Temperature Measurement Applications Research Articles

In-line microfiber MZI operating at two sides of the dispersion turning point for ultrasensitive RI and temperature measurement

An in-line microfiber Mach-Zehnder interferometer (MZI) is demonstrated for ultrasensitive refractive index (RI) and temperature measurement by operating at two sides of the dispersion turning point (DTP), respectively. An ultrahigh RI sensitivity of 24,209 nm/RIU (RI unit) around 1.3320 and a high temperature sensitivity of -2.47 nm/℃ are experimentally achieved by a microfiber MZI with taper waist diameter of about 4.8 μm. By embedding this microfiber MZI into polydimethylsiloxane (PDMS), the temperature sensitivity is improved from -2.47 nm/℃ to about 8.33 nm/℃. The positive temperature sensitivity of this PDMS-coated microfiber MZI and the negative thermo-optic coefficient of PDMS show that this microfiber MZI has a negative RI sensitivity around the material RI of PDMS (about 1.405), which indicates that the microfiber MZI works at two sides of the DTP for RI measurement and temperature measurement, respectively. The PDMS-coated microfiber MZI could achieve a temperature measurement resolution of about 0.0024 ℃ if the resolution of the optical spectrum analyzer were 0.02 nm, making it suitable for temperature measurement applications with high precision requirement. The bare microfiber MZI is promising for liquid analytical measurement in fields like biochemistry for its advantages of ultrahigh sensitivity, small size, and little sample consumption.

A Modified Spin Pulsed Readout Method for NV Center Ensembles Reducing Optical Noise

The optical-noise-limited spin readout sensitivity determines the precision of quantum measurement based on nitrogen-vacancy (NV) center. This article investigates the fluorescence dynamics of NV centers by solving the optical rate equations and obtains complete theoretical formulas for the existing optical spin readout method. A transfer coefficient of optical noise to signal noise in the existing differential methods at different frequencies is introduced so as to analyze the optical noise suppression ability and the signal-to-noise ratio (SNR) results under the influence of photon shot noise and optical noise. To further reduce the influence of optical noise on the signal, we propose a modified method to minimize the transfer coefficient by adding a first-order compensation term. Compared with conventional methods, our modified method showed a twofold optical noise suppression ability improvement in the measurement frequency bandwidth. The experiment proves that the final SNR is increased by 43.4% for a long-term measurement. This modified method should lead to immediate improvements in pulsed spin readout of NV center ensembles without extra instrumentation for applications in magnetic field, electric field, and temperature measurements.

Upconversion Luminescence and Optical Temperature-Sensing Properties of LaNbO4:Yb3+/Er3+ Phosphors

In recent years, upconversion (UC) luminescence has attracted considerable attention because of its potential application in temperature measurement. In this work, LaNbO4:Er3+/Yb3+ phosphors are synthesized using a solid-state method. The x-ray diffraction patterns show that the phosphors obtained exhibit a single monoclinic structure, and doping does not change the crystal structure. Intense green and red emissions are observed upon 980-nm excitation. The emission intensity varies with the doping concentration, and the best doping concentrations are 1 mol.% and 10 mol.% for Er3+ and Yb3+ ions, respectively. The possible luminescence mechanism is investigated based on the UC emission dependence on pump power. The temperature-sensing ability is also investigated based on the fluorescence intensity ratio between two thermally coupled levels 2H11/2 and 4S3/2. The maximum sensitivity achieved is 0.81% K−1 at around 430 K, suggesting that the phosphor is a potential candidate for temperature sensing applications.

Monitoring a Heatsink Temperature Field Using Raman-Based Distributed Temperature Sensor in a Vacuum and −173 °C Environment

A heatsink is a large experimental device which is used to simulate the outer space environment. In this paper, a Raman-based distributed temperature sensor was used for real-time and continuous heatsink temperature monitoring, and a special Raman-based distributed temperature sensing method and system have been proposed. This method takes advantage of three calibration parameters ( ) to calculate the temperature. These three parameters are related to the attenuation of the optical fiber, the Raman translation, and the difference of optoelectronic conversion, respectively. Optical time domain reflectometry was used to calculate the location. A series of heatsink temperature measurement experiments were performed in a vacuum and −173 °C environment. When the temperature dropped to −100 °C, the parameter was found to vary. A method was proposed to recalculate and modify the traditional Raman fiber temperature equation. The results of the experiments confirmed the validity of this modified Raman fiber temperature equation. Based on this modified equation, the temperature field in the heatsink was calculated. The Raman-based distributed temperature sensor has potential applications in temperature measurement and judging the occurrence of faults in space exploration.

Thin-film four-resistor temperature sensor for measurements in air

A temperature sensor based on four thin-film resistors is presented. Four resistors are made in the form of thin metal layer meanders on the surface of a silicon chip. Two resistors are covered with a layer of 2.3 µm thick hard baked photoresist. Two other resistors are exposed to ambient air. The photoresist cover on two of the resistors makes a mismatch in the temperature coefficient of resistance between the covered and exposed resistors, thus enabling functionality of the system as a temperature sensor. The resistors are connected in the Wheatstone bridge configuration in order to enhance the sensitivity of the structure. Resistor meanders are 500 µm × 500 µm in lateral dimensions, each consisting of a 10 µm wide metal strip with 10 µm clearance between the strips. The total length of each strip is 12.5 mm. The material used for the meanders is 100 nm thick sputtered gold. The sensor was tested in a temperature chamber in the range from 80 °C to −50 °C. The matching between the sensor’s output and the readings obtained by the Pt1000 reference sensor was within ±0.1 °C (static), but the influence of water vapor adsorption at the exposed resistors surface on temperature measurements was visible. The sensor has potential applications in temperature measurements in air.

Transient heat fluxes measurement analysis from platinum based thin film gauges in open and closed cavities

Platinum thin film gauges (PTFGs) measure heat fluxes in the applications involving very short duration of the heating environment. Heat transfer measurement is the frequently used technique for measuring the surface heat flux using thin film gauges. The present investigation has been focused on the design and manufacturing methods for heat transfer gauge, their stability, and dynamic calibrations in certain situations where the heat load suddenly build up. PTFGs measure heat fluxes in heating environments applications during the very duration. The measurement for heat transfer is a technique used often with thin film gauges to measure the surface heat flux. The convection devices are regarded as the best measuring units in short-term transient temperature measurement applications and are usually used when the heat transfer mode is dominant means gas turbine engines, high speed aircraft, etc. In addition to that, there are many difficulties incurred for convection based measurement practically and few interdisciplinary research fields. A convective heat load is provided with a hot air gun to get the temperature signal. By using thin film gauge through present investigations, it is very ambitious to explore the possibility of short term conduction based transient measurements with pure conduction heat transfer mode. A simple experimental set up is used to supply the thin film gauges with heat flux, which is manually manufactured with platinum as a sensing material and quartz as a substrate material. The body's nose tip to high speed flow is expected to be the maximum heat transfer at the stagnation point. The stagnation point probes are fabricated for PTFGs, and baking material is quartz. The recorded temperature histories are compared with the experimentally recorded temperature signals from the gauges through the finite element method. The heat flux forecast was configured by using the one dimension thermal conduction equation convolution integral and by comparison with the heat input loads. This study reveals the ability of PTFGs to be used for a short period.

Thin film thermocouple fabrication and its application for real-time temperature measurement inside PEMFC

Temperature distribution in proton exchange membrane fuel cell (PEMFC) is of great importance to water and thermal management. In this study, 25 μm thick Type-T thin film thermocouples (TFTCs) were fabricated using micro-electro-mechanical system (MEMS) to realize the real-time measurement of temperature distribution inside PEMFC. Besides, fifteen sheathed thermocouples were used to measure the temperature distribution outside the cell. The effect of inserting TFTCs on the cell performance was confirmed to be negligible. The experimental results show that the embedded TFTCs can rapidly response to temperature regime while have a minimal interference to the performance of the fuel cell. The temperature variation of the inside TFTCs with current generally has the same trend with the outside sheathed thermocouples, but with a more frequent fluctuation due to their small thermal inertia and inside complex environment. In this work, the details of MEMS-based techniques of making TFTCs and measured distribution of inside cell temperature are provided.

Liquid refractive index and temperature sensor using multimode interference-based corroded polarization-maintaining fiber

A cost-efficient multimode interference-based sensor with corroded polarization-maintaining fiber (PMF) is proposed and experimentally demonstrated for the measurement of liquid refractive index (RI) and temperature. The sensor consists of a segment of corroded PMF and two segments of multimode fiber (MMF). Two segments of MMF, which are used as beam splitter and combiner are embedded on both ends of the PMF. The all-fiber sensor is put in the middle of the single-mode fiber. The RI and temperature characteristics of the sensor are investigated experimentally. The results show that two resonant peaks have different spectral responses of RI and temperature changes, which indicate that the sensor can realize simultaneous RI and temperature measurements. The experimental result shows that the high RI sensitivity is up to 318.279 nm / RIU in the RI range from 1.333 to 1.350 and the high temperature sensitivity is 0.188 nm / ° C in the range from 20°C to 40°C. This sensor exhibits the advantages of low cost and high sensitivity and may have potential application in RI and temperature measurements.

Nanoceramic NiMn2O4 Powder-Based Resistance Thermometer for Soil Temperature Measurement Application in Agriculture

A thermometer for soil temperature measurement application using sol-gel derived nanoceramic NiMn2O4 powder is constructed and tested in the field. The nanoceramic NiMn2O4 powder has been synthesized using solution route and characterized using FESEM/EDS and XRD. FESEM result confirms its uniform morphology and the formation of the nanopowder. EDS confirms that the powder consists of Ni, Mn, and O2. Based on the XRD analysis with the help of the Scherrer equation, the average crystallite size becomes 34nm. The powder is then compressed in electrically insulator but thermally conductor tube to make the thermometer. Two pieces of folded and rolled Aluminum foils as electrical contacts followed by lead wires were connected to the two opposite terminals of the tube. The thermometer is calibrated using homemade LM35 IC temperature sensor integrated with Atmega328 microcontroller and FTO film coated based glass electric heater. The thermometer can measure a soil temperature up to 42℃ in two or three digit precision.

COMPARISON OF SOIL TEMPERATURE MEASUREMENT BY CONE PENETRATION TESTING AND BOREHOLE THERMOMETRY

Development of infrastructure located in cryolithozone requires the use of modern geotechnical technologies for frozen soil investigation. Accurate soil temperature measurement is the necessary condition for engineering-geocryological survey and geotechnical monitoring. In the article a new method is considered on how to measure soil temperature by cone penetration testing (CPT). The cone temperature stabilization is described in detail, including the existing criteria of thermal stabilization of a cone. The results of temperature measurements are presented for both frozen and non-frozen soils and obtained by CPT (cone with a temperature sensor) and using borehole thermometry (thermistor string), which measured in both holes drilled by a rig and left after the cone penetration testing completion. Detailed analysis of accuracy of soil temperature measurement is also provided. The comparison of the obtained results is performed and the discrepancy of the measured soil temperature in absolute values is estimated. As a result of the analysis, it was shown that all the soil temperature values measured by different methods are sufficiently close to each other and the true value of the natural soil temperature are all located in the zone of intersection of the confidence intervals of each temperature measurement, performed at corresponding depths by different methods. All obtained temperature values do not cross the accuracy limits of temperature sensors, used both in cone penetration testing and borehole thermometry. High accuracy of temperature measurement by CPT is proved and feasibility of CPT application for soil temperature measurement is justified as an express-monitoring method.

Demonstration of a pyroelectric wireless temperature sensor

Energy generation systems operating at high temperatures are becoming increasing dependent on real-time measurements to enhance the overall performance. Since most sensors in energy systems are exposed to high temperature, high pressure, or corrosive environments where wiring is not desirable, harsh environment temperature sensing is preferred to be measured wirelessly. In this study, Pb(Zr0.52Ti0.48)O3 (PZT) pyroelectric ceramic was used to develop a wireless temperature sensor. An electromagnet was built with a set number of loops of wire, length, and radius. A PZT ceramic exposed to a heating source to induce a rate of temperature change with time. Generated current from the PZT due to experiencing a rate of temperature change with time was then supplied to the electromagnet to generate a magnetic field. The magnetic field was measured remotely with a milligaussmeter. The electromagnet was first characterized by measuring the magnetic field at different distances from the edge of the electromagnet along its axis. The milligaussmeter was able to detect the magnetic field generated by PZT pyroelectric ceramics at the specified distances from the electromagnet. A PZT sensor with a thickness of 0.1 cm was tested for use in a wireless temperature measurement configuration. Due to the non-linear pyroelectric response of PZT, the temperature dependent pyroelectric coefficient of PZT was also measured with a dynamic pyroelectric measurement technique in the temperature range from room temperature to 122 °C. The temperature dependent pyroelectric coefficient of PZT was found to increase from −40 × 10−5 C m−2 °C to −71.84 × 10−5 C m−2 °C. The PZT sensor was then tested for wireless temperature measurement applications at 100 °C, 150 °C, and 200 °C, and showed a maximum 10% deviation from baseline measurements.

Characteristics of few-mode fibre and its application in simultaneous strain and temperature measurement

This paper discusses a novel detection scheme to measure strain and temperature simultaneously using a section of specially designed few mode fibre (FMF). The work shows that the propagation constant difference between LP01 and LP02 modes, Δβ, has a maximum at the critical wavelength (CWL) in the transmission spectrum. Theoretical analysis and experimental verification indicate that the peaks located on each side of the CWL shift to opposite directions under strain and temperature variations. The two peaks located closest to the CWL from both sides, Left Peak 1 and Right Peak 1, shift linearly with indeed different and high strain and temperature sensitivities, when an appropriate length of FMF is chosen, allowing such a device to be used to simultaneously measure strain and temperature over a known range.

Nanoceramic NiMn2O4 Powder-Based Resistance Thermometer for Soil Temperature Measurement Application

The objective of this study is to construct a thermometer for soil temperature measurement application using sol-gel derived nanoceramic NiMn2O4 powder. The nanoceramic NiMn2O4 powder has been prepared using wet chemical method and characterized by FESEM/EDS and XRD. FESEM results confirmed its uniform morphology and the formation of the nanopowder. EDS confirmed that the powder consists of Ni, Mn, and O2. Based on the XRD analysis results and Scherrer’s formula the average crystallite size became 34nm. The powder then compressed in electrically insulator but thermally conductor tube manually to make the thermistor based thermometer. Two pieces of folded and rolled Aluminum foils as electrical contacts followed by two Aluminum lead wires were connected to the two opposite terminals of the tube. The thermometer is calibrated and characterized using LM35 IC temperature sensor integrated with Arduino Atmega328. The thermometer can measure a soil temperature up to 42℃. The embedded system for the thermometer is done using Arduino microcontroller and Arduino software with signal conditioning circuits. This is the first kind of thermometer which is based on nanomaterials for soil temperature measurement application in Agriculture. Keywords: NiMn2O4; nanoceramic powder; thermometer; thermistor; soil temperature; calibration Figure 1

Multimode interference-based fiber-optic strain and temperature sensor using polarization-maintaining fiber

A cost-efficient fiber-optic strain and temperature sensor has been proposed and demonstrated experimentally. The sensor consists of a segment of polarization-maintaining fiber (PMF) and two segments of multimode fiber (MMF). Two segments of MMF, which are used as beam splitter and combiner, are embedded on both ends of the PMF. The all-fiber sensor is put in the middle of the single-mode fiber. Due to the ratio of the strain and temperature responses of the sensor, the measurement of strain and temperature can be achieved by monitoring the transmission spectrum. The experimental result shows that the strain sensitivity is up to −3.16 pm / μϵ in the range of 0 to 1000 μϵ and the temperature sensitivity is 0.071 nm / ° C in the range from 10°C to 45°C. This sensor exhibits the advantages of low cost and high sensitivity and may have potential application in strain and temperature measurement.

Thermal and optical characterization of up-converting thermographic phosphor polymer composite films

AbstractUp-converting thermographic phosphors are of significant interest due to specific advantages for temperature measurement applications over traditional contact-based methods. Typically, infrared excitation stimulates visible fluorescence only from the target phosphor and not the surrounding medium. This is in contrast to ultraviolet excitation which may also produce interfering luminescence from cells and other biological tissue in the vicinity, for instance. When traversing a material, usually infrared losses due to scattering and absorption are less than for ultraviolet wavelengths. An example is human skin. This investigation follows logically from earlier efforts incorporating thermographic phosphors into elastomers and aerogels and their function as a reusable temperature sensor has been previously demonstrated by the authors. Layered phosphor/PDMS/aerogel composites are also currently under investigation by the authors for heat flux sensing. For maximum utility and understanding; physical, optical and thermal properties are characterized over a wide range of temperatures. Y2O2S:Yb,Er and La2O2S:Yb,Er up-converting phosphor composites with a fixed doping concentration were synthesized for this study and fully characterized as a function of temperature. The excitation/ emission characteristics of the powder alone and the prepared composites were investigated between -50 °C and +200 °C in an environmental chamber and the decay behavior of each sample type was measured. Here, the authors report on decay behavior and emission intensity of the PDMS composites as a function of temperature. Results were compared with powder –only parameters and are reported here.

Micro-structured fibers and their applications in fiber-optic sensors and random fiber lasers

Micro-structured fibers are important devices that have drawn intensive attentions and proved to be powerful platforms for various applications over the past decades due to their remarkable merits and advantages, such as small footprint, immunity to electromagnetic interferences, light weight, high physical flexibility, and low cost. Modifications in optical fibers can be used as light-steering elements to excite and couple back different core and cladding modes and form various in-fiber structures, including in-line fiber interferometer, fiber micro-cantilever, fiber random gratings, and so on. These micro-structures, when applied as fiber-optic sensors in the presence of external disturbances, show high sensitivity in terms of the significant changes in the guided light features. Novel micro-structured bend-insensitive fiber-based in-line fiber interferometer and micro-cantilever have been proposed to realize both static and dynamic parameter measurements, including temperature, axial strain, surrounding refractive index, and vibration. We have also developed a novel fiber random grating along with a spectral correlation algorithm for simultaneous measurement of three static measurands. To move a step forward, random fiber lasers based on fiber random grating are achieved for either improving the laser performances or sensing applications of temperature, strain, and ultrasound measurements with high sensitivity.

Applications of continuous body temperature measurements in pigs – a review

Applications of continuous body temperature measurements in pigs – a review

Erbium-doped fiber ring laser sensor for high temperature measurements based on a regenerated fiber Bragg grating

ABSTRACTThis article presents an erbium-doped fiber ring laser for high temperature measurement with high accuracy. The proposed laser sensor employs a regenerated fiber Bragg grating (RFBG) as a sensor element. Through thermal treatments, the RFBG with enhanced thermal resistance was obtained. The laser emission optical spectrum presents good performance with a high optical signal-to-noise ratio of 58dB. Experimental results demonstrate a wavelength sensitivity to the temperature is 15.5 pm/ºC with the temperature range from 300ºC to 900ºC, and the correlation coefficient is 0.999. The results prove it is able to provide potential applications in high temperature measurement.

Improving sensing sensitivity of Er/Yb co-doped NaYF4 nanorods via selecting non-thermally-coupled levels

The temperature-dependent up-conversion luminescence of the Yb3+-Er3+ doped NaYF4:Er3+/Yb3+ nanorods, which can emit green, red and blue emissions, was investigated under 980 nm laser excitation. Our results showed that the natural log of I 520/I 550, I 654/I 550, I 520/I 407 and I 654/I 407 had well linear relationship with the reciprocal of temperature, suggesting their potential application in temperature measurement. At 471 K, the maximal sensing sensitivities of the above thermometry methods reached 0.007, 0.032, 0.6, 2.7 K−1, respectively. Moreover, the luminescence color shifted from green to yellow with the temperature increasing from 296 to 471 K. The calculated CIE coordinates varied linearly with the temperature, which also can be used in thermometry. These excellent properties make NaYF4:Er3+/Yb3+ nanorods an excellent candidate as a temperature sensor.

The capacity of active heat method in evaluation of seepage

AbstractThe analysis of temperature variation inside an embankment dam is known as a feasible approach for seepage estimation in an embankment dam. The time needed for temperature surveillance could be considerably reduced when it is implemented under the condition of heat injection. However, a detailed description about the method as well as its capability has not been sufficiently presented in previous research. To fill this void, a realistic scale finite‐element modeling was conducted to explain and assess the abilities of the approach. A 15 m dam segment containing a suffusion layer was simulated with 11 scenarios, where it was found that the applications of temperature measurement with the complement of high‐power line heat sources in standpipes could give a solution for seepage determination in a dam segment with length up to 6 m, and the combination of fiber optic sensors and electrical wires provides an ability to assess seepage in a long dam distance. It is noteworthy that the efficiency in the perpendicular plane to the fiber optic sensor and electrical wire is limited.