High Precision Temperature Research Articles

Design of PT100 high-precision temperature measurement systems based on third-order model

In view of the non-linearity of the output of the PT100 sensor, this article describes the temperature characteristics of the PT100 with a third-order model. The mathematical model of pt100 and standard thermometer IRTD is analyzed. The transfer function of pt100 and IRTD is evaluated by step response experiment. A least squares method based on transfer function is proposed as a compensation algorithm, MATLAB is used for simulation calculation. The proposed algorithm can make the maximum error of pt100 temperature measurement to 0.05, and the minimum error can reach to 0.0001, which is achieving the requirements of high precision.

Terahertz Thermal Sensing by Using a Defect-Containing Periodically Corrugated Gold Waveguide

A terahertz (THz) thermal sensor has been developed by using a periodically corrugated gold waveguide. A defect was positioned in the middle of this waveguide. The periodicities of waveguides can result in Bragg and non-Bragg gaps with identical and different transverse mode resonances, respectively. Due to the local resonance of the energy concentration in the inserted tube, a non-Bragg defect state (NBDS) was observed to arise in the non-Bragg gap. It exhibited an extremely narrow transmission peak. The numerical results showed that by using the here proposed waveguide structure, a NBDS would appear at a resonance frequency of 0.695 THz. In addition, a redshift of this frequency was observed to occur with an increase in the ambient temperature. It was also found that the maximum sensitivity can reach 11.5 MHz/K for an optimized defect radius of 0.9 times the mean value of the waveguide inner tube radius, and for a defect length of 0.2 (or 0.8) times the corrugation period. In the present simulations, a temperature modification of the Drude model was also used. By using this model, the thermal sensing could be realized with an impressive sensitivity. This THz thermal sensor is thereby very promising for applications based on high-precision temperature measurements and control.

On Line Monitoring System of Non-contact Infrared Temperature Measurement for Distribution Switchgear

This paper proposes online monitoring and early warning system based on MLX90640 non-contact busbar temperature measurement switchgear. It uses MLX90640 infrared sensor module to measure the temperature of the switchgear busbar and then uses the E30-433T20D wireless communication method to transmit the temperature data to the local terminal. The practice test shows that the temperature measurement point terminal can accurately measure the bus temperature and feed the temperature back to the local switchgear terminal, which can achieve high-precision temperature measurement and early warning of the temperature of the switchgear busbar and can abnormally the temperature of the busbar in the cabinet. The position is accurately positioned to facilitate fault condition maintenance, improve the reliability of the switchgear operation, and ensure the safety of the switchgear system.

Novel freeze-casting device with high precision thermoelectric temperature control for dynamic freezing conditions.

A novel freeze-casting device utilizing a thermoelectric element for high precision temperature control allowing for dynamic freezing conditions of freeze-cast materials is presented. Freeze-casting is a processing route for producing materials of anisotropic porosity in the form of aligned and well-defined microchannels. In freeze-casting, particulates of a material are suspended in a fluid and a thermal gradient is applied across for directional freezing. Controlling the thermal gradient across the suspension amounts to controlling the kinetics and freezing direction in the suspension and thus the resulting structural features and dimensions of the microchannels. The performance of the device presented here was evaluated by directional freezing of both water and aqueous ceramic suspension samples using both linear and exponential freezing profiles. The freezing front was successfully tracked by continuously measuring the temperature gradient along the sample using thermocouples directly mounted on the freeze-casting mold. The current minimum operational temperature of the freeze-caster is ∼220 K, with freezing front velocities in the range of ∼5 μm/s to 30 μm/s for sample lengths of 5 mm-25 mm.

Calibration source for OH radical based on synchronous photolysis

<sec> OH radical is the most important oxidant in the atmosphere, and controls the tropospheric concentration of tropospheric trace gases such as CO, SO<sub>2</sub>, NO<sub>2</sub>, CH<sub>4</sub> and other volatile organic compounds. Accurate measurement of the concentration of OH radical in troposphere is the key to clarifying the formation mechanism of secondary pollution in China. The laser-induced fluorescence (LIF) technique is widely used in tropospheric OH radical field observation due to its high sensitivity, high selectivity, and small interference. However, the LIF technique is not an absolute measurement technology. In recent years, OH radical measurements and simulations in many field observations show that the improvement of accuracy of calibration is a way to reduce the differences. Currently, the common calibration methods are ozone-alkene method and water photolysis method. Further improving the accuracy of calibration is a key factor to ensure the accurate measurement of OH radicals.</sec><sec> In this paper, a portable calibration method of OH radicals based on simultaneous photolysis is introduced. The synthetic air with a certain water vapor concentration is irradiated in laminar flow by 185 nm light of mercury lamp, and the photolysis of water vapor and O<sub>2</sub> produce OH, HO<sub>2</sub> radicals and O<sub>3</sub>. The concentration of OH radicals is calculated by oxygen concentration, water vapor concentration, ozone concentration, oxygen absorption cross section and water vapor absorption cross section. The water vapor is measured by a high-precision temperature and humidity probe, and the systematic error of the probe is corrected by 911-0016 ammonia (NH<sub>3</sub>, H<sub>2</sub>O) analyzer. As the ozone concentration is only 0.5－1 ppb in the calibration, the commercial ozone analyzer cannot meet the requirement for the measurement. A high-precision ozone analyzer O<sub>3</sub>-CRDS based on cavity-ring-down spectrocopy is built to achieve the detection limit of 15 ppt (1σ). Using the O<sub>3</sub>-CRDS analyzer, the concentration distribution coefficient of ozone in laminar flow along the radial direction of the flow tube (<i>P</i> = 1.9) is measured. Because the absorption cross section of oxygen at 185 nm is seriously affected by oxygen column concentration and the characteristics of mercury lamp, the oxygen absorption cross section is remeasured based on Lambert’s law, which is <italic/><inline-formula><tex-math id="Z-20200420115213-1">\begin{document}$ \sigma_{\rm O_2} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20200153_Z-20200420115213-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20200153_Z-20200420115213-1.png"/></alternatives></inline-formula><sub><sub> </sub></sub>= (1.25 ± 0.08)×10<sup>–20</sup> cm<sup>2</sup>. The portable calibration device is established by establishing the corresponding relationship between ozone concentration and light intensity. By changing the concentration of water vapor in the flow tube, the OH radicals with concentrations in a range of 3×10<sup>8</sup>－2.8×10<sup>9</sup> cm<sup>–3</sup> are produced, which are used to calibrate the atmospheric OH radical measurement instrument based on LIF technique. The fluorescence signal has a good correlation with the concentration of OH. The calibration device of OH radical is used to calibrate the LIF system during “a comprehensive study of the ozone formation mechanism in Shenzhen” (STORM) field observation in Autumn 2018. The calibration results under the field condition show that the calibration uncertainty of the calibration device for LIF instrument is 13.0%, which has good stability and accuracy.</sec>

A novel low-cost, high-precision sea temperature sensor for coral reef monitoring

The role of elevated sea temperatures in coral bleaching has been well documented. Many of the sea temperature records utilized for purposes of widespread, multi-species bleaching predictions in recent publications have been acquired through satellite remote sensing. Satellites estimate sea temperatures at only a narrow range of depths near the surface of the ocean and may therefore not adequately represent the true temperatures endured by the world's coral ecosystems. To better characterize sea temperature regimes that coral reef ecosystems experience, as well as better define the individual thresholds for each species that bleaches, in situ sea temperature sensors are required. Commercial sensors are expensive in large quantities, however, reducing the capacity to conduct large- scale research programs to elucidate the range of significant scales of temperature variability. At the National Oceanic and Atmospheric Administration's (NOAA) Atlantic Oceanographic and Meteorological Laboratory (AOML), we designed a low-cost (roughly US$9 in parts) and high- precision sea temperature sensor that uses an Arduino microprocessor board and a high accuracy thermistor. This new temperature sensor autonomously records temperatures onto a memory chip and provides better accuracy (+0.05 °C) than a comparable commercial sensor (+0.2 °C). Moreover, it is not difficult to build; anyone who knows how to solder can build the temperature sensor. In March 2019, students at middle and high schools in Broward County, Florida, built close to 60 temperature sensors. During 2019, these sensors will be deployed by Reef Check, a global-scale coral reef monitoring organization, as well as by other programs to determine worldwide sea temperature regimes through the Opuhala Project (https://www. coral. noaa. gov/opuhala). This paper chronicles results from the initial proof-of-concept deployments for these AOML-designed sensors.

用于TDLAS气体检测系统的高精度温控设计

用于TDLAS气体检测系统的高精度温控设计

激光吸收光谱系统中气室的高精度温控设计

激光吸收光谱系统中气室的高精度温控设计

用于TDLAS气体检测系统的高精度温控设计

用于TDLAS气体检测系统的高精度温控设计

Design and Application of High-Precision Temperature Measuring Instrument for Ice Cover Profile of River Based on the Resistance Residual Compensation Method

Based on the temperature characteristics of the air, ice and water in the vertical direction of the river ice cover, an automatic temperature measuring instrument for ice cover profile was designed. The sensor used NTC thermistor as a temperature detection unit. In order to improve the actual detection accuracy of the sensor units in a wide temperature range [223.15 K (-50°C), 293.15 K (20°C)], a calibrating method of the thermistor using the resistance residual compensation method was proposed and compared with the existing seven calibration methods. The results show that the accuracy of the calibrated temperature sensor units can reach 0.1 K in the testing range, which can satisfy the accuracy requirements in thermodynamics research of ice cover profile. We further designed a temperature measuring instrument and carried out a deployment of the instrument and in-situ observation of data in cold region of the upstream of Heilongjiang River in late December 2017. The evolution process of ice thickness was analysed and discussed by the collected data. It can be proved that this instrument is an effective scheme for intelligent detection of river ice environment in cold regions.

Study on a High Performance MEMS Infrared Thermopile Detector.

This paper presents a high-performance micro-electromechanical systems (MEMS) thermopile infrared detector. It consists of a double-end beam and a dual-layer thermocouple structure, which improves the responsivity of the detector. The etch-stop structure is integrated into the detector to prevent isotropic etching-caused damage on the device. The responsivity of the detector achieved 1151.14 V/W, and the measured response time was 14.46 ms. The detector had the potential to work as a high-precision temperature sensor and as a vacuum sensor.

High-precision strain-insensitive temperature sensor based on an optoelectronic oscillator.

We have proposed and experimentally demonstrated a high-precision and strain-insensitive temperature sensor based on an optoelectronic oscillator (OEO). The oscillation frequency of the OEO is determined by the single passband microwave photonic filter (MPF) by using stimulated Brillouin scattering (SBS). The sensing fiber, which acts as the SBS gain medium, is exposed to temperature variations. The Brillouin frequency shift (BFS) changes along with the temperature. Since the central frequency of the MPF is a function of the BFS, the oscillation frequency of the OEO is varied. Besides, due to the mode competition in the OEO, the influence of the strain is eliminated. Thus, the temperature variations can be estimated through measuring the oscillation frequency. We carry out a proof-to-concept experiment. Temperature sensing with a high sensitivity of 1.00745 MHz/°C is achieved. The maximum measurement error of temperature obtained is within ± 0.5 °C. The proposed scheme has merits of simplicity and compact configuration. In addition, the proposed temperature sensor can realize quasi-distributed measurement by utilizing wavelength division multiplexing (WDM).

Graphene-assisted high-precision temperature sensing by long-period fiber gratings

The tapered long-period fiber grating (TLPFG) and rotated chiral long-period fiber gratings (CLPFG) heated by a CO2 laser were fabricated by periodically tapering and rotating standard single-mode fibers (SMF). The temperature sensing characteristics of the TLPFG and CLPFG between 30 °C and 60 °C were experimentally investigated, and the slopes of the wavelength shift corresponded to 0.115 nm °C−1 and 0.04 nm °C−1, respectively. The graphene films were coated on gratings to fabricate graphene-coated TLPFG (GTLPFG) and graphene-coated CLPFG (GCLPFG). Given the thermal effects of graphene, the slopes of the resonance dip shift of the GTLPFG and GCLPFG between 30 °C and 60 °C increased to 0.196 nm °C−1 and 0.113 nm °C−1, respectively. Additionally, the high temperature sensing properties of TLPFG and CLPFG between 100 °C and 1000 °C were investigated. The slopes of the higher-order resonance dips of the TLPFG and CLPFG corresponded to 0.119 nm °C−1 and 0.09 nm °C−1, respectively, during the heating process, and to 0.116 °C−1 and 0.09 nm °C−1, respectively, during the cooling process. In the low and high temperature zones, the TLPFG exhibited higher sensitivity when compared to that of the CLPFG, while the CLPFG exhibited higher sensing precision with linearity approaching 1. Given the simple and unsophisticated fabrication process and the high quality and sensitivity of the fabricated gratings, the proposed sensors can play an important role in high-precision temperature-sensing applications.

Design and Implementation of Accurate Measurement System for EEG Skin Impedance

This paper proposes a method of generating a square wave excitation signal through an analog circuit, using an analog switch to select the detection channel. In addition, high precision and low temperature drift resistors have been added for calibration. The calibration calculation and impedance detection are performed every 5 minutes. This system greatly reduces the errors caused by analog circuit and external factors and improves the accuracy of measurement. It can be used in the multi-lead EEG acquisition system and has good application value.

High-Precision 13CO2/12CO2 Isotopic Ratio Measurement Using Tunable Diode Laser Absorption Spectroscopy at 4.3 μm for Deep-Sea Natural Gas Hydrate Exploration

For the detection of deep-sea natural gas hydrates, it is very important to accurately detect the 13CO2/12CO2 isotope ratio of dissolved gas in seawater. In this paper, a 13CO2/12CO2 isotope ratio sensor is investigated, which uses a tunable diode laser absorption spectroscopy (TDLAS) technique at 4.3 μm. The proposed sensor consists of a mid-infrared interband cascade laser (ICL) operating in continuous wave mode, a long optical path multi-pass gas cell (MPGC) of 24 m, and a mid-infrared mercury cadmium telluride (MCT) detector. Aiming at the problem of the strong absorption intensity of the two absorption lines of 13CO2 and 12CO2 being affected by temperature, a high-precision temperature control system for the MPGC was fabricated. Five different concentrations of CO2 gas were configured to calibrate the sensor, and the response linearity could reach 0.9992 for 12CO2 and 0.9996 for 13CO2. The data show that the carbon isotope measurement precision was assessed to be 0.0139‰ when the integration time was 92 s and the optical path length was 24 m. The sensor is combined with a gas–liquid separator to detect the 13CO2/12CO2 isotope ratio of CO2 gas extracted from water. Results validate the reported sensor system’s potential application in deep-sea natural gas hydrate exploration.

Error correction of temperature measurement data obtained from an embedded bifilar optical fiber network in concrete dams

Conventional distributed optical fiber systems employed for internal temperature sensing in concrete dams suffer from low survival rate, insufficient measurement data, and low-accuracy temperature measurements that are subject to large fluctuations. Therefore, the present study proposes a bifilar optical fiber embedding technique running within each of the concrete dam blocks forming a dam. The proposed fiber optic network design is based on multiple considerations, including the embedding requirements of optical fiber to ensure good system longevity, the requirements of internal temperature monitoring in concrete dams to ensure the capture of adequate monitoring data, and the temperature measurement principle of distributed temperature sensing (DTS) systems to develop effective error correction methods. In terms of error correction, the light intensity attenuation caused by transmission- and wavelength-related losses is calculated based on the symmetrical temperature measurement points of the primary and secondary strands of the embedded bifilar optical fiber in conjunction with error correction theory to correct for temperature measurement fluctuations and thereby ensure the capture of accurate and stable temperature measurement data. Experimental error correction test results demonstrate that the mean absolute error (MAE) and root mean squared error (RMSE) of the error corrected temperature data obtained under various temperature conditions are reduced by 0.28 °C and 0.34 °C, with fluctuations that are decreased by 53.4% and 52.4%, respectively. The results derived from an actual engineering application under construction demonstrate that the survival rate of the embedded bifilar optical fibers is 100%. In addition, the average MAE and RMSE values of the temperature data obtained by the DTS system during the first water cooling stage are reduced by 0.14 °C and 0.22 °C, and their fluctuations are decreased by 41.5% and 47.0%, respectively. These results verify the reliability and feasibility of the error correction method proposed in this paper, and the method is demonstrated to provide reliable technical support for obtaining stable and high-precision DTS temperature data in concrete dams.

Implementation of a Broad Range Smart Temperature Measurement System using Auto-Selected Multi-Sensor Core in LabVIEW Environment

A conventional temperature sensing system employs a single transducer to convert temperature into an electrical signal. Such a system suffers from the limitation of the sensing range of the sensing device thereby affecting its accuracy and its capability. Therefore to make an accurate measurement in a typically abrupt temperature varying environment, a broad range high precision sensor is required. In this paper, an attempt is made to implement a wide spectrum temperature measurement system using auto-selected multi-sensor core in LabVIEW. This multi-sensor core can be composed of a set of different sensors having different capabilities to measure different temperatures ranges. These sensors are auto-selected by the program depending on the environment. This concept may be useful for space applications or it can also be useful for the monitoring of temperature and pressure in an oil/gas transportation or supply by means of underground/sea pipeline system or in a refinery plant. Further, this may also be applied for high precision temperature sensing in magnetic resonance imaging system applications.

Methods of isothermal nucleic acid amplification-based microfluidic chips for pathogen microorganism detection

Rapid detection of pathogenic microorganisms is key to the epidemiologic identification, prevention and control of disease in the field of public health. PCR-based pathogen detection methods have been widely used because they overcome the time-consuming issues that traditional culture-based methods required including the limited window required by immunological detection. However, the requirement on precision temperature-controlled thermal cyclers severely limits their use in resource-limited areas. The detection methods of pathogenic microorganisms based on isothermal amplification of nucleic acids are free of dependence on high-precision temperature control equipment, but requirements for nucleic acids extraction, amplification and detection must be defined. In recent years, a number of alternative methods for pathogenic microorganism detection have been developed by combining microfluidic technology with nucleic acid isothermal amplification technology. By designing the chip structures, optimizing the injection modes, and utilizing multiple detection and quantitative methods, the integration of pathogen nucleic acid extraction, amplification and detection is achieved. The method provides advantages of less instrument dependence, decreased operator requirements, smaller sample size, and higher automation which are suitable for the rapid detection of pathogenic microorganisms in various environments. In this review, we summarize several microfluidic detection methods based on nucleic acid isothermal amplification for pathogens including amplification principles, injection methods and detection methods. These methods provide more capability for the rapid screening of pathogenic microorganisms which enhances the management of infectious diseases in the field of public health.

High-precision temperature sensor based on weak measurement.

High-precision temperature sensor is demonstrated based on weak measurement using spectrum domain analysis. By introducing an extra phase to the postselection, the operating temperature range and temperature precision can be conveniently modulated. Spectral shifts resulted from temperature variation are robust to practical imperfections. The precision of 2.4 × 10-6°C can be achieved by a currently available spectrometer. The maximum operating range is associated with the nematic temperature range of nematic liquid crystals (NLCs) sample. Moreover, the temperature sensitivity of 16.16 nm/°C is obtained experimentally in different linear operating intervals.

A digital interface integration circuit design for high precision quartz-gyro

A design of digital application specific integrated circuit (ASIC) of quartz-gyro is proposed in this paper. The digital drive circuit with fast-start oscillation and digital detection circuit with low noise are adopted to implement the digital output of the main circuit node and high precision angular velocity detection. The interface circuit is fabricated in a standard 0.35 [Formula: see text]m CMOS technology and test result shows the angular random walk and zero stability are [Formula: see text]/[Formula: see text] and [Formula: see text]/h ([Formula: see text]), respectively. The bias-instability is [Formula: see text]/h (Allen). The nonlinearity is limited to 0.035% and the zero temperature drift is [Formula: see text]/h from [Formula: see text] to [Formula: see text]. The chip exhibits great superiority on the aspects of high precision angular velocity digital detection and temperature characteristics of overall system.