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Many RTD elements consist of a length of fine wire wrapped around a heat-resistant ceramic or glass core but other constructions are also used. The RTD wire is a pure material, typically platinum (Pt), nickel (Ni), or copper (Cu). The material has an accurate resistance/temperature relationship which is used to provide an indication of temperature.
An RTD can be fabricated using many different types of materials (such as III–V, type IV, II–VI semiconductor) and different types of resonant tunneling structures, such as the heavily doped p–n junction in Esaki diodes, double barrier, triple barrier, quantum well, or quantum wire.
Thermowells are typically installed in piping systems and subject to both hydrostatic and aerodynamic forces. Vortex shedding is the dominant concern for thermowells in cross-flow applications and is capable of forcing the thermowell into resonance with the possibility of fatigue failure not only of the thermowell but also of the temperature sensor.
A pipe filled with hair restricts the flow of water more than a clean pipe of the same shape and size. Similarly, electrons can flow freely and easily through a copper wire, but cannot flow as easily through a steel wire of the same shape and size, and they essentially cannot flow at all through an insulator like rubber, regardless of its shape.
Four-point measurement of resistance between voltage sense connections 2 and 3. Current is supplied via force connections 1 and 4. In electrical engineering, four-terminal sensing (4T sensing), 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements ...
[4] [citation needed] This direct routing method has the advantage of reduced cost by allowing use of the shortest possible lengths of wire, but the major disadvantage is that a detailed building wiring diagram is needed for other electricians to understand multiple interwoven circuits, especially if the wiring is not fully visible throughout ...
Special wiring rules apply to wet or corrosive locations, [13] and to locations which present an explosion hazard. [14] Wiring materials for use in the United States must generally be made and tested to product standards set by NEMA and Underwriters Laboratories (UL) and must bear approval marks such as those set by UL.
Insulated wires may be run in one of several forms between electrical devices. This may be a specialised bendable pipe, called a conduit, or one of several varieties of metal (rigid steel or aluminium) or non-metallic (PVC or HDPE) tubing. Rectangular cross-section metal or PVC wire troughs (North America) or trunking (UK) may be used if many ...