Array Of Temperature Sensors Research Articles

High spatial resolution temperature field measurements by apodized short fiber Bragg grating sensors

To realize the high spatial resolution measurement of the temperature field, a temperature sensor array composed of eight apodized short fiber Bragg gratings with grating length of 1 mm and spatial spacing of 2 mm are fabricated. To suppress the side lobes, apodization methods by single-slit diffraction are designed. The sensor array is proposed to measure the real-time temperature distribution. The experimental results show that the temperature-sensing array can accurately measure the temperature field distribution with high spatial resolution and rapid response.

Experimental Study on Thermal Balance in Soft Clay Area During GSHP Operation

Geothermal energy resources, such as a green and clean renewable energy, are utilized all over the world, especially in soft clay areas along coastal cities in China, such as Shanghai. However, the operation of the ground-buried heat exchanger potentially affects the initial temperature field and the thermal balance, which will probably result in some potential engineering or environmental problems. This paper presents results from a series of large-scale laboratory modeling experiments which were conducted to study the thermal balance in saturated soft clay during the operation of the ground source heat pump (GSHP) system. In experiments, thermal phenomena are induced by a heat exchanger which is embedded in the testing soils and investigated by temperature sensor arrays. It summarizes the experimental methodologies and presents the time-dependent temperature distribution within the testing soils both in operation stage and the re-stabilization duration. Characteristics of thermal balance are discussed in two specific parameters of relative time ratio and temperature factor by comparing summer and winter cases. The thermal mattress effect is proposed to provide valuable guidelines for the utilization and operation of the GSHP system in soft clay areas.

Experimental characterization and model validation of liquid jet impingement cooling using a high spatial resolution and programmable thermal test chip

High efficiency direct liquid jet impingement cooling with locally distributed outlets is very promising in high power electronic devices. In order to elucidate the flow-thermal interaction for micro-scale jet impingement cooling, sensitive temperature measurements with high spatial and temporal resolution are required. In this work, a programmable thermal test chip with 832 heater cells with 75% heater uniformity and 32 × 32 array of temperature sensors is introduced. The detailed measured temperature maps for different power dissipation patterns allow the in-depth study of the thermal performance of liquid jet impingement coolers and the detailed experimental validation of complex CFD models. The modeling and measurement study is applied to two jet impingement cooling implementations: (1) a single jet cooler with a 2 mm diameter nozzle, and (2) a multi-jet cooler with a 4 × 4 array of 500 µm inlet nozzles and distributed outlet nozzles. For both cooler configurations, the temperature measurements and CFD modeling results are investigated and compared for uniform and hot spot power dissipation patterns.

High‐Sensitivity, Skin‐Attachable, and Stretchable Array of Thermo‐Responsive Suspended Gate Field‐Effect Transistors with Thermochromic Display

AbstractThe fabrication of a skin‐attachable, stretchable array of high‐sensitivity temperature sensors is demonstrated. The temperature sensor consists of a single‐walled carbon nanotube field‐effect transistor with a suspended gate electrode of poly(N‐isopropylacrylamide) (PNIPAM)‐coated gold grid/poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate and thermochromic leuco dye. The sensor exhibits a very high sensitivity of 6.5% °C−1 at temperatures between 25 and 45 °C. With increasing temperature, the suspended gate electrode bends due to the deswelling of the PNIPAM, resulting in the reduction of the air gap to increase the drain current under a constant gate voltage. At the same time, the leuco dye coated on top of the transparent gate electrode changes color to visualize changes in temperature. The 4 × 6 integrated temperature sensor array integrated using liquid metal interconnections exhibits mechanical and electrical stability under 50% biaxial stretching and allows for the spatial mapping of temperature with visual color display regardless of wrist movement while attached to the skin of the wrist. This work is expected to be widely useful in the development of skin‐attachable electronics for medical and health‐care monitoring.

In-fiber integrated quasi-distributed high temperature sensor array.

An in-fiber integrated quasi-distributed high temperature sensor array is proposed and demonstrated. The sensor array consists of some weakly reflective joint surfaces which are welded by single mode fiber (SMF) and double-clad fiber (DCF). The characteristics of the reflected signal of the sensor array are analyzed, and the relationship between the signal intensity and the number of sensors is simulated for evaluating sensor multiplex capacity. Due to its all-silica structure, the sensor array could test temperature up to 1000°C for a long time. This sensor array is flexible and easy to be fabricated only by splicing without any connector, which will be beneficial to space constrained quasi-distributed high temperature sensing applications.

Crop Water Stress Index of an irrigated vineyard in the Central Valley of California

Water-limiting conditions in many California vineyards necessitate assessment of vine water stress to aid irrigation management strategies and decisions. This study was designed to evaluate the utility of a Crop Water Stress Index (CWSI) using multiple canopy temperature sensors and to study the diurnal signature in the stress index of an irrigated vineyard. A detailed instrumentation package comprised of eddy covariance instrumentation, ancillary surface energy balance components, soil water content sensors and a unique multi-canopy temperature sensor array were deployed in a production vineyard near Lodi, CA. The instrument package was designed to measure and monitor hourly growing season turbulent fluxes of heat and water vapor, radiation, air temperature, soil water content directly beneath a vine canopy, and vine canopy temperatures. April 30–May 02, June 10–12 and July 27–28, 2016 were selected for analysis as these periods represented key vine growth and production phases. Considerable variation in computed CWSI was observed between each of the hourly average individual canopy temperature sensors throughout the study; however, the diurnal trends remained similar: highest CWSI values in morning and lowest in the late afternoon. While meteorological conditions were favorable for plant stress to develop, soil water content near field capacity due to frequent irrigation allowed high evapotranspiration rates resulting in downward trending CWSI values during peak evaporative demand. While the CWSI is typically used to evaluate plant stress under the conditions of our study, the trend of the CWSI suggested a lowering of plant water stress as long as there was adequate soil water available to meet atmospheric demand.

Strain gauges debonding fault detection for structural health monitoring

Physical redundancy is a common approach in applications with safety-critical systems. But that is not always possible in some structural health monitoring (SHM) applications whether for economic, spatial, or safety reasons. Many SHM sensor validating applications only rely on analytical redundancy. In such circumstances, sensor faults and structural damage need to be assuredly discriminated. A self-diagnosis strain sensor operating in a continuous online SHM scenario is considered. The sensor is based on a full electric resistance strain gauge Wheatstone bridge. The state of the art shows that such a sensor has not yet been developed. The loop current step response (LCSR) is a well-known method to detect strain gauge debonding. However, applying the LCSR method to a full strain gauge Wheatstone bridge has some limitations analyzed in this paper. Two new methods for detecting strain gauge debonding are proposed and evaluated. These methods are based on consistency checking of the strain gauges grids temperature measurements—employing an array of (a) digital contact temperature sensors or (b) quasi-contact microelectromechanical system thermopile sensors. The experimental results reveal that both methods are suitable for application in an SHM self-diagnosis sensor scenario. However, the quasi-contact measuring method showed to be more sensitive to the strain gauge grid debonding fault though.

A novel approach for examining downstream thermal responses of streams to contemporary forestry

Temperature is a fundamental driver of aquatic environments. Changes in thermal regimes due to timber harvest may be detrimental for cold-water instream biota. Although it is understood that stream temperature may increase immediately below timber harvest operations, the understanding of how thermal responses propagate downstream is less clear. Here, we examine the effects of timber harvest on stream temperature pre- (2–3 years) and post-harvest (5 years) at 16 sites (average annual streamflow rates <0.283 m3 s−1) located in the Coast Range, Oregon, USA. At each site, an array of temperature sensors were deployed on the extremes of three consecutive reaches: an upstream unharvested reference reach, a treatment reach, and a downstream unharvested reach. We used several metrics to describe and evaluate changes over time and space focusing on the responses of downstream reaches. Primarily, we evaluated the differences over time in daily maximum temperature between the two sensors located at the downstream unharvested reach. Furthermore, using a statistical ordination technique, we examined the spatial and temporal variability of an array of sensors for daily maximum temperature. Moreover, we assessed distributional shifts (statistical moments) of hourly temperature differences between the two sensors at the downstream unharvested reach over time. Lastly, we used a combination of statistical moments and the ordination technique to provide an index that describes the behavior of site-specific thermal disturbance over time. We found that stream reaches responded differently to upstream timber harvest operations between pre and post-harvest summer seasons. In addition, we showed distinct patterns of longitudinal variability of temperature across sites and summer seasons with increases, decreases or mixed responses including no change downstream. Overall, the net change of daily maximum temperature at the downstream reach revealed that the highest difference occurred during the first and second year post-harvest and, in some cases, a distinctive shift in stream warming and cooling occurred between the day and the night. Observed temperature patterns in downstream reaches were most similar to the pre-harvest conditions at the fifth year post-harvest. Collectively, we offer a novel approach for assessing stream temperature regime change using multiple metrics that can improve our understanding of thermal effects downstream of timber harvest, taking in consideration idiosyncratic responses across sites and time.

Large diurnal bottom temperature oscillations around the Saint Pierre and Miquelon archipelago

Here, we report large, near-daily oscillations of near-bottom temperatures, with ranges of up to 11.5 °C at depths of 30–60 m in September 2011 around the Saint Pierre and Miquelon archipelago (south-eastern Canada). These oscillations were detected on velocity and temperature profiles from moorings in Miquelon Bay and on an array of near-bottom temperature sensors around the archipelago. The oscillations coincided with the seasonal stratification period. In addition to their remarkable range, they exhibited a near-diurnal period centred on the O1 tidal component (~26 h), contrasting with the dominant semi-diurnal sea-level periodicity in the area. They appear to be the manifestation of an internal wave, triggered by the diurnal surface tide and trapped by the bathymetric configuration of the area. We argue that the archipelago is nearly resonant for island-trapped waves at near-diurnal frequencies. Our data demonstrate that these coastal-trapped waves propagate clockwise around the archipelago in roughly two days, and thus approximate an azimuthal, mode 2 pattern. Simplified calculations show that cross-shore motions are bottom-amplified. In addition, bottom friction acts to rotate the axes of the diurnal tidal current ellipses with depth, and this combination of effects explains the large range of observed bottom temperature oscillations.

The cold wake of typhoon Chaba (2010)

The cold wake of typhoon Chaba (2010) is investigated using an array of temperature sensors connected from the surface to 540 m along the mooring line of an air-sea interaction buoy. Initially, surface forcing caused upper ocean water to entrain across the base of the thermocline, producing a mixed layer cooling and subthermocline warming between 42 and 100 m. However, this warm layer lasted just 12 h before it became overwhelmed by an upwelling of cold water. Observations indicate this upwelling occurred to at least 540 m while further analysis suggests that the actual depth of the ocean response to Chaba was closer to 700 m. This caused a massive reduction in heat content at the mooring site. The sea surface temperature decreased 2.5 °C. Due to the lateness of the season, the ocean didn’t recover to its pre-typhoon state, however, after sixteen days it did match the temperature outside the wake. These observations reveal intricate processes in a cold wake that redistribute heat between the mixed layer, the subthermocline region, and greater depths. This has implications for tropical storm intensity—by altering enthalpy fluxes, and climate—through the lateral and vertical movement of water which modifies the local temperature profile and impacts the transportation of heat to high latitudes.

Posture Detection Using Sounds and Temperature: LMS-Based Approach to Enable Sensory Substitution

Sensors are used to determine a variety of health and security parameters. Pressure mats and camera analysis are frequently used to determine a person’s chair posture. Measurement of parameters can be derived from a variety of different sensor types, which may already be present in an environment. This paper presents the use of the concept of “sensory substitution,” where a sensor designed to measure Quantity X is used to measure Quantity Y. The concept is used to enable alternative sensing techniques for medical and security applications, such as determining chair occupancy, postural shift times, and even current postural state, without using cameras or pressure sensors. Specifically, the postural state of a subject is determined in a laboratory study using various arrays of both temperature sensors and acoustic sensors. This method can be used standalone, can augment other sensors, or can validate data from pressure or visual-based systems. These alternative sensors could also be used for other aspects of smart infrastructure. The system was tested with different types and styles of furniture, including chairs, armrests, cushions, and beds. A least mean square algorithm was deployed to remove noises enabling acoustic posture detection. Using a thresholding algorithm, postural changes are then identified using audio. In a controlled environment, over 90% of postural change events were detected. Thus, the paper shows two alternative instrumentation and measurement methods to determine occupancy, postural change timings, and even posture states of a person in a chair.

A low-cost, high-accuracy temperature sensor array

Real-time two-dimensional mapping of temperature for totally or partially concealed medium- or large-sized surfaces is necessary in a variety of applications. In these cases, an array of thermistors can provide a good solution. This article describes a low-cost, scalable array of thermistors (maximum size 8 × 8), together with high-precision reading electronics. To select the electronics, which produced the best results in the array reading, two proposals from the literature were implemented and the performances were assessed taking into consideration different array sizes and thermistor resistance values. The precision of the readings was evaluated using the best electronic solution, with a maximum error of 0.036 °C, taking into account only the error in the resistance measurement and the manufacturer data. The sampling period of the complete array was 58.5 ms, thus allowing the sensor to be used in real-time applications.

Investigating thermal performance of different chairs at the user-seat interface by a temperature sensor array system while participants perform office work

Recently, there has been an escalating trend towards sedentary lifestyle in the modern society (i.e. reading books, watching movies or driving cars). It has been estimated that the proportion of time spent sitting accounts for more than one third of a person's total life-time [1]...

Subsurface Lateral Heat Flux within the Heterogeneous Surface of a Subtropical Wetland and Its Potential Contribution to Energy Imbalance

AbstractIn the eddy covariance technique, lateral heat fluxes in the atmosphere, surfaces, and subsurfaces are often ignored under the assumption of a homogeneous surface. Among lateral heat fluxes, the surface and subsurface fluxes, which might affect the surface energy balance closure over a heterogeneous surface, are less studied. Many wetlands are heterogeneous, with a mix of vegetated areas and shallow open water. This study examined the subsurface lateral heat fluxes between a reed bed and the adjacent water of a subtropical wetland in Hong Kong, China. An array of temperature and water-level sensors was installed in the soil of the reed bed and in the adjacent water. An eddy covariance system was also set up on the reed bed. The subsurface lateral heat fluxes were largest close to the interface of the reed bed and water and decreased as the distance from the interface increased, as expected. However, the subsurface lateral heat fluxes could not account for the energy imbalance because their magnitudes were relatively small and fluctuated in phase with the energy budget residuals during the winter months. The uncertainties of the turbulent fluxes and the lateral heat fluxes were estimated to be 10%–20% and 10%–30%, respectively. This study explored another potential reason behind the energy imbalance of the eddy covariance technique. The results enhance the understanding of water and energy exchanges between a terrestrial biotope and the surrounding water, which might further generate insights into the biochemical processes in wetlands.

Prefrontal bore mixing

AbstractRainbow Ridge, a 1950 m deep upthrusted ultramafic block along the axis of the Mid‐Atlantic Ridge, has an active hydrothermal vent system at 2400 m on its western slope. However, within 1 km from the vent excessive temperatures are barely measurable, probably due to strong turbulent mixing. This mixing is studied here using a 400 m long high‐resolution temperature sensor array moored with a 600 m ranging 75 kHz acoustic Doppler current profiler. Rich internal wave turbulence was recorded, characterized by 100–200 m upshoots and &gt;200 m large overturning in particular near the end of the warming phase of the up and down moving tide. These highly nonlinear internal waves of tides interacting with buoyancy frequency waves extend up to 400 m above the sloping bottom of the ridge. While a turbulent “bottom boundary layer” could barely be defined, the more intense turbulence higher up in the water column is suggested to lead to the strong dispersion of the hydrothermal plume.

Robust fibre optic sensor arrays for monitoring early-age performance of mass-produced concrete sleepers

This study investigates integrating fibre optic sensing technology into the production process of concrete railway sleepers. Robust fibre Bragg grating strain and temperature sensor arrays were developed specifically for this application and were designed for long-term monitoring of sleeper performance. The sensors were used to monitor sleeper production and to help gain a deeper understanding of their early-age behaviour which can highly influence long-term performance. In total, 12 sleepers were instrumented and strain data were collected during the entire manufacturing process including concrete casting and curing, prestressing strand detensioning and qualification testing. Following the production process, sleepers were stored temporarily and monitored for 4 months until being placed in service. The monitoring results highlight the intrinsic variability in strain development among identical sleepers, despite high levels of production quality control. Using prestress loss as a quality control indicator, the integrated sensing system demonstrated that sleepers were performing within Eurocode-based design limits prior to being placed in service. A three-dimensional nonlinear finite element model was developed to provide additional insight into the sleepers’ early-age behaviour. Based on the fibre Bragg grating–calibrated finite element model, more realistic estimates for the creep coefficient were provided and found to be 48% of the Eurocode-predicted values.

Parameterization of Battery Electrothermal Models Coupled With Finite Element Flow Models for Cooling

Developing and parameterizing models that accurately predict the battery voltage and temperature in a vehicle battery pack are challenging due to the complex geometries of the airflow that influence the convective heat transfer. This paper addresses the difficulty in parameterizing low-order models which rely on coupling with finite element simulations. First, we propose a methodology to couple the parameterization of an equivalent circuit model (ECM) for both the electrical and thermal battery behavior with a finite element model (FEM) for the parameterization of the convective cooling of the airflow. In air-cooled battery packs with complex geometries and cooling channels, an FEM can provide the physics basis for the parameterization of the ECM that might have different convective coefficients between the cells depending on the airflow patterns. The second major contribution of this work includes validation of the ECM against the data collected from a three-cell fixture that emulates a segment of the pack with relevant cooling conditions for a hybrid vehicle. The validation is performed using an array of thin film temperature sensors covering the surface of the cell. Experiments with pulsing currents and drive cycles are used for validation over a wide range of operating conditions (ambient temperature, state of charge, current amplitude, and pulse width).

Design and development of a thermal imaging system based on a temperature sensor array for temperature measurements of enclosed surfaces and its use at the body-seat interface

Abstract We describe a mapping system based on 64 evenly spaced digital sensors (thermal in this example) and interpolation algorithms. Current pressure mapping systems are suspect to noise, signal drift (creep), hysteresis and drop out of pixels, requiring frequent recalibration all of which impact on accuracy and experimental protocols. The system described here uses a one-wire-based protocol for easy configuration and reliable measurement without requiring frequent recalibration and can continuously measure temperature over a surface (seat or mattress) for hours. Additionally, in this example, the system can be used to overcome inherent drawbacks of traditional temperature (or humidity) assessment, being capable of mapping entire regions simultaneously. It greatly outperforms visual imaging (i.e. infrared) techniques at enclosed surfaces. The system, as shown here, could prove invaluable in future development of monitoring systems as it allows for more accurate parameter modelling at enclosed surfaces such as the body-seat interface. This will be useful when creating more realistic understanding of the changes occurring and how to moderate them effectively in order to reduce problems associated with prolonged wheelchair use.

Compact Thermal-Diffusivity-Based Temperature Sensors in 40-nm CMOS for SoC Thermal Monitoring

An array of temperature sensors based on the thermal diffusivity (TD) of bulk silicon has been realized in a standard 40-nm CMOS process. In each TD sensor, a highly digital voltage-controlled oscillator-based ΣΔ ADC digitizes the temperature-dependent phase shift of an electrothermal filter (ETF). A phase calibration scheme is used to cancel the ADC's phase offset. Two types of ETF were realized, one optimized for accuracy and one optimized for resolution. Sensors based on the accuracy-optimized ETF achieved a resolution of 0.36 °C (rms) at 1 kSa/s, and inaccuracies of ±1.4 °C (3σ, uncalibrated) and ±0.75 °C (3σ, room-temperature calibrated) from -40 °C to 125 °C. Sensors based on the resolution-optimized ETFs achieved an improved resolution of 0.21 °C (rms), and inaccuracies of ±2.3 °C (3σ, uncalibrated) and ±1.05 °C (3σ, room-temperature calibrated). The sensors draw 2.8 mA from supply voltages as low as 0.9 V, and occupy only 1650 μm 2 , making them some of the smallest smart temperature sensors reported to date, and well suited for thermal monitoring applications in systems-on-chip.

The effects of salt exclusion during ice formation on circulation in lakes

Laboratory experiments have been performed to investigate the effects of salt exclusion on the behaviour of lakes with salinities up to 8 g L−1. At these salinities the freezing temperature is less than the temperature of maximum density and, unlike sea-ice, a reverse temperature stratification forms beneath the ice that can support at least some of the excluded salt. Temperature time series at four depths showed that salt exclusion drives cascades of localised overturning, while the persistence of reverse temperature stratification indicated that mixing was not complete. While our array of temperature sensors had insufficient spatial resolution to provide full details of the flow, we hypothesize that: at salinities of 1 and 2 g L−1 salt is released relatively uniformly and forms a layer of elevated salinity immediately below the ice, which supports double-diffusive salt-fingering; and at salinities of 4 and 8 g L−1, salt plumes penetrate the reverse stratification. After the ice melted, a relatively fresh surface layer formed above a more saline layer, sufficient to suppress spring turnover. Our measurements compare favourably with field observations from lakes, and highlight the importance of salt exclusion on biogeochemical processes in lakes.