Thermocouple

About: Thermocouple is a research topic. Over the lifetime, 12244 publications have been published within this topic receiving 93172 citations. The topic is also known as: thermal junction & thermoelectric thermometer.

Kinetic Parameters from Thermogravimetric Data

Abstract: THE use of thermogravimetric data to evaluate kinetic parameters of solid-state reactions involving weight loss (or gain) has been investigated by a number of workers1–4. Freeman and Carroll2 have stated some of the advantages of this method over conventional isothermal studies. To these reasons may be added the advantage of using one single sample for investigation. However, the importance of procedural details, such as crucible geometry, heating rate, pre-history of sample, and particle size, on the parameters has yet to be fully investigated. It is also necessary to ensure accurate temperature measurement, both for precision and also to detect any departure from a linear heating rate due to endo- or exo-thermic reactions. (The effect of these may be largely eliminated by the use of small samples.) In our present work (using a Stanton HT–D thermobalance) the sample temperature is measured directly by means of a thermocouple the bead of which is positioned in or near the sample, depending on crucible design, the wires of which run down a twin-bore rise rod. The connexion between the end of the thermocouple wires on the balance arm and the terminal block is made by 0.001 in. platinum and platinum/rhodium wires5. It has been shown that these wires do not affect the performance of the balance but act merely as a subsidiary damping. From the terminal block compensated cable leads to the cold junction and a potentiometric arrangement for direct measurement of the thermocouple output.

Observation of the spin Seebeck effect

Abstract: The generation of electric voltage by placing a conductor in a temperature gradient is called the Seebeck effect. Its efficiency is represented by the Seebeck coefficient, S, which is defined as the ratio of the generated electric voltage to the temperature difference, and is determined by the scattering rate and the density of the conduction electrons. The effect can be exploited, for example, in thermal electric-power generators and for temperature sensing, by connecting two conductors with different Seebeck coefficients, a device called a thermocouple. Here we report the observation of the thermal generation of driving power, or voltage, for electron spin: the spin Seebeck effect. Using a recently developed spin-detection technique that involves the spin Hall effect, we measure the spin voltage generated from a temperature gradient in a metallic magnet. This thermally induced spin voltage persists even at distances far from the sample ends, and spins can be extracted from every position on the magnet simply by attaching a metal. The spin Seebeck effect observed here is directly applicable to the production of spin-voltage generators, which are crucial for driving spintronic devices. The spin Seebeck effect allows us to pass a pure spin current, a flow of electron spins without electric currents, over a long distance. These innovative capabilities will invigorate spintronics research.

Eine einfache Technik der extrem schnellen Abkühlung größerer Gewebestücke

Abstract: 1. A pair of tongs was designed the mouth of which consists of two blocks of a metal of high thermal conductivity (aluminum). Prior to use the metal is cooled in liquid air or nitrogen. With this tool large tissue pieces and whole organs of animals can be compressed in situ to a thin layer and can thus be frozen in a fraction of a second. The fall in temperature was measured with a thermocouple and was recorded with a loop oscillograph. Measurements of the cooling velocity in liquid air and in isopentane of −150°C were carried out for comparison. 2. The cooling process in the compressed tissue was analyzed with the aid of the theory of heat conduction, and the heat conduction equation holding for the present system was derived. It yields values for velocity of cooling which agree well with the experimental data in the temperature range 38°2-0°C. The cause of the deviation at lower temperatures is discussed. 3. Instructions are given for the estimation of the time required to cool down the central layer of the tissue held in the tongs to any specified temperature.

Thermoelectric Materials: New Approaches to an Old Problem

Abstract: Thermoelectrics is an old field. In 1823, Thomas Seebeck discovered that a voltage drop appears across a sample that has a temperature gradient. This phenomenon provided the basis for thermocouples used for measuring temperature and for thermoelectric power generators. In 1838, Heinrich Lenz placed a drop of water on the junction of metal wires made of bismuth and antimony. Passing an electric current through the junction in one direction caused the water to freeze, and reversing the current caused the ice to quickly melt; thus thermoelectric refrigeration was demonstrated (figure 1).