Resistive Temperature Sensor Research Articles

Measurement and Modelling of the Thermal Response of the Resistance Temperature Sensors

Knowledge of the dynamic properties of thermometers is of particular importance for successful automation of process management in real time. The dynamic behaviour, i.e. the thermal response of the thermometers, is primarily determined by the thermal time constants of the thermo sensor and the protective housing in which it is located (thermo immersion probe, thermowell). In this paper, we presented a simple, but for a large number of applications acceptably accurate method of determining the thermal time constants of the temperature sensor. The procedure for determining the thermal time constants of a thermometer is shown on the example of a thermometer with a resistance temperature sensor. The paper presents the thermal model of the resistance temperature sensor and the protective housing of the sensor. By suddenly immersing the immersion probe in a container with heated water, the temperature response was recorded. Based on the presented thermal model, the thermal time constants of the temperature sensor and the protective case were determined.

PEDOT:PSS-Based Wearable Flexible Temperature Sensor and Integrated Sensing Matrix for Human Body Monitoring.

Flexible temperature sensors have been widely used in electronic skins and health monitoring. Body temperature as one of the key physiological signals is crucial for detecting human body's abnormalities, which necessitates high sensitivity, quick responsiveness, and stable monitoring. In this paper, we reported a resistive temperature sensor designed as an ultrathin laminated structure with a serpentine pattern and a bioinspired adhesive layer, which was fabricated with a composite of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)/single-wall carbon nanotubes/reduced graphene oxide (PEDOT:PSS/SWCNTs/rGO) and polydimethylsiloxane (PDMS). The temperature sensor exhibited a high temperature sensitivity of 0.63% °C-1, coupled with outstanding linearity of 0.98 within 25-45 °C. Furthermore, it showed fast response and recovery speeds of 4.8 and 5.8 s, respectively, between 25 and 36 °C. It also demonstrated exceptional stability when subjected to stress and bending disturbances with the maximum bending interference deviation of 0.03%. Additionally, it displayed good cyclic stability over a broad temperature range from 25 to 85 °C, and the standard deviation at 25 °C is 0.14%. A series of experiments including blowing detection, respiratory monitoring with or without a mask, and during rest or sleep were conducted to show the potential of the flexible temperature sensors in human body monitoring. Furthermore, a 4 × 4 flexible temperature sensor matrix was integrated to detect and map objects such as wrenches and blood vessels through human hand skin. The results were consistent with those of infrared measurements. The flexible temperature sensor is capable of real-time temperature monitoring and has the potential in tracking human respiration, assessing sleep quality, and mapping the temperature of various objects.

Flexible thermistors based on laser-induced graphene from polyetherimide

Abstract The importance of temperature sensors has notably increased in recent years, paralleling the surge in demand for flexible and stretchable sensor technologies. In this study, we fabricate and characterize a flexible resistive temperature sensor based on Laser-Induced Graphene (LIG) on Polyetherimide (PEI). The structure and morphology of LIG are thoughtfully characterized proving the formation of a graphitic-based structure. Subsequently, the sensors were evaluated in terms of their temperature response, impact of relative humidity (RH), and bending cycles. The results reveal that the PEI-LIG flexible thermistor exhibits a high sensitivity of -0.159%/°C, with minimal influence from humidity. These findings contribute to advancing the research in inexpensive flexible temperature sensing technology, providing insights into material selection and sensor design for diverse applications.

Effects of annealing on the microstructure and performance of thin-film Pt resistance temperature sensors: experiments and finite element simulations

Platinum resistance temperature sensors have a wide range of applications in various fields, where a high temperature coefficient of resistance (TCR) is a crucial requirement. In this study, thin-film Pt resistance temperature (TPRT) sensors were fabricated on an Al2O3 substrate using a micro-electro-mechanical system (MEMS) based surface micromachining process, and Pt resistance wafers were annealed at a temperature range from 500°C to 800°C using rapid thermal process (RTP). Experimental and simulation results show that TPRT sensors fabricated on the substrate with a rough surface exhibit lower thermal stress. Meanwhile, more pores appear in the Pt thin film, reducing TCR. However, high temperature annealing significantly influences the microstructure of the Pt film and brings about an obvious increase in TCR despite, introducing thermal stress at the interface. Considering the impact of the heat treatment process, the fabricated TPRT sensors demonstrate excellent performance with a TCR of 3512 ppm/°C.

Plant Tattoo Sensor Array for Leaf Relative Water Content, Surface Temperature, and Bioelectric Potential Monitoring

AbstractThis study presents a wearable plant tattoo sensor array designed for continuous monitoring of leaf temperature, relative water content, and biopotential. Current plant wearable sensor technologies often require relatively bulky substrates for sensor support and adhesives for leaf attachment, which potentially can hinder plant growth and affect long‐term measurements. The multifunctional tattoo sensor array overcomes these issues by adhering directly to the leaf surface without the need for additional supporting structures or glues. This array includes a biopotential electrode, a resistive temperature sensor, and an impedimetric water content sensor, all constructed using laminated gold‐on‐polymer thin‐film patterns. Due to their mechanical flexibility, stretchability, and conformability, the sensors can seamlessly attach to leaves via van der Waals force. Performances of these sensors are evaluated to explore plant responses under diverse growth environments. This sensor array is capable of both short‐term and long‐term monitoring, offering continuous data and detailed insights into plant physiological responses to various stress conditions.

Time Constant as the Main Component to Optimize the Resistance Temperature Sensors' Calibration Process.

Temperature sensor calibration in the majority of measurement laboratories is performed on the ground of measurement procedures. The procedures specify the timespan for the temperature of the tested sensor to stabilize. In practice, the fact of time constant increase above expectations can be observed. This results from the method of operation, time of use, and level of contamination of individual sensors. The paper proposes a method to optimize the calibration process of resistance temperature sensors based on the measurement of the time constant and, on this basis, to determine the sensor stabilization time during calibration.

Способ реализации беспроводного резистивного датчика контроля температуры

Technological equipment is often provided with external wired sensors characterized by low noise immunity in the case of a significant length of the connecting cable. To ensure the possibility of monitoring the temperature of objects located at a considerable distance from the technological installation, it is necessary to use wireless sensors that allow transmitting a signal over a radio channel for tens of meters. The paper proposes a method for replacing a wired resistive temperature sensor with a wireless one, which does not require changing the circuits of the technological installation. The temperature of the remote object is controlled using a thermistor based on the voltage incident on it using a sigma-delta analog-to-digital converter. The received digital code is transmitted over the radio channel to the receiving part of the device located near the technological installation. Further, using the emulation circuit on the connector of the technological installation, a resistance equivalent to the resistance of the measuring thermistor is provided. To solve this problem, a digital potentiometer controlled by a microcontroller is used. The error of setting the equivalent resistance for the Pt-100 platinum sensor using the developed method does not exceed 1.3 % for the temperature range –40...100 °C.

Eco-friendly alkali lignin-assisted water-based graphene oxide ink and its application as a resistive temperature sensor

Inkjet-printable ink formulated with graphene oxide (GO) offers several advantages, including aqueous dispersion, low cost, and environmentally friendly production. However, water-based GO ink encounters challenges such as high surface tension, low wetting properties, and reduced ink stability over prolonged storage time. Alkali lignin, a natural surfactant, is promising in improving GO ink’s stability, wettability, and printing characteristics. The concentration of surfactant additives is a key factor in fine-tuning GO ink’s stability and printing properties. The current study aims to explore the detailed effects of alkali lignin concentration and optimize the overall properties of graphene oxide (GO) ink for drop-on-demand thermal inkjet printing. A meander-shaped temperature sensor electrode was printed using the optimized GO ink to demonstrate its practical applicability for commercial purposes. The sensing properties are evaluated using a simple experimental setup across a range of temperatures. The findings demonstrate a significant increase in zeta potential by 25% and maximum absorption by 84.3%, indicating enhanced stability during prolonged storage with an optimized alkali lignin concentration compared to the pure GO dispersions. The temperature sensor exhibits a remarkable thermal coefficient of resistance of 1.21 within the temperature range of 25 °C–52 °C, indicative of excellent sensitivity, response, and recovery time. These results highlight the potential of alkali lignin as a natural surfactant for improving the performance and applicability of inkjet-printable GO inks in various technological applications.

Aerosol jet printed resistive temperature sensors with high sensitivity

Aerosol jet printing provides a facile, cost-efficient, and environmentally friendly approach to pattern thin films with nanomaterial inks. Printed flexible resistive thin-film temperature sensors play an important role in human body temperature monitoring, soft robotics, prosthetics, and real-time temperature monitoring of large area curved surfaces due to their linear response to temperature, low-cost, scalability, and flexibility. However, the temperature coefficient of the resistance of the printed resistive temperature sensors reported in the literature is much less than that of their bulk metals. In this work, we demonstrate aerosol jet printed resistive temperature sensors with silver nanoparticle ink that have a temperature coefficient of resistance close to that of bulk silver. We report a temperature coefficient of resistance of 3.7 × 10−3 ◦C−1 for the aerosol jet printed resistive temperature sensors, the highest value yet reported in literature for resistive temperature detectors composed of thermally sintered silver nanoparticle thin films. The mechanisms for the increased performance are investigated using metrological and thermal techniques with regard to the source ink and traces. Additionally, we show that the overall sensitivity of the printed sensors can be modulated by controlling the thickness of the printed thin films. Finally, we evaluate the response of the printed resistive sensors to bending strain and humidity, including an investigation into the effects of organic passivation. Overall, this work presents printed sensors with performance on par with vacuum deposited resistive temperature detectors, enabling the fabrication technique to make an industrial impact.

Preparation and Performance Analysis of 3D Thermoformed Fluidic Polymer Temperature Sensors for Aquatic and Terrestrial Applications.

Employing a combination of Polyethylene terephthalate (PET) thermoforming and 3D-printed cylindrical patterns, we carefully engineer a linear resistive temperature sensor. This intricate process involves initial PET thermoforming, yielding a hollow cylindrical chamber. This chamber is then precisely infused with a composite fluid of graphite and water glue. Ensuring electrical connectivity, both ends are affixed with metal wires and securely sealed using a hot gun. This cost-effective, versatile sensor adeptly gauges temperature shifts by assessing composite fluid resistance alterations. Its PET outer surface grants immunity to water and solubility concerns, enabling application in aquatic and aerial settings without extra encapsulation. Rigorous testing reveals the sensor's linearity and stability within a 10 °C to 60 °C range, whether submerged or airborne. Beyond 65 °C, plastic deformation arises. To mitigate hysteresis, a 58 °C operational limit is recommended. Examining fluidic composite width and length effects, we ascertain a 12 Ω/°C sensitivity for these linear sensors, a hallmark of their precision. Impressive response and recovery times of 4 and 8 s, respectively, highlight their efficiency. These findings endorse thermoforming's potential for fabricating advanced temperature sensors. This cost-effective approach's adaptability underscores its viability for diverse applications.

A 0.9-V 6400-μm2 Resistor-Based Temperature Sensor With a One-Point Trimmed 3σ Inaccuracy of ±0.64 °C from −50°C to 125 °C

This paper describes a compact and precise resistive temperature sensor based on a frequency-locked loop (FLL) intended for thermal monitoring in system-on-chips. The FLL incorporates a switched-capacitor loop filter improving the sensors inaccuracy and FLL outputs are converted into a digital code with an edge-combined counter for efficient frequency-to-digital conversion. A prototype sensor is fabricated in 65-nm CMOS process and occupies only 6,400 μm2. It achieves a one-point trimmed 3σ inaccuracy of 10.64 ∘C over a wide temperature range of.50 to 125 ∘C. Operating at 0.9 V supply, it consumes 40 μW and achieves 2.2 mK resolution in a 1-ms conversion time, which corresponds to a resolution FoM of 0.19 pJ7K2.

Electrohydrodynamic Printed PEDOT:PSS/Graphene/PVA Circuits for Sustainable and Foldable Electronics

AbstractThe generation of electronic waste (e‐waste) poses a significant environmental challenge, necessitating strategies to extend electronics’ lifespan and incorporate eco‐friendly materials to enable their rapid degradation after disposal. Foldable electronics utilizing eco‐friendly materials offer enhanced durability during operation and degradability at the end of their life cycle. However, ensuring robust physical adhesion between electrodes/circuits and substrates during the folding process remains a challenge, leading to interface delamination and electronic failure. In this study, electrohydrodynamic (EHD) printing is employed as a cost‐effective method to fabricate the eco‐friendly foldable electronics by printing PEDOT:PSS/graphene composite circuits onto polyvinyl alcohol (PVA) films. The morphology and electrical properties of the printed patterns using inks with varying graphene and PEDOT:PSS weight ratios under different printing conditions are investigated. The foldability of the printed electronics is demonstrated, showing minimal resistance variation and stable electronic response even after four folds (16 layers) and hundreds of folding and unfolding cycles. Additionally, the application of printed PEDOT:PSS/graphene circuit is presented as a resistive temperature sensor for monitoring body temperature and respiration behavior. Furthermore, the transient features and degradation of the PEDOT:PSS/graphene/PVA based foldable electronics are explored, highlighting the potential promise as transient electronics in reducing electronic waste.

Evaluation of the Curing Process Effects on the TCR of Temperature Sensors Printed by Aerosol Jet Printing

Temperature sensors have been widely developed to control the course of diseases, improve haptic feelings, and in multi-sensing systems to compensate for the output of other temperature-sensitive sensors. The use of additive manufacturing to produce resistive temperature detectors (RTDs) with reduced dimensions and bulkiness is attracting great interest. Among the relevant process parameters and design choices, the curing process must be considered. In this work, two different commercial metallic-based materials are cured at various temperatures to evaluate the differences in their microscopic and macroscopic behavior. The sensors were designed, developed, and evaluated for their temperature coefficient of resistance (TCR) at different curing temperatures using a programmable climatic chamber. A scanning electron microscope has been used to microscopically inspect the sensing structures with respect to the different curing temperatures. The results show insightful correlations between the macroscopic and microscopic behavior of the used inks as well as the performance of the sensors. In particular, increasing the curing temperature decreased the room-temperature resistance in all the samples by up to 70% and increased the sensitivity by up to 95%. These findings will help propose better processes as well as design choices for the development of printed resistive temperature sensors.

Study on High-Temperature Oxidation Behavior of Platinum-Clad Nickel Composite Wire

Platinum-clad nickel composite wires with platinum layer thicknesses of 5 μm and 8 μm were prepared by a cladding drawing process. Oxidation experiments were performed using a muffle furnace at temperatures of 500 °C, 600 °C, 700 °C, and 800 °C for 1 h, 2 h, and 3 h. The oxidized samples were examined for high-temperature oxidation behavior using scanning electron microscopy (SEM) with an energy-dispersive X-ray (EDX) spectrometer attached. The results showed that the interface bond between the platinum cladding and the nickel core wire was serrated and that the thickness of the platinum cladding was not uniform. At low temperatures (500 °C and 600 °C), the diffusion rate of the nickel was low. The composite wire could be used for a short time below 600 °C. When the temperature reached 700 °C and above, the nickel diffused to the surface of the composite wire and was selectively oxidized to form a nickel oxide layer. The research results provide a theoretical reference for the selection of a service temperature for platinum-clad nickel composite wires used as the lead material for thin-film platinum resistance temperature sensors.

Preparation and performance optimization of resistive flexible temperature sensors prepared by inkjet printing method

In recent years, inkjet printing has been widely used in the field of flexible sensor preparation. However, the effects of inkjet printing parameters and post-processing conditions on sensor performance have not been systematically investigated. Simple fabrication and optimized performance are eagerly desired for the practical use of temperature sensors in wearable healthcare devices. Herein, we report the resistive flexible temperature sensor fabricated on polyethylene terephthalate (PET) substrates with silver nanoparticles (AgNPs)-based ink using an inkjet printer. We have thoroughly investigated and optimized the sensitivity and linearity between the resistance and temperature of inkjet-printed temperature sensors by adjusting droplet spacing and curing conditions (temperature and time). In conclusion, the droplet spacing of 20 µm and the curing condition of 30 min at 150 °C were determined as the optimized parameters. With optimized process parameters, the temperature sensor has a high sensitivity of 0.084 °C−1 and a linear coefficient of 0.999 between relative resistance and temperature in the range of 30 °C–100 °C. Furthermore, it has a fast response time (7 s) and high stability against repeated bending deformation of 500 cycles. The prepared wearable sensors have potential application prospects in temperature monitoring.

Development of an Implantable Capacitive Pressure Sensor for Biomedical Applications.

In this study, a subminiature implantable capacitive pressure sensor is proposed for biomedical applications. The proposed pressure sensor comprises an array of elastic silicon nitride (SiN) diaphragms formed by the application of a polysilicon (p-Si) sacrificial layer. In addition, using the p-Si layer, a resistive temperature sensor is also integrated into one device without additional fabrication steps or extra cost, thus enabling the device to measure pressure and temperature simultaneously. The sensor with a size of 0.5 × 1.2 mm was fabricated using microelectromechanical systems (MEMS) technology and was packaged in needle-shaped metal housing that is both insertable and biocompatible. The packaged pressure sensor immersed in a physiological saline solution exhibited excellent performance without leakage. The sensor achieved a sensitivity of approximately 1.73 pF/bar and a hysteresis of about 1.7%, respectively. Furthermore, it was confirmed that the pressure sensor operated normally for 48 h without experiencing insulation breakdown or degradation of the capacitance. The integrated resistive temperature sensor also worked properly. The response of the temperature sensor varied linearly with temperature variation. It had an acceptable temperature coefficient of resistance (TCR) of approximately 0.25%/°C.

Painting sustainable wearables: facile and economical all-recycled dual temperature-motion wearable sensor for monitoring of human temperature and joint movements

World is seeing rapid increase in smart wearable electronic devices and gadgets especially for personal healthcare and activity monitoring. It is estimated that e-waste generation will reach 75 million tons by 2030 which is posing life-threatening complication by polluting environment. To build sustainable and green world; facile, economical, multi-functional, biodegradable, and recyclable wearable sensors have great potential in human health and activity monitoring in developing countries, especially in rural areas due to budgetary constraints and geographic inaccessibility. This paper presents a facile, and economical, all-recycled dual temperature-motion (ARDTM) wearable sensor patch to monitor human body temperature and joint movements. The proposed ARDTM wearable sensor is fabricated by recycling/re-using e-waste (dry cells) to get graphite and paper. Paper is employed as the substrate due to its low-cost, abundance, flexibility, biocompatibility, biodegradability, and disposability. The graphite extracted from the discarded dry cells is mixed with gel pen ink to make conductive graphite paste. Resistive temperature sensor and capacitive motion sensor are brush painted on sticky-note paper using conductive graphite paste. The sensors are integrated together to monitor body movements and temperature simultaneously in a compact and decoupled manner. To demonstrate the isolation of both sensors, the response of the dual sensor patch is examined simultaneously for body temperature and wrist movement. The temperature sensor is characterized by measuring change in resistance over a temperature range of 25 °C – 65 °C in addition to body temperature and it demonstrated a sensitivity of ∼335 Ω/°C. For monitoring human body movements, the capacitive response of motion sensors is tested on several body parts especially the wrist, knee, elbow, and finger. The ARDTM wearable sensor is facile, low-cost, multipurpose, biodegradable, compact and can be used to simultaneously monitor human activities and health. Our approach realized multi-purpose wearable sensor by recycling/re-using paper and e-waste, which provides a way forward for the sustainable and green development of wearable sensors by mitigation of e-waste.

Гибкий датчик влажности и температуры на основе пленочных структур полимерных нанокомпозитов с углеродными нанотрубками

A brief review of humidity and temperature sensors based on film structures of nanocomposite materials is presented. The possibilities and prospects of sorption-impedance humidity sensors and resistive temperature sensors based on polymer nanocomposites with carbon fillers are considered. The studies results of the electrical conductivity dependences of nanocomposite films based on polyvinyl alcohol with magnetically sensitive multi-walled carbon nanotubes on humidity and temperature are presented. The structure and electrical circuit of a flexible two-parameter humidity and temperature sensor are proposed, in the form of two series-connected nanocomposite film resistors placed on a flexible silicone substrate, one of which is protected by a moisture-proof coating. Issues of sensor calibration are discussed.

Controlled synthesis of Cu-/Ni-based 1D c-MOFs and their application in near-linear temperature sensing

In this paper, the Cu-/Ni-based one-dimensional (1D) conductive metal-organic frameworks (c-MOFs) nanorods (Cu3(HHTP)2/Ni3(HHTP)2) have been synthesized successfully through a one-pot hydrothermal method. The effect of reaction time, MOFs compositions and ratio of solvent on the performance of Cu3(HHTP)2-/Ni3(HHTP)2- based resistive temperature sensors was studied by sensing platforms. Compared with Ni3(HHTP)2-based sensor, Cu3(HHTP)2-based sensor, which was assembled under DMF volume of 0.5 mL and reaction time of 12 h (Cu7), provided the optimal performance, for example, relative variation of resistance (RVR) near-linearly decreased by 85.9% from 20 °C to 80 °C, and the temperature coefficient of resistance (TCR) reached up −0.0157 °C-1. Moreover, the resistance value of the Cu3(HHTP)2-based sensor is 0.106 kΩ, which exhibited a minimum resistance under different temperatures. These results demonstrate that the use of Ni3(HHTP)2-based 1D c-MOFs for fabrication of temperature sensor provides good conductivity and high thermo-responsive sensitivity. Hence, this study provided an excellent example for the simple preparation and practical application of 1D c-MOFs-based near-linear temperature sensor.

УДОСКОНАЛЕННЯ АЛГОРИТМУ РОЗРАХУНКУ ТЕМПЕРАТУРИ КВАЗІЛІНІЙНОГО РЕЗИСТИВНОГО СЕНСОРА PT100

The paper investigates iterative algorithms for solving the equation according to the Kalendar-Van Dusyn formula, which describes the dependence of the electrical resistance of the Pt100 family sensor on temperature. This family of platinum sensors is considered quasi-linear, but for high-precision measurements the nonlinearity of the sensor cannot be neglected, so it is necessary to solve the nonlinear equation of Pt100. At minus temperatures, the equation according to the Kalendar-Van Dusyn formula reaches the fourth power and has no solution with respect to temperature in an analytical form. The analysis of the previously published iterative algorithm for the approximate solution of the equation reveals a desadvantage of this algorithm. The residual error of the solution is not a monotonic function of the argument, because it contains extrema, moreover, the sign of the error changes to the opposite after each extremum. The purpose of this study was to obtain an algorithm that provides the residual error in the form of a monotonic deterministic function of the argument with the minimization of the maximum error value. The possibility to modify the iterative algorithm-prototype in an elementary way by fixing the number of iterations is shown. The residual error of solving the equation according to the modified algorithm has the form of a monotonic deterministic function of the argument. It is assumed that any iterative calculation algorithm can be improved in this way. At the same time, the minimization of the error values of the modified algorithm is achieved by setting the maximum number of iterations compared to the prototype algorithm. To overcome this desadvantage of the modified algorithm, a new algorithm is proposed, in which, in addition to a fixed number of iterations, the property of the smallness of the components of higher degrees is used. The high efficiency of the new algorithm is shown, which reduces the residual error of the solution to a negligible value in just four iterations. It is claimed that the high efficiency of the new algorithm makes further research in the direction of its improvement unnecessary. The article presents a scheme of the new algorithm and a corresponding program on the VBA platform for Excel, which is suitable for direct use in the software of temperature meters based on Pt100 resistance temperature sensors. References 5, figures 4, tables 3.