Sensitive Temperature Measurements Research Articles

TEMPERATURE AND WATER LEVEL MEASUREMENT OF LIQUID IN A TANK USING FIBER BRAGG GRATING

In this work, measurement of temperature and liquid level were performed simultaneously using fiber Bragg grating (FBG) sensors. A multi-channel Fibre Interrogator with built-in ASE laser source operating around 1552 to 1568 nm was employed to record a shift in Bragg wavelength due to contribution from both temperature and hydrostatic pressure of liquid weight in the tank. Results show a linear response between liquid level and temperature readings against the shift in Bragg wavelength for liquid level up to 85 cm in height and the temperature range of 27 to 77 oC. The sensitivity of the sensor head for water level measurement is 10.57 pmcm-1, while the sensitivity for temperature measurement is 11.28 pm/oC respectively.

Empowering a mesophilic inoculum for thermophilic nitrification: Growth mode and temperature pattern as critical proliferation factors for archaeal ammonia oxidizers

Cost-efficient biological treatment of warm nitrogenous wastewaters requires the development of thermophilic nitrogen removal processes. Only one thermophilic nitrifying bioreactor was described so far, achieving 200 mg N L−1 d−1 after more than 300 days of enrichment from compost samples. From the practical point of view in which existing plants would be upgraded, however, a more time-efficient development strategy based on mesophilic nitrifying sludge is preferred. This study evaluated the adaptive capacities of mesophilic nitrifying sludge for two linear temperature increase patterns (non-oscillating vs. oscillating), two different slopes (0.25 vs. 0.08 °C d−1) and two different reactor types (floc vs. biofilm growth). The oscillating temperature pattern (0.25 °C d−1) and the moving bed biofilm reactor (0.08 °C d−1) could not reach nitrification at temperatures higher than 46 °C. However, nitrification rates up to 800 mg N L−1 d−1 and 150 mg N g−1 volatile suspended solids d−1 were achieved at a temperature as high as 49 °C by imposing the slowest linear temperature increase to floccular sludge. Microbial community analysis revealed that this successful transition was related with a shift in ammonium oxidizing archaea dominating ammonia oxidizing bacteria, while for nitrite oxidation Nitrospira spp. was constantly more abundant than Nitrobacter spp.. This observation was accompanied with an increase in observed sludge yield and a shift in maximal optimum temperature, determined with ex-situ temperature sensitivity measurements, predicting an upcoming reactor failure at higher temperature. Overall, this study achieved nitrification at 49 °C within 150 days by gradual adaptation of mesophilic sludge, and showed that ex-situ temperature sensitivity screening can be used to monitor and steer the transition process.

A fast and remote magnetonanothermometry for a liquid environment

This study reports on a new approach for remote nanothermometry with short response time (milliseconds) aiming to operate in liquid media using AC susceptibility components of a suspended magnetic nanoparticle subjected to the Brownian relaxation mechanism. A simple, low cost, and accurate system was designed to measure AC susceptibility using an AC magnetic field at small amplitude (6 Oe) and frequency range (5 kHz) superimposed on a weak DC magnetic field (up to 30 Oe). A model based on the AC susceptibility of magnetic nanoparticles (30 nm average diameter) was constructed to describe the temperature measurement sensitivity of the dominated Brownian relaxation time. A new approach for remote nanothermometry was achieved with measured AC susceptibility by the designed system and the proposed model. Our experimental results show that our magnetonanothermometer allows temperature errors lower than 0.3 K with standard deviations lower than 0.1 K in the temperature range from 310 to 320 K.

Hygroscopic polymer microcavity fiber Fizeau interferometer incorporating a fiber Bragg grating for simultaneously sensing humidity and temperature

This work proposes a hygroscopic polymer microcavity fiber Fizeau interferometer (PMFFI) incorporating a fiber Bragg grating (FBG) for the simultaneous measurement of relative humidity (RH) and temperature (T). The PMFFI was fabricated by attaching the hygroscopic polymer to a single-mode fiber endface to form a low-finesse Fabry–Perot resonant microcavity. This work is the first to investigate polymer of the Norland Optical Adhesive (NOA) series with particular porous structures that responds well to the moisture and can thus be used in the fiber-optic sensing of relative humidity. Additionally, the NOA materials have a high thermal expansion coefficient and so can be used in the highly sensitive measurement of temperature. The adsorption/desorption of water molecules and variations in temperature both change the optical path of the microcavity, shifting the fringes in the interference spectra. Incorporating a general FBG that is nonreactive to RH but sensitive to T judges the variation in T. The combined sensor supports the simultaneous measurement of both parameters RH and T by gauging of the individual spectral responses of PMFFI and FBG, respectively. Experimental results demonstrate that the RH and T can be simultaneously measured with high sensitivity and accuracy using the proposed sensing configuration.

Mach–Zehnder interferometer formed by a large core-offset splicing fiber for temperature and displacement measurement

A novel, versatile, compact all-fiber Mach–Zehnder interferometer (MZI) for temperature and displacement sensing was proposed and demonstrated in this paper. It was fabricated by splicing a section of single mode fiber (SMF) between two SMFs with a large core-offset at two splicing joints, which were used to excite cladding modes and couple to the fiber core. And then the interference occurred between the cladding and external substances was utilized to measure temperature and displacement. Experimental results showed that the sensitivity of temperature measurement could be up to 25.26pm/°C and the sensitivity of displacement measurement was 96.72nW/mm. In addition, because the measurement of temperature and displacement could be implemented respectively by recording the light wavelength shifts and light intensity variation, temperature and displacement could be measured simultaneously with only one sensor probe. Meanwhile, there were some other advantages of the sensor, such as simple structure, small size, high sensitivity and low cost.

Optical Temperature Sensing Behavior of High‐Efficiency Upconversion: Er3+–Yb3+ Co‐Doped NaY(MoO4)2 Phosphor

A class of Yb3+/Er3+ co‐doped NaY(MoO4)2 upconversion (UC) phosphors have been successfully synthesized by a facile hydrothermal route with further calcination. The structural properties and the phase composition of the samples were characterized by X‐ray diffraction (XRD). The UC luminescence properties of Yb3+/Er3+ co‐doped NaY(MoO4)2 were investigated in detail. Concentration‐dependent studies revealed that the optimal composition was realized for a 2% Er3+ and 10% Yb3+‐doping concentration. Two‐photon excitation UC mechanism further illustrated that the green enhancement arised from a novel energy‐transfer (ET) pathway which entailed a strong ground‐state absorption of Yb3+ ions and the excited state absorption of Yb3+–MoO42− dimers, followed by an effective energy transfer to the high‐energy state of Er3+ ions. We have also studied the thermal properties of UC emissions between 303 and 523 K for the optical thermometry behavior under a 980 nm laser diode excitation for the first time. The higher sensitivity for temperature measurement could be obtained compared to the previous reported rare‐earth ions fluorescence based optical temperature sensors. These results indicated that the present sample was a promising candidate for optical temperature sensors with high sensitivity.

Noninvasive and real-time plasmon waveguide resonance thermometry.

In this paper, the noninvasive and real-time plasmon waveguide resonance (PWR) thermometry is reported theoretically and demonstrated experimentally. Owing to the enhanced evanescent field and thermal shield effect of its dielectric layer, a PWR thermometer permits accurate temperature sensing and has a wide dynamic range. A temperature measurement sensitivity of 9.4 × 10−3 °C is achieved and the thermo optic coefficient nonlinearity is measured in the experiment. The measurement of water cooling processes distributed in one dimension reveals that a PWR thermometer allows real-time temperature sensing and has potential to be applied for thermal gradient analysis. Apart from this, the PWR thermometer has the advantages of low cost and simple structure, since our transduction scheme can be constructed with conventional optical components and commercial coating techniques.

Automated Microfluidic Platform for Serial Polymerase Chain Reaction and High-Resolution Melting Analysis.

We report the development of an automated genetic analyzer for human sample testing based on microfluidic rapid polymerase chain reaction (PCR) with high-resolution melting analysis (HRMA). The integrated DNA microfluidic cartridge was used on a platform designed with a robotic pipettor system that works by sequentially picking up different test solutions from a 384-well plate, mixing them in the tips, and delivering mixed fluids to the DNA cartridge. A novel image feedback flow control system based on a Canon 5D Mark II digital camera was developed for controlling fluid movement through a complex microfluidic branching network without the use of valves. The same camera was used for measuring the high-resolution melt curve of DNA amplicons that were generated in the microfluidic chip. Owing to fast heating and cooling as well as sensitive temperature measurement in the microfluidic channels, the time frame for PCR and HRMA was dramatically reduced from hours to minutes. Preliminary testing results demonstrated that rapid serial PCR and HRMA are possible while still achieving high data quality that is suitable for human sample testing.

Simplified Hollow-Core Fiber-Based Fabry–Perot Interferometer With Modified Vernier Effect for Highly Sensitive High-Temperature Measurement

In this paper, a high-temperature fiber sensor based on an optical fiber Fabry–Perot interferometer is fabricated by splicing a section of simplified hollow-core fiber between two single-mode fibers (SMFs) and cleaving one of the two SMFs to a certain length. With the superposition of three beams of light reflected from two splicing joints and end face of the cleaved SMF, the modified Vernier effect will be generated in the proposed structure and improve the sensitivity of temperature measurement. The envelope of spectrum reflected from the proposed sensor head is modulated by the ambient temperature of the sensor head. By monitoring and measuring the shift of spectrum envelope, the measurement of environment temperature is carried out experimentally, and high temperature sensitivity of 1.019 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$\hbox{nm}/^{\circ}\hbox{C} $</tex-math></inline-formula> for the envelope of the reflected spectrum was obtained. A temperature measurement as high as 1050 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$^{\circ}\hbox{C}$</tex-math></inline-formula> has been achieved with excellent repeatability.

Variations of Temperature Sensitivity Measurements of Several Packages Under Different Environments

Temperature sensitivity is used to measure the junction temperature of semiconductor devices without using external temperature sensors. Temperature sensitivity may vary due to the measurement environments, which affects the accuracy of the junction temperature. A single sided cold plate is widely used for thermal transient measurement. It would be useful if a single sided cold plate can be used not only for thermal transient measurements but also for temperature sensitivity measurements. However, it is presumed that temperature sensitivity measurement is not reliable when a single sided cold plate is used. It is due to the temperature gradient between the cold plate and the ambient, through the junction of the semiconductor. Unless the device is put inside the temperature controlled chamber, it is hard to eliminate the temperature gradient. However, this fact hasn’t been well recognized. In order to clarify whether single sided cold plate has a chance for the temperature sensitivity measurement or not, this paper presents the results of several temperature sensitivity measurements using 2 types of temperature controlled environments: a single sided cold plate and a temperature controlled chamber. Also, we have tested with several packages such as TO-220, TO-264, SOT-227, and D3 package, to see how it varies. We have come to the conclusion that it is better to use a temperature controlled chamber to measure temperature sensitivity, while some devices allow us to use a single sided cold plate as well. The differences due to the devices and environments are discussed by using Computational Fluid Dynamics (CFD) simulation, visualizing the temperature gradient inside the packages.

Development of a semi-adiabatic isoperibol solution calorimeter.

A semi-adiabatic isoperibol solution calorimeter has been indigenously developed. The measurement system comprises modules for sensitive temperature measurement probe, signal processing, data collection, and joule calibration. The sensitivity of the temperature measurement module was enhanced by using a sensitive thermistor coupled with a lock-in amplifier based signal processor. A microcontroller coordinates the operation and control of these modules. The latter in turn is controlled through personal computer (PC) based custom made software developed with LabView. An innovative summing amplifier concept was used to cancel out the base resistance of the thermistor. The latter was placed in the dewar. The temperature calibration was carried out with a standard platinum resistance (PT100) sensor coupled with an 8½ digit multimeter. The water equivalent of this calorimeter was determined by using electrical calibration with the joule calibrator. The experimentally measured values of the quantum of heat were validated by measuring heats of dissolution of pure KCl (for endotherm) and tris (hydroxyl methyl) amino-methane (for exotherm). The uncertainity in the measurements was found to be within ±3%.

Wireless passive high-temperature sensor based on multifunctional reflective patch antenna up to 1050 degrees centigrade

A novel wireless passive temperature sensor based on a reflective patch is demonstrated up to 1050°C herein. This reflective patch acts as a patch resonator (temperature sensor) and an integrated antenna at the same time. The temperature sensing mechanism is the monotonic increase of the dielectric constant of alumina versus temperature, which reduces the resonant frequency of a patch resonator formed on such an alumina substrate. By properly designing the shape and dimensions of the patch, it can also act as a transmit/receive antenna for wireless passive sensing. Therefore, temperatures can be wirelessly sensed by measuring the resonant frequency of the temperature sensor using an interrogation antenna. This temperature sensor uses robust alumina and platinum materials for high-temperature applications. In addition, this wireless passive temperature sensor is simple in mechanical structure and low in profile, with the potential to be in conformal shape. A temperature sensor using this reflective patch was designed, fabricated and tested from 50 to 1050°C in ambient. The resonant frequency of the sensor decreases from 5.07 to 4.58GHz, which corresponds to a dielectric constant change from 9.7 to 11.4 for the alumina substrate. The temperature measurement sensitivity is found to be 0.58MHz/°C at 1050°C. Being wireless, passive, planar and low profile, the proposed high-temperature sensor can be used for various harsh-environment applications.

ALD thin ZnO layer as an active medium in a fiber-optic Fabry–Perot interferometer

A novel optical fiber sensor of temperature using a thin ZnO layer fabricated by atomic layer deposition (ALD) is demonstrated for the first time. The thin ZnO layer was grown on the face of a standard optical telecommunication fiber SMF-28 and operates as a Fabry–Perot interferometer sensitive to temperature. The interferometer characterization was made in the temperature range extending from 50 to 300°C with resolution equal to 1°C. The output signal was analyzed by measurement of the shift of the maxima in spectral pattern. The sensitivity of temperature measurement is about 0.05nm/°C. Furthermore, very good linearity of the sensor was achieved with correlation coefficient R2=0.9984.

Sensitive detection of CO2 concentration and temperature for hot gases using quantum-cascade laser absorption spectroscopy near 4.2 μm

Mid-infrared quantum-cascade laser (QCL) absorption spectroscopy of CO2 near 4.2 mu m has been developed for measurement of temperature and concentration in hot gases. With stronger absorption line-strengths than transitions near 1.5, 2.0, and 2.7 mu m used previously, the fundamental band (00(0)1-00(0)0) of CO2 near 4.2 mu m provides greatly enhanced sensitivity and accuracy to sense CO2 in high-temperature gases. Line R(74) and line R(96) are chosen as optimum pair for sensitive temperature measurements due to their high-temperature sensitivity, equal signal-to-noise ratio (SNR), weak interference of H2O transitions, as well as relatively strong line-strengths in high temperature and weak absorption in room temperature. The high-resolution absorption spectrum of the far wings of the R-branch (R56-R100) in the fundamental vibrational band of CO2 is measured in a heated cell over the range 2,384-2,396 cm(-1) at different temperatures from 700 to 1,200 K. Taking three factors into consideration, including SNR, concentration detectability, and uncertainty sensitivity, the absorption line R(74) is selected to calculate CO2 concentration. The tunable QCL absorption sensor is validated in mixtures of CO2 and N-2 in a static cell for temperature range of 700-1,200 K, achieving an accuracy of +/- 6 K for temperature and +/- 5 % for concentration measurements.

Fiber Fabry–Pérot Interferometers Based on Air-Bubbles/Liquid in Hollow Core Fibers

This letter develops a miniature and highly sensitive fiber Fabry-Perot interferometer (FFPI) that is based on an air-bubble and liquid in a hollow core fiber (HCF). The endface of the proposed FFPI is sealed off by an optical fiber plug to ensure the optical/chemical stability of the used liquids. The fiber plug is fabricated with a single-mode fiber taper to close the end of the liquid core fiber. The proposed technique ensures that the filled liquid neither effuses nor becomes contaminated. Experimental results show that the presence of both an air-bubble and liquid in the FFPI enables the highly sensitive measurement of temperature (T), the sensitivity of which can be controlled by changing the ratio of the volume of air to that of liquid in the HCF.

Multi-band infrared CO2 absorption sensor for sensitive temperature and species measurements in high-temperature gases

A continuous-wave laser absorption diagnostic, based on the infrared CO2 bands near 4.2 and 2.7 μm, was developed for sensitive temperature and concentration measurements in high-temperature gas systems using fixed-wavelength methods. Transitions in the respective R-branches of both the fundamental υ 3 band (~2,350 cm−1) and combination υ 1 + υ 3 band (~3,610 cm−1) were chosen based on absorption line-strength, spectral isolation, and temperature sensitivity. The R(76) line near 2,390.52 cm−1 was selected for sensitive CO2 concentration measurements, and a detection limit of <5 ppm was achieved in shock tube kinetics experiments (~1,300 K). A cross-band, two-line thermometry technique was also established utilizing the R(96) line near 2,395.14 cm−1, paired with the R(28) line near 3,633.08 cm−1. This combination yields high temperature sensitivity (ΔE” = 3,305 cm-1) and expanded range compared with previous intra-band CO2 sensors. Thermometry performance was validated in a shock tube over a range of temperatures (600–1,800 K) important for combustion. Measured temperature accuracy was demonstrated to be better than 1 % over the entire range of conditions, with a standard error of ~0.5 % and µs temporal resolution.

A miniature temperature high germanium doped PCF interferometer sensor

We report in this paper a high thermal sensitivity (78 pm/°C) modal interferometer using a very short Photonic Crystal Fiber stub with a shaped Germanium doped core. The Photonic Crystal Fiber is spliced between two standard fibers. The splice regions allow the excitation of the core and cladding modes in the PCF and perform an interferometric interaction of such modes. The device is proposed for sensitive temperature measurements in transmission, as well as in reflection operation mode with the same high temperature sensitivity.

Highly Sensitive Temperature Measurements With Liquid-Core Microbubble Resonators

The thermal shifting of whispering gallery modes (WGMs) in a microbubble resonator is investigated. The thermal shift rate is determined for different modes when the core of the microbubble is filled with air, water and ethanol. Sensitivities as high as 100 GHz/K (0.2 nm/K at wavelength of 775 nm) are observed when the microbubble core is filled with ethanol. This is the largest thermal shift rate reported for a WGM resonator. We also show that thermal behavior of the WGMs in a thin-shelled, air-filled microbubble is different from a solid microsphere. The measured shifts are compared against finite element model simulations. Q-factors for the higher order modes are typically 105, equivalent to a measurement resolution of 8.5 mK.

Strong functional stability of soil microbial communities under semiarid Mediterranean conditions and subjected to long-term shifts in baseline precipitation

We investigated the effect of soil microclimate on the structure and functioning of soil microbial communities in a Mediterranean Holm-oak forest subjected to 10 years of partial rain exclusion manipulations, simulating average drought conditions expected in Mediterranean areas for the following decades. We applied a high throughput DNA pyrosequencing technique coupled to parallel measurements of microbial respiration (RH) and temperature sensitivity of microbial respiration (Q10). Some consistent changes in the structure of bacterial communities suggest a slow process of community shifts parallel to the trend towards oligotrophy in response to long-term droughts. However, the structure of bacterial communities was mainly determined by short-term environmental fluctuations associated with sampling date (winter, spring and summer) rather than long-term (10 years) shifts in baseline precipitation. Moreover, long-term drought did not exert any chronic effect on the functioning of soil microbial communities (RH and Q10), emphasizing the functional stability of these communities to this long-term but mild shifts in water availability. We hypothesize that the particular conditions of the Mediterranean climate with strong seasonal shifts in both temperature and soil water availability but also characterized by very extreme environmental conditions during summer, was acting as a strong force in community assembling, selecting phenotypes adapted to the semiarid conditions characterizing Mediterranean ecosystems. Relations of climate with the phylogenetic structure and overall diversity of the communities as well as the distribution of the individual responses of different lineages (genera) to climate confirmed our hypotheses, evidencing communities dominated by thermotolerant and drought-tolerant phenotypes.

Thin photothermal endoscope for biomedical applications

A thin photothermal (PT) endoscope (∼80 μm ) for the noninvasive/minimally invasive hybrid-optical diagnosis of biological specimens is demonstrated. The technique has the unique advantage that the pump laser delivery fiber itself acts as the thermal wave sensor, which is a Bragg grating. It detects only the conductive component of the PT signal, thus enabling an emissivity independent measurement. The device is slidable through a syringe needle and PT analysis of exposed organs with limited accessibility for conventional PT techniques, and constricted regions can be examined noninvasively. For regions buried in thick tissues, a minimally invasive injection mode may be considered. Temperature measurement sensitivity is about 0.03°C. The amplitude and phase channels are sensitive up to about 3 and 10 kHz, respectively. The endoscope has been used for the simultaneous estimation of flow velocity, absorption coefficient, and diffusivity for a phantom-blood flow. The endoscopically estimated values are in agreement with true flow velocities over a range of 1 to 1000 cm −1 . The endoscope has been used for the optical biopsy of goat bone marrow.