Internal Temperature Sensor Research Articles

Temperature-Based Long-Term Stabilization of Photoacoustic Gas Sensors Using Machine Learning

In this study, we address the challenge of estimating the resonance frequency of a photoacoustic detector (PAD) gas cell under varying temperature conditions, which is crucial for improving the accuracy of gas concentration measurements. We introduce a novel approach that uses a long short-term memory network and a self-attention mechanism to model resonance frequency shifts based on temperature data. To investigate the impact of the gas mixture temperature on the resonance frequency, we modified the PAD to include an internal temperature sensor. Our experiments involved multiple heating and cooling cycles with varying methane concentrations, resulting in a comprehensive dataset of temperature and resonance frequency measurements. The proposed models were trained and validated on this dataset, and the results demonstrate real-time prediction capabilities with a mean absolute error of less than 1 Hz for frequency shifts exceeding 30 Hz over four-hour periods. This approach allows continuous, real-time tracking of the resonance frequency without interrupting the laser operation, significantly enhancing gas concentration measurements and contributing to the long-term stabilization of the sensor. The results suggest that the proposed approach is effective in managing temperature-induced frequency shifts, making it a valuable tool for improving the accuracy and stability of gas sensors in practical applications.

Internal Temperature Estimation for Lithium-Ion Cells Based on a Layered Electro-Thermal Equivalent Circuit Model

In the domain of Battery Management System (BMS) research, the precise acquisition and estimation of internal temperature distribution within lithium-ion cells is a significant challenge. The commercial viability precludes the use of internal temperature sensors, and existing methodologies for online estimation of internal temperatures under various electrical loads are constrained by computational limitations and model accuracy. This study presents a layered electro-thermal equivalent circuit model (LETECM), developed by integrating a layered second-order fractional equivalent circuit model with a layered thermal equivalent circuit model. A lithium-ion battery divided into three layers was employed to illustrate the development of this LETECM. The model’s precision was validated against a 3D Newman Finite Element Model (3DNFEM), constructed using actual battery parameters. Given that the thermal gradient inside the battery is usually more pronounced under high load conditions, a 10C direct current discharge for 60 s followed by a rest period of 240 s was adopted as the test condition in the simulation. The results indicate that at the end of the DC discharge, the temperature difference between the inner layer and the surface of the battery was the largest and the maximum temperature difference predicted by the LETECM was 3.58 °C, while the 3DNFEM exhibited a temperature difference of 3.74 °C. The trends in each layer temperature and battery surface temperature obtained by the two models are highly consistent. The proposed model offers computational efficiency and maintains notable accuracy, suggesting its potential integration into BMS for real-time online applications. This advancement could provide critical internal temperature data for refining battery charging and discharging performance assessments and lifespan predictions, thereby optimizing battery management strategies.

Insights into Thermal Runaway of Cylindrical Lithium-ion Batteries by Internal Temperature Sensors

Insights into Thermal Runaway of Cylindrical Lithium-ion Batteries by Internal Temperature Sensors

DEVELOPMENT OF ADVANCED WATER/LIBR ABSORPTION CHILLER WITH CONDENSATION HEAT RECOVERY FOR SIMULTANEOUS COOLING AND HEATING APPLICATIONS

A prototype of an advanced single-stage water/LiBr absorption chiller with a design cooling capacity of 40 kW was developed. The prototype is designed to operate in a simultaneous cooling and heating mode by recovering condensation heat. This paper presents and discusses the newly developed advanced chiller prototype and the modified multifunctional test rig for prototype characterization in different operation modes. The test rig has four external heat carrier loops to characterize and validate the prototype during the simultaneous cooling and heating operation. External and internal temperature sensors and volumetric flow rate measuring devices are installed in the prototype. The design conditions of the advanced absorption chiller are chilled water inlet/outlet temperatures of 12/7 °C, driving hot water and cooling water (absorber external loop) inlet temperatures of 100 °C and 30 °C, respectively, and produced hot water inlet/outlet temperatures of 40/55 °C. The prototype also operates as a conventional absorption chiller to provide only cooling by rejecting the absorber and condenser heat to cooling water (heat rejection medium). Finally, developing such absorption chillers improves overall performance and provides dual useful outputs (cooling and heating).

Optimizing winter climate control in high-altitude smart greenhouse through renewable energy integration

In the context of food security in mountain regions, this study explores the potential of a Smart Greenhouse (SGH) to address the challenges posed by climate change and limited resources. The SGH utilizes an 8 m2 solar water heating system, weather stations for external temperature and humidity monitoring, as well as internal light, humidity, and temperature sensors to create an optimized environment for crop cultivation. Experiments were conducted with various crops within the SGH during the harsh winter months, typically rendering the cultivable land fallow due to extreme cold conditions. The SGH is equipped with sensors and communication technologies, ensuring continuous data collection and the automated regulation of heating, ventilation, and air conditioning systems. Located in Genekha, Thimphu, this pilot SGH seamlessly integrates renewable energy technology to provide heat during the cold winter season, obviating the need for external heating sources in the summer. The study employed TRNSYS and OpenStudio simulation software to assess the SGH's performance, focusing on temperature and humidity control inside and outside the greenhouse. Additionally, soil pH and nutrient content were examined, and the time required for crop growth and harvesting was recorded. In conclusion, this paper acknowledges some of the current design's limitations and presents recommendations for future enhancements, with a focus on the specific context of improving crop production and food security in mountainous regions.

Winter Carbon Dioxide Measurement in Honeybee Hives

Sensor technologies have sufficiently advanced to provide low-cost devices that can quantify carbon dioxide levels in honeybee hives with high temporal resolution and in a small enough package for hive deployment. Recent publications have shown that summer carbon dioxide levels vary throughout the day and night over ranges that typically exceed 5000 ppm. Such dramatic changes in a measurable parameter associated with bee physiology are likely to convey information about the colony health. In this work, we present data from four UK-based hives collected through the winter of 2022/2023, with a focus on seeing if carbon dioxide can indicate when colonies are at risk of failure. These hives have been fitted with two Sensirion SCD41 photoacoustic non-dispersive infrared (NDIR) carbon dioxide sensors, one in the queen excluder, at the top of the brood box, and one in the crown board, at the top of the hive. Hive scales have been used to monitor the hive mass, and internal and external temperature sensors have been included. Embedded accelerometers in the central frame of the brood box have been used to measure vibrations. Data showed that the high daily variation in carbon dioxide continued throughout the coldest days of winter, and the vibrational data suggested that daily fanning may be responsible for restoring lower carbon dioxide levels. The process of fanning will draw in colder air to the hive at a time when the bees should be using their energy to maintain the colony temperature. Monitoring carbon dioxide may provide feedback, prompting human intervention when the colony is close to collapse, and a better understanding may contribute to discussions on future hive design.

Direct measurement of internal temperatures of commercially-available 18650 lithium-ion batteries

Direct access to internal temperature readings in lithium-ion batteries provides the opportunity to infer physical information to study the effects of increased heating, degradation, and thermal runaway. In this context, a method to insert temperature sensors into commercial 18650 cells to determine the short- and long-term effects through characterization testing is developed. Results show that sensor insertion only causes a decrease in capacity of 0.5–2.3%, and an increase in DC resistance of approximately 15 mΩ. The temperatures of the modified cells are approximately 0.5 °C higher than the control cells, the difference between the internal and external temperature readings of the modified cells is approximately 0.4 °C, and the modified cells exhibit the same temperature behavior and trend during cycling as the control cells. The cells are able to operate and collect data for 100–150 cycles before their capacities fade and resistances increase beyond what is observed in the control cells. The results of the testing show that cells modified with internal temperature sensors provide useful internal temperature data for cells that have experienced little or no cyclic aging.

ETAM: Next Generation Event Timer for Picosecond-Precision Time and Amplitude Measurements.

Riga Event Timers have the ability to measure the interval between events with high resolution, on the order of picoseconds. However, they have several drawbacks, such as sensitivity to environmental temperature changes and an inability to capture the amplitude of the events. In this work, we present the ETAM: a next generation Event Timer. Its innovative features include adaptive correction of measurement errors based on an internal temperature sensor, and integrated peak-detector circuit to determine the amplitude of nanosecond-duration pulses. Evaluation shows that the ETAM has high thermal stability with a root mean square error (RMSE) of <3 ps in a temperature range between 0 and +40 °C, and accurate event amplitude measurement capability, with <2.3 mV RMSE in the 100-1000 mV range. These improvements allow the ETAM to be used in satellite laser ranging, optical time-domain reflectometry, and other field applications that require temperature- and amplitude-based time correction in addition to high robustness, performance, and stability.

SRAM-Based PUF Readouts

Large-scale parameter characterization of Physical Unclonable Functions (PUFs) is of paramount importance in order to assess the quality and thus the suitability of such PUFs which would then be developed as an industrial-grade solution for hardware root of trust. Carrying out a proper characterization requires a large number of devices that need to be repeatedly sampled at various conditions. These prerequisites make PUF characterization process a very time-consuming and expensive task. Our work presents a dataset for the study of SRAM-based PUFs on microcontrollers; it includes full SRAM readouts along with internal voltage and temperature sensors of 84 microcontrollers of STM32 type. Data has been gathered with a custom-made and open platform designed for the automatic acquisition of SRAM readouts of such devices. This platform also provides possibilities of experimenting aging and reliability properties.

Battery Internal Temperature Measurement Using LC Resonant Tank for Battery Management Systems

This paper suggests an embedded battery impedance measurement based on an Inductor Capacitor (LC) resonant tank to measure the battery’s internal temperature for battery management systems (BMS). The purpose of the BMS is to provide state-of-charge (SoC) balancing and the preheating mechanism at sub-zero temperatures. Battery Impedance Spectroscopy (BIS) for battery internal temperature measurement is achieved by an LC resonant tank connected to the batteries in parallel to induce created resonant current and voltage into the battery. The peaks of the voltage and current waveforms are measured and recorded. Then, the resistance of the battery can be calculated by comparing the peak voltage and current waveforms. Since the resistance of the battery is affected by the battery’s internal temperature, the internal temperature of the battery can be estimated. The benefit of using the LC tank for the battery’s internal temperature is to reduce data processing since no window and Fast Fourier Transform (FFT) is needed for this method. In addition, the proposed method measures the battery’s internal temperature without any internal or external temperature sensor. Power Simulation (PSIM) simulation software is used in this proposed method. Panasonic batteries 18650 and a dSPACE DS1104 are used for the experiment to verify the proposed method. The proposed method shows that the LC resonant tank can measure three batteries B1, B2, and B3 internal resistance with 17.87%, 18.14%, and 17.73% errors compared to the Frequency Response Analyzer (FRA). In addition, the total time needed for balancing is 400 s, and the total energy consumed by the preheating mechanism is 0.214%/°C to preheat the lithium-ion batteries (LIBs) from −5 °C to 10 °C.

FastICA Algorithm Applied on Black Sea Water-Level Ultrasound Measurements

The parameters influencing the sea level measured with ultrasonic devices that are analyzed in this paper are the air temperature, atmospheric pressure and wind speed. As these variations are independent to each other and to the sea level, they can be removed from the measured sea level by applying a filtering algorithm based on independent component analysis (FastICA), adapted and improved for this application. The sound speed increases with temperature, so an internal temperature sensor is required to compensate for the sound-speed variation. Though this may improve the measurement accuracy, it is not enough to achieve the best results because there is a discrepancy between the internal sensor and the actual environment temperature. For high accuracy measurements, an external temperature sensor is required. In our case, we imported temperature datasets from a weather station, along with other datasets regarding atmospheric pressure and wind speed. The use of these external datasets, along with an algorithm based on principal component analysis (PCA) for error removal and the filtering algorithm based on FastICA for environmental phenomena extraction, allows us to achieve more accurate values for the Black Sea level in Constanta (2017–2020), independent of external influences.

Secure smart home automation and monitoring system using internet of things

As a result of the rapid increase in the number of users in internet of things (IoT) technologies, IoT becomes one of the most important technologies that play an important and essential role in various areas of human life, it provides service over 24 hours. In this paper, the proposed system relies on the implementation of a set of sensors for the Internet of things, which accomplish tasks inside the home automation, for example, controlling the main door, boiler and lock, as well as the ability to control lighting and air, internal temperature sensors, it based on the Arduino, to collect multimedia data, and remote-controlled sensors. The proposed system provides an efficient way to control and monitor the various devices in the home for security and safety purposes, and through sensors that rely on wireless technologies. The results show the abnormal alarm notification for heathcare/security purposes with the distance as 27 cm, smoke carbon monoxide on indoor air quality as 10211 degree Co as 6256 degree, Liquefied petroleum gas as 5097 degree, the delayed 3.4 ms and network latency as 0.0012 seconds of alarm notification with long distance as 60 m and high packet delivery ratio as 98.7%.

Inaccuracies in the inverse heat conduction problem solution and their effect on the estimation of heat fluxes during quenching

Solving the Inverse Heat Conduction Problem (IHCP) is a common approach to estimate the surface heat fluxes involved in transient, quenching experiments. The inverse problem presents several challenges, such as accounting for the non-uniqueness of its solution, for the effects of noise, or for other practical issues affecting the experimental input data, such as the thermal contact of the internal temperature sensors. In this paper, possible sources of inaccuracy in the IHCP solution and their effect on the estimated surface heat flux in experiments on quenching by water jet impingement are systematically investigated. A “virtual experiment” approach is followed to analyze the effect of a noise cancelling technique, the ambiguity in initial conditions and the quality of the thermocouple contact on the accuracy of the heat flux estimations. The results show that the invalid assumption of perfect thermal contact between thermocouple and test plate leads to overestimation of surface temperature in the initial stages of quenching. Based on these results, two measures are proposed to avoid misinterpretation of quenching heat flux estimations when solving the IHCP.

Online Internal Temperature Sensors in Lithium-Ion Batteries: State-of-the-Art and Future Trends

The temperature of the lithium-ion battery is a crucial measurement during usage for better operation, safety and health of the battery. In-situ monitoring of the internal temperature of the cells is an important input for temperature control of battery management systems and various other related measurements of the battery, such as state-of-charge and state-of-health. Currently, most commercial battery management systems rely on the surface temperature measurements of the cell. However, the internal temperature is comparatively higher than the surface temperature due to heat generation within the cell and lower heat rejection compared to the surface; therefore, accurate internal temperature monitoring methods are essential to improve our knowledge of battery safety and health. This paper reviews the most recent studies of various online internal temperature monitoring techniques under two main themes of hard sensors and soft sensors. The hard sensors include sensors that need to be inserted into the cell and other methods that use contact-less measuring techniques to infer the internal temperature. The soft sensors include estimators/observers that use surface measurements and various models to estimate the internal temperature. More focus is given to the soft sensors due to the lack of an existing, in-depth review of these. These methods are analyzed in detail with their accuracy, implementation, measurement frequency, and the common challenges and benefits are discussed. Further, possible future trends in internal temperature sensing are also discussed.

An Accuracy-Improved and Internal Regulator-Free Temperature Sensor With a Non-Linear Current Mode Feedback Pseudo-PLL

An accuracy-improved and internal regulator-free temperature on-chip sensor is proposed. The proposed sensor outputs an accuracy-enhanced pulse width modulation (PWM) signal with a nonlinear current mode feedback pseudo-PLL (Phase-Locked Loop). The pseudo-PLL is able to greatly mitigate the nonlinearity caused by process parameters (eg. threshold voltage and mobility of MOS transistor) without careful compensation. Furthermore, to optimize the area and power supply rejection without an internal regulator, a current mode input and feedback approach in the pseudo-PLL is also presented. The proposed sensor is fabricated with 0.18 μm standard CMOS process. The measurement results show that the power consumption of the sensor is only 2 μW under 1.2V supply voltage. With the supply voltage varying within 1~1.2V, the temperature detection error is maintained within +/-0.2°C in the range of -20°C to 100°C. And the corresponding power supply rejection (PSR) ratio and resolution achieve about 0.15°C/100mV and 0.12°C, respectively.

18650 vs. 21700 Li-ion cells – A direct comparison of electrochemical, thermal, and geometrical properties

Li-ion cells of the classic 18650 format are directly compared with the new 21700 format regarding electrochemical, thermal, and geometrical properties. Both types of cells were reproducibly built on pilot scale with the same electrodes, separator, and electrolyte allowing a direct comparison for the first time. Internal temperature sensors give insights on the heating behaviour. Similarities are found in the voltage curves and capacity fade at 1C cycling at 25 °C. The capacity and energy increase per cell is ~50% from 18650 to 21700 for discharge in the range of 0.5C–3.75C. The results are compared with calculations of electrode areas based on Archimedean spiral's arc lengths and geometrical data extracted from X-ray computed tomography (CT) measurements. Two evaluation methods for extraction of the number of electrode windings from CT images are compared. Calculations are made for the winding number as a function of the periodic winding distance (thicknesses of anode, cathode, and 2x separator) as well as on electrode curvature for both cell formats. The influences of intended extensions of the cell diameter by few μm (as observed in commercial cylindrical cells), as well as larger formats such as 30700 on additional electrode windings and cell capacity are estimated.

The Heat-Dissipation and Dehumidification System of the Hybrid Multi-Layer Gravity Heat Pipe Applied to Granary

Based on the basic working principle and heat transfer characteristics of gravity heat pipe in combination with the grain stack particle&amp;#39;s stacking characteristics, this study changes the structure of traditional heat pipe to change the heat transfer mode between the grain stack and the gravity heat pipe so as to improve the grain&amp;#39;s heat-dissipation rate and heat-dissipation efficiency. Generally, this system can satisfy the internal heat dissipation requirements of grain stack only under the action of a non-power fan driven by the air in the atmosphere and the temperature difference between inside and outside of the fan. When the internal temperature sensor of the grain stack detects that the internal temperature of the grain stack is high only under the action of the non-power fan, the pipeline booster fan will be started. At the same time, when the gas exchange occurs between the internal gas in grain stack and the external air, the dehumidification and drying of the grain stack can be realized through the gas drying device of the product. Through theory and simulation, this paper conducts a comparative analysis on the variation law of grain stack&amp;#39;s temperatures under the action of gravity heat pipe and no gravity heat pipe so as to explore the heat-dissipation system&amp;#39;s working efficiency of the new structure gravity heat pipe. The gravity heat pipe and the non-power fan in the system are all green products, which makes this design product have better heat-dissipation effect and less energy consumption.

Humidity and temperature sensor system demonstrator with NFC tag for HySiF applications

Abstract. Hybrid System-in-Foil (HySiF) is one of the emerging branches of flexible electronics in which ultra-thin silicon chips are integrated with flexible sensors in polymeric foils (Elsobky et al., 2018; Alavi et al., 2018). Intensive attention was given to the implementation of flexible environmental sensing platforms for logistics and food packaging (Cartasegna et al., 2011; Liu et al., 2016). The aim of this work is the implementation of a sensor system demonstrator using HySiF components, namely an ultra-thin microcontroller chip in addition to an on-chip temperature and an on-foil humidity sensors. The measurement concept for the relative humidity sensor is measuring the capacitance difference between an off-chip (on the foil substrate) humidity dependent sensor capacitor, and another humidity independent reference capacitor. The electrical readout technique is based on the charge amplifier switched capacitor circuit. It is implemented using a commercially available microcontroller (EM microelectronics EM6819) which has the advantage of being available as single chips to enable post-processing steps such as backthining and chip embedding in a thin polymer package. Sensor and reference capacitors are homogeneously integrated on-foil. 400 and 30 µm thick microcontroller dies (MCU) are used in this application. The charge amplifier result is digitized using an internal 10-bit analog-to-digital converter (ADC). The 10-bit ADC is time multiplexed between the charge amplifier structure and the internal temperature sensor. Linear interpolation is used to fit the digital output of the ADC and calibrate the output of the sensor system. Readings of the humidity level and the temperature are written to an NFC tag (from the company EM microelectronics based on chip EM NF4) using the contact interface. Readings can be accessed using a customized android application on a smartphone.

(Invited) In Situ Measurement of Temperature Distributions in Lithium-Ion Cells Under Extreme Conditions for Failure Analysis

Lithium-ion (Li-ion) batteries are susceptible to failures, even thermal runaway, when operating under extreme conditions that exceed safety limits, such as overcharge, overheating and short circuit. Temperature plays an important role in such failures due to its interaction with electrochemical reactions and heat generation (1). With very low thermal conductivity of battery materials (2, 3) and typically non-uniform heat generation under such extreme conditions, the local temperatures inside Li-ion cells can be very different from surface temperature. In situ measurement of temperature distributions in Li-ion cells can be therefore very useful for safety and failure analysis. Various efforts have been reported in measuring Li-ion cells internal temperatures with insightful findings obtained, typically using embedded thermocouples (4-18), RTD (19, 20) or fiber optic sensors (21-23), or via electrochemical impedance (24-27). But most of these studies only address normal operating conditions. In the few studies that address extreme conditions, only one internal temperature sensor was embedded (4, 10, 18), providing very limited information. In this research temperature distributions in Li-ion cells under extreme conditions are measured for detailed failure analysis. The progress will be reported in the presentation.

Two Solutions of Soil Moisture Sensing with RFID for Landslide Monitoring.

Two solutions for UHF RFID tags for soil moisture sensing were designed and are described in this paper. In the first, two conventional tags (standard transponders) are employed: one, placed close to the soil surface, is the sensor tag, while the other, separated from the soil, is the reference for system calibration. By transmission power ramps, the tag’s turn-on power levels are measured and correlated with soil condition (dry or wet). In the second solution, the SL900A chip, which supports up to two external sensors and an internal temperature sensor, is used. An interdigital capacitive sensor was connected to the transponder chip and used for soil moisture measurement. In a novel design for an UHF RFID tag the sensor is placed below the soil surface, while the transponder and antenna are above the soil to improve communication. Both solutions are evaluated practically and results show the presence of water in soil can be remotely detected allowing for their application in landslide monitoring.