Thermocouple Signals Research Articles

Measurement of thermophysical parameters of artificial skin

Computer methods for process research and methods for processing the measurement results of the parameters of these processes are widely used in biology and medicine. Therefore, the problem of automation of biophysical measurements and computer processing of the results of such experiments is relevant. In the treatment of wounds and burns with a large surface area of tissue damage, medicine has to resort to artificial skin. A procedure for studying thermal processes in artificial skin and measuring its thermophysical parameters was developed. The measurement process was described. The thermophysical parameters of the artificial skin samples used in medicine for the treatment of wounds and burns were determined. The samples of the artificial skin used were made in Ukraine. Each sample was made from six layers of skin. To control the temperature distribution in the sample between the skin adjacent layers and on the surface of the sample, thermocouples were placed. The surface of the sample was heated with an incandescent lamp. The thermocouple signals were sent to an analog-to-digital converter (ADC), amplified, and digitally transmitted to a computer. Processing was carried out using the ADC software and the MATHCAD program. A mathematical model was obtained. For this purpose, a differential equation describing thermal processes in the sample was solved. The found temperature distribution function and its changes over time are in a good agreement with experimental data. The analysis of the function allows finding the thermal conductivity coefficient of artificial skin, its volume heat capacity, thermal diffusivity coefficient, and heat exchange coefficient with the external environment. The proposed method of measuring and processing experimental data makes it possible to detect main thermophysical parameters of artificial skin. Based on these results, a theoretical model was obtained that well describes the course of thermal processes in artificial skin, which makes it possible to predict the course of these processes. Such method is based on heating the skin with optical radiation. The thermal conductivity and thermal diffusivity of artificial skin are significantly less than such parameters of human skin, which should be considered when using it.

Temperature Measurements at Tyre Tread Rubber on Sandpaper Oscillatory Sliding Contacts Using Acicular Grindable Thermocouples

The tribological performance of tyre–road contacts depends crucially on the contact temperature. This study investigates the reliability and accuracy of acicular grindable thermocouples possessing an original needle-shaped wearable part as applied to measuring temperature at the oscillatory sliding contact between a rubber tyre tread sample and a sandpaper. A linear oscillatory tribometer is used to imitate the sliding phase of tyre–road contact under mild friction conditions. It is shown that the acicular grindable thermocouple measurements are generally test–retest repeatable. Moreover, the thermocouple signal becomes more stable with increasing contact pressure. Compared to the conventional thermocouple technique, the acicular grindable thermocouple overestimates temperature at the rubber friction surface by about 23% due to involvements of its wearable part in friction with the sandpaper. The findings suggest an expansion of the acicular grindable thermocouple technique to full-scale experiments with tyres on the road.

Hybrid-Input FCN-CNN-SE for Industrial Applications: Classification of Longitudinal Cracks during Continuous Casting

In the presented research, machine learning methods were applied to the prediction of longitudinal cracks in steel slabs during continuous casting. We employ a deep learning approach to process 68 thermocouple signals as a multivariate time series (MTS) along with 32 static features, which encompass both chemical composition and process information. Our deep learning approach integrates two distinct parallel modules, followed by an aggregation block; a Convolutional Neural Network (CNN) processes the thermocouple MTS, while in parallel, the static data undergo processing via a Fully Connected Network (FCN). To enhance the performance of the CNN, we incorporate two Squeeze and Excitation (SE) blocks, which act as an attention mechanism across different channels. By integrating chemical information with MTS in the detection system, we improve the performance of defect detection by 15% relatively.

Underlying Methodology for a Thermal Process Monitoring System for Wire and Arc Additive Manufacturing

The Wire and Arc Additive Manufacturing (WAAM) process has a high potential for industrial applications in aviation. The interlayer temperatures influence the dimensions and geometric deviations of the part. Monitoring the absolute interlayer temperature values is necessary for quantifying these influences. This paper presents an approach for determining the absolute values of the interlayer temperatures during the process using Ti-6Al-4V. The emissivity and transmittance are determined and calibrated, enabling precise thermographic measuring during the WAAM process. The recorded thermographic data are then compared to signals of thermocouples so that the absolute temperature values can be aligned. The methodology is validated by its transfer to measure the interlayer temperature at different regions of interest. The effect of a heat accumulation using Ti-6Al-4V in WAAM was determined. The methodology enables a reproducible and non-tactile measurement of the interlayer temperature during the WAAM process. The results show that with an interlayer temperature of 200 °C, a heat accumulation occurs within a layer. The heat accumulates in the center of the layer because the free ends of the layer cool down faster than the center of the layer.

Technical note: a nose ring sensor system to monitor dairy cow cardiovascular and respiratory metrics.

Monitoring cardiovascular and respiratory measurements corresponds to the precision livestock farming (PLF) objective to continuously monitor and assess dairy cows' welfare and health. Changes in heart rate, breathing rate, and oxygen saturation (SpO2) are valuable metrics in human and veterinary medicine to assess stress, pain, illness, and detect critical conditions. The common way to measure heart rate is either manually or with a stethoscope. Under research conditions, heart rate is usually measured with a sports watch chest belt. Breathing rate is obtained by counting the cow's flank movements which is a time-consuming and labor-intensive method that requires training and is prone to human error. No devices are available on the market that enable practical and easy pulse oximetry in farm animals. This study presents a wireless nose ring sensor system (NoRS) composed of thermal and photoplothysmography sensors that attach to the nostrils of four Holstein dairy cows. The NoRS's thermocouple measured the cow's nasal cavity air temperature; an optic sensor measured the IR (660 nm) and RED (660 nm) signals reflected from the cow's nasal septum. Breathing was calculated from the thermocouple signal's center frequency with a fast Fourier transformation or the signal peak count (i.e., oscillations). The breathing rate was compared to breathing observed by concurrently counting the flank movements. Heart rate and SpO2 were measured by integrated pulse oximetry and heart rate monitor module (MAX30101 TinyCircuit) assembled on the NoRS circuit. Heart rate was also measured with FFT and by counting the number of peaks from the optic sensor's raw IR and RED signals. These measures were compared to an off-the-shelf hand-held pulse oximeter's heart rate and SpO2 readings during the same time. The comparisons revealed highly significant correlations for the heart rate readings where the strength of the correlation was sensitive to the method. The correlation between breathing rate and the veterinarian's visual observations was low, albeit significant. Thus, inhale-exhale cycle counting constitutes a more precise approach than flank movement counts. The hand-held device's 96% SpO2 is compatible with near-saturation values expected in healthy cows. The mean NoRS SpO2 reading was 3% less. After further piloting under field conditions, the NoRS will require no animal restraining to automatically and continuously record cows' breathing rate, heart rate, and SpO2.

Contact High Temperature Strain Automatic Calibration and Precision Compensation Technology

In order to solve the problem of contact high temperature strain precision measure-ment, this paper established an automatic calibration device for high temperature strain gauges. The temperature of the high temperature furnace was automatically con-trolled by the temperature control device. The electric cylinder was driven by the servo motor to apply the load to the calibration beam. The output signal of the high temperature strain gauge, the thermocouple signal and the displacement signal of the grat-ing ruler were collected at the same time. The deformation measurement results obtained after temperature correction were used to calculate the theoretical mechanical strain, which were fed back to control the loading action to complete the automatic calibration process. Based on the above calibration device, the high temperature strain measurement accuracy correction software was developed to calibrate the high temperature strain gauge with multi-parameters, and the curves of sensitivity coefficient, thermal output, zero drift and creep characteristics with temperature were obtained, and a strain measurement accuracy compensation model was established. The high temperature strain measurement experiment was carried out to verify that the modified model can meet the requirements in each temperature range.

Microprocessor temperature control device for a thermal object

The article deals with a device for temperature control of a thermal object. The device is based on a single-chip AVR ATmega32 microcontroller. There are two modes of temperature regulation. The first is designed for temperature regulation within the range of -55 ° C to +125 ° C, and the second is from +126 ° C to +1000 ° C. The first range uses a DS18B20 digital serial output temperature sensor. The temperature measurement resolution in the first temperature range of -55 °C to +125 °C is 0.0625 °C. The second range uses a K-type thermocouple and a MAX6675 thermocouple signal converter with I2C interface. The discreteness of temperature measurement in the range from +126 C to +1000 C is 2 C. The microprocessor based controller has a very wide temperature control range from -55 to +1000°C, which is well within the temperature range required by the process. In the first area, due to high accuracy digital temperature sensor DS18B20, the resolution is very good ±0.0625 °C, which enables the use of the controller in climate control systems.

Thermocouple response time estimation and temperature signal correction for an accurate heat flux calculation in inverse heat conduction problems

Many heat transfer processes do not allow temperature measurements with advanced instruments like IR cameras, and thus require the use of thermocouples – often inserted sheathed thermocouples – in order to measure the temperature in some key-regions. Nevertheless, thermocouples have an intrinsic response time that can dampen substantially temperature measurements and, when applicable, affect heat flux estimations by inverse methods. In this study, a thermocouple measurement correction method is proposed, especially for fast thermal transients like quenching, to avoid underestimation of the boundary heat fluxes due to delayed temperature responses. A simplified energy balance at the hot junction allowed modeling the temperature measurement by a thermocouple, in which heat losses and the response time were taken into account so they can be estimated using the least squares method on experimental data. A series of tests was performed to validate the present method with a heated jet impinging on a copper body instrumented with two thermocouples: one ungrounded and sheathed, then with high response time (”slow”); and another with exposed welded wires, hence with low response time (”fast”). After having estimated the slow thermocouple response time and heat loss parameters, the model allowed a good reconstruction of the fast thermocouple signal using the slow thermocouple measurements. Also, the heat flux estimation by the inverse method using the reconstructed signal resulted in practically the same results obtained using the fast thermocouple data. A parametric sensitivity analysis showed the heat loss parameters can be neglected for heat flux estimations, while simulations showed that temperature noises degrade the response time estimation but data filtering can mitigate this noise effect. Finally, the present method was applied to a large scale jet-cooling of a hot plate – near industrial conditions – and showed a substantially higher dissipated heat flux than the initially estimated. In fact, the results using reconstructed signals demonstrated that the heat flux dissipated by the jet has a higher dependence on the jet Reynolds number than the observed with the original thermocouple measurements, showing how important the temperature measurement correction is to evaluate fast thermal processes.

A change in the air temperature inside a 20-liter chamber when air is added from the receiver

Introduction. One of the reasons for the overestimation of the explosion hazard of dust inside a (20 ± 2)-liter chamber is the elevated initial temperature of the air suspension. The initial temperature is also raised by the process of filling the pre-emptied chamber with air from the receiver, used to distribute dust over the chamber. In this work, an increase in the air temperature inside an 18.7-liter chamber was identified in an experiment for the case of addition of air from the receiver.The methodology of an experiment. The air temperature in the chamber was measured at the time when the air from the receiver was added using a WR 5/20 thermoelectric converter (a thermocouple). The thermocouple junction was located at the distance of 70 mm from the inner wall of the chamber. The thermocouple signal was processed by an MCLab PRO programmable logic controller (the time resolution is 1 ms).Research results. The measuring instruments recorded an increase in the temperature of the thermocouple junction by +14 degrees. Due to the comparability of the inertia of the thermocouple (3 s) and the characteristic time of air cooling by the chamber walls (5 s), the measurement results underestimated the real value of a jump in the air temperature inside the chamber. Measurement results were refined using a simple model of heat transfer between the objects involved in the process (thermocouple junction – air – chamber wall) that entailed the exponential relaxation of the temperature difference over time. As a result, an estimated increase in the initial temperature inside the chamber of +30 degrees was identified.Results and discussion. The temperature jump by +30 degrees makes a noticeable contribution to the total jump in the initial temperature, which was previously tied solely to the burnout of the ignition source (+80 degrees).Conclusions. Given the known increase in the temperature inside the chamber caused by the burnout ofa standard ignition source (2 kJ), the real value of the initial temperature of the environment can reach 135 °C in the course of studying dust in a (20 ± 2)-liter chamber.

Obstructive sleep apnea predicts 10-year cardiovascular disease-related mortality in the Sleep Heart Health Study: a machine learning approach.

Obstructive sleep apnea (OSA) is considered to be an important risk factor for the development of cardiovascular disease (CVD). This study aimed to develop and evaluate a machine learning approach with a set of features for assessing the 10-year CVD mortality risk of the OSA population. This study included 2,464 patients with OSA who met study inclusion criteria and were selected from the Sleep Heart Health Study. We evaluated the importance of potential features by mutual information. The top 9 features were selected to develop a random forest model. We evaluated the model performance on a test set (n = 493) using the area under the receiver operating curve with 95% confidence interval and confusion matrix. A random forest model awarded the highest area under the receiver operating curve of 0.84 (95% confidence interval: 0.78-0.89). The specificity and sensitivity were 73.94% and 81.82%, respectively. Sixty-three years old was a threshold for increased risk of 10-year CVD mortality. Persons with severe OSA had higher risk than those with mild OSA. This study demonstrated that a random forest model can provide a quick assessment of the risk of 10-year CVD mortality. Our model may be more informative for patients with OSA in determining their future CVD mortality risk. Li A, Roveda JM, Powers LS, Quan SF. Obstructive sleep apnea predicts 10-year cardiovascular disease-related mortality in the Sleep Heart Health Study: a machine learning approach. J Clin Sleep Med. 2022;18(2):497-504.

Sleep time and efficiency in patients undergoing laboratory-based polysomnography.

Sleep quality in patients studied with laboratory-based polysomnography may differ from sleep quality in patients studied at home but remains clinically relevant and important to describe. We assessed objective sleep quality and explored factors associated with poor sleep in patients undergoing laboratory-based polysomnography. We reviewed diagnostic polysomnography studies from a 10-year period at a single sleep center. Total sleep time (TST) and sleep efficiency (SE) were assessed as markers of sleep quality. Poor sleep was defined as TST ≤ 4 hours or SE ≤ 50%. Multivariable analysis was performed to determine associations between objective sleep quality as an outcome and multiple candidate predictors including age, sex, race, body mass index, comorbidities, severity of obstructive sleep apnea, and central nervous system medications. Among 4957 patients (age 53 ± 15 years), average TST and median SE were 5.8 hours and 79%, respectively. There were 556 (11%) and 406 (8%) patients who had poor sleep based on TST and SE, respectively. In multivariable analysis, those who were older (per 10 years: 1.48 [1.34, 1.63]), male (1.38 [1.14,1.68]), and had severe obstructive sleep apnea (1.76 [1.28, 2.43]) were more likely to have short sleep. Antidepressant use was associated with lower odds of short sleep (0.77 [0.59,1.00]). Older age (per 10 years: 1.48 [1.34, 1.62]), male sex (1.34 [1.07,1.68]), and severe obstructive sleep apnea (2.16 [1.47, 3.21]) were associated with higher odds of poor SE. We describe TST and SE from a single sleep center cohort. Multiple demographic characteristics were associated with poor objective sleep in patients during laboratory-based polysomnography. Harrison EI, Roth RH, Lobo JM, et al. Sleep time and efficiency in patients undergoing laboratory-based polysomnography. J Clin Sleep Med. 2021;17(8):1591-1598.

HIFiRE-5b Boundary-Layer Transition Length and Turbulent Overshoot

Hypersonic International Flight Research Experimentation 5 (HIFiRE-5) is a hypersonic flight-test experiment designed to investigate the aerothermodynamics of a 3-D geometry. The vehicle is an elliptic cone with a 2:1 aspect ratio and 2.5 mm nose radius. The HIFiRE-5b achieved a Mach number of 7.7–7.9 and freestream unit Reynolds number of to during descent. Heat flux was calculated from thermocouple pairs and boundary-layer transition locations were identified from these heating rates. A multilobed transition front was observed; it is suspected that a different mechanism is responsible for each of these lobes. The vehicle’s attitude oscillated, which has been exploited to assess the sensitivity of heat flux to yaw angle along the leading edges and ascertain the appropriateness of the filtering applied to the thermocouple signals. Spatial heat-flux profiles have been constructed for constant freestream unit Reynolds numbers. The heat-flux rate at the end of transition is examined; turbulent overshoot was present along some azimuths, but not others. This flight-test result indicates the phenomenon is not specific to ground test, freestream noise level, or wall-to-stagnation-temperature ratio. Finally, transition length (its end location normalized by its onset location) is reported and connected to turbulent spot generation rates.

The characteristics of a 1 m methanol pool fire

A series of measurements was made to characterize the structure of a 1 m diameter methanol (CH3OH) pool fire steadily burning with a constant lip height in a quiescent environment. Time-averaged local measurements of gas-phase temperature were conducted using 50 μm diameter, Type S, bare wire, thermocouples with a bead that was approximately spherical with a diameter of about 150 μm. The thermocouple signals were corrected for radiative loss and thermal inertia effects. The mass burning rate was measured by monitoring the mass loss in the methanol reservoir feeding the liquid pool. The heat release rate was measured using oxygen consumption calorimetry. The heat flux was measured in the radial and vertical directions and the radiative fraction was estimated, which correspond to previous results.

Experimental determination of crack velocities in steel

One of the little-studied problems of modern mechanics and the physics of fracture is the branching of the crack, which is observed in materials of a different nature. To experimentally determine the rate of crack branching velocity in steels, a series of tests were carried out on the fracture by internal pressure of steel thin-walled cylindrical shells (vessels) with measuring of the crack velocity by the method of breaking the conductive strips. A measurement setup was created on the basis of a precision converter “Tercon” signals of resistance thermometers and thermocouples, connected to a computer. Velocity measurements showed that in the case of straight-line propagation, the crack velocity is 350-541 m/s, and when crack branching, the crack velocity is 679-746 m/s. The results show that the crack branching velocity is a critical (limiting) crack propagation velocity, and the energy entering the top of a moving crack is not spent on increasing the crack velocity, but on creating new cracks by branching.

Experimental Study of Crack Branching Velocity in Polymers

One of the little-studied problems of modern mechanics and the physics of destruction is crack branching, which is observed in materials of varying nature. In order to study this phenomenon, the criteria and mechanisms for crack branching are analyzed. Studies of crack branching in polymers and steel, as well as fractographic studies of the fracture surface, are considered. It is found that the crack at branching in brittle plastics reaches the limiting propagation velocity V* = 500–800 m/s. Tensile tests of flat samples made of polymethyl methacrylate (PMMA) at temperatures of +20 and –60°C are carried out with measurement of crack velocity by the method of rupture of conductive strips. A measuring device based on a TERCON precision converter of signals of resistance thermometers and thermocouples connected to a computer is created. Crack velocity is measured for (i) rectilinear crack propagation in the mirror, matte, and feather zones of PMMA fracture surface, (ii) single branching of the crack, and (iii) multiple crack branching with parallel movement of the front of several cracks. A hypothesis for the physical mechanism of crack branching is proposed.

Design and analysis of gas temperature measurement module in motor vehicle exhaust online measurement system

The mass flow rate of vehicle exhaust significantly influences the measurement of the exhaust pollutants emission factors, meanwhile the exhaust gas temperature measurement is most important in the measurement of exhaust gas mass flow. In order to measure the temperature of exhaust gas accurately and sensitively, a motor vehicle exhaust online measurement experimental system has been developed. The article reports on the design and analysis of gas temperature measurement module in this system. The gas temperature measurement consists of a high-precision K-type thermocouple and a weak signal amplifier circuit. The K-type thermocouple was used to measure the temperature of exhaust gas. Based on the AD595AQ, which was a complete instrumentation amplifier chip with a cold junction compensator for thermocouple, the weak signal of thermocouple was amplified to achieve accurate and rapid measurement of exhaust gas temperature. The real experimental results showed that the detection time is 0.5 s, the deviation is + 0.2°C, and the detection limit is 573°C. The subsequent analysis showed that the gas temperature measurement module performed well to support the system.

Minor fault detection of thermocouple sensor in nuclear power plants using time series analysis

This paper addresses a scheme for detection a minor deflection of thermocouple signal reading in nuclear power plants (NPPs). These minor deflection signal does not exceed the system threshold value, therefore they are neither separated by the data classification methods nor detected by the data approximation methods. The proposed approach is based on time series analysis methods. In this approach, the minor failure signals are detected by computing the distance between the empirical cumulative distribution function of test signal and the standard signal. The moving average method is applied to smooth out the small fluctuation and noise of the signals before computing the empirical distribution. The time series mean shift detection technique is employed to the faulty signal for surety that the signal has a fault and find out its change point. The proposed method is validated by the real data from the Fast Breeder Test Reactor (FBTR).

A Through-Hole Lead Connection Method for Thin-Film Thermocouples on Turbine Blades.

To solve the current problems with thin-film thermocouple signals on turbine blades in ultra-high temperature environments, this study explores the use of a through-hole lead connection technology for high-temperature resistant nickel alloys. The technique includes through-hole processing, insulation layer preparation, and filling and fixing of a high-temperature resistant conductive paste. The through-hole lead connection preparation process was optimized by investigating the influence of the inner diameter of the through-hole, solder volume, and temperature treatment on the contact strength and surface roughness of the thin-film for contact resistance. Finally, the technology was combined with a thin-film thermocouple to perform multiple thermal cycling experiments on the surface of the turbine blade at a temperature of 1000 °C. The results show that the through-hole lead connection technology can achieve a stable output of the thin-film thermocouple signal on the turbine blade.

A modern data measurement system to study and test thermionic heat to electricity converters

Studies and tests are conducted to determine the performance of thermionic nuclear power plants (TNPP) a stage in which is pre-irradiation testing of laboratory thermionic converters (TIC) with flat and cylindrically shaped electrodes using test facilities fitted with automated data measurement systems (DMS). The TIC volt-ampere characteristics (VAC) are measured in the DMS jointly with the measured test section and experimental test facility temperature fields. The structure and the characteristics of a DMS based on products from ICP DAS Co., Ltd are presented. A developed VAC measurement program providing the operator with a convenient graphic interface and enabling adjustment of the measurement parameters has been considered. The VAC recording errors in the process of measurements have been determined using TIC simulators. The error in the VAC diffusion portion on a simulator (with a current of less than 3 A) is not more than 1%. Thanks to the use of modern components, the developed DMS offers extended functional capabilities for measuring the thermocouple signals in an experimental electrophysical test facility. The DMS structure provides for the convenience of scaling (through a larger number of measuring channels) and makes it possible to add modules from other manufacturers. The experience of operating this DMS will be used to develop the DMS for an in-pile test system designed for similar functions.

EXPERIMENTAL STUDY OF THE CRACK BRANCHING SPEED IN POLYMERS

One of the little-studied problems of modern mechanics and the physics of fracture is the branching of the crack, which is observed in materials of a different nature. For his research, an analysis of the criteria and mechanisms for crack branching. The investigations of crack branching in polymers and steel, fractographic investigation of the fracture surface are considered; criteria for crack branching as a dynamic stress intensity factor, crack speed. It is established that the crack at branching in brittle plastics reaches the limiting propagation speed V * = 500 – 800 m/sec. Tensile tests of flat samples from polymethylmethacrylate (PMMA) at temperatures of +20 and –60°C were carried out, with measurement of crack speed by the method of rupture of conducting strips. A measuring device based on a precision converter of signals of resistance thermometers and thermocouples «TERCON», connected to a computer, was created. Measured crack speed for rectilinear crack propagation in the mirror, matte, and feather zones of fracture surface of the PMMA; with single branching of the crack; with multiple branching of cracks with parallel movement of the front of several cracks. A hypothesis is proposed for the physical mechanism of fracture branching.