna produces less uncertainty and improved estimate of the true lossy load temperature. During body movement, the antenna mounted at bone-filled areas shows greatest potential for improved performance.

Absolute Radiometry for the MeP-K: The Irradiance Measurement Method

The “Mise en pratique for the definition of the kelvin” (MeP-K) as a guide for the realization of the kelvin is presently revised to incorporate the temperature scales in current use as the best formal approximations of the thermodynamic temperature and, additionally, direct methods of thermodynamic temperature measurement. Within the MeP-K, the CCT WG 5 “Radiation Thermometry” develops a document to facilitate the implementation of thermodynamic temperature measurements at temperatures above the silver fixed point (961.78 °C). Three thermodynamic temperature measurement methods, all relying on absolute spectral-band radiometry, are proposed. To make these techniques more accessible for the broader thermometry community, each of these methods is described in detail in an accompanying paper to the MeP-K. These descriptions shall not be understood as a restriction to other possible radiometric methods of thermodynamic temperature measurement. One of the methods of radiometric temperature measurement above the silver point is the absolute measurement of irradiance in a well-defined spectral band. This is a straightforward method, which relies on filter radiometers with known spectral irradiance responsivity and a well-defined observation geometry, without any imaging technique. It has been developed for thermodynamic temperature measurements of precision blackbodies as primary standards for radiometry and thermometry and for the investigation of the uncertainty of the ITS-90 as an approximation of the thermodynamic temperature over a period of nearly 20 years at PTB. The article describes the design of the applied filter radiometers, their calibration chain, and their long-term stability. Additionally, the details and requirements of the experimental procedure for obtaining thermodynamic temperatures with this method are presented. Finally, relevant results obtained with this method, which is also applicable for temperatures significantly below the silver fixed point, are reviewed.

Radiation thermometry of silicon wafers based on emissivity-invariant condition

An emissivity-invariant condition for a silicon wafer was determined by simulation modeling and it was confirmed experimentally. The p-polarized spectral emissivity at a wavelength of 900 nm and at temperatures over 900 K was constant at 0.83 at an angle of about 55.4° irrespective of large variations in the oxide layer thickness and the resistivity due to the different impurity doping concentrations of the silicon wafer. The expanded uncertainty, U(c) = ku(c) (k = 2), of the temperature measurement is estimated to be 4.9 K. This result is expected to significantly enhance the accuracy of radiometric temperature measurements of silicon wafers in actual manufacturing processes.

X-ray diffraction in the pulsed laser heated diamond anvil cell

We have developed in situ x-ray synchrotron diffraction measurements of samples heated by a pulsed laser in the diamond anvil cell at pressure up to 60 GPa. We used an electronically modulated 2-10 kHz repetition rate, 1064-1075 nm fiber laser with 1-100 μs pulse width synchronized with a gated x-ray detector (Pilatus) and time-resolved radiometric temperature measurements. This enables the time domain measurements as a function of temperature in a microsecond time scale (averaged over many events, typically more than 10,000). X-ray diffraction data, temperature measurements, and finite element calculations with realistic geometric and thermochemical parameters show that in the present experimental configuration, samples 4 μm thick can be continuously temperature monitored (up to 3000 K in our experiments) with the same level of axial and radial temperature uniformities as with continuous heating. We find that this novel technique offers a new and convenient way of fine tuning the maximum sample temperature by changing the pulse width of the laser. This delicate control, which may also prevent chemical reactivity and diffusion, enables accurate measurement of melting curves, phase changes, and thermal equations of state.