Single-point Temperature Measurement Research Articles

Excited state lifetimes in diamond nitrogen vacancy centers depend on temperature

Single-point temperature measurements will aid development of optical sensors under extreme conditions.

Temperature-dependent excited state lifetimes of nitrogen vacancy centers in individual nanodiamonds

Nitrogen vacancy (NV) centers are fluorescent defects widely employed for thermometry, most commonly via temperature-dependent shifts of their optically detected magnetic resonance. Recently, all-optical approaches based on temperature-dependent features of the NV center fluorescence spectrum have also gained traction. Excited state lifetime thermometry is an all-optical technique that has been implemented using other fluorophores but has not previously been demonstrated for NV centers in individual nanodiamonds (NDs). Here, we report temperature-dependent excited state lifetime measurements of NV centers in individual NDs between 300 K and 500 K. We measure a 32 ± 7.0% and 35 ± 8.3% average decrease in the excited state lifetimes of individual NDs on silicon and glass substrates, respectively, over this temperature range. A linear approximation applicable to nearly all measured NDs yields temperature coefficients of −2000 ± 240 ppm/K and −2600 ± 280 ppm/K for NDs on silicon and glass, respectively. In addition to all-optical operation, single-ND excited state lifetime thermometry offers ∼100 ns temporal resolution and utilizes time-correlated single photon counting measurements ideally suited to low emission intensities, a limiting factor for other NV center thermometry techniques above 700 K. We demonstrate that atomic force microscope nanomanipulation can position individual NDs at critical locations on a sample of interest, enabling single-point temperature measurements that combine ∼100 ns temporal resolution and ∼100 nm spatial resolution. This work also has broader implications for other single-ND excited state lifetime sensing applications, where care is required to avoid conflating changes in temperature and other environmental parameters.

Automatic and rapid calibration method for temperature coefficient of fiber grating temperature sensor

Bare fiber Bragg grating (FBG) is packaged by thermal conductive materials and to be used as a temperature sensor. In the oil bath calibration of the temperature coefficient of the FBG temperature, it is difficult to accurately synchronize the single point temperature measurement and the simultaneously record FBG central wavelength using different devices. An automatic, fast and high precision calibration method for temperature coefficient of FBG temperature sensor is proposed. The experimental results show that the temperature coefficient obtained by the proposed method can accurately measure the temperature, and the calibration process is fast and avoids the error caused by manual recording and formula derivation. The system is suitable for rapid calibration of mass-produced FBG sensors.

Research on the Temperature Control System of 6KA Neodymium Oxide Electrolysis Furnace with BAS_PID Algorithm

In order to solve the obvious temperature fluctuations in the cell during the neodymium oxide electrolysis process, the traditional PID control algorithm has a large lag, the timeliness of the multi-variable electrolysis temperature control system is poor, and the manual parameter adjustment is difficult, the beetle PID automatic temperature control system is proposed. Through the control of the key variable cathode current density, speed up the system to adjust the output speed; use the orthogonal temperature measurement method to replace the traditional single point temperature measurement, and use the domain temperature to represent the point temperature to solve the problem of large temperature measurement errors. This algorithm model is based on MATLAB2017 platform for modeling simulation and experimental research. Compared with traditional PID, this method has better adaptive ability and robust performance. The maximum deviation between the actual electrolysis temperature and the set target temperature is 45°C, and the overshoot is 3.3 %, to meet the process index requirements in the actual production process, and provide a reference case for the improvement of neodymium oxide electrolysis process.

Fiber Bragg Grating Sensors for Millimetric-Scale Temperature Monitoring of Cardiac Tissue Undergoing Radiofrequency Ablation: A Feasibility Assessment.

Radiofrequency ablation (RFA) is the most widely used technique for the treatment of cardiac arrhythmias. A variety of factors, such as the electrode tip shape, the force exerted on the tissue by the catheter and the delivered power, combine to determine the temperature distribution, and as consequence, the lesion shape and size. In this context, being able to know the temperature reached in the myocardium during the RFA can be helpful for predicting the lesion dimensions to prevent the occurrence of undesired tissue damage. The catheters used so far in such procedures provide single-point temperature measurements within the probe (by means of embedded thermocouples or thermistors), so no information regarding the temperature changes occurring in myocardial tissues can be retrieved. The aim of this study was to assess the feasibility of fiber Bragg grating sensors (FBGs) to perform multi-point and millimetric-scale temperature measurements within myocardium subjected to RFA. The assessment has been performed on ex vivo porcine myocardium specimens undergoing RFA. Data show the feasibility of the proposed solution in providing spatial temperature distribution within the myocardial tissue during the entire RFA. These high-resolved measurements may allow reconstructing the temperature distribution in the tissue. This study lays the foundations for the implementation of 3D thermal maps to investigate how the supplied power, treatment time, force of contact and irrigation flow of the catheter influence the thermal effects within the tissue.

Quantitative traceable temperature measurement using novel thermal imaging camera.

Conventional thermal imaging cameras, based on focal-plane array (FPA) sensors, exhibit inherent problems: such as stray radiation, cross-talk and the calibration uncertainty of ensuring each pixel behaves as if it were an identical temperature sensor. Radiation thermometers can largely overcome these issues, comprising of only a single detector element that can be optimised and calibrated. Although the latter approach can provide excellent accuracy for single-point temperature measurement, it does not provide a temperature image of the target object. In this work, we present a micromechanical systems (MEMS) mirror and silicon (Si) avalanche photodiode (APD) based single-pixel camera, capable of producing quantitative thermal images at an operating wavelength of 1 µm. This work utilises a custom designed f-theta wide-angle lens and MEMS mirror, to scan +/- 30° in both x- and y-dimensions, without signal loss due to vignetting at any point in the field of view (FOV). Our single-pixel camera is shown to perform well, with 3 °C size-of-source effect (SSE) related temperature error and can measure below 700 °C whilst achieving ± 0.5 °C noise related measurement uncertainty. Our measurements were calibrated and traceable to the International Temperature Scale of 1990 (ITS-90). The combination of low SSE and absence of vignetting enables quantitative temperature measurements over a spatial field with measurement uncertainty at levels lower than would be possible with FPA based thermal imaging cameras.

Thermal Behavior of a Catalytic Packed-Bed Milli-reactor Operated under Radio Frequency Heating

An approach for analysis of thermal gradients in a catalytic packed bed milli-reactor operated under radio frequency (RF) heating has been presented. A single-point temperature measurement would cause the misinterpretation of the catalytic activity in an RF-heated reactor, because of the presence of a temperature gradient. For reliable data interpretation, the temperature should be measured at three positions along the reactor length. The temperature profile can be accurately estimated with the exact analytical solution of a one-dimensional (1D) convection and conduction heat-transfer model, and it can also be approximated with a second-order polynomial function. The results revealed that the position of maximum temperature in the catalytic bed shifts toward a downstream location as the flow rate increases. The relative contribution of conduction and convection to the overall heat transport has been discussed. The design criteria for a near-isothermal milli-reactor have been suggested.

Spatial predictive control using a thermal camera as feedback

The sensors being used in industrial settings are becoming increasingly complex and capable of acquiring significantly more data with higher functionality. One of these sensors is the thermal camera, which has the potential of capturing the spatial temperature profile of any surface. Through the extension of the conventional model-based control theory, a new model-based control scheme was formulated verify the novel concept of utilizing the spatial data from the thermal camera. To analyze this new model based control algorithm, a three zone heater barrel apparatus was designed and constructed for closed-loop testing to be performed. The experiments demonstrated the benefit of thermal camera feedback through the alterations in the control scheme. The availability of thermal profile of the system in comparison to single point temperature measurements resulted in the enhanced controller achieving better closed-loop transient responses, reduction in settling times. In addition, the use of spatial thermal images provides the possibility of controlling profiled temperature setpoints, showing the benefit and potential of using more advanced sensors in industry.

Inverse estimation of near-field temperature and surface heat flux via single point temperature measurement

A concept was developed to inversely estimate the near-field temperature as well as the surface heat flux for the transient heat conduction problem with boundary condition of the unknown heat flux. The mathematical formula was derived for the inverse estimation of the near-field temperature and surface heat flux via a single point temperature measurement. The experiments were carried out in a vacuum chamber and the theoretically predicted temperatures were justified in specific positions. The inverse estimation principle was validated and the estimation deviation was evaluated for the present configuration.

Online Cutting Temperature Measurement System Based Thermocouple

In order to measure cutter temperature, the on-line thermocouple temperature measurement system was proposed. In this system, temperature sensing element thermocouple was welded in the flank face close to the cutting edge with double bare wires welding way. With this method, this system has advantages of a single point temperature measurement and no effect on cutter temperature distribution. For a higher sampling rate, two AD were used to sample alternately; and for the convenient signal transmission when the cutter is rotating at high speed, wireless transmission was adopted to transmit thermocouple output signal and cold side temperature signal to the host computer. After temperature compensation to the cold side, the compensated temperature will be real-time displayed, stored and played back. System measurement range is 0 ~ 1300 ° C, and the measurement uncertainty is 0.58%. For 8000rpm rotational speed of XH714D machine, experimental results show that the system can measure cutter temperature online, and has advantages of low cost and great practicability.

Thermography as a technique for monitoring early age temperatures of hardening concrete

The exothermal character of cement hydration reactions causes concrete to endure temperature changes during the first days after casting, with associated volumetric deformations that may induce undesired cracking. The capability to predict temperature evolution in concrete since casting is thus important to back decisions that avoid detrimental thermal cracking in concrete structures. Even though several approaches exist to model the early age behavior of concrete, the laboratory or in situ verification of numerical predictions is scarce, and mostly done with embedded temperature sensors, with limited sampling points. The present research intends to evaluate the performance of the thermography technique in the continuous monitoring of surface temperatures of a hydrating 0.40 × 0.40 × 0.40 m 3 concrete cube, in which embedded thermal sensors are also used. By using thermography, simultaneous monitoring of the visible surfaces of the specimen is possible, thus providing comprehensive information regarding the evolution of surface temperatures. The temperatures monitored with the thermography, as well as with the embedded temperature sensors, are finally used as a benchmark example for validation of a 3D finite element numerical code for thermal analysis developed by the authors. The use of thermography images for validation of finite element results is rather more advantageous than the use of standard single point temperature measurements, in view of the large facility and wide range of comparison provided by the simultaneous visualization of temperature surface color maps (measured and simulated).

Interface Temperature Measurement and Experimental Studies of Super-High Speed Polishing of CVD Diamond Films

Super-high speed polishing of diamond film is a newly proposed method due to its outstanding features such as low cost and simple apparatus. The interface temperature rise is due to the friction force and the relative sliding velocity between the CVD diamond film and the polishing metal plate surface. In this paper, the interface temperature rise in super-high speed polishing of CVD diamond film was investigated by using the single-point temperature measurement method. Additionally, the influence of polishing plate material on the characteristics of super-high speed polishing has been studied. The results showed that cast iron is not suitable for super-high polishing, while both 0Cr18Ni9 stainless steel and pure titanium can be used for the super-high polishing of CVD diamond film. The quality and efficiency of polishing with 0Cr18Ni9 stainless steel plate is much higher than those of pure titanium, and the material removal rate could reach to 36-51 m/h when the polishing speed and pressure are 100 m/s and 0.17-0.31 MPa, respectively.

Inverse problem of transpiration cooling for estimating wall heat flux by LTNE model and CGM method

In this work, a transient inverse problem of transpiration cooling is investigated in detail. The heat flux on the wall to be cooled is estimated by single point temperature measurement. The local thermal non-equilibrium (LTNE) model is utilized to describe the energy conservation of transpiration cooling process, and the conjugate gradient method (CGM) is extended to solve the inverse problem. The accuracy of the solutions of the inverse problem is examined through three given heat fluxes with given measurement errors. The examination shows that with the LTNE model and CGM, satisfactory solutions can be obtained. The influences of the variation in thermal properties, compressibility and the location of sensor on the accuracy of the solutions are analyzed. The analysis indicates that the variation in thermal properties and compressibility should be considered when a large temperature gradient exists, and the sensor location should be as close as possible to the hot wall. The inverse solutions obtained by the measurements of solid and fluid temperatures are compared. Through the comparison, it is found that using the solid temperature measurement as the input of the inverse problem is better than using the fluid temperature measurement.

Pressure-Sensitive Paint measurement of the flow around a simplified car model

In applying Pressure-Sensitive Paint (PSP) to low-speed flow wind tunnel testing, it is important to minimize any measurement uncertainties. There are various error sources such as camera noise, misalignment of images due to model displacement and temperature distribution over the model. Among these factors, the effects of temperature distribution change during tests on pressure measurement accuracies were studied in the present paper. Pressure and temperature distributions over a simplified car model (1/10 scale Ahmed model) were measured using PSP and Temperature-Sensitive Paint (TSP). Sequential images were acquired at the same intervals over the entire test period, including for the conditions before and after the tunnel run. As a result, it was found that the measurement error caused by temperature distribution over the model could be reduced using a single-point temperature measurement. In addition, by measuring surface temperature distributions on the model using TSP, it was proved that the most accurate pressure measurement could be made by rationing the wind-off image acquired immediately after shutting down the tunnel to the wind-on image acquired immediately before shutting down the tunnel. Using the present measurement technique, complicated pressure fields over the Ahmed model were successfully visualized.

Liquid crystal images of the transition from jet impingement convection to nucleate boiling part II: Nonmonotonic distribution of the convection coefficient

This paper reports the second phase of a two-part study of jet impingement boiling. Liquid crystal thermography was used to study nucleate boiling incipience on a thin uniform-heat-generation surface that was cooled by a submerged impinging jet of refrigerant R-11. Thermographic images of the temperature distribution on the test surface were acquired synchronously with single-point temperature measurements from three locations on the surface. The nozzle-to-plate spacing was such that the single-phase flow produced a nonmonotonic radial distribution of the convective heat transfer coefficient. The convection coefficient displayed a secondary peak at approximately 3.5 jet radii from the stagnation point and decreased smoothly for radii beyond that value. Single-phase and boiling regions were found to coexist stably when the interface between the two regions, the boiling front, was positioned at a radius greater than the radius of the secondary peak. The front was observed to suddenly collapse across the part of the surface associated with the nomonotonic behavior of the convection coefficient. The collapse was attributed to the surface temperature at more than one radius reaching the incipience level simultaneously. A simple model for correlating the typical radius of the boiling front to the convection coefficient and to a specific surface temperature at incipience was successfully applied at radii beyond the location of the secondary peak.

Liquid crystal images of the transition from jet impingement convection to nucleate boiling part I: Monotonic distribution of the convection coefficient

Liquid crystal thermography was used to study nucleate boiling incipience on a thin, uniform-heat-generation surface that was cooled by a submerged impinging jet. The fluid was the refrigerant R-11. Thermographic images of the temperature distribution on the test surface were acquired synchronously with single-point temperature measurements from three locations on the surface. These measurements provide a framework for interpreting the images and quantifying the incipience temperature overshoot. The nozzle-to-plate spacing was such that the convective heat transfer coefficient in the single-phase flow decreased monotonically with radial distance from the stagnation point. The images clearly reveal a large temperature gradient, or boiling front, that existed at the interface between areas cooled by convection and areas cooled by boiling. In the wall jet region of the flow, the orientation and average radial location of the front were determined by the distribution of the convection coefficient in the single-phase flow field. A simple model was developed to demonstrate this dependence. The shape of individual segments of the front indicated that the precise position of the front on a specific portion of the surface depended on the local distribution of surface microcavities. Near the stagnation point, boiling was initiated when fluctuations in the direction of the jet flow allowed a momentary rise in the surface temperature to above the nucleation temperature.

Response Surface Technique forEx SituProcess Uniformity Optimization in a Multi-Zone RTP System

AbstractMany RTP reactors used in production presently employ single point temperature measurement along with multiple lamp zone control. Optimum zone settings in these systems are known to vary depending on the radiative properties of the wafer and the process. Therefore, tuning the system to meet specifications for a new process is achieved by an operator analyzing metrology results and drawing on experience with the system to determine proper zone settings. It would be desirable to have a technique which can be used to optimize the lamp zone settings in an automatic manner that would be the same for every user. Furthermore, such a technique should be both simple to use and robust. In this work a method is presented which relies on an empirical response surface and an interative computational technique to minimize process variance. The results show that the method works regardless of the process variable being optimized, i.e. temperature, oxide thickness, etc., and that the method relies on no user input.