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Laser based method for dynamic calibration of thermocouples
摘要： In dynamic temperature measurement, thermocouple sensors are widely used in harsh environments, and their dynamic characteristics directly affect the accuracy of dynamic temperature measurement. When the dynamic characteristics do not meet the requirements of dynamic test, dynamic errors will occur. In order to obtain the dynamic characteristics, it is necessary to calibrate the thermocouple dynamically. In this paper, a dynamic calibration system for the thermocouple was built. In the system, a high power laser was used to generate pulse temperature excitation. In order to realize the uniform heating, the laser beam homogenization system based on microlens array was studied and added to the dynamic calibration system. The homogenization system was designed and simulated, and the uniformity of the laser spot was measured after homogenization. A K-type butt-welded thermocouple was dynamically calibrated by using the dynamic calibration system. The dynamic mathematical model of the thermocouple was obtained by the system identification method, and the dynamic characteristics of the thermocouple were analyzed.
关键词： pulse excitation,laser,dynamic calibration,microlens array,thermocouple
更新于2025-09-23 15:21:01
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Thermocouple-tip-exposing temperature assessment technique for evaluating photothermal conversion efficiency of plasmonic nanoparticles at low laser power density
摘要： A new thermocouple (TC) tip-exposing temperature assessment technique that combines experimental temperature measurements with a numerical model of the photothermal conversion efficiency η is presented. The proposed technique is designed to evaluate η for a gold-coated superparamagnetic iron oxide nanoparticle (SPIO-Au NP) solution (26 nm, 12–70 ppm) at low continuous wave laser power (103 mW, 532 nm) irradiation in a convenient manner under ambient conditions. The TC tip temperature is measured during the first 30 s of the laser exposure, and the results are combined with a finite element model to simulate the temperature rise of the NP solution for a given concentration. The value of η is adjusted in the model until the model agrees with the measured transient TC temperature rise. Values of η = 1.00 were observed for all concentrations. Theoretical predictions of η derived by Mie theory confirmed the near unity conversion efficiency of the as-synthesized SPIO-Au NPs. Advantages of the current technique include co-locating the TC tip in the geometric center of the laser-heated region, rather than outside of this region. In addition, the technique can be done under ambient room conditions using unmodified commercially available hardware.
关键词： finite element model,plasmonic nanoparticles,low laser power density,thermocouple,photothermal conversion efficiency
更新于2025-09-16 10:30:52
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Measurement and Evaluation of Local Surface Temperature Induced by Irradiation of Nanoscaled or Microscaled Electron Beams
摘要： Electron beams (e-beams) have been applied as detecting probes and clean energy sources in many applications. In this work, we investigated several approaches for measurement and estimation of the range and distribution of local temperatures on a subject surface under irradiation of nano-microscale e-beams. We showed that a high-intensity e-beam with current density of 105-6 A/cm2 could result in vaporization of solid Si and Au materials in seconds, with a local surface temperature higher than 3000 K. With a lower beam intensity to 103-4 A/cm2, e-beams could introduce local surface temperature in the range of 1000–2000 K shortly, causing local melting in metallic nanowires and Cr, Pt, and Pd thin films, and phase transition in metallic Mg-B films. We demonstrated that thin film thermocouples on a freestanding Si3N4 window were capable of detecting peaked local surface temperatures up to 2000 K and stable, and temperatures in a lower range with a high precision. We discussed the distribution of surface temperatures under e-beams, thermal dissipation of thick substrate, and a small converting ratio from the high kinetic energy of e-beam to the surface heat. The results may offer some clues for novel applications of e-beams.
关键词： Vaporization,Local temperature,Nanoscale thermometry,Transmission electron microscopy,Thin film thermocouple,Energy converting,Electron beam,Scanning electron microscopy,Melting point
更新于2025-09-11 14:15:04