Temperature Measurement Technique Research Articles

Time-Resolved Temperature-Jump Measurements and Theoretical Simulations of Nanoscale Heat Transfer Using NaYF4:Yb3+:Er3+ Upconverting Nanoparticles

We introduce for the first time a time-resolved temperature measurement technique which relies on temperature-jump luminescence thermometry using NaYF4:Yb3+:Er3+ upconverting nanocrystals. This new time-resolved technique is based on optical thermometry using upconverting nanoparticles (UCNPs) and does not have to infer temperature from changes in the optical properties of the heater or surrounding local environment. We have prepared gold-decorated UCNPs that function as a dual single-heater thermometer system. We measure the time-resolved temperature jump from nanocrystal clusters and compare our results to simulated thermal transfer data generated using finite element methods. The simulated data show that temperature dissipation follows a power law where the temperature change is inversely related to time. This result agrees with a thermal diffusion model where a semi-infinite medium is exposed to a sudden temperature change at its surface, but the simulated results do not agree that the heat transfer p...

Feasibility study of long-wave infrared thermometry technique for simultaneous temperature and heat flux measurement

Feasibility study of long-wave infrared thermometry technique for simultaneous temperature and heat flux measurement

A New Online Temperature Compensation Technique for Electronic Instrument Transformers

Electronic instrument transformers are expected to play a significant protection and control role in the future smart grids. This paper aims at improving the performance and accuracy of electronic instrument transformers that are replacing the conventional current and potential transformers in the future digital substations. One of the main issues associated with the electronic instrument transformer is its poor thermal stability that affects the accuracy of the measurements. In this paper, to overcome this issue, a new wireless temperature measurement and compensation technique is proposed. In this technique, the operating temperature of the electronic transformer is continuously monitored and its impact on the measurements is compensated in real-time. The experimental results reveal that the proposed technique can effectively improve the thermal stability and measurement accuracy of the electronic instrument transformers.

A Novel Surface <inline-formula> <tex-math notation="LaTeX">$LC$ </tex-math> </inline-formula> Wireless Passive Temperature Sensor Applied in Ultra-High Temperature Measurement

In this paper, we demonstrate a passive wireless surface temperature sensor, based on a high-temperature co-fired ceramic process and a thick-film technology, which is functional up to 1400 °C. In addition, we propose a temperature measurement technique that makes use of the absolute amplitude of the S11 parameter. The sensor comprises an inductor (created from platinum) deposited on a ceramic substrate (99% alumina), making it cheap and easy to fabricate using a screen-printing technology, due to its simple structure. The use of temperature resistant materials, and a completely passive structure, means that this sensor is robust to harsh environments. The device operates using the principle of $LC$ resonance, illustrated in this paper with a lumped circuit model. The dielectric constant of the substrate increases with increasing temperature, leading to a monotonic variation in the resonant frequency of the sensor, which is retrieved wirelessly via a readout antenna. We set the test distance between the sensor and the antenna to 10 mm and observed a repeatable response between 26 °C and 1400 °C. S11 amplitude and resonant frequency are used to reflect the change temperature, respectively. And we found that it is more accurate to test the temperature by resonant frequency after comparing the experimental results. The average sensitivity of temperature test by resonance frequency is obtained, which is 14.3 kHz/°C.

Temperature measurement using infrared thermometry within semi-transparent media

ABSTRACTInfrared thermometry is a widely used technique for contactless temperature measurement, which is often conducted through semi-transparent media. In the present work, influences on the measurement results stemming from semi-transparent media and from the optical characteristics of the measurement setup are discussed. Results of two experimental setups, containing low, medium, and high transmission media are presented and compared to calculated data using a one-dimensional analytical approach and a three-dimensional ray-tracing algorithm. It is shown through modeling and experiments that the surroundings and, in particular, the (semi)transparent materials within the optical path are critical for accurate temperature measurements.

Fiber-optic simultaneous distributed monitoring of strain and temperature for an aircraft wing during flight.

We applied a fiber optic distributed simultaneous strain and temperature measurement technique to the structural monitoring of the main wing of a middle-sized passenger jet aircraft during flight. We used 40 10cm long fiber Bragg gratings (FBGs), inscribed in a highly birefringent polarization-maintaining fiber. The FBGs were interrogated by optical frequency domain reflectometry, which could measure Bragg wavelength distributions at a sampling rate of 151Hz. The simultaneous measurement technique could detect structural behaviors of the wing during flight under temperature-changing conditions. In addition, we discuss the effect of the polarization mode-coupling and the apparent position shift of the FBGs over time, which occurred during flight.

Infrared Thermopile Temperature Measurement Technique in Microwave Heating Systems

Temperature measurement in microwave systems is essential for thermally driven processes, namely, catalytic reactions and ceramic sintering. Although, the application of direct thermometry methods, namely, thermocouples, have been commonly articulated in the available literature, however, contacted temperature measurement mechanisms have aroused concerns associated with the disruption of the electromagnetic field and local distortion of the field pattern leading to unprecedented measurement uncertainties. Consequently, the application of optical measurement methods has been advocated to diminish the associated concerns. However, due to the economical constrains and measurement range restrictions, the application of optical measurement systems, namely, pyrometers and optical fibers, has been deferred. In this study, an infrared thermopile, a precise and feasible temperature measurement system has been developed and calibrated to perform in microwave irradiation. Furthermore, the accuracy of the developed temperature system has been compared with the thermometry technique. It was concluded that thermopile stipulates unrivalled precision, succeeding a profound calibration procedure. It was further demonstrated that the thermopile is capable of the temperature measurement of the dielectric surfaces, exclusively, while the grounded thermocouple monitored the bulk temperature, a proportion of the gas phase and the solid phase temperature values. Consequently, the application of a thermopile coupled with a thermometry measurement method has been proposed to monitor the temperature of the dielectric catalyst active sites in gas-solid catalytic microwave-heated reactions.

Heat transfer in the flow with forced pulsations in a rib-roughened channel

Heat transfer in pulsating air flow in a rib-roughened channel has been studied experimentally. Heat transfer was estimated using the technique of simultaneous wall heating and wall temperature measurement by the same copper tracks. Distributions of heat transfer coefficient over the channel wall in steady and pulsating regimes of flow have been obtained. 30% augmentation of heat transfer compared with the steady flow values has been revealed in pulsating flow. The frequency range of (0–100) Hz and the relative amplitude of forced velocity pulsations of 0.3 have been studied.

Temperature and velocity instrumentation and measurements within a separate-effects facility representing modular reactor core

Temperature and velocity sophisticated measurement techniques have been integrated in a novel way for plenum-to-plenum natural circulation thermal hydraulics investigations in a separate-effects dual-channel facility designed with a representative geometry of prismatic modular reactor core. Time-and-frequency domain analysis has been conducted for the time series data obtained to determine the appropriate sampling time and frequency needed to collect data that statistically represents the time-averaged mean value. Preliminary tests have been conducted to examine the validity of implementing these techniques as well to investigate if flow fields inside prismatic core heated channels are affected by other different temperatures core channels. It is worth mentioning that the velocity measurements (i.e., obtained by using hot wire anemometry) were corrected to account for temperature differences between calibration and experimental conditions. Preliminary results reveal that the top section of the heated channel is significantly affected by cooled channel. This implies that naturally-driven flow has a delicate nature and flow fields inside core heated channels are influenced by temperature gradients exist within the prismatic reactor core after loss of flow accidents.

A volumetric temperature and velocity measurement technique for microfluidics based on luminescence lifetime imaging

A novel optical measurement technique is introduced and qualified which enables the simultaneous determination of the three-dimensional temperature field and the three components of the three-dimensional velocity field in microfluidic applications with only one camera. The temperature is obtained by evaluating the emission decay of individual luminescent polymer particles, whereas the velocity field can be calculated simultaneously from the flow-induced shift of individual particle images in time. To acquire the depth information, the well-established astigmatism particle-tracking velocimetry technique is employed. With this method, systematic errors caused by volume illumination and the reduced spatial resolution due to window averaging as in micro particle image velocimetry (µ-PIV) or laser-induced fluorescence (LIF) can be avoided. The technique can easily be optimized for the investigated temperature range and flow velocities and offers an exceptionally high spatial resolution and accuracy.

Error Reduction in Infrared Thermography by Multiframe Super-Resolution

Accurate temperature measurement techniques are critical for monitoring hotspots that induce thermal stresses in electronics packages. Infrared thermography is a popular nonintrusive method for emissivity mapping and measuring surface temperature distribution, but is often impeded by the low native resolution of the camera. A promising technique to mitigate these resolution limits is multiframe super-resolution, which uses multiple subpixel shifted images to generate a single high-resolution image. This study quantifies the error reduction offered by multiframe super-resolution to demonstrate the potential improvement for infrared imaging applications. The multiframe super-resolution reconstruction is implemented using an algorithm developed to interpolate the sub-pixel-shifted low-resolution images to a higher resolution grid. Experimental multiframe super-resolution temperature maps of an electronic component are measured to demonstrate the improvement in feature capture and reduction in aliasing effects. Furthermore, emissivity mapping of the component surface is conducted and demonstrates a dramatic improvement in the temperature correction by multiframe super-resolution. A sensitivity analysis is conducted to assess the effect of registration uncertainty on the multiframe super-resolution algorithm; simulated images are used to demonstrate the smoothing effect at sharp emissivity boundaries as well as improvement in the feature size capture based on the native camera resolution. These results show that, within the limitations of the technique, multiframe super-resolution can be an effective approach for improving the accuracy of emissivity-mapped temperature measurements.

Soft X-ray backlighter source driven by a short-pulse laser for pump-probe characterization of warm dense matter.

Here we propose a pump-probe X-ray absorption spectroscopy temperature measurement technique appropriate for matter having temperature in the range of 10 to a few 100 eV and density up to solid density. Atomic modeling simulations indicate that for various low- to mid-Z materials in this range the energy and optical depth of bound-bound and bound-free absorption features are sensitive to temperature. We discuss sample thickness and tamp layer considerations. A series of experimental investigations was carried out using a range of laser parameters with pulse duration ≤5 ps and various pure and alloyed materials to identify backlighter sources suitable for the technique.

Application of the photoacoustic technique for temperature measurements during hyperthermia

ABSTRACTNon-invasive monitoring of tissues’ temperatures is necessary for some diagnostic and therapeutic applications. Photoacoustic is a new hybrid biomedical imaging technique, combining the high-contrast of optical properties with the high spatial resolution of ultrasound. The estimation of model parameters that are temperature dependent was used in this work to indirectly measure the temperatures of tissues, as the solution of an inverse problem within the Bayesian framework of statistics. A two-dimensional case was examined, which is related to the hyperthermia treatment of cancer with laser heating in the near infrared range. Simulated measurements were used in the inverse analysis. The Markov Chain Monte Carlo method provided accurate estimation of the spatial distribution of the Gruneisen parameter and the temperature distribution in the region of interest could be recovered with discrepancies smaller than 0.03°C.

Plasma temperature measurements using black-body radiation from spectral lines emitted by a capillary discharge

Optically thick spectral line emssion from plasmas is often difficult to use for the diagnosis of plasma parameters. We demonstrate a technique for temperature measurement using the peak intensity of optically thick lines as their intensities approach a black-body distribution. Recording optical emission in the wavelength range 300–1000 nm from a plasma formed by radio-frequency heating and electrical discharges in a 0.2 m long capillary plasma, we show that the high wavelength Rayleigh-Jeans form of the black-body emission can be fitted to the most intense spectral lines to give a measurement of plasma temperatures in the 1–1.5 eV range. The temperature measurement technique should have wider applicability in diagnosing plasmas with optically thick spectral lines.

Development of a novel anemometry technique for velocity and temperature measurement

Hot-wire anemometry is a widely used measurement technique for obtaining local velocities or temperatures in a flow-field. Operated under constant temperature or constant current the small diameter wires can resolve high-frequency velocity or temperature fluctuations with a high degree of spatial and temporal resolution. Therefore, more or less sophisticated hardware, e.g. using a Wheatstone bridge for constant temperature anemometry (CTA), is used with relatively high acquisition costs. In this paper a new technique is used, where the wire temperature or current is digitally controlled via a FPGA unit. The electric circuit is simpler than the usual set-ups and the hardware used is very robust, allowing to operate the control unit under harsh environments. This allows also to reduce the cable lengths, and therefore, eventually to increase the frequency response of the hot wire. The application of this technique for measurements of aerodynamic and thermal boundary layers under varying Reynolds numbers for laminar and turbulent boundary layers is demonstrated. The results are compared to measurements with standard CTA system and show that similar results are obtained with this new technique.

Adhesion of Rhodococcus ruber IEGM 342 to polystyrene studied using contact and non-contact temperature measurement techniques

Adhesion of industrially important bacteria to solid carriers through the example of actinobacterium Rhodococcus ruber IEGM 342 adhered to polystyrene was studied using real-time methods, such as infrared (IR) thermography and thermometry with platinum resistance (PR) detectors. Dynamics of heat rate and heat production was determined at early (within first 80min) stages of rhodococcal cell adhesion. Heat rate was maximal (1.8 × 10-3-2.7 × 10-3W) at the moment of cell loading. Heat production was detected for the entire length of adhesion, and its dynamics depended on concentration of rhodococcal cells. At high (1 × 1010CFU/ml) cell concentration, a stimulative (in 1.7 and 1.4 times consequently) effect of polystyrene treatment with Rhodococcus-biosurfactant on the number of adhered rhodococcal cells and cumulative heat production at rhodococcal cell adhesion was revealed. The values of heat flows (heat rate 0.3 × 10-3-2.7 × 10-3W, heat production up to 8.2 × 10-3J, and cumulative heat production 0.20-0.53J) were 5-30 times higher than those published elsewhere that indicated high adhesive activity of R. ruber IEGM 342 towards polystyrene. To analyze experimental results and predict effects of boundary conditions on the temperature distribution, a mathematical model for heating a polystyrene microplate with distributed heat sources has been developed. Two independent experimental methods and the numerical modeling make it possible to verify the experimental results and to propose both contact and non-contact techniques for analyzing kinetics of bacterial adhesion.

Air temperature measurement challenges in precision metrology

The measurement of air temperature is important in many types of metrology. Despite being generally an auxiliary measurement, in some fields poor knowledge of air temperature represents a limiting uncertainty. Applications where this is the case include interferometric dimensional measurements, in which the air refractive index correction is required, and the determination of relative humidity. Yet despite its ubiquity, relatively little attention has been paid to determining air temperature with low uncertainty. In this paper we discuss an under-appreciated systematic error in air temperature measurements: the diameter-dependence of the radiation correction for cylindrical and spherical sensors. After a discussion of the typical magnitude of the effect we consider ways to mitigate the effect by the careful design of air temperature sensors, and through use of non-contact air temperature measurement techniques.

Ultrasonic Waveguide-Based Multi-Level Temperature Sensor for Confined Space Measurements

This paper reports the feasibility of using an ultrasonic waveguide sensor for distributed temperature measurement in two different case studies, that is: 1) skin temperature of a solid structure (pipe) and 2) fluid (water). This technique improves upon the conventional multiple thermocouples approach for multi-level temperature measurements. The range of temperatures is from room temperature to maximum utility temperature for the two case studies (85 °C for water and 200 °C for pipe). Using the interaction of the propagating ultrasonic waves in a thin rodlike waveguide with intentionally designed geometric discontinuities (bends, axisymmetric, non-axisymmetric notches, and so on), the localized information on the temperature is extracted. An ultrasonic technique for accurate temperature measurement by tracking the time-of-flight of reflected guided wave modes from appropriately spaced notch reflectors is therefore proposed here, while using the reflection from a bend is used as a reference. Using a finite element model approach, the notch size and/or the bend radius were selected in order to reduce mode conversion effects as well as to obtain uniform amplitudes of the reflected signals from these designed discontinuities. The numerical results were experimentally validated for the L(0,1) wave mode using a stainless steel waveguide sensor. This paper is of interest to industrial applications including mould cooling jacket temperature monitoring during the steel manufacturing process as well as for furnace wall temperature measurements in petrochemical industries.

Accurate measurement and estimation of solar cell temperature in photovoltaic module operating in real environmental conditions

There is a growing need for the precise outdoor performance measurement of photovoltaic (PV) modules for low-cost onsite performance measurement, monitoring, and failure diagnosis. For the precise evaluation of a PV module, an accurate temperature measurement technique is required. It is necessary to measure the temperature of the solar cell in a module structure (junction temperature) because it determines the temperature characteristics of the PV module, rather than the temperature of the backsheet. In this study, a PV module with an internal thermocouple was fabricated. A thermocouple was inserted immediately below the solar cell so that it could be in direct contact with the cell, enabling an accurate temperature measurement. Moreover, the temperature of the solar cell in the PV module structure was predicted by heat flux calculation using the backsheet temperature, which can be measured easily. In this manner, the solar cell temperature was estimated accurately within an error of ±1 °C.

A New Precision Spectroscopy Based Method for Boltzmann Constant Determination and Primary Thermometry.

We propose a new independent thermometry method, line strength ratio thermometry (LRT), based on optical spectroscopy measurement of the line strength intensity ratio R between pairs of molecular transitions. Due to strong dependence of R on kT, a given measurement uncertainty δR for R reflects in a small uncertainty of kT determination. By assuming experimental uncertainties of R and T to be those reported in literature, we foresee a k determination at the 5 ppm level, which is better than the most precise k determination by using Doppler broadening thermometry (DBT). In the frame of a new definition of the SI Kelvin unit, based on k as fixed constant, once the k constant is exactly established, LRT is proposed as a high resolution noncontact thermometry technique for absolute temperature measurements of gas samples at the ppm level.