Precision Of Temperature Measurements Research Articles

L-DNA-Based Melt Analysis Enables Within-Sample Validation of PCR Products.

The melt analysis feature in most real-time polymerase chain reaction (PCR) instruments is a simple method for determining if expected or unexpected products are present. High-resolution melt (HRM) analysis seeks to improve the precision of melt temperature measurements for better PCR product sequence characterization. In the area of tuberculosis (TB) drug susceptibility screening, sequencing has shown that a single base change can be sufficient to make a first-line TB drug ineffective. In this study, a reagent-based calibration strategy based on synthetic left-handed (L)-DNA, designated LHRM, was developed to confirm validation of a PCR product with single base resolution. To test this approach, a constant amount of a double-stranded L-DNA melt comparator was added to each sample and used as a within-sample melt standard. The performance of LHRM and standard HRM was used to classify PCR products as drug-susceptible or not drug-susceptible with a test bed of nine synthetic katG variants, each containing single or multiple base mutations that are known to confer resistance to the first-line TB drug isoniazid (INH). LHRM achieved comparable classification to standard HRM relying only on within-sample melt differences between L-DNA and the unknown PCR product. Using a state-of-the-art calibrated instrument and multiple sample classification analysis, standard HRM was performed at 66.7% sensitivity and 98.8% specificity. Single sample analysis incorporating L-DNA for reagent-based calibration into every sample maintained high performance at 77.8% sensitivity and 98.7% specificity. LHRM shows promise as a high-resolution single sample method for validating PCR products in applications where the expected sequence is known.

High-precision and wide-range temperature measurement and control system of satellite-borne calibration blackbody

The accurate measurement and control of blackbody temperature can play an important role in radiometric calibration. A novel circuit suitable for the aerospace environment is designed to measure and control the temperature of the blackbody. A coarse-fine measurement method considering the wire resistance and self-heating effect of the platinum resistance is presented to calculate the resistance values of the platinum resistors. The precision of temperature measurement is improved using a line fitting algorithm with error calibration and temperature drift error compensation. A fuzzy self-adaptive PID controller is designed to improve the temperature control effect. The performances of the developed system are implemented on an FPGA/A3PE3000-FG484I controller board. The test results show that the device temperature measurement precision can reach ±0.03K for the entire temperature range 238 K to 367 K, the temperature stability is better than 0.02 K/20 s, and the temperature uniformity is better than 0.1 K.

Thermographic device with a calibrating element for enhanced precision of human temperature measurement

Elevated temperature of humans can be an indicator of many diseases and its measurement is therefore a common diagnostic tool. Thermographic methods allow of non-contact, fast and automated measurement. Their main disadvantage, however, is a lower accuracy than is usually required for the measurement of the core body temperature. Athermographic device with an internal calibrating element for enhanced precision measurement is introduced in this study. It is a compact device for face/eyes temperature diagnostics, which uses a micro-bolometer based infrared detector and the active calibrating element. The calibrating element is embedded in the device casing and heated to a temperature close to the body core temperature 37 °C. It allows a high precision body temperature measurement with an accuracy comparable with a thermographic measurement enhanced by an external blackbody, but it keeps the device very compact and mobile. The device and its function are described in the paper. Results of verification and calibrating experiments with a black body are presented. A fairly good standard deviation of about ± 0.2 °C is demonstrated. The mean eyes maximum temperature 35.77 ± 0.42 °C obtained by an evaluation of a long-term temperature measurement on faces of human testers confirmed accuracy and effectivity comparable with a standard thermographic devices measurement enhanced by and external blackbody.

Assessing the Precision of Local Temperature Measurement by Plasmon Energy in In-Situ Heating Electron Microscopy

Assessing the Precision of Local Temperature Measurement by Plasmon Energy in In-Situ Heating Electron Microscopy

High‐pressure gas temperature sensing for exit plane of aero‐engine combustor using tunable diode laser absorption spectroscopy

AbstractWe have developed a sensor for the temperature measurement in the test section after the combustion chamber of an aero engine model by using direct absorption spectroscopy. Five distributed feedback diode lasers at near 1392, 1393, 1339, 1343, and 1469 nm are utilized as the light sources to detect H2O absorptions to improve the precision of temperature measurement combining with the Boltzmann plot method and the polynomial‐based spectral fitting model. The sensor shows a good performance in terms of its temperature measurement accuracy under high temperature of 673–1373 K and high pressure of 100–600 kPa condition in a tube furnace, which was lower than 4%. Moreover, three‐dimensional temperature distributions have been reconstructed via applying algebraic reconstruction technique at the test section after the combustion chamber of an aero engine model. The single‐point position temperature extracted from the algebraic reconstruction technique agrees well with that measured from the coherent anti‐stokes Raman scattering technique, where the relative error is within 5%. All the above results prove the reliability of our developed temperature sensor.

Self-calibrated multi-mode optical thermometry in up-converting phosphor Cs2NaErCl6: Yb3+

With the development of temperature measurement technology, people put forward higher requirements for the accuracy and precision of temperature measurement. However, most of the current luminescent thermometers use a single optical signal for temperature detection, which has a certain range of temperature insensitivity, resulting in inaccurate temperature measurement. Here, an all-inorganic rare-earth halide double perovskite Cs2NaErCl6: Yb3+ (CNEC: Yb3+) phosphor was synthesized, which not only expressed triple-mode thermometric properties based on thermally coupled levels (TCLs), non-thermally coupled levels (N-TCLs) and lifetime (FL), but also capable of providing self-referencing and high-sensitivity temperature measurements under excitation at 980 nm. Benefiting from the low phonon energy of the matrix, high doping concentration and the excellent internal up-conversion quantum efficiency (UCQY) about 6.52% of optimal composition CNEC: 40%Yb3+, all modes exhibit superior sensitivities, reversibility and thermal resolution under 980 nm irradiation. In addition, a flexible thin film thermometer composed of CNEC: 40%Yb3+ was prepared to realized multi-mode thermal monitoring of local hot spots of electronic components. The excellent three-mode temperature measurement results indicated that CNEC: Yb3+ phosphors have great potential in temperature sensing.

Dynamic optical spectroscopy and pyrometry of static targets under optical and x-ray laser heating at the European XFEL

Experiments accessing extreme conditions at x-ray free electron lasers (XFELs) involve rapidly evolving conditions of temperature. Here, we report time-resolved, direct measurements of temperature using spectral streaked optical pyrometry of x-ray and optical laser-heated states at the High Energy Density instrument of the European XFEL. This collection of typical experiments, coupled with numerical models, outlines the reliability, precision, and meaning of time dependent temperature measurements using optical emission at XFEL sources. Dynamic temperatures above 1500 K are measured continuously from spectrally- and temporally-resolved thermal emission at 450–850 nm, with time resolution down to 10–100 ns for 1–200 μs streak camera windows, using single shot and integrated modes. Targets include zero-pressure foils free-standing in air and in vacuo, and high-pressure samples compressed in diamond anvil cell multi-layer targets. Radiation sources used are 20-fs hard x-ray laser pulses at 17.8 keV, in single pulses or 2.26 MHz pulse trains of up to 30 pulses, and 250-ns infrared laser single pulses. A range of further possibilities for optical measurements of visible light in x-ray laser experiments using streak optical spectroscopy are also explored, including for the study of x-ray induced optical fluorescence, which often appears as background in thermal radiation measurements. We establish several scenarios where combined emissions from multiple sources are observed and discuss their interpretation. Challenges posed by using x-ray lasers as non-invasive probes of the sample state are addressed.

Accuracy and Precision Improvement of Temperature Measurement Using Statistical Analysis/Central Limit Theorem

This paper describes a method for increasing the accuracy and precision of temperature measurements of a liquid based on the central limit theorem. A thermometer immersed in a liquid exhibits a response with determined accuracy and precision. This measurement is integrated with an instrumentation and control system that imposes the behavioral conditions of the central limit theorem (CLT). The oversampling method exhibited an increasing measurement resolution. Through periodic sampling of large groups, an increase in the accuracy and formula of the increase in precision is developed. A measurement group sequencing algorithm and experimental system were developed to obtain the results of this system. Hundreds of thousands of experimental results are obtained and seem to demonstrate the proposed idea's validity.

Evaluation of a novel mid-infrared pyrometer for dynamic material experiments.

Temperature is a complicated thermodynamic parameter to measure in dynamic compression experiments. Optical pyrometry is a general-purpose "work-horse" technique for measuring temperature from a radiant surface on these experimental platforms. The optical pyrometry channels are commonly held to the visible or Near-Infrared spectrum, which provides high fidelity temperature measurement for shock temperature above ∼1200-1500K. However, low temperature (T < 1200K) dynamic material experiments, including low pressure or quasi-isentropic studies, as well as experiments with complex thermodynamic paths, require Mid-Infrared (Mid-IR) for high fidelity measurements. This article outlines the design, testing, and characterization of a novel Mid-IR pyrometer system that can be configured between 2.5 and 5.0 µm, suitable for lower temperature measurements and for increasing the fidelity and precision of higher temperature measurements. Experimental validation was done on two separate gas gun platforms, with two separate impact velocities, achieving temperatures between 450 and 1100K.

Effects of the distance and test angle on the precision of infrared temperature measurement

The target distance and test angle are the main factors that affect the accuracy of infrared temperature measurement. To study the infrared temperature measurement precision of different heat source intensities at different distances and test angles, a temperature measurement test with built-in heat source within the rod of the insulator was designed. By setting four different heat source temperatures on the heating film, the temperature data were collected by infrared camera at the distances of 3, 6, 9, 12 m and 15 m and three test angles of 0 °, 90° and 180°, respectively, and the variation law of the measurement results was analysed. The main conclusions are as follows. As the distance increases, the measured values basically show a downward trend. When the distance reaches 12 m, the temperature fluctuates significantly. When the angle between the observation direction and the heat source is 0 °, the measurement value is the highest, followed by the 90° direction, and the lowest is the 180° direction, which indicates that the test angle has an obvious influence on the measurement results. With the increase of heat source temperature, the infrared temperature measurement value increases gradually and tends to be saturated. When an infrared device is adopted to measure the temperature of the insulators in service, it is necessary to pay attention to the influence of the distance and angle on the value in engineering practice.

Precise surface temperature measurements at kHz-rates using phosphor thermometry to study flame-wall interactions in narrow passages

The thermographic phosphor ScVO4:Bi3+ is used to obtain time-resolved surface temperature measurements with sub- °C precision at 5 kHz. Measurements are used to study transient heat loss and flame-wall interactions (FWI) within a dedicated narrow two-wall passage (crevice) in an optically accessible fixed volume chamber. This passage emulates a crevice relevant in many technical environments, where FWI is less understood due to lack of detailed measurements. Chemiluminescence (CH*) imaging is performed simultaneously with phosphor thermometry to resolve how the flame's spatiotemporal features influence the local surface temperature. ScVO4:Bi3+ is benchmarked against Gd3Ga5O12:Cr,Ce, a common phosphor used at low-kHz rates in FWI environments. ScVO4:Bi3+ is shown to offer higher luminescence signal levels and temperature sensitivity as well as negligible cross dependence on the excitation laser fluence, improving the precision and repeatability of the wall temperature measurement. ScVO4:Bi3+ is further used to resolve transient heat loss for variations in crevice spacing and uniquely capture temperature transients associated with flame dynamics. Taking advantage of these precise surface temperature measurements the wall heat flux is calculated with crevice spacing of 1.2 mm, where flame extinction is prevalent. Wall heat flux and estimated quenching distance are reported for flames that actively burn or extinguish at the measurement location.

Real-time holographic quantitative measurement of vapor density distribution of suspended droplets.

We applied digital holography (DH) technology in a quantitative measurement of the density distribution of a low refractive index transparent substance (e.g., the vapor of suspended droplets). An optical setup was built based on the Mach-Zehnder interferometer. A measurement performance test showed the mean relative error of the measurement error was about 2.0%; that of the environment disturbance error was about 0.47%. By a quantitative method to assess the precision limit, the temperature measurement precision could achieve 0.01°C, and the vapor density measurement precision could achieve 0.0001kg/m3. We believe that all the benefits above make the setup a good choice for application in the Chinese space station.

Divers as Citizen Scientists: Response Time, Accuracy and Precision of Water Temperature Measurement Using Dive Computers

There is a lack of depth-resolved temperature data, especially in coastal areas, which are often commonly dived by SCUBA divers. Many case studies have demonstrated that citizen science can provide high quality data, although users require more confidence in the accuracy of these data. This study examined the response time, accuracy and precision of water temperature measurement in 28 dive computers plus three underwater cameras, from 12 models. A total of 239 temperature response times (τ) were collected from 29 devices over 11 chamber dives. Mean τ by device ranged from (17 ± 6) to (341 ± 69) s, with significant between-model differences found for τ across all models. Clear differences were found in τ by pressure sensor location and material, but not by size. Two models had comparable τ to designed-for-purpose aquatic temperature loggers. 337 mean data points were collected from equilibrated temperatures in hyperbaric chamber (n = 185) and sea (n = 152) dives, compared with baseline mean temperature from Castaway CTDs over the same time period. Mean bias, defined as mean device temperature minus baseline temperature, by model ranged from (0.0 ± 0.5) to (−1.4 ± 2.1) °C and by device from (0.0 ± 0.6) to (−3.4 ± 1.0) °C. Nine of the twelve models were found to have “good” accuracy (≤0.5 °C) overall. Irrespective of model, the overall mean bias of (−0.2 ± 1.1) °C is comparable with existing commonly used coastal temperature data sets, and within global ocean observing system accuracy requirements for in situ temperature. Our research shows that the quality of temperature data in dive computers could be improved, but, with collection of appropriate metadata to allow assessment of data quality, some models of dive computers have a role in future oceanographic monitoring.

Comparative Analysis on the Deployment of Machine Learning Algorithms in the Distributed Brillouin Optical Time Domain Analysis (BOTDA) Fiber Sensor

This paper demonstrates a comparative analysis of five machine learning (ML) algorithms for improving the signal processing time and temperature prediction accuracy in Brillouin optical time domain analysis (BOTDA) fiber sensor. The algorithms analyzed were generalized linear model (GLM), deep learning (DL), random forest (RF), gradient boosted trees (GBT), and support vector machine (SVM). In this proof-of-concept experiment, the performance of each algorithm was investigated by pairing Brillouin gain spectrum (BGS) with its corresponding temperature reading in the training dataset. It was found that all of the ML algorithms have significantly reduced the signal processing time to be between 3.5 and 655 times faster than the conventional Lorentzian curve fitting (LCF) method. Furthermore, the temperature prediction accuracy and temperature measurement precision made by some algorithms were comparable, and some were even better than the conventional LCF method. The results obtained from the experiments would provide some general idea in deploying ML algorithm for characterizing the Brillouin-based fiber sensor signals.

Assessing iMET-XQ Performance and Optimal Placement on a Small Off-the-Shelf, Rotary-Wing UAV, as a Function of Atmospheric Conditions

The accuracy and precision of iMET-XQ (InterMET Inc., Grand Rapids, MI, USA) temperature measurements in ten different locations on an off-the shelf rotary-wing unmanned aerial vehicle (rw-UAV) were assessed, as a function of atmospheric conditions. The rw-UAV hovered near an instrumented South Alabama Mesonet tower. The mean ± standard deviation of all the temperature differences between the tower and the ten iMET-XQ sensors for all experiments are −0.23 °C ±0.24 °C. Both the UAV and the environment influence the accuracy and precision of the iMET-XQ temperature measurements. Heat generated by the electronic components within the UAV body has a significant influence on the iMET-XQ temperature measurements, regardless of solar radiation conditions, and is highly dependent on wind direction. Electronic components within the UAV body heat up and can cause sensors downwind from the UAV body to record temperatures that are too warm, even if the sensors are aspirated by propeller wash. iMET-XQ sensors placed on rotor arms not near UAV body heat sources, and properly aspirated by propeller wash, perform well. Measurements from iMET-XQ sensors suspended below the UAV are also accurate. When using an off-the-shelf UAV for atmospheric temperature sensing, the electronic components inside the body of the UAV must be properly located. It is recommended that multiple sensors are placed on the UAV. Sensor redundancy will mitigate data loss in case of malfunction during flight and the identification of poorly performing sensors.

Phosphor thermometry for in-cylinder surface temperature measurements in diesel engines

Phosphor thermometry is a temperature measurement technique that has previously been employed in technically relevant applications to obtain surface temperature. The technique is based on temperature-dependent changes in a phosphor's luminescence. To improve the accuracy and precision of temperature measurements with this technique, the present study considers, by way of example, the impact of conditions inside the cylinder of a diesel engine on decay time based single-shot phosphor thermometry measurements. After an initial, general assessment of the effect of prevailing measurement conditions, this research investigates errors caused by soot luminosity, extinction, signal trapping and changes of phosphors' luminescence properties due to exposure to the harsh environment. Furthermore, preferable properties of phosphors which are suitable for in-cylinder temperature measurements are discussed. 16 phosphors are evaluated, including LaAlGe2O7:Tm, YVO4:(Dy,Ce), ZnS:(Tm,Ag), and ZnS:(Tm,Li) which – to the authors' knowledge – have previously not been used in thermometry. Results indicate that errors due to photocathode bleaching, extinction, signal trapping and changes of luminescence properties may cause an erroneous temperature evaluation with temperature errors in the order of several tens of Kelvin.

Porcelain Insulator Inspection Using Infrared Thermography

Inspection with thermography is a non-invasive, non-destructive process used in Power Systems facilities. Most temperature signatures that are not in the visible light range can be measured using thermal cameras, thus enabling the search of thermal behavior of porcelain insulators. Overheating can help to detect problems, concerning the proper operation of insulators. The precision of temperature measurement using an infrared camera is influenced by the value of emissivity parameter that is set on camera. In the present study the influence of distance and angle between the camera and the insulator on emissivity parameter value selection in camera is examined experimentally.

Phosphor thermometry at 5 kHz rate using a high-speed fiber-optic spectrometer

A simple kHz-rate spectral phosphor thermometry technique with sub-millisecond temporal resolution for contactless point measurements of short duration transient surface temperature changes was developed by employing a compact high-speed fiber-optic spectrometer, a high repetition rate pulsed green laser, and a fast decaying thermographic phosphor. Temperature changes were determined from the temperature-dependent emission spectra of the YAG:Ce phosphor using a spectral slope method. The precision of single-shot temperature measurements was better than 4% for temperatures up to 700 K. An application of the technique for time-resolved measurements of local transient temperature changes at 5 kHz during repetitive long CO2 laser pulse heating is presented. The measured temperature transients are well-predicted using a two-dimensional axisymmetric heat transfer model.

A flexible 9-channel coil array for fast 3D MR thermometry in MR-guided high-intensity focused ultrasound (HIFU) studies on rabbits at 3 T

Signal-to-noise ratio (SNR) is a critical factor in MR-guided high-intensity focused ultrasound (HIFU) for local heating, which can affect the accuracy of temperature measurement. In order to achieve high SNR and higher temporal resolution, dedicated coil arrays for MR-guided HIFU applications need to be developed. In this work, a flexible 9-channel coil array was designed, and constructed at 3 T to achieve fast temperature mapping for MR-guided HIFU applications on rabbit leg muscle. Coil performance was evaluated for SNR, and parallel imaging capability by in-vivo studies. Compared to a commercially available 4-channel flexible coil array, the dedicated 9-channel coil array has a much higher SNR, with at least a 2.6-fold increment in the region of interest (ROI). The inverse g-factors maps demonstrated that the dedicated 9-channel coil array has a better parallel imaging capability than the Flex Small 4. With accelerations normal to the array direction, both coil arrays showed much higher g-factors than those of accelerations along the array direction. Room temperature mapping was implemented to evaluate the temperature measurement accuracy by in-vivo experiments. The precisions of the 9-channel coil, ±0.18 °C for un-acceleration and ± 0.56 °C for acceleration at R = 2 × 2, both improved by an order of magnitude than these of the 4-channel coil, which were ± 1.45 °C for un-acceleration and ± 3.52 °C for acceleration at R = 2 × 2. In the fast temperature imaging on the rabbit leg muscle with heating, a high temporal resolution of 3.3 s with a temperature measurement precision of ±0.56 °C has been achieved using the dedicated 9-channel coil. This study demonstrates that the dedicated 9-channel coil array for rabbit leg imaging provides improved performance in SNR, parallel imaging capability, and the accuracy of temperature measurement compared to a commercial 4-channel coil, and it also achieves fast temperature mapping in practical MR-guided HIFU applications.

Impact of moderate pump–Stokes chirp on femtosecond coherent anti‐Stokes Raman scattering spectra

AbstractThe effects of inducing moderate chirp in the pump and Stokes beams in chirped‐probe‐pulse femtosecond coherent anti‐Stokes Raman scattering (CARS) spectroscopy are discussed. This is an important issue for measurements in high‐pressure systems where the CARS beams must be transmitted through glass of significant thickness to reach the probe volume of interest. The effects were investigated both experimentally, by inserting disks of SF‐11 glass into the pump and Stokes beam paths, and theoretically, by incorporating pulse chirp into our time‐dependent density matrix (TDDM) simulations. Experimentally, we found that inducing moderate pump and Stokes chirp produced significant spectral narrowing of the nonresonant four‐wave mixing contribution to the CARS signal, and this allowed us to control the resonant excitation bandwidth to eliminate interferences from neighboring species. The temperature measurement accuracy and precision were essentially unchanged with respect to the unchirped pump and Stokes case. The effect of moderate pump and Stokes chirp on the narrowing of the Raman excitation efficiency envelope was investigated by solving the full set of TDDM through direct numerical integration. The numerical efficiency of the solutions was enhanced dramatically by developing a parallel version of the TDDM code. The calculated Raman excitation efficiency profile was incorporated in our phenomenological spectral fitting codes.