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Miscellaneous Sensors
Published in Clarence W. de Silva, Sensor Systems, 2016
The presence of any other junctions, such as the ones formed by the wiring to the voltage sensor, does not affect the reading as long as these leads are maintained at the same temperature. Very low temperatures (e.g., −250°C) as well as very high temperatures (e.g., 3000°C) can be measured using a thermocouple. Since the temperature–voltage relationship is nonlinear, a correction has to be made when measuring changes in temperature; usually by using polynomial relations. The thermocouple sensitivity is about 0.1 mV/°C and depends on the metal pair. Typically, signal conditioning will be needed before using the sensor signal. The thermocouple “type” is based on the metal pair that is used, for example, Type E (chromel–constantan), Type J (iron–constantan), Type K (chromel–alumel), Type N (nicrosil–nisil), and Type T (copper–constantan). Of these, Type E has the highest sensitivity (70 μV/°C). Fast measurements are possible with miniature thermocouples having low time constants (e.g., 1 ms). Important considerations in selecting a thermocouple (or any temperature sensor) include (1) temperature range, (2) sensitivity, (3) speed (time constant), (4) robustness (to vibration, and to environment including chemicals), and (5) ease of use (installation, etc.).
Thermoelectric Phenomena
Published in Daniel D. Pollock, PHYSICAL PROPERTIES of MATERIALS for ENGINEERS 2ND EDITION, 2020
The ASC of Nicrosil (Type NP) is similar to that of Type KP alloys. The smaller thermoelectric deviations of Type NP alloys (TN ≅ 600 K, TP ≅ 773 K), compared to those of Type KP alloys, result from its higher chromium content (15.2 At% vs. 10.3 At%). The ASC of Nisil (Type NN) (TFN ≅ 290 K, TP ≅ 573 K) is more linear than that of Type NP alloys as a result of its high silicon content. The relatively large difference in the ASCs of these materials causes the RSC of Type N thermocouples to be smaller and more nonlinear than Type K thermocouples (Section 9.6, Sections 8.3.4 and 8.3.6).3
Examination of Transmutation Effect on Responses of K-Type and N-Type Thermocouples at Fusion Blanket
Published in Fusion Science and Technology, 2019
Teruya Tanaka, Hiroyuki Noto, Fuminobu Sato, Yoshimitsu Hishinuma, Hiroyuki A. Sakaue, Masahito Yoshino
Nuclear transmutation in sensor wires used for K-type thermocouples (chromel, alumel) and N-type thermocouples (Nicrosil, Nisil) was calculated using the FISPACT-2005 transmutation calculation code.5 In the FISPACT calculation, all natural isotopes in a material are input, and all possible production and decay of isotopes during neutron irradiation are calculated for a given neutron spectrum. Assuming the blanket modules are replaced when irradiation damage of the structaural material reaches 100 displacements per atom (dpa), the replacement would be required every ~7 years. On the other hand, the radiation shield is considered as a permanent component used for the lifetime of a reactor, i.e., 30 to 40 years. The fast neutron fluence of >0.1 MeV is calculated to be 9.3 × 1022 n/cm2 in 7-year use at the first wall and 5.0 × 1022 n/cm2 in 40-year use at the front surface of the radiation shield.
Quantitative volumetric identification of precipitates in dilute alloys using high-precision isothermal dilatometry
Published in Philosophical Magazine Letters, 2018
E. Hengge, R. Enzinger, M. Luckabauer, W. Sprengel, R. Würschum
The measurements were performed in a self-developed, high-stability laser dilatometer, the design and operation of which is described in detail elsewhere [10]. Chemical analysis of the EN AW-6060 Al–Mg–Si alloy by means of optical emission spectroscopy revealed a Mg- and Si-content of 0.65 at.% and 0.52 at.%, respectively, with additional traces of primarily Fe (0.11 at.%). For the dilatometric measurements cylindrical-shaped samples with a length of 20 mm and a diameter of 5.7 mm were used. Solution annealing was performed in the dilatometer at 540°C for 30 min with subsequent quenching down to 32°C in a helium gas stream with a rate sufficiently high for achieving a supersaturated solid solution [12]. After keeping the sample for 4 min at this temperature, heating up to the temperature of isothermal precipitation treatment between 170°C and 260°C was performed with a rate of 100°C/min. As onset for the isothermal length change measurements the time was chosen when the temperature approached the final temperature by C; the dead time up to the onset is in the range of 100 s. The temperature was measured by means of Nicrosil-Nisil thermocouple directly welded to the sample under Ar atmosphere. Prior to the experiments, the sample was annealed at 540°C for 24 hours to obtain a fully recrystallised microstructure in order to exclude any influence of grain boundaries on the length change measurements. For comparison with precipation studies in literature, standard characterisation of the progress of precipation by means of hardness measurements was performed, applying the Brinell method with a hardness tester (type EMCO-TEST DuraJet).
Optimization of heat treatment and calibration procedures for high temperature irradiation resistant thermocouples
Published in Instrumentation Science & Technology, 2018
Richard Skifton, Joe Palmer, Pattrick Calderoni
The HTIR-TCs, as in times past, have shown robust performance when compared to other thermocouples.[11] The signal is responsive and accurate in the temperature range between 400 and 1600°C. This can be seen in Figure 4 when compared to TC Types B, S, R, and N. The different comparison thermocouple types presented here are common industry standards with the Type B, Type S, and Type R TCs comprising of thermoelements that are Platinum-based with varying degrees of a Platinum–Rhodium alloy, and the Type N TC comprising of nickel based thermoelements (i.e., Nicrosil and Nisil).