Thin Film Thermocouple Sensors Research Articles

Research of transient temperature measuring based on thin-film thermocouple and Wi-Fi wireless DAQ method

The thin-film thermocouple temperature sensor is a new type of temperature sensor which was emerged with the development of thin-film materials. It features on a small heat capacity and a rapid response speed for transient temperature measurement on the surface of objects. The existing temperature data acquisition systems for filamentary thermocouples do not yet meet the conditions for distortion-free measurement of transient temperature signals in terms of sampling frequency and transmission rate. In addition, it is less flexible in terms of data transmission methods, while the cold end of the thermocouple compensation method has not yet compensated for the non-linear phenomenon of thermocouples, which affects the final measurement accuracy. This paper devised a wireless temperature data acquisition system for K-type thin-film thermocouples using a Wi-Fi wireless network to transmit sampling data, then applied the devised system as a data acquisition method to investigate the measurement of transient temperatures in conjunction with thin-film thermocouple sensors. The results of performance test indicated that the devised system is capable of transient temperature measurement of K-type thin-film thermocouples in the range of 0–650°C with a maximum sampling rate of 100 kHz, a temperature resolution of 0.16 degrees Celsius, an accuracy of 0.2% after non-linear compensation and the ability to measure transient temperature signals with a maximum frequency component of 25 kHz. Taken advantage of the devised wireless data acquisition system to measure the impulse response of a thin-film thermocouple sensor specimen, the meausured response curve is consistent with the law of first-order system, and the time constant of the sensor was obtained as approximately 1.16 ms. A comparison between the existing data acquisition apparatuses of type K thermocouple was made. The limitations of the devised system are also discussed.

Temperature measurement performance of thin-film thermocouple cutting tool in turning titanium alloy

The measurement of cutting temperature is one of the most important research topics in the field of cutting. Traditional technology for cutting temperature measurement has limitations because it cannot accurately measure the real transient temperature change in the cutting area. In this study, a thin-film thermocouple sensor with high temperature measurement accuracy and rapid response was positioned near the cutting tool tip to prepare a thin-film thermocouple temperature-measurement tool. Its Seebeck coefficient was 48.13 μV/°C, and the highest temperature difference measured between cold and heat regions was 600 °C. The cutting temperature of a TC4 titanium alloy was measured using an infrared thermal imager and the proposed thin-film thermocouple temperature measurement tool in an orthogonal turning test. The test results were analysed to verify the reliability, accuracy, and repeatability of cutting temperature measurements. The cutting length could extend beyond 1500 m.

Stress Analysis of Thin Film Thermocouple Sensor Based on Finite Element Simulation

As a new type of micro device, the reliability of thin film thermocouple sensor is very important in actual work. Aiming at a thin-film thermocouple sensor with NiCr as the functional layer, three main stresses of the thin-film sensor in actual work are analyzed: thermal stress, vibration stress and centrifugal stress. Various stress analyses have been verified through theoretical calculations or finite element simulations. The results show that thermal stress is the main influence stress, and the critical areas of reliability have been obtained. The prepared thin film sensor samples were tested through high temperature experiments, and the analysis results were verified. When a thermal load of 700 degrees Celsius is applied, the stress environment of the protective layer, the functional layer and the insulating layer of the structure is severe, and it is vulnerable to severe damage, and cracks are found in the insulating layer, which becomes a weak area of reliability.

Laser deposited high temperature thin film sensors for gas turbines

Purpose Accurate measurements of the temperature distributions in hot section components are indispensable for the prognostic and health management of gas turbines. Thin film thermocouple (TFTC) sensors, directly fabricated on the surface of a component, add negligible mass and create little or no disturbance to airflow, and therefore, can provide accurate measurements of fast temperature fluctuations of gas turbines. The purpose of this paper is to evaluate TFTC sensors fabricated by combining pulsed laser deposition (PLD) and micromachining techniques (LM). Design/methodology/approach The “dry” PLD/LM fabrication approach allows for excellent control of the chemical composition and physical characteristics of the constituent layers and their interfaces, thus achieving good adhesion of the layers to the substrate. Findings The results of thermal cyclic durability testing of the fabricated TFTC sensors demonstrated that the proposed PLD-based approach can be used to fabricate sensors that are fully functional at temperatures up to 750°C. Analyses of the sensor performance during durability testing revealed: the existence of a threshold temperature below which accurate temperature measurements were achieved; an abrupt drop in the sensor output occurring when the sensor temperature exceeded the threshold value, with a fast recovery of the sensor output once the temperature was reduced below the threshold level; and sensor “training” capable of increasing the threshold value of the TFTC through its exposure to above-the-threshold temperatures. Originality/value The work is the first time to demonstrate that simple PLD and LM processes can be used to fabricate TFTC that are fully functional at temperatures up to 750°C.

Impact of Magnetron Sputtering Parameters on Thermoelectric Properties of Tungsten-Rhenium Thin-Film Thermocouples Sensor

In this paper, we present the analysis of the impact of radio frequency magnetron sputtering parameters on the average Seebeck coefficient and maximum reliable working time of thin-film thermocouple (TFTC) sensor based on tungsten-rhenium, and the effect of subsequent optimization of sputtering parameters on the performance of these thermocouples. It can be observed that the repeatability error of TFTCs with magnetron sputtering parameters optimization is ±1.5%, the nonlinear error is ±0.29%, the hysteresis error is ±1.93%, and the average Seebeck coefficient ranges from 26.87 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$27.3~\mu \text{V}/^{\circ }\text{C}$ </tex-math></inline-formula> at thermal cycle experiments for 40 h. The electromotive force behavior experiments show optimized TFTCs with protection subjected to a temperature difference of 900 °C is 19.3 mV. Compared with TFTCs without magnetron sputtering parameters optimization and protection, it has improved the thermoelectric properties of tungsten-rhenium TFTCs sensor to be a viable replacement candidate for the requirement of high-temperature measurement.

Magnetron Sputtering of NiCr/NiSi Thin-Film Thermocouple Sensor for Temperature Measurement when Machining Chemical Explosive Material

Temperature plays a vital role in the machining industry today. A Nickel-Chrome versus Nickel-Silicon thin-film thermocouple system has been established for measuring instantaneous workpiece temperature in chemical explosive material machining. The NiCr/NiSi thin-film thermocouples have been deposited inside high speed steel cutters by magnetron sputtering. The typical deposition conditions are summarized. Static and dynamic calibrations of the NiCr/NiSi thin-film thermocouples are presented. The Seebeck coefficient of the TFTC is 40.4 μV/°C which is almost the same as that of NiCr/NiSi wire thermocouple. The response time is about 0.42ms. The testing results indicate that the developed NiCr/NiSi thin-film thermocouple sensors can respond fast enough to catch the very short temperature pulse and perform excellently when machining chemical explosive material in situ.

Development of Cutting Tools with Built-in Thin Film Thermocouple for Monitoring Machining Temperature

Temperature plays a vital role in the machining industry today. NiCr/NiSi thin-film thermocouples have been deposited on the rake face of polycrystalline cubic boron nitride (PCBN) tools by magnetron sputtering. The typical deposition conditions are summarized. Static and dynamic calibrations of the NiCr/NiSi thin-film thermocouples are presented. The Seebeck coefficient of the TFTC is 37.3 μV/°C. The response time is about 3.9 ms. The testing results indicate that the developed NiCr/NiSi thin-film thermocouple sensors perform excellently when machining A3 steel in situ.

Monitoring of Machining Processes Using Sensor Equipped Tools

AbstractA different to conventional monitoring systems sensor equipped tools give the possibility to gain information about the process status directly from the contact zone between tool and component to be machined. For example this can be realized by the integration of small temperature sensors into grinding wheels. The transmitting of the process data is performed by a telemetric unit attached to the grinding wheel's core. In this paper, the development of a new thin film thermocouple sensor concept is described. The unique feature of this sensor is the continuous contacting of the thermocouple through the grinding process inherent wear which leads to smearing of the thermoelectric layers and thus forming the measuring junction of a thermocouple. The system was used in OD grinding processes aiming to detect grinding burn and process instabilities. By reducing the volume of the sensors a fast response and high time resolution can be obtained. By this way, observance of the key parameters of the practical operation as closely as possible to the cutting area is enabled and so observance of process efficiency and tool status independent from workpiece machining conditions can be realized. All sensors used are thermocouples of type K, a combination of Chromel (NiCr) and Alumel (NiAlMnSi) material. The maximum temperature to be measured by this sensor is about 1350 °C, which ensures the applicability in the grinding process. Telemetry components to amplify and send the thermovoltage signals are adjusted to this type of thermocouple. The ability of the set‐up to detect thermal influences was demonstrated in grinding processes with a continuously increasing specific material removal rate. The approach serves to measure temperatures between fast sliding surfaces in harsh environments (fluids, high pressure, heat), similar to the grinding process. Therefore their application is not limited to tools but also applicable for other rotating components such as bearings, gears and shafts in powertrains.

Tools with built-in thin film thermocouple sensors for monitoring cutting temperature

The ability to monitor in real time, the thermal activation and thermal impact to cutting tools has been very appealing to the manufacturing industries. Such responses can be measured with appropriate sensors such as thin film thermocouples (TFTs) built in cutting tools. The challenges have been to instrument the tool, equipment and sensors, which can withstand high stress and temperature in machining process. In this work, the sequence of fabricating the built-in TFTs and experimental setups are proposed and demonstrated. The cutting experiments are carried out under different cutting conditions for A6061-T6 aluminum alloy and finally cutting temperature is measured at very high cutting speeds up to 16 m/s.

DEVELOPMENT OF THIN-FILM THERMOCOUPLE FOR MEASUREMENT OF WORKPIECE TEMPERATURE IN CHEMICAL EXPLOSIVE MATERIAL MACHINING

In allusion to the features of cutting chemical ex- plosive material, a new type of fast response temperature sensor -NiCr/NiSi thin film thermocouple is developed, which integrates both cutting and temperature measuring functions. The NiCr/NiSi thin-films are plated directly inside a high speed steel cutter. A SiO2 insulating layer between the thin-films and high speed steel substrate is deposited by Microwave ECR Plasma source enhanced reactive RF magnetron sputtering for the first time. Static and dynamic calibrations for the thin-film thermocouple are carried out. It is concluded that the temperature sensor has good linearity and thermal stability within the temperature range and can response very fast. Its response time is only 0.8 ms. The NiCr/NiSi thin-film and insulating film are deposited onto the cutter strong enough. The thin-film thermocouple sensor is being used in China Academy of Engineering Physical, which provides efficient and safe production for war industry enterprise.

Thin film thermocouple arrays for sliding surface temperature measurement

Methods for measurement of sliding surface temperatures using thin film thermocouples (TFTCs) were developed and are described in this paper. Multi-junction copper–nickel TFTCs have been made using thin film deposition techniques. A thin hard dielectric coating was deposited on the TFTC for sensor protection. The thin film thermocouple sensors have been used to measure surface temperatures accurately in a variety of sliding contact situations including oscillatory sliding in a reciprocating seal configuration and unidirectional sliding in a rotary face seal configuration. Tests were run under liquid-lubricated as well as dry sliding conditions. In all of the tests, one of the test specimens (the moving one) was made from a thermoplastic polymer, ultra-high molecular weight polyethylene (UHMWPE). The surface temperature was measured during the tests at a number of points on the counterface, using an array of TFTCs. Correlation with analytical results was made and good agreement with theory was found. The total surface temperature measured in the tests has contributions from both flash (local) temperature rise and large-scale (nominal) temperature rise. The local surface temperature rise was found to be similar for both dry and liquid-lubricated cases, as long as the frictional heat input was the same. The nominal temperature rise was, however, considerably lower in the lubricated case owing to more efficient convective cooling.

Thin film thermocouple sensors for measurement of contact temperatures during slider asperity interaction on magnetic recording disks

Thin-film thermocouple sensors have been fabricated on a magnetic recording slider. Both the sensors and the reference junctions are located on the air bearing surface of the slider. The effective size of the junctions is 4 mu m, and response time is faster than 0.5 mu s. The sensitivity of these thermocouples is measured to be 7 mu V/ degrees C. The thermocouple signals obtained at the slider asperity contacts show a temperature rise of 1-5 degrees C. Incorporating the sensor dimensions and assuming asperities of 0.5 mu m width, the actual temperatures are estimated to be in the range of 90-450 degrees C.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>