Temperature Drift Research Articles

Development of Temperature Sensor Based on AlN/ScAlN SAW Resonators

Temperature monitoring in extreme environments presents new challenges for MEMS sensors. Since aluminum nitride (AlN)/scandium aluminum nitride (ScAlN)-based surface acoustic wave (SAW) devices have a high Q-value, good temperature drift characteristics, and the ability to be compatible with CMOS, they have become some of the preferred devices for wireless passive temperature measurement. This paper presents the development of AlN/ScAlN SAW-based temperature sensors. Three methods were used to characterize the temperature characteristics of a thin-film SAW resonator, including direct measurement by GSG probe station, and indirect measurement by oscillation circuit and antenna. The temperature characteristics of the three methods in the range of 30–100 °C were studied. The experimental results show that the sensitivities obtained with the three schemes were −28.9 ppm/K, −33.6 ppm/K, and −29.3 ppm/K. The temperature sensor using the direct measurement method had the best linearity, with a value of 0.0019%, and highest accuracy at ±0.70 °C. Although there were differences in performance, the characteristics of the three SAW temperature sensors make them suitable for sensing in various complex environments.

Is the combination of conventional ultrafiltration and modified ultrafiltration superior to modified ultrafiltration in pediatric open-heart surgery?

ABSTRACT Background: Cardiopulmonary bypass (CPB) during open-heart surgery is associated with increased body fluids as a consequence of hemodilution due to the use of CPB. Ultrafiltration (UF) is a method used to decrease the body fluid volume on CPB. Aims and Objectives: This study aimed to compare the effects of combined conventional UF (CUF) and modified UF (MUF) versus MUF on the clinical outcomes of pediatric patients undergoing open-heart surgery for congenital heart disease. Materials and Methods: This was a prospective, single-center, randomized, and double-blinded clinical study that involved 74 pediatric patients undergoing open-heart surgery on CPB. Patient management was standardized. Preoperative Aristotle comprehensive complexity level, ultrafiltrate volumes, hematocrit, hemodynamic data, transesophageal echocardiographically (TEE) determined ejection fraction (EF), fractional area change (FAC), temperature drift, arterial oxygenation, time of extubation, ventilation, comparison of inotropic drugs, postoperative chest tube drainage, cardiac care unit (CCU), and hospital length of stay (LOS) were recorded in both groups. The analysis was conducted using SPSS-23.0, IBM, Armonk, NY, USA. Results: There was no mortality in both groups. Technical difficulties prevented the completion of MUF in two patients out of 37 in the CUF + MUF group. In this study, there were 43.26% of females and 56.75% of males, with a median age of 439 days, a mean weight of 9.98 kg, and an Aristotle Comprehensive Complexity score of level 2. Group CUF + MUF had a greater ultrafiltrate volume of 122 ± 39.7 ml (P = 0.036). The duration of ventilatory support was 11.2 ± 6.4 h versus 34.4 ± 5.7 h (P = 0.013), average CCU LOS was 4.3 ± 3.5 days versus 7.2 ± 3.6 days (P = 0.008), and chest tube drain in the first 48 h was 89.76 ± 34.82 ml versus 106.65 ± 47.29 ml (P = 0.029) in groups CUF + MUF and MUF, respectively. Inotropic infusion requirements were significantly lower in the CUF + MUF group compared to the MUF group. EF and FAC were 14% and 5% higher at 45 min in group CUF + MUF, respectively. Conclusions: The advantage of combining CUF and MUF over MUF is the significant improvement in the hemodynamic status of patients, which significantly decreases the duration of mechanical ventilation, average CCU LOS, inotrope requirements after surgery, and chest tube drain in the first 48 h.

Linear Variable Differential Transformer in Harsh Environments—Analysis of Temperature Drifts for Different Plunger Materials

Linear Variable Differential Transformer in Harsh Environments—Analysis of Temperature Drifts for Different Plunger Materials

Temperature Drift Compensation of Fiber Optic Gyroscopes Based on an Improved Method.

This study proposes an improved multi-scale permutation entropy complete ensemble empirical mode decomposition with adaptive noise (MPE-CEEMDAN) method based on adaptive Kalman filter (AKF) and grey wolf optimizer-least squares support vector machine (GWO-LSSVM). By establishing a temperature compensation model, the gyro temperature output signal is optimized and reconstructed, and a gyro output signal is obtained with better accuracy. Firstly, MPE-CEEMDAN is used to decompose the FOG output signal into several intrinsic mode functions (IMFs); then, the IMFs signal is divided into mixed noise, temperature drift, and other noise according to different frequencies. Secondly, the AKF method is used to denoise the mixed noise. Thirdly, in order to denoise the temperature drift, the fiber gyroscope temperature compensation model is established based on GWO-LSSVM, and the signal without temperature drift is obtained. Finally, the processed mixed noise, the processed temperature drift, the processed other noise, and the signal-dominated IMFs are reconstructed to acquire the improved output signal. The experimental results show that, by using the improved method, the output of a fiber optic gyroscope (FOG) ranging from -30 °C to 60 °C decreases, and the temperature drift dramatically declines. The factor of quantization noise (Q) reduces from 6.1269 × 10-3 to 1.0132 × 10-4, the factor of bias instability (B) reduces from 1.53 × 10-2 to 1 × 10-3, and the factor of random walk of angular velocity (N) reduces from 7.8034 × 10-4 to 7.2110 × 10-6. The improved algorithm can be adopted to denoise the output signal of the FOG with higher accuracy.

Removing temperature drift and temporal variation in thermal infrared images of a UAV uncooled thermal infrared imager

A thermal infrared (TIR) imager mounted on an unmanned aerial vehicle (UAV) has been widely used to obtain land surface temperature (LST) at very high-spatial resolutions. The TIR images are valuable for various applications, including mapping fine-scale surface evapotranspiration and monitoring crop water stress. However, UAV-borne uncooled TIR imagers generally suffer from temperature drift and temporal variation impact due to a long data acquisition period, significantly decreasing the initially acquired brightness temperature (BT) reliability and hindering subsequent applications. Here, a so-called DRAT (Digital number probability density function fitting and RAdiative Transfer simulation-based) method is proposed for simultaneously removing such temperature drift and temperature variation on the temporal scale. The DRAT is post-processing-based and only needs very few ground BT observations for calibration, thus significantly reducing dependence on auxiliary data. Test results show that the visual effect of the normalized TIR mosaics has been significantly improved, displaying more reasonable temperature distribution and good consistency with the land cover. The corrected BT has a root mean square error of 1.51 K and a mean bias error of 0.19 K by in situ data. The DRAT is valuable for obtaining high-accuracy LST and is feasible for other UAV uncooled TIR imagers with similar sensor structures and working principles. Therefore, it can significantly enhance the applicability of UAV TIR remote sensing.

Low-Pass Filters for a Temperature Drift Correction Method for Electromagnetic Induction Systems.

Electromagnetic induction (EMI) systems are used for mapping the soil's electrical conductivity in near-surface applications. EMI measurements are commonly affected by time-varying external environmental factors, with temperature fluctuations being a big contributing factor. This makes it challenging to obtain stable and reliable data from EMI measurements. To mitigate these temperature drift effects, it is customary to perform a temperature drift calibration of the instrument in a temperature-controlled environment. This involves recording the apparent electrical conductivity (ECa) values at specific temperatures to obtain a look-up table that can subsequently be used for static ECa drift correction. However, static drift correction does not account for the delayed thermal variations of the system components, which affects the accuracy of drift correction. Here, a drift correction approach is presented that accounts for delayed thermal variations of EMI system components using two low-pass filters (LPF). Scenarios with uniform and non-uniform temperature distributions in the measurement device are both considered. The approach is developed using a total of 15 measurements with a custom-made EMI device in a wide range of temperature conditions ranging from 10 °C to 50 °C. The EMI device is equipped with eight temperature sensors spread across the device that simultaneously measure the internal ambient temperature during measurements. To parameterize the proposed correction approach, a global optimization algorithm called Shuffled Complex Evolution (SCE-UA) was used for efficient estimation of the calibration parameters. Using the presented drift model to perform corrections for each individual measurement resulted in a root mean square error (RMSE) of <1 mSm-1 for all 15 measurements. This shows that the drift model can properly describe the drift of the measurement device. Performing a drift correction simultaneously for all datasets resulted in a RMSE <1.2 mSm-1, which is considerably lower than the RMSE values of up to 4.5 mSm-1 obtained when using only a single LPF to perform drift corrections. This shows that the presented drift correction method based on two LPFs is more appropriate and effective for mitigating temperature drift effects.

A maximum efficiency point tracking control method for ultrasonic motors with temperature compensation

AbstractTo compensate for the influence of temperature on the efficiency of an ultrasonic motor (USM), this paper proposed a maximum efficiency point tracking control method for temperature drift by analysing the relationships between the maximum efficiency point and the voltage and frequency of the driving circuit. The method first calculates the frequency update step of the driving circuit by the polynomial surface fitting method, considers the influence of temperature rise on the voltage‐efficiency‐frequency characteristics, and then adjusts the frequency in real time to compensate for temperature effects. Simulation and experimental results show that our method can improve the USM performance at the maximum efficiency point under changing temperature. Maximum efficiency point tracking algorithm with temperature compensation algorithm achieves maximum efficiency in experiment.

Vulcanization failure mechanism analysis of lead-frame LED package

Light-emitting diodes (LED) failure can be attributed to various factors such as vulcanization, which is considered as one of the primary causes. The main consequence of vulcanization is the production of black silver sulfide, a result of silver and sulfur ion interaction within the plating layer. The consequences of this reaction can be quite severe, leading to a reduction in luminous flux, color temperature drift, golden ball and support fracture. In this work, following an analysis of the process structure characteristics of LED support, four vulcanization failure paths have been identified. To determine the main vulcanization path of the LED stent, various tests, such as the vulcanization corrosion test, the red ink test, and the cross-section test, have been conducted. This work provides an innovative and constructive approach for directing failure research in LED package.

A temperature-controlled cooling system for accurate quantitative post-mortem MRI.

To develop a temperature-controlled cooling system to facilitate accurate quantitative post-mortem MRI and enable scanning of unfixed tissue. A water cooling system was built and integrated with a 7T scanner to minimize temperature drift during MRI scans. The system was optimized for operational convenience and rapid deployment to ensure efficient workflow, which is critical for scanning unfixed post-mortem samples. The performance of the system was evaluated using a 7-h diffusion MRI protocol at 7T with a porcine tissue sample. Quantitative T1 , T2 , and ADC maps were interspersed with the diffusion scans at seven different time points to investigate the temperature dependence of MRI tissue parameters. The impact of temperature changes on biophysical model fitting of diffusion MRI data was investigated using simulation. Tissue T1 , T2 , and ADC values remained stable throughout the diffusion MRI scan using the developed cooling system, but varied substantially using a conventional scan setup without temperature control. The cooling system enabled accurate estimation of biophysical model parameters by stabilizing the tissue temperature throughout the diffusion scan, while the conventional setup showed evidence of significantly biased estimation. A temperature-controlled cooling system was developed to tackle the challenge of heating in post-mortem imaging, which shows potential to improve the accuracy and reliability of quantitative post-mortem imaging and enables long scans of unfixed tissue.

Removing temperature drift for bee colony weight measurements based on linear regression model and Kalman filter

Removing temperature drift for bee colony weight measurements based on linear regression model and Kalman filter

Differential spectrometric gas sensor with dual out-of-phase microplasma sources

This Letter presents a method for gas sensing based on differential microplasma emission spectroscopy. The method used two strip line split-ring resonator microplasma sources that were powered differentially by modulated power supplies. It was shown to reduce 1/f noise and improve the signal-to-noise ratio and exhibited good accuracy and linearity for sensing CO2 concentration over close to two orders of magnitude. The focus of the study was improved response time and stability, and the results show a 0.2 s response time dominated by advection through the integrated fluidics, and a more than six times stability improvement compared to previous studies. The latter was likely due to several parallel effects, including reduced heat loss in the microplasma sources, and the differential embodiment of the system that balanced temperature and pressure-dependent drift. In a preliminary evaluation, the system displayed a sensitivity of 19 μV/% CO2, a linearity of 0.999, an accuracy of 580 ppm, a response time of 0.2 s, and a maximum averaging time of 620 s, along with ample opportunities for further optimization. Overall, the proposed sensing method shows promise for many kinds of gas sensing applications, particularly for stable and precise measurements in environments where drift is a concern.

Theoretical and experimental investigation on performance enhancement effect for a novel capacitive pressure sensor with double-cavity

This study presents the enhanced sensitivity and low temperature drift effect on the performance of a novel double-cavity capacitive pressure sensor for micr-pressure detection. For theoretical analysis, the relative capacitance change of the sensor are formulated by using COMSOL Multiphysics. In experiments, a sensor model is fabricated by 3D printing technology. The obtained result of the sensor having a flexible diaphragm shows the sensitivity is improved by employing additional double-cavity at room temperature. In addition, the temperature drift effect of the designed pressure sensor is measured and examined through comparison with the traditional sensor. The temperature drift effect can be effectively suppressed by adopting the novel structure. It is expected to realize the micro-pressure detection technology which integrates the characteristics of high sensitivity, large linearity range and low temperature drift.

Metal-based sandwich type thick-film platinum resistance temperature detector for in-situ temperature monitoring of hot-end components

High-temperature resistance temperature detectors (RTDs) are gaining significant attention for various promising applications, including aeroengines, steel metallurgy, and construction machinery. However, it remains a critical challenge in developing RTDs on curved metal substrates without involving high-cost and complicated manufacturing processes. Herein, a metal-based sandwich type thick-film platinum (Pt) RTD for in-situ temperature monitoring of hot-end components is developed through a facile and high-efficient tape mask process and direct ink writing (DIW) technology. The liquid-formed glass–ceramic insulating layer and protective layer effectively immobilize the Pt particles within a sandwich structure, resulting in adequate protection from volatilization and aggregation of the Pt sensitive layer. Meanwhile, the insulating/protective layer exhibits outstanding insulation performance. Additionally, the fabricated Pt RTD achieved excellent repeatability, ultra-high stability (with a temperature drift rate of 0.7%/h at 800 °C), and high accuracy (0.92% full-scale) in the range of 50–800 °C. As an application example, the Pt RTD was fabricated on the surface of a turbine blade to verify its functionality at temperatures up to 800 °C. The exceptional performance and flexible fabrication process indicate that the Pt RTD is a promising candidate for in-situ temperature monitoring of critical aeroengine components.

Dual-polarization interferometric fiber optic gyroscope with Shupe effect compensation

Dual-polarization (DP) interferometric fiber optic gyroscope (IFOG) has been studied for over a decade, which has important applications in inertial navigation and rotational seismology. Currently, the Shupe effect is an important factor degrading the accuracy of the DP IFOG. Here, a dual-quadrupolar winding pattern is proposed to compensate for the Shupe effect. The finite-element simulation experiments verify that the phase shifts induced by the Shupe effect in two polarizations are almost reversed and well compensated. Static laboratory test results show that, in this configuration, the angle random walk is reduced 10-fold to 7.1×10−5 °/h, while the bias instability is reduced ninefold to 1.7×10−4 °/h. Moreover, a 3-h temperature variation experiment is carried out. The results show that, compared with the original output, the net rotation rate errors originating from the Shupe effect are effectively compensated and the temperature drift is reduced by 13 times. To summarize, the dual-quadrupolar-wound method is a valid approach to compensate for the Shupe effect, and the temperature adaptability of this DP configuration is greatly enhanced.

Spatio-temporal species kinetics, thermal and electrical field evolution in an argon EFCAP under different rates of nitrogen seeding: A one-dimensional simulation study

Nitrogen seeding is crucial in cold plasma devices for production of reactive nitrogen species. Excitation Frequency Controlled Cold Atmospheric Pressure Plasma (EFCAP) devices belong to recent concepts in cold plasma where discharge kinetics can be controlled via tuning of external field frequency. The study presents time dependent modelling of such an atmospheric pressure non-DBD argon discharge between two bare electrodes in one dimension under different rates on nitrogen seeding using commercial software COMSOL Multiphysics version 5.4. A square alternating high voltage power source of frequency 11 kHz and peak voltage of 500V drives the discharge in the model. In every half-period, there is an electrical breakdown. Spatio-temporal variations in the electron density, ion density, electric field, electric potential, and electron temperature are investigated. Observed unique spatial oscillations in the species densities, species temperature and distinct drift in the observed characteristics with different rates of nitrogen seeding are some of the appealing aspects revealed by the study. The excitation and dissociation of molecules, generation and losses of ions, plasma mediated reactions and collisional excitations are accounted elaborately in the model developed. The study could explain the origin of typical non-uniform discharge patterns reported experimentally under different excitation frequencies in EFCAP. Obtained results are expected to be useful for better understanding of device physics towards development of improved cold plasma sources with desired characteristics.

A differential miniaturized thickness measurement calibration system based on laser triangulation sensors

Steel plate thickness inspection is important in high-precision steel processing and manufacturing. Traditional inspection methods use manual contact measurement, which has low inspection efficiency and large human error, so we proposed a differential non-contact thickness measurement system based on laser triangulation sensors. Firstly, we designed a differential measurement structure by placing the laser triangulation sensors on the top and bottom of the steel plate to be measured, so that the data from the top and bottom sensors can be sampled and the steel plate thickness can be calculated simultaneously. Secondly, based on the principle of error averaging effect, we proposed a multi-point measurement averaging method to take multiple points on the surface of the steel plate and calculate the average value as the thickness of the steel plate. Further, to improve the measurement system’s long-term stability, the temperature drift is corrected by the polynomial fitting method. Finally, the experiment proves that the repeatability accuracy of our proposed measurement system can reach ±0.5um and the measurement drift is better than ±0.1% of the steel plate thickness.

A Long-Term Dynamic Analysis of Heat Pumps Coupled to Ground Heated by Solar Collectors

In agreement with the decarbonization of the building sector to meet the 2050 climate neutrality targets, borehole thermal storage for solar energy represents a potential solution to increase the energy efficiency of renewable energy plants. As is well known, electricity is not the optimum solution to integrate large inflows of fluctuating renewable energy. In the present paper, we investigate the possibility to use the solar collector to give energy to the borehole field. In detail, a solar-assisted geothermal heat pump is applied to a school located in Milan, Italy. In winter, both the energy from the solar collector and the heat pump are collected into a storage tank connected to the emission terminals, whereas, in summer, as there is no energy demand, the hot water from the solar collector flows into the geothermal probes. By means of this seasonal thermal energy storage technology, the intermittent solar energy collected and stored during the summer months can be utilized during the winter months when the heating demand is high. A long-term dynamic analysis is performed by employing Trnsys. The results show that solar collectors coupled with ground-source heat pumps can give an important contribution to the soil temperature drift, and this also applies in cases of un-balanced loads during the heating season. Moreover, the employment of solar collectors increases the seasonal coefficient of performance of the heat pumps and may rise to reductions to the probes field.

In-situ calibration method for thermocouples in accelerating rate calorimeter based on multiple fixed-points and Joule heat

To solve the problem of temperature drift of thermocouples in accelerating rate calorimeter caused by long-term operation, an in-situ calibration method based on multiple fixed-points and Joule heat is proposed in this article. Firstly, the heat transfer model of the calorimeter is established, and the validity of the method is verified by numerical simulation. Secondly, a multiple fixed-points graphite calibrator and a cylindrical electronic resistance element are designed. Finally, the in-situ calibration is carried out. The calibration results show that the maximum permissible measurement error of the sample thermocouple after calibration is better than 0.220 °C and that the bias of consistency in-situ calibration method is smaller than 0.110 °C. In addition, a di‑tert‑butyl peroxide in toluene solution with a mass percent of 20% is selected as the experimental sample. The sample experiment results show that the kinetic and thermodynamic parameters are closer to the reference values after thermocouples calibration.

Temperature Bias Drift Phase-Based Compensation for a MEMS Accelerometer with Stiffness-Tuning Double-Sided Parallel Plate Capacitors

This paper reports an approach of in-operation temperature bias drift compensation based on phase-based calibration for a stiffness-tunable MEMS accelerometer with double-sided parallel plate (DSPP) capacitors. The temperature drifts of the components of the accelerometer are characterized, and analytical models are built on the basis of the measured drift results. Results reveal that the temperature drift of the acceleration output bias is dominated by the sensitive mechanical stiffness. An out-of-bandwidth AC stimulus signal is introduced to excite the accelerometer, and the interference with the acceleration measurement is minimized. The demodulated phase of the excited response exhibits a monotonic relationship with the effective stiffness of the accelerometer. Through the proposed online compensation approach, the temperature drift of the effective stiffness can be detected by the demodulated phase and compensated in real time by adjusting the stiffness-tuning voltage of DSPP capacitors. The temperature drift coefficient (TDC) of the accelerometer is reduced from 0.54 to 0.29 mg/°C, and the Allan variance bias instability of about 2.8 μg is not adversely affected. Meanwhile, the pull-in resulting from the temperature drift of the effective stiffness can be prevented. TDC can be further reduced to 0.04 mg/°C through an additional offline calibration based on the demodulated carrier phase representing the temperature drift of the readout circuit.

High-Sensitivity Graphene MOEMS Resonant Pressure Sensor.

Nanomechanical resonators made from suspended graphene exhibit high sensitivity toward pressure variations. Nevertheless, these devices exhibit significant energy loss in nonvacuum environments due to air damping, as well as inevitably weak gas leakage within the reference cavity because of the slight permeation of graphene. We present a new type of graphene resonant pressure sensor utilizing micro-opto-electro-mechanical systems technology, which features a multilayer graphene membrane that is sealed in vacuum and adhered to pressure-sensitive silicon film with grooves. This approach innovatively employs an indirectly sensitive method, exhibiting 60 times smaller energy loss in atmosphere, and solving the long-standing issue of gas permeation between the substrate and graphene. Notably, the proposed sensor exhibits a high pressure sensitivity of 1.7 Hz/Pa, which is 5 times higher than the sensitivity of the silicon counterparts. Also, the all-optical encapsulating cavity structure contributes a high signal-to-noise ratio of 6.9 × 10-5 Pa-1 and a low temperature drift (0.014%/◦C). The proposed method offers a promising solution for long-term stability and energy loss suppression of pressure sensors using two-dimensional materials as the sensitive membrane.