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A History of Thermology and Thermography
Published in James Stewart Campbell, M. Nathaniel Mead, Human Medical Thermography, 2023
James Stewart Campbell, M. Nathaniel Mead
Development of sensitive and accurate contact-free detectors of the infrared radiation emitted by the body was needed. The first breakthrough came from the discovery of the thermoelectric effect by Thomas Johann Seebeck in 1821. Seebeck showed that a small electric current will flow between different conductive materials (i.e., a closed circuit of two dissimilar metallic conductors) if the two junctions are kept at different temperatures. This discovery helped bring about the discovery of the thermocouple in 1829 by the Italian physicist Leopoldo Nobili. The thermocouple is a temperature sensor formed by the electrical junction of two dissimilar metals, which generates a temperature-dependent voltage. Any change in this voltage is directly proportional to the temperature of the junction as long as the reference end of the two conductors is held at a fixed reference temperature.
Servo Feedback Devices and Motor Sensors
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
Thermocouples are known for their versatility, lack of required excitation, simple structure, long-term stability, and low cost. Some disadvantages of thermocouples are: (a) Since the magnitude of the Seebeck voltage is of the order of a few μV, precise amplifiers are often required to amplify the magnitude of the output voltage. (b) Thermocouples are susceptible to external noise. When measuring microvolt-level signal changes, noise from stray electrical and magnetic fields can be a problem. (c) The outputs of thermocouples are not linearly proportional to any temperature scale. They require linearization or linearity calibration. (d) Because thermocouples are made from two dissimilar metals, in harsh environments corrosion may occur after long time services.
Temperature Measurements
Published in James Agalloco, Phil DeSantis, Anthony Grilli, Anthony Pavell, Handbook of Validation in Pharmaceutical Processes, 2021
Clarence A. Kemper, Göran S. Bringert
A thermocouple is a simple, versatile temperature sensor constructed by joining two wires of different composition to form a “thermocouple junction”. When a thermocouple is connected to a well-designed reference and measuring system, the indicated output is a unique function of the junction temperature. It will be shown that the total output of a thermocouple circuit is not a sensor characteristic, however, so the entire measuring system must be considered in a proper calibration procedure.
Thermal Design and Experimental Verification of Double Helium Gap Conduction Test Facility
Published in Nuclear Science and Engineering, 2021
Hongyi Yang, Song Li, Zhiwei Zhou
The main body of the gap heat transfer device is composed of an electric heating element, a three-layer heat transfer sleeve, a mounting flange, a supporting base, and a water circuit sleeve. The structure of the device is shown in Fig. 5. There are two-layer helium gaps among three layers of sleeves. The innermost heat transfer sleeve is made of pure copper, and the other two layers are austenitic stainless steel. The inner and middle sleeves can be replaced in order to carry out the helium transfer test under different conditions. The specific parameters of the sleeves in this test are shown in Table I. The inner and outer sides of the copper inner sleeve, the middle sleeve, and the outer sleeve are slotted symmetrically, and eight armored thermocouples are inserted to monitor the helium gap temperature. The measurement range of the thermocouple is 0°C to 800°C. The overall size of the gap heat transfer device is Φ190 × 610 mm, which is sealed mainly by the bearing seat and the mounting flange of the O-ring and sealant seal. The helium pressure is 0.1 MPa (at room temperature), and the maximum pressure is not more than 0.3 MPa. The highest heating power of the rod is 3.04 kW while the maximum line power density is 26 kW/m. The maximum temperature of the heat component is designed to not exceed 800°C. The flow rate of the cooling water in the heating section is 0.4 to 0.6 m/s, and the inlet cooling water temperature is about 20°C.
Environmental impact of VCR diesel engine characteristics using blends of cottonseed oil with nano additives
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
S. Ganesan, S. Padmanabhan, S. Mahalingam, C. Shanjeevi
Experimental investigation of biodiesel on performance and emission characteristics was conducted in Kirloskar VCR engine setup with 3.5 kW at a constant 1500 rpm as shown in Figure 2. The detailed specification given in Table 4. Two separate fuel tanks with a fuel switching system are used, one for diesel and the other for cottonseed biodiesel. The eddy current dynamometer coupled with the engine and engine torque controlled through the computer. Eddy current dynamometer controller used to control the engine speed and load by varying excitation current on dynamometer. Combustion pressure was measured by a piezoelectric pressure transducer installed in the engine cylinder head. A precise crank angle encoder was used to measure the crank angle and piston positions. An AVL exhaust di-gas analyzer and AVL smoke meter were used to measure emission parameters and smoke intensity, respectively. Thermocouples are used to measure coolant temperature, exhaust temperature, and inlet air temperature.
Wearable electronic textiles
Published in Textile Progress, 2019
David Tyler, Jane Wood, Tasneem Sabir, Chloe McDonnell, Abu Sadat Muhammad Sayem, Nick Whittaker
Traditional mercury or alcohol-based thermometers are not fit-for-purpose for being attached to garments to measure temperature, whereas thermocouples are capable of being integrated within textiles or developed directly on the surface of textile materials [128] for detecting biothermal signals. In principle, a thermocouple includes conductive materials that can detect voltage difference caused by temperature difference on a surface. As discussed in the previous section, it is technologically possible to impart conductivity on textile surfaces, and thermocouples can be developed on and within textile substrates by integrating fine metal yarn into the fabric structure by weaving [129], entrapping metal wires between fabric layers [130], forming thin film of metal on textile surface by magnetron sputter deposition [131] or by printing the textile surface with conductive materials [132]. Commercial products such as Siren diabetic socks (Siren Care, San Francisco, CA, USA) use a thermal micro-sensor embedded into fabric to monitor temperature changes at the lower side of the feet of diabetic patients [133].