Thermal properties thermocouples, power

Instruments based on the contact principle can further be divided into two classes mechanical thermometers and electrical thermometers. Mechanical thermometers are based on the thermal expansion of a gas, a liquid, or a solid material. They are simple, robust, and do not normally require power to operate. Electrical resistance thermometers utilize the connection between the electrical resistance and the sensor temperature. Thermocouples are based on the phenomenon, where a temperature-dependent voltage is created in a circuit of two different metals. Semiconductor thermometers have a diode or transistor probe, or a more advanced integrated circuit, where the voltage of the semiconductor junctions is temperature dependent. All electrical meters are easy to incorporate with modern data acquisition systems. A summary of contact thermometer properties is shown in Table 12.3. 

IR spectrometers have the same components as UY/visible, except the materials need to be specially selected for their transmission properties in the IR (e.g., NaCl prisms for the monochromators). The radiation source is simply an inert substance heated to about 1500 °C (e.g., the Nernst glower, which uses a cylinder composed of rare earth oxides). Detection is usually by a thermal detector, such as a simple thermocouple, or some similar device. Two-beam system instruments often work on the null principle, in which the power of the reference beam is mechanically attenuated by the gradual insertion of a wedge-shaped absorber inserted into the beam, until it matches the power in the sample beam. In a simple ( flatbed ) system with a chart recorder, the movement of the mechanical attenuator is directly linked to the chart recorder. The output spectrum is essentially a record of the degree of... 

Thermoelectric Properties. Tables 3.1-206-3.1-209 [1.216,217] and Figs. 3.1-269, 3.1-270 [1.216,218] give data of absolute thermoelectric power, thermal electromotive force of pure Pd and Pd alloys at different tenqreratures. Special alloys for thermocouples with high corrosion resistance are shown in Table 3.1-210 [1.217]. 

Armed with this knowledge a set of boundary conditions was proposed which offered more hope of success. Results using these from a new set of calculation showed that, althou the test objectives were achievable, uncertainties m shroud properties would necessitate on line control of the power driven to the bundle. This control is based on the temperature measurements inside the bun e with thermocouples and ultrasonic thermometers and, after failure of these components, on estimated temperatures deduced from the shroud temperatures. Hi humidities in the containment were shown to be difficult to achieve without extensive thermal hydraulic testing of the containment vessel so it was dedded to aim for a lower humidity in this... 

---