Design of Cold-Junction Compensation and Disconnection Detection Circuits of Various Thermocouples and Implementation of Multi-Channel Interfaces Using Them-A Secondary Publication

Cold-junction compensation(CJC)and disconnection detection circuit design of various thermocouples(TC)and multi-channel TC interface circuits were designed.The CJC and disconnection detection circuit consists of a CJC semiconductor device,an instrumentation amplifier(IA),two resistors,and a diode for disconnection detection.Based on the basic circuit,a multi-channel interface circuit was also implemented.The CJC was implemented using compensation semiconductor and IA,and disconnection detection was detected by using two resistors and a diode so that IA input voltage became-0.42 V.As a result of the experiment using R-type TC,the error of the designed circuit was reduced from 0.14 mV to 3μV after CJC in the temperature range of 0°C to 1400°C.In addition,it was confirmed that the output voltage of IA was saturated from 88 mV to-14.2 V when TC was disconnected from normal.The output voltage of the designed circuit was 0 V to 10 V in the temperature range of 0°C to 1400°C.The results of the 4-channel interface experiment using R-type TC were almost identical to the CJC and disconnection detection results for each channel.The implemented multi-channel interface has a feature that can be applied equally to E,J,K,T,R,and S-type TCs by changing the terminals of CJC semiconductor devices and adjusting the IA gain.

Improving the Quality of Thermocouple Wire Made of Platinum-rhodium Alloys

For the manufacture of S-type thermocouple the so-called thermocouple wire of platinum and platinum-rhodium alloy is used.One of the main technical requirements for the quality of the wire,according to State Standard of Russia(GOST 10821),is the uniformity of its largest thermoelectric force(Thermo-emf) in the length different sections.It was found that a determining impact on the uniformity of the wire thermo-emf is the distribution of rhodium along the length of the wire.The impact of platinum-rhodium melt crystallization conditions on the inhomogeneity of wire manufactured from it.It was suggested that the chemical inhomogeneity of the wire is related to the liquation phase of platinum-rhodium alloy.

Dynamic Calibration of the Cutting Temperature Sensor of NiCr/NiSi Thin-film Thermocouple

In high-speed cutting, natural thermocouple, artificial thermocouple and infrared radiation temperature measurement are usually adopted for measuring cutting temperature, but these methods have difficulty in measuring transient temperature accurately of cutting area on account of low response speed and limited cutting condition. In this paper, NiCr/NiSi thin-film thermocouples（TFTCs） are fabricated according to temperature characteristic of cutting area in high-speed cutting by means of advanced twinned microwave electro cyclotron resonance（MW-ECR） plasma source enhanced radio frequency（RF） reaction non-balance magnetron sputtering technique, and can be used for transient cutting temperature measurement. The time constants of the TFTCs with different thermo-junction film width are measured at four kinds of sampling frequency by using Ultra-CFR short pulsed laser system that established. One-dimensional unsteady heat conduction model is constructed and the dynamic performance is analyzed theoretically. It can be seen from the analysis results that the NiCr/NiSi TFTCs are suitable for measuring transient temperature which varies quickly, the response speed of TFTCs can be obviously improved by reducing the thickness of thin-film, and the area of thermo-junction has little influence on dynamic response time. The dynamic calibration experiments are made on the constructed dynamic calibration system, and the experimental results confirm that sampling frequency should be larger than 50 kHz in dynamic measurement for stable response time, and the shortest response time is 0.042 ms. Measurement methods and devices of cutting heat and cutting temperature measurement are developed and improved by this research, which provide practical methods and instruments in monitoring cutting heat and cutting temperature for research and production in high-speed machining.

EMF CHANGES MADE BY COLD DRAWING AND HEATING TREATMENT IN TYPE K HEAVY-GAUGE SHEATHED THERMOCOUPLE CABLES

The electromotive force (EMF) changes in type K heavy gauge sheathed thermocouple cables was investigated. To cope with this discrepancy owing to EMF steep reduction and understand the difference between type K heavy gauge sheathed thermocouple cables and small ones, the affects of EMF from sheath pipe, drawing times, annealing temperature, annealing time and annealing way were mainly studied and appropriately analyzed. The results show the change in the thermal EMF is related with the residual stress and crystal defects, which are imparted by cold work during manufacture. The affects of cold work can be removed by annealing. Finally, a feasible way of fabricating heavy gauge sheathed thermocouples was suggested according to practical situation.

The Linearized Design Of Thermocouple Sensor

There are large errors of linear measurement when the thermocouple measure temperature as temperature sensor.In order to improve the measurement precision,the sensor cold junction compensation and nonlinear compensation are usually needed.For the circumstances that the cold junction’s temperature is determinate,there is biggish nonlinear between thermoelectric power and temperature signals of the thermocouple sensor’s output.In order to solve the problem,this paper proposed a practical method of linear compensation,introduced the principle of linear compensation and gave the corresponding compensation circuit and circuit analysis.This circuit has the characteristic of simpleness,high reliability,small linear error and so on.

Erosion thermocouple temperature acquisition system

Aiming at high requirements of temperature measurement system in high temperature,high pressure,highly corrosive and other special environments,a temperature acquisition system based on field-programmable gate array(FPGA) which is the controller of the system is designed.Also a Flash memory is used as the memory and an erosion thermocouple is used as sensor of the system.Compared with the traditional system using complex programmable logic device(CPLD)and microcontroller unit(MCU)as the main body,this system has some advantages,such as short response time,small volume,no loss of data once power is off,high precision,stability and reliability.And the sensor of the system can be reused.In this paper,boiling water experiment is used to verify accuracy of the system.The millisecond level signal from firecrackers is for verifying the stability and fast response characteristics of the system.The results of experiment indicate that the temperature measurement system is more suitable for the field of explosion and other environments which have high requirements for the system.

THERMOCOUPLE USED FOR TEMPERATURE MEASUREMENT OF ALUMINIUM CELLS BY DYNAMIC METHOD

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Proposal and Verification of Simultaneous Measurement Method for Three Thermoelectric Properties with Film-Type Thermocouple Probe

A new simultaneous measurement method for the measurement of the three thermoelectric properties with a film-type thermocouple probe was proposed. Seebeck coefficient was measured using the steady-state condi-tion of the differential method. The electrical resistivity was measured us-ing the four-probe method and the thermal diffusivity is measured using the periodic heating method. The effectiveness of the proposed method was verified using constantan as a reference material. After describing the effectiveness of the method, the measurement of three thermoelectric properties of Bi0.3Sb1.7Te3, which is a thermoelectric material, was per-formed.

Flexible thermocouple using a thermoelectric graphene fiber with a seamless junction

Temperature is an important physical variable that indicates the condition of the human body and artificial systems.Advanced wearable applications require the development of temperature sensors with different form factors.In this study,a fiber-shaped thermoelectric temperature sensor is fabricated using a continuous graphene fiber whose two halves possess different reduction states.A seamless junction is formed by partially reducing a wet-spun graphene oxide fiber with hydroiodic acid(HI)solutions of different concentrations.One-half of the fiber is mildly reduced with 0.97 wt%HI,while the other half is highly reduced with 30.6 wt%HI.The different reduction states of the graphene composite fiber result in different Seebeck coefficients,allowing for the fabrication of a fiber-shaped graphene thermocou-ple without any laborious assembly.The flexible graphene thermocouple exhibits high sensitivity with a thermopower of 12.5μV K^(-1)in the temperature range of room temperature to∼70℃.Furthermore,it exhibits high linearity with a correlation coefficient exceeding 0.995 and fast response with a time constant of 0.24 s.Owing to its mechanical robustness and flexibility,the stand-alone graphene ther-mocouple can be knitted into a cotton fabric glove,which presents a fast response to environmental changes without any external power source.This work offers a unique fabrication method for producing a high-performance,flexible thermocouple that features a seamless and clear junction without the use of additional materials.This alternative method eliminates the complicated assembly processes typically required for conventional thermocouples.

Irregular initial solidification by mold thermal monitoring in the continuous casting of steels:A review

Occasional irregular initial solidification phenomena,including stickers,deep oscillation marks,depressions,and surface cracks of strand shells in continuous casting molds,are important limitations for developing the high-efficiency continuous casting of steels.The application of mold thermal monitoring(MTM) systems,which use thermocouples to detect and respond to temperature variations in molds,has become an effective method to address irregular initial solidification phenomena.Such systems are widely applied in numerous steel companies for sticker breakout prediction.However,monitoring the surface defects of strands remains immature.Hence,indepth research is necessary to utilize the potential advantages and comprehensive monitoring of MTM systems.This paper summarizes what is included in the irregular initial solidification phenomena and systematically reviews the current state of research on these phenomena by the MTM systems.Furthermore,the influences of mold slag behavior on monitoring these phenomena are analyzed.Finally,the remaining problems of the formation mechanisms and investigations of irregular initial solidification phenomena are discussed,and future research directions are proposed.

Enhanced thermoelectric property and stability of NiCr–NiSi thin film thermocouple on superalloy substrate

Thin film thermocouples（TFTCs） can provide fast and accurate surface temperature measurement with minimal impact on the physical characteristics of the supporting components. In this study, NiCr and NiSi films were prepared with radio frequency（RF） magnetron sputtering and the influences of vacuum annealing on the resistivity of the films were investigated. Afterward, NiCr-NiSi films were deposited on Ni-based superalloy substrates to form TFTCs. The overall dimension of the thermocouple is 64 mm in length, 8 mm in width and 30 lm in thickness. Compared with those of as-deposited sample, the thermoelectric property and stability of the TFTC are significantly improved by vacuum annealing of NiCr and NiSi films. The variation of the Seebeck coefficient of TFTC was discussed based on the size effect of NiCr and NiSi films. And a lower Seebeck coefficient of TFTC of 38.4 μV·℃^-1 is obtained.

High-temperature investigation of mould slag crystallization by single and double hot thermocouple techniques

Methods for the characterization of mould slag crystallization with special emphasis on the single/double hot thermocouple technique(SHTT/DHTT)are reviewed.In the continuous casting process of steels,horizontal heat transfer is mainly influenced by the crystallization behaviour of the mould flux film.Here,both precipitation of crystals out of a liquid phase and devitrification of the glassy film in contact with the mould are of main interest.Therefore,various investigation methods are implemented to characterize different slag properties related to crystallization:a viscometer for determining the break temperature,differential thermal analysis(DTA),confocal scanning laser microscopy,and the water-cooled copper finger test.For near-service conditions,DHTT reveals the most detailed information,including not only the crystallization or devitrification temperature but also the morphology as well as the crystallization velocity.Due to improvements in the device and the representation of the results,a comparison of different samples is possible.Nevertheless,the application field of SHTT/DHTT is restricted to slag systems with low contents of evaporating components.Furthermore,the time required for data analysis is significantly longer than that required for other methods,e.g.DTA.Therefore,the application of DHTT is mainly advisable for mould slag research and development,whereas DTA can also be used for incoming inspections.

A Thermometer Based on Diverse Types Thermocouples and Resistance Temperature Detectors

A universal and low-cost temperature thermometer is realized via a special circuit,integrated circuit chip with microprocessor and analog to digital converter,and digital bus interface.Various thermocouples and resistance temperature detectors used for temperature sensing may be connected to same thermometer.A special signal condition circuitry is designed and a matching algorithm is proposed.A novel calibration method named disassembled calibration is proposed in order to enhance efficiency and flexibility for the whole system.Additionally,it presents a combination method of low order polynomial fitting and piecewise linearity for the nonlinearity calibration of the thermocouple and the resistance temperature detector.A cold junction compensation based on digital way is described.And the matching algorithm and calibration method may eliminate errors stemming from excitation voltage source and reference voltage source,and can weaken quantization error of analog to digital converter and drift of components,too.Furthermore,the 400 times oversampling is completed by sequential and equal interval sampling to upgrade accuracy of analog to digital converter from original 12 to 15 bits and to raise signal-to-noise ratio.Finally,during a long time monitoring,experiment results show that errors at each static point are less than±0.2°C for the thermocouple system and less than±0.1°C for the resistance temperature detector system.

Analysis of Crystallization Behavior of Mold Fluxes Containing TiO_2 Using Single Hot Thermocouple Technique

The crystallization behavior of mold fluxes containing 0-8 mass% TiO2 was investigated using the single hot therrnocouple technique （SHTT） and X ray diffraction （XRD） to study the possible effects on the coordination of heat transfer control and strand lubrication for casting crack sensitive peritectic steels. Time-temperature-transforma tion （TTT） and continuous-cooling transformation （CCT） curves were plotted using the data obtained from SHTT to characterize the crystallization of the mold fluxes. The results showed that crystallization of the mold fluxes during isothermal and non-isothermal processes was suppressed with TiO2 addition. From the TTT curves, it could be seen that the incubation and growth time of crystallization increased significantly with TiO2 addition. The CCT curves showed that the crystallization temperature initially decreased, and then suddenly increased with increasing the TiO2 content. XRD analysis suggested the presence of cuspidine in the mold fluxes with lower TiO2 content （〈4 mass%） , while both perovskite and cuspidine were detected in the mold fluxes when the TiO2 content was increased to 8 mass%. In addition, the growth mechanisms of the crystals changed during the isothermal crystallization process from interface controlled growth to diffusion-controlled growth with increasing the TiO2 content.

Crystallization behavior of blast-furnace slag by single hot thermocouple technique

The crystallization behavior of blast-furnace slag under isothermal and continuous-cooling conditions was studied using the single hot thermocouple technique.The crystallization phases were obtained using FactSage software and X-ray diffractometry.The crystallization kinetic parameters were calculated by combining these results with the Johnson-Mehl—Avrami model.Under isothermal conditions,the shortest crystallization incubation time was 24 and 18 s when the temperatures were 1300 and 1150℃,and the corresponding critical cooling rates were 4.5 and 14.3℃/s,respectively.At 1270℃,the slag was difficult to crystallize and the fiber-forming rate improved.When the continuous-cooling rate was 6.5℃/s,the slag solidified into a glassy state.The main crystallization phases,gehlenite,akermanite,anorthite,and melangite,were most easily precipitated.The growth factors of melangite and anorthite were approximately 1.63 and 1.68,respectively,which indicated that the crystals nucleated on the surface and grew in two dimensions.

Flexible temperature sensor with high sensitivity ranging from liquid nitrogen temperature to 1200℃

Flexible temperature sensors have been extensively investigated due to their prospect of wide application in various flexible electronic products.However,most of the current flexible temperature sensors only work well in a narrow temperature range,with their application at high or low temperatures still being a big challenge.This work proposes a flexible thermocouple temperature sensor based on aerogel blanket substrate,the temperature-sensitive layer of which uses the screen-printing technology to prepare indium oxide and indium tin oxide.It has good temperature sensitivity,with the test sensitivity reaching 226.7μV℃^(−1).Most importantly,it can work in a wide temperature range,from extremely low temperatures down to liquid nitrogen temperature to high temperatures up to 1200℃,which is difficult to be achieved by other existing flexible temperature sensors.This temperature sensor has huge application potential in biomedicine,aerospace and other fields.

Improvement of a temperature response function for divertor heat flux monitoring in fusion devices

Temperature response functions have been developed to investigate sensor design and divertor heat flux estimation in magnetically confined plasmas. The time-dependent heat flux can be derived by fitting the response function to experimental thermocouple(TC) data. Because the TC signals have a time delay to transit events such as discharge start or confinement transition, the time delay is taken into account in a temperature response function. Such a function accurately describes the signal from each TC channel with time delay in a sensor test using a neutral beam injection. Measurement for commercial TCs shows that the time delay is caused by the finite heat capacity of TC wire and contact heat resistance between TC and target surface.

Analysis of performance and optimum configuration of two-stage semiconductor thermoelectric module

In this paper, the theoretical analysis and simulating calculation were conducted for a basic two-stage semiconductor thermoelectric module, which contains one thermocouple in the second stage and several thermocouples in the first stage. The study focused on the configuration of the two-stage semiconductor thermoelectric cooler, especially investigating the influences of some parameters, such as the current I1 of the first stage, the area A1 of every thermocouple and the number n of thermocouples in the first stage, on the cooling performance of the module. The obtained results of analysis indicate that changing the current I1 of the first stage, the area A1 of thermocouples and the number n of thermocouples in the first stage can improve the cooling performance of the module. These results can be used to optimize the configuration of the two-stage semiconductor thermoelectric module and provide guides for the design and application of thermoelectric cooler.

Nose-Tip Transition Control by Surface Roughness on a Hypersonic Sphere

The surface heat flux on a 100 mm diameter hypersonic sphere was reduced through surface roughness on its forebody. The test model was subjected to a hypersonic freestream of Mach 8.8 and Reynolds number 1.98 million/m, in a shock tunnel. Forebody surface heat transfer rates measured on smooth and rough spheres, under the same free-stream conditions, were compared. The comparison of heat flux indicated an overall reduction in surface heating rates on the rough model, which could be attributed to the delayed nose tip transition. The surface roughness on the forebody of the model generated miniature cavities. Stability of the free shear layer over the miniature cavities and entrapment of the destabilizing vortices in the cavities, make the flow over the rough test model more stable than the attached boundary layer over the smooth model, under transitional conditions.

Design of Experimental System of USB Data Acquisition Card-based Temperature Acquisition

In order to design a more efficient and more convenient temperature acquisition system, an approach combining USB data acquisition card with K type thermocouple temperature sensor is proposed under the circumstance of LabVIEW 2012 programming software. Firstly, the LabVIEW 2012 programming software is used to complete a temperature acquisition control program. Secondly, K type thermocouple temperature sensor is employed to transfer the temperature information. Thirdly, Then the USB data acquisition card can collect the voltage of K type thermocouple temperature sensor and convert it to a temperature scale. And, the simplification of experimental procedure can reduce the cost of development greatly. Finally, the experimental results illustrate that the range of measurement temperature is more wide and the temperature scale is more accurate.