Multi-temperature Measurement Research Articles

Simultaneous multipoint emissivity measurement via Zebra-patterned blackbody spray method and application to gas tungsten arc welding process

Thermography is a temperature measurement method that can measure low temperatures but requires an emissivity setting. Because emissivity depends on the material, surface condition, and temperature, referring to a database is generally difficult in practical measurements. Hence, it is desirable to measure emissivity based on an object. Herein, a new emissivity measurement method, termed the zebra-patterned blackbody spray method, is proposed. By spraying a blackbody in a striped pattern and calculating the temperature at the unsprayed area via interpolation, the luminance and true temperatures of the measurement area are measured simultaneously; subsequently, the emissivity is calculated. In addition, simultaneous, multipoint, and multitemperature measurements are performed by heating the back of the sample. The emissivity of stainless steel and mild steel measured via this method agrees well with the emissivity measured using a thermocouple. In addition, bead-on-welding using a tungsten inert gas arc is performed and the difference in emissivity between the welded bead and the base metal is presented based on the welding current. The emissivity of a 200 A bead is higher than that of the base metal and a 100 A bead, and the variation increases with the variation in the surface condition. Additionally, the temperature during TIG welding is measured. When a constant emissivity is used, the temperature distribution across the beads becomes discontinuous. Applying the emissivity obtained using this method yields a continuous temperature distribution.

Nonequilibrium Vibrational, Rotational, and Translational Thermometry via Megahertz Laser Absorption of CO

A mid-infrared laser absorption strategy for simultaneously measuring translational, rotational, and vibrational temperatures of carbon monoxide (CO) at high speeds was developed for application to high-temperature nonequilibrium environments relevant to Mars atmosphere entry. Rapid-tuning scanned wavelength techniques were used to spectrally resolve the R(0,66), P(0,31), P(2,20), and P(3,14) lines of the CO fundamental vibrational bands at a rate of 1 MHz to infer multiple temperatures of CO behind incident and reflected shock waves in a shock tube. A distributed feedback quantum cascade laser was used to probe the P-branch transitions near and an external cavity quantum cascade laser was used to probe the R-branch transition near , both using bias-tee circuitry. The sensing method is shown to resolve each targeted transition with temporal and spectral resolution sufficient for quantitative multi-temperature measurements over a wide range of temperatures and pressures (2100–5500 K, 0.03–1.02 atm), including behind incident shock waves traveling up to 3.3 km/s. Measured temperature results were compared to equilibrium and nonequilibrium simulations.

Disappearing disorder

Disorder in crystal structures can disappear, depending on the circumstances, as shown by multi-temperature measurements, aspherical-atom refinement and computational analyses.

Comparative Accuracies of Fiber Bragg Grating Sensing Systems for Temperature Measurement

In this study, using state-of-the-art optical simulation software, we design, simulate and quantify the comparative accuracies of two types of FBG-based optical sensing systems: one is designed for lengthy, multiplexed multi-temperature measurements, the other for single-point measurements. Results and discussion are made to analyze the comparative performances, particularly in terms of linearity and accuracy.

Application for optical thermometers calibration based on virtual instruments

In this paper we present a new developed application for calibration of optical thermometers which is implemented in the Serbian Metrology Institute. The method for calibration of optical thermometer–pyrometer is based on measuring blackbody temperature via thermocouple standards and measuring voltage on pyrometer in temperature range from 550 to 1650 °C. The objective is to precisely determinate calibration curve of pyrometer—transfer function. The metrology traceability was realized through thermocouples standard which has traceability to the international standard. A developed application has a role to control and supervise calibration process. Based on virtual instruments (VI), application offers monitoring measurement parameters in real time on three charts. The main advantage of the developed VI application is reduction of measurement uncertainty of type A by increased accuracy with multi—temperature measurement up to 3 thermocouples on temperature equilibrium in the measurement system and automatic data processing by converting voltage to temperature, calculating the mean value and standard deviation of the mean value. Advantage is also reflected in permanent data logging while application is running and low cost and user friendly interface One of the goals is to improve quality of metrological services through this application and support the establishment of a traceability chain to SI.

α-Tris(2,4-pentanedionato-κ2O,O′)cobalt(III) at 240, 210, 180, 150 and 110 K

The crystal structure of the title compound, [Co(C(5)H(7)O(2))(3)], has been investigated by a multi-temperature measurement. In contrast to the isomorphous Al compound, the title compound exists in the studied temperature range as its monoclinic alpha polymorph (space group P2(1)/c) and does not undergo a phase transition. Rigid-body TLS analyses have been performed and the anisotropic thermal expansion tensor alpha(ij) has been determined. The cell axes show a linear expansion behavior with respect to the temperature, but the slope is significantly different. A possible explanation are the different strengths of different intermolecular C-H...O contacts, which run in different crystallographic directions.

α-Tris(2,4-pentanedionato-κ2O,O′)aluminium(III) at 240, 210, 180, 150 and 110 K: a new δ phase at 110 K

The crystal structure of the title compound, [Al(C(5)H(7)O(2))(3)], has been investigated by a multi-temperature measurement to provide information on thermal vibrations and disorder in the structure. At 110 K, the structure of a new delta polymorph could be determined. A disorder-order phase transition takes place between 150 and 110 K and is klassengleich. The unit-cell volume increases by a factor of three and the diffraction pattern shows weak supercell reflections.

Observation of 4f electron transfer from Ce to B6 in the Kondo crystal CeB6 and its mechanism by multi-temperature X-ray diffraction.

Electron density distributions (EDD) in CeB(6) were measured by X-ray diffraction at 100, 165, 230 and 298 K. Analysis with a weak-field model, in which the spin-orbit interaction dominates the energy splitting of the 4f levels, revealed that more 4f electrons were donated from Ce to B(6) at the lower temperature. Donated electrons localize around the B-B bonds connecting B(6) octahedra. The localized electrons and an expansion of the outermost 5p orbitals change the effective atomic potentials and enhance the anharmonic vibration (AHV) of constituent atoms at lower temperature. Enhanced AHV increases the entropy and makes the electron donation inevitable. Changes in crystal structure, EDD, electron configuration and AHV are found to be closely correlated with one another and the mechanism of the electron transfer in the Kondo crystal CeB(6) in the studied temperature range was elucidated. This is, to the authors' knowledge, the first multi-temperature measurement of EDD that elucidates a mechanism of change from the temperature dependence of the EDD. Parameters change consistently at all the temperatures except 298 K, at which the excited states Gamma(7) of the Ce 4f states have significant electron population. The thermal excitation to Gamma(7) levels expands the B(6) octahedra, since Gamma(7) has main lobes along <111> or from Ce to the centre of B(6) octahedra. The energy gap between the ground state Gamma(8) and Gamma(7) was calculated to be 470 K from the ratio of electron populations of both states. The present experiment opens the door to accurate X-ray EDD analyses of rare earth complexes.

Wireless multi-temperature measurement for rotating cryogenic machines

A method of wireless and multitemperature measurement is proposed, in which the resonant frequency shift of the sensors caused by temperature is the detectable signal. LC resonant circuit sensors consisting of a ferrite yoke coil and a mica-type capacitance were used in the demonstration experiment. The experimental data show that the temperature of several points is discriminatively detectable in the rotating machine. The response time of the method for every measurement is about one minute to attain 10 mK resolution. It is believed that a frequency tracer technique for each sensor may be a way to improve the response time. However, the proposed measurement system should be restricted to the observation of the stationary temperature profile in a rotating cryogenic machine. >

Temperature dependence of the shift, width and asymmetry of the potassium (4p←7s) 5802 AA line perturbed by argon

The effects of temperature upon the Ar-perturbed K I 5802 AA emission line (4p 2P32/-7s 2S12/f) were measured with a Fabry-Perot interferometer. Low-pressure measurements were made between 443 and 760K in a positive-column discharge. Computer analyses of the line shapes are based upon the semiclassical theory in the impact approximation, and experimental values of shift, width and near-wing asymmetry are obtained. Empirically, the width varies approximately as T0.37+or-0.04. On the basis of an assumed potential form( Sigma nCn/Rn, the parameters C6 and C8 are adequate to yield shift and width values in close agreement with experiment. The experimental parameters set is C6 approximately=-8.3*10-56 erg cm6, C8 approximately=8.9*10-70 erg cm8 and C12 approximately=0. The importance of multitemperature measurements in reducing the ambiguity of C6 and C8 is demonstrated. The existence of the theoretically predicted near-wing red asymmetry is shown, and the experimental value is in quantitative agreement with the calculated value. The calculated K(7s)/Ar potential does not agree with the Baylis-type pseudopotential in which the effective noble-gas atom radius r0 corresponds to the ground state; however, a reduction in this radius yields moderately good agreement in the range R>or=19 AA, which is shown to be the approximate validity range for the potential derived from these low-pressure measurements.