Non-contact Temperature Research Articles

DEVELOPMENT OF A METHOD FOR CONTACTLESS TEMPERATURE MEASUREMENT IN 3 SPECTRAL RANGES

A 3-spectral method for non-contact temperature measurement has been developed. Three silicon photodiodes were used. The separation of the spectrum is done by optical bandpass filters and beamspliters. It is possible to work in three modes: three-spectral, two-spectral (spectral ratio) and one-spectral. In the first mode, the temperature of objects with an unknown and variable emissivity can be measured. The last two modes give good results respectively for gray bodies and for objects with known emissivity.

Research on accurate non-contact temperature measurement method for telescope mirror.

Non-contact temperature measurement for a solar telescope mirror is critical for improving the mirror seeing and thermal deformation of solar telescopes, a long-standing challenge in astronomy. This challenge arises from the telescope mirror's inherent weak thermal radiation, often overwhelmed by reflected background radiations due to its high reflectivity. In this work, an infrared mirror thermometer (IMT) is equipped with a thermally-modulated reflector, and a measurement method based on an equation for extracting mirror radiation (EEMR) has been developed for probing the accurate radiation and temperature of the telescope mirror. Using this approach, we can extract the mirror radiation from the instrumental background radiation via the EEMR. This reflector has been designed to amplify the mirror radiation signal incident on the infrared sensor of IMT, while inhibiting the radiation noise from the ambient environment. In addition, we also propose a set of evaluation methods for IMT performance based on EEMR. The results reveal that the temperature measurement accuracy of IMT to the solar telescope mirror using this measurement method can be achieved better than ±0.15°C.

Design and development of a multifunctional moxibustion treatment machine based on heat-sensitive moxibustion therapy

A multifunctional moxibustion treatment machine is designed and developed to assist the heat-sensitive moxibustion therapy. Through the motion control of the stepping motor by programmable logic controller (PLC), the automatic control is obtained for the acupoint detection of heat-sensitive moxibustion therapy and the manual operation of moxibustion. The skin temperature is monitored in real-time, using infrared non-contact temperature measurement technology. Based on the deviation of the temperature set value and the monitoring one, the distance between the moxibustion device and the exerted region is adjusted automatically by PLC so that the temperature is controlled practically. The multifunctional moxibustion treatment machine based on the heat-sensitive moxibustion therapy is capable of the operation control of mild moxibustion, circling moxibustion, sparrow-pecking moxibustion and along-meridian moxibustion techniques, as well as real-time monitoring of skin temperature. The temperature change curve of this machine is coincident with that obtained by the manual operation of heat-sensitive moxibustion. This multifunctional moxibustion treatment machine assists the delivery of heat-sensitive moxibustion therapy and it is satisfactory in temperature control and precise in operation.

Errors of non-contact temperature measurement

In recent years, there is a trend of improving the performance and efficiency of all existing measuring instruments due to a leap in technology. Almost every industry uses a variety of technologies that apply temperature control. Temperature of a heated body can be estimated by measuring the parameters of its thermal radiation, which are electromagnetic waves of different lengths. Temperature measurement is necessary for comfortable automatic control and management of production processes. The use of non-contact means makes it possible to measure the temperature of, firstly, moving objects, secondly, objects in inaccessible places, thirdly, to avoid damage to the measuring instruments when controlling large temperatures. High speed, the possibility of measuring temperature without disconnecting the object from the technological process, ensuring personnel safety, temperature measurement up to 3000 °C – these are the advantages of non-contact temperature measurement method. To obtain reliable values when measuring thermophysical quantities it is necessary to know the processes occurring in interaction of the measuring device or sensor with the object of measurement. These processes affect the magnitude of the measurement error, that is, magnitude of the result deviation from the true value of the measured parameter. This paper describes the errors of non-contact temperature measurement of pyrometers, namely total radiation pyrometer, partial radiation pyrometer, spectral ratio pyrometer, as well as shows the results of comparative calculations between them. Expressions for the evaluation of methodical errors of total radiation, partial radiation and spectral ratio pyrometers are given, as well as the results of comparative calculations of errors are shown.

Remote sensing of human skin temperature by AI speckle pattern analysis

Analysis of dynamic differential speckle patterns, scattered from human tissues illuminated by a laser beam, has been found by many researchers to be applicable for noncontact sensing of various biomedical parameters. The COVID-19 global pandemic brought the need for massive rapid-remote detection of a fever in closed public spaces. The existing non-contact temperature measurement methods have a significant tradeoff between the measurement distance and accuracy. This paper aims to prove the feasibility of an accurate temperature measurement system based on speckle patterns analysis, enabling the sensing of human temperature from an extended distance greater than allowed by the existing methods. In this study, we used speckle patterns analysis combined with artificial intelligence (AI) methods for human temperature extraction, starting with fever/no fever binary classification and continuing with temperature measurement at higher resolution.

Enhanced non-contact optical temperature sensing performance based on upconversion luminescence in Ho3+/Yb3+ codoped ferroelectric 0.94Na0.5Bi0.5TiO3-0.06BaTiO3

The upconversion luminescence of ferroelectric 0.94Na0.5Bi0.5TiO3-0.06BaTiO3: xHo3+/0.01Yb3+ is investigated in detail. The prepared samples show intense characteristic emission from Ho3+ ions with a dominant green emission peak located at 547 nm under 980 nm excitation. Among these solid solutions, the 0.94Na0.5Bi0.5TiO3-0.06BaTiO3: 0.0075Ho3+/0.01Yb3+ ceramic possesses the optimum emission. Optical temperature sensing behavior of Ho3+/Yb3+ codoped ferroelectric 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 are investigated through fluorescence intensity ratio (FIR, I656/I547) induced by non-thermally coupled energy levels 5F5→5I8 and 5F4/5S2→5I8 in the range of 303–483 K. A moderate amount of Yb3+ doping in 0.94Na0.5Bi0.5TiO3-0.06BaTiO3: Ho3 + ceramic contributes to the improvement of their optical temperature sensing performance. At T = 303 K, the calculated highest relative sensitivity SR is 0.0042 K-1, which indicates that the optimized 0.94Na0.5Bi0.5TiO3-0.06BaTiO3: 0.0075Ho3+/0.01Yb3+ ceramic is promising as the candidate materials for noncontact optical temperature sensing devices.

Improved sensitivity of temperature sensor based on three-photons pumped upconversion in highly transparent Er3+ doped lead lanthanum zirconate titanate ceramics

Efficient two-photons and three-photons pumped upconversion emission were investigated in highly transparent Er3+ ions doped lead lanthanum zirconate titanate ceramics excited by using near infrared lasers centered at 980 nm, 1064 nm, and 1550 nm. Temperature dependent spectral changes of the multi-photons upconversion emission were explored, and highly sensitive temperature sensors were obtained based on the energy difference between 2H11/2 and 4S3/2. Using this temperature sensor, the temperature changes of the Er3+ ions doped lead lanthanum zirconate titanate ceramics was tested by irradiating the sample with a high-energy femtosecond laser at 1550 nm. This work is useful for developing a highly sensitive non-contact temperature measurement sensors, which provides the necessary theoretical basis for its practical application.

Optical temperature sensing behavior of aluminum sheet fused with CaSrSiO4:Yb3+, Er3+ phosphor

In this work, Al–CaSrSiO4:Yb3+,Er3+ temperature sensing materials were prepared by the high-temperature solid-phase reaction method, and the upconversion photoluminescence characteristics and optical temperature sensing properties were measured and discussed. Two intense green emissions were observed under the excitation of 980 nm semiconductor laser. The temperature sensing performance of the thermally coupled energy levels was evaluated based on the fluorescence intensity ratio technique in the temperature range from 303 to 723 K, and the maximum sensor sensitivity of the synthesized sample reaches 0.0059 K−1 at 453 K. Furthermore, the relationships between the absolute sensitivity SA and temperature T as well as between SA and energy gap ΔE are analyzed in depth. And then, a strategy to quickly match the temperature measurement range to a suitable temperature sensing material was proposed, and the as-prepared Al–CaSrSiO4:Yb3+,Er3+ sample was determined to be suitable for measuring the high-temperature environment. These observations suggest that Al–CaSrSiO4:Yb3+,Er3+ samples have promising applications for non-contact optical temperature measurement at high temperature and high sensitivity.

Structural and optical properties of a new structural modification of Na3+3xYb2−x(PO4)3:1% Eu phosphate, where x = 0,1-0,5 and prospective thermometric applications of the compound

The powders of Na3+3xYb2-x(PO4)3: 1% Eu3+ (where x = 0.1, 0.2, 0.3, 0.4 and 0.5) have been synthesized using thermal method in solid state. Their structural and spectroscopic properties were investigated by powder X-ray diffraction, microcalorimetric method (DSC), Raman, infrared, absorption and luminescence studies. It was find that the studied materials belong to the NASICON-type compounds and crystallize in rhombohedral or monoclinic type of structure. Photoluminescence of investigated samples presents typical emission of Eu3+ ions with the dominance of electric dipole transitions and near-infrared bands attributed to Yb3+ ions. Efficient red and infrared emissions under the excitation of 395 nm can be attractive for LED lighting. The highest Yb3+ emission intensity has been registered for the sample with the Na3.9Yb1.7(PO4)3: 1% Eu3+ composition (x=0.3). Ytterbium excited level can be populated by the energy transfer from the Eu3+ ions and can be enhanced by sample heating. Due to the non-radiative processes, the Eu3+ luminescence decay times monitored at 619 nm were bi-exponental. Because of the strong influence of temperature on emission intensities, obtained compounds can be useful for non-contact temperature readout, especially in the high-temperature region (above 600 K). The maximum value of relative sensitivity Sr is equal 2.91%K-1 at 855 K for the sample Na3+3xYb2-x(PO4)3: 1% Eu3+ (x=0.3).

Energy transfer of Tb3+→Eu3+ in Ca2Al2SiO7 phosphors with multicolor tunable and optical temperature sensing properties

Luminescent temperature sensors based on photoluminescent materials have received considerable attention for their advantages of quick and noninvasive measurement. In this paper, a series of Tb3+, Eu3+ single-doped and co-doped Ca2Al2SiO7 (CAS) phosphors were synthesized by sol-gel method. The phase purity, surface morphology, energy transfer, luminescence characteristics and temperature sensing properties of Tb3+, Eu3+ doped CAS phosphors have been studied carefully. Due to the energy transfer of Tb3+→Eu3+, CAS: Tb3+, Eu3+ phosphors demonstrate tunable luminescence under 238 nm excitation, in which the luminescence color gradually changes from purple-red to cool white, and then to warm white by continuously increasing the concentration of Tb3+ ions. The elongation of the fluorescence lifetime of Eu3+ with increasing Tb3+ ions content further confirms the energy transfer of Tb3+→Eu3+. The thermal behavior of CAS: Tb3+, Eu3+ phosphors shows enhanced luminescence intensity for 404 nm emission while suppressed luminescence intensity for 616 nm emissions with raising temperature, implying its potential in optical temperature sensing. Therefore, the temperature sensing performance is evaluated by using the fluorescence intensity ratio (I404 nm /I616 nm) in CAS: Tb3+, Eu3+ phosphors, showing a maximum relative sensitivity of 1.17%K−1 at 443 K. These results indicate that CAS: Tb3+, Eu3+ phosphors are promising candidates for tunable luminescence and non-contact temperature sensing.

Data recovery of 2D lifetime-based phosphor thermometry using deep neural networks

Thermographic phosphor (TP) thermometry has been widely used as one of the newly developed non-contact surface temperature measurement methods. However, temperature information is frequently lost locally because chemical bonding coatings are easily damaged during the measurement. This limits its application, such as in the case of jet impact, high-speed motion, high vibration, etc. We proposed to use of deep neural networks (DNNs) as a tool for recovering lost data. In this study, we captured the dynamic two-dimensional (2D) temperature field of jet impingement cooling a high temperature plate by TP thermometry. Different parts of the temperature information, including jet impact area and non-impact area, were then removed to assume the coating was damaged. A prediction model was established by the DNNs using the 2D space and time coordinates as the input dataset and using the temperature information corresponding to the coordinates as the output dataset. The removed temperature information was then recovered using the developed regression model and compared with the raw temperature field to evaluate predicted results. The results showed that the removed data can be successfully recovered using the established DNN prediction model, in which the predicted accuracy was greater than 94.94%. While in the central and the boundary area of the jet, the model has a relatively poor performance, which is mainly due to the large temperature gradients. These results indicate that the established DNN model can be used to recover the lost temperature information but it is limited for applications in regions with drastic temperature changes.

Designing dual mode of non-contact optical thermometers in double perovskite Ca2LaTaO6:Bi3+, Eu3+ phosphors

Optical performance for rigorous non-contact temperature measurement needs to overcome the disadvantages of low sensitivity and poor signal discriminability. In this work, Bi3+ and Eu3+ co-doped Ca2LaTaO6 (CLTO) phosphors were synthesized by a solid phase method. The crystal structures of the cations in various coordination environments were confirmed by means of XRD, XPS, and DRS. Using SEM and TEM techniques, the morphology of the samples was investigated in detail. Furthermore, the occupancy of the two luminescent centers of Bi3+ was analyzed in detail based on the luminescence properties of the CLTO:Bi3+ phosphor. Additionally, dipole–dipole interaction contributes to the energy transfer from Bi3+ to Eu3+ ions in the CLTO host, and the transfer efficiency is as high as 100%. Finally, given the different responses of Bi3+ and Eu3+ to temperature, a dual-mode optical thermometer was designed. Based on FIR technology, the maximum Sa and Sr values are 0.041 K-1 and 0.76% K−1, respectively. Also, the maximum value of Sr of the Bi3+ temperature-dependent lifetime is 1.04%K−1 at 293 K. These results indicate that the designed dual-mode optical thermometers of CLTO:Bi3+,Eu3+ have great potential in temperature measurement.

Design of a Compact Analog Complex Correlator for Millimeter-Wave Radiation Temperature Measurement System.

Human body temperature is a fundamental physiological sign that reflects the state of physical health. It is important to achieve high-accuracy detection for non-contact human body temperature measurement. In this article, a Ka band (32 to 36 GHz) analog complex correlator using the integrated six-port chip is proposed, and a millimeter-wave thermometer system based on the designed correlator is completed for human body temperature measurement. The designed correlator utilizes the six-port technique to achieve large bandwidth and high sensitivity, and miniaturization of the correlator is achieved through an integrated six-port chip. By performing the single-frequency test and the broadband noise measurement on the correlator, we can determine that the dynamic range of input power of the correlator is -70 dBm to -35 dBm, and the correlation efficiency and equivalent bandwidth are 92.5% and 3.42 GHz, respectively. Moreover, the output of the correlator varies linearly with the input noise power, which reveals that the designed correlator is suitable for the field of human body temperature measurement. Then, a handheld thermometer system, with a size of 140 mm × 47 mm × 20 mm, is proposed using the designed correlator, and the measurement results show that the temperature sensitivity of the thermometer is less than 0.2 K.

A Traceable Spectral Radiation Model of Radiation Thermometry

Despite great technical capabilities, the theory of non-contact temperature measurement is usually not fully applicable to the use of measuring instruments in practice. While black body calibrations and black body radiation thermometry (BBRT) are in practice well established and easy to accomplish, this calibration protocol is never fully applicable to measurements of real objects under real conditions. Currently, the best approximation to real-world radiation thermometry is grey body radiation thermometry (GBRT), which is supported by most measuring instruments to date. Nevertheless, the metrological requirements necessitate traceability; therefore, real body radiation thermometry (RBRT) method is required for temperature measurements of real bodies. This article documents the current state of temperature calculation algorithms for radiation thermometers and the creation of a traceable model for radiation thermometry of real bodies that uses an inverse model of the system of measurement to compensate for the loss of data caused by spectral integration, which occurs when thermal radiation is absorbed on the active surface of the sensor. To solve this problem, a hybrid model is proposed in which the spectral input parameters are converted to scalar inputs of a traditional scalar inverse model for GBRT. The method for calculating effective parameters, which corresponds to a system of measurement, is proposed and verified with the theoretical simulation model of non-contact thermometry. The sum of effective instrumental parameters is presented for different temperatures to show that the rule of GBRT, according to which the sum of instrumental emissivity and instrumental reflectivity is equal to 1, does not apply to RBRT. Using the derived models of radiation thermometry, the uncertainty of radiation thermometry due to the uncertainty of spectral emissivity was analysed by simulated worst-case measurements through temperature ranges of various radiation thermometers. This newly developed model for RBRT with known uncertainty of measurement enables traceable measurements using radiation thermometry under any conditions.

The dual-mode sensing of pressure and temperature based on multilayer structured flexible sensors for intelligent monitoring of human physiological information

Flexible multifunctional sensor with excellent performance via unsophisticated fabrication method is imperatively anticipated for the development of smart human health monitoring systems and wearable electronic devices. Here, we report a multilayer dual-mode flexible sensor (DMFS) by integrating different sensing layers on the two sides of a flexible dielectric substrate for sensing pressure and temperature. The introduction of elastic nanofiber skeleton structure and internal “sea urchin” like conductive materials is the top priority for the DMFS to have excellent sensing performance and durability. As a result, the fabricated DMFS ultimately shows excellent pressure sensitivity of 111.96 kPa−1 within a wide sensing range up to 70 kPa. In the case of temperature stimulus, the DMFS accomplishes a high, linear response to the ambient temperature variation within the range from 20 °C to 50 °C, while maintaining high stability and durability after long-term bending cycles. In addition, DMFS reveals its great potential for non-contact dynamic temperature measurement by being integrated into an intelligent temperature monitoring system. Most importantly, a novel smart human health-monitoring system, which attributes to the coordination and common work of multiple DMFS, has been developed and realizes simultaneous detection of multiple physiological signals of human beings in real-time.

Freezing characteristics of supercooled water in gas diffusion layer of proton exchange membrane fuel cells

The freezing characteristics of supercooled water in a gas diffusion layer (GDL), which are the bases for the cold start-up of proton exchange membrane fuel cells (PEMFCs), were investigated. An experimental apparatus for noncontact temperature measurement and observation systems was developed. GDL and GDL with a microporous layer (MPL) were prepared, and freezing experiments using a water-containing GDL under various cooling rates were performed with variations in polytetrafluoroethylene (PTFE) content and water saturation. Furthermore, based on the experimental results, the freezing initiation probability was theoretically investigated to elucidate the freezing characteristics. Results showed that, with increasing supercooling of water in GDL, the freezing probability of water increased abruptly. The effect of saturation showed a different trend depending on PTFE addition. For the GDL without PTFE, the freezing initiations occurred at approximately 6 °C of supercooling degree, and the probability approached 1.0 at approximately 9.5–11.5 °C, with saturation dependency. In contrast, for both GDL and GDL + MPL containing PTFE, the initiation temperature characteristics were relatively similar, which were approximately 8–12 °C, regardless of the saturation and PTFE content. In these cases, the ice-nucleating activity of water in the GDL was possibly stronger than that in the MPL.

Excellent Sensitive Temperature Sensing Performance Based on Fluorescence Intensity Ratio Technique of Yb3+/Er3+ Codoped Gd2(WO4)3

For noncontact temperature sensing, the fluorescence intensity ratio (FIR) technique based on thermally coupled levels has great prospects. Within this technique, Yb3+/Er3+ codoped upconversion (UC) particles are regarded as efficient material. Juanqin Xue and co-workers (article number 2200471) have prepared Yb3+/Er3+ codoped Gd2(WO4)3 particles by a facile coprecipitation method and subsequent calcination. The crystal structure, microstructure, and UC emission of the particles are studied in detail, and the optimum temperature sensing performance is systematically measured. Excellent temperature-sensitive properties of Gd2(WO4)3:Yb3+/Er3+ demonstrate great potential for its application in noncontact optical temperature sensors.

Parametric study on four station ball mill for synthesis of ultrafine powders

One of the most common approaches to creating ultrafine materials is ball milling. Among the various types of ball mills, planetary ball mills are widely used by the research community. A planetary type ball mill is economical, simple to operate, and ideally suited for small-quantity batch type synthesis of powders and alloys and for reactive processing of powders. The size of the jar and balls, rotational speed, milling duration, ball-to-powder ratio, jar material, milled material, and temperature are the most important process factors in ball milling. Temperature was determined with the help of non-contact temperature measuring device. The rate of grain size reduction and the minimum grain size that can be achieved for a given powder material depend on the above parameters. A huge number of tests would be needed to find the optimal values for the approximately ten process parameters with interaction effects. As part of this research effort, a Taguchi Design of Experiments (DOE) approach was adopted to determine the optimum process parameters to obtain the fine grain sizes for iron, cobalt, and nickel powders. Although the ball-to-powder ratio and ball milling time each have around a 20–25% impact on the grain size reduction rate, ball milling speed has almost a 48% impact. The powders were characterised for grain size using an x-ray diffraction technique, and the powder morphology was studied using a scanning electron microscope.

Boosting temperature sensing capacity within isoreticular zinc(II) metal-organic frameworks luminescent thermometers

Developing a convenient and accurate temperature detection method is of great importance in industrial production, biochemical processes and scientific research. As a noncontact optical temperature sensing technique, luminescence thermometry has been attracted increasing interest. Here we present two Zn(II) metal-organic frameworks (MOFs) with the formulas of {(H3O)[Zn2(btca)2(taz-NH2)x(taz-CH3)1-x]·H2O}n (x ​= ​1 (1); x ​= ​0 (2)) (H2btca ​= ​benzotriazole-5-carboxylic acid, Htaz-NH2 ​= ​5-amino-1H-tetrazole and Htaz-CH3 ​= ​5-methyl-1H-tetrazole) by virtue of the mixed-ligand approach for photoluminescence sensors as luminescence thermometries over tunable temperature range. Two MOFs exhibit 1D hexagonal nano-channels along the [100] direction, occupied by lattice water molecules. The temperature dependent photoluminescent characteristic of 1 and 2 reveal that the luminescence signals can be decreased as temperature rises from 120 to 400 ​K, thereby achieving the non-destructive temperature detection. Furthermore, linear correlations are presented between the luminescence intensities and the low temperatures for 1 and 2. Satisfying relative sensitivities of 0.49% K−1 for 1 and 0.61% K−1 for 2, and small temperature uncertainties of 0.062 ​K for 1 and 0.049 ​K for 2 ​at 400 ​K could be acheieved. Notably, the intensity-based luminescent thermometer measurements reveal that 2 shows extremely more linear with temperature and wider temperature range than those of 1, indicating that 2 is a more considerable luminescence thermometry over tunable temperature range.

Luminescence intensity ratio based wide range contactless temperature sensing properties of Er3+/Yb3+ ions co-doped La2Ti2O7 ceramics

Temperature sensing in the range (93–773 K) using luminescence intensity ratio method has been studied in rare earth ion modified La2-x-yErxYbyTi2O7 powders and ceramics. The optimised composition with (x = 0.025, y = 0.05) shows improved upconversion luminescence. For temperature sensing applications the need for excellent phase purity and better densification is emphasized in ceramics. In comparison to phase-impure calcined powders, single phase dense ceramic shows improved upconversion emission and better thermometric performance. The sintered ceramic is found useful for non-contact temperature sensing with a wider operating temperature range (243–1293 K) in comparison to calcined powders (163–863 K). The optimised phosphor in ceramic form exhibits good linearity in the range (173–393 K). Repeatability experiments reveal measurement accuracy within the range − 0.5 to + 0.8 K. Repeated heating and cooling cycles from 190 to 455 K show minimal thermal fatigue. The precision of the temperature read-out from the optical sensor by the intensity ratio method is found to be better (0.24%) at higher temperatures (>373 K) in comparison to the estimated precision of 2.1% at lower temperatures.