What is a thermocouple?
Thermocouples are used in many industrial, scientific, applications. They can be found in nearly all industrial markets: Power Generation, Mining, Oil/Gas, Pharmaceutical, Biotech, Cement, Paper, Glass, and many more. Thermocouples are also used in everyday appliances like stoves, furnaces, kilns, and pizza ovens. Thermocouples are typically selected because of their low cost, high-temperature limits, wide temperature ranges, and durable nature. When it comes to choosing the right one, it is all about the research and your manufacture’s knowledge. The correct temperature of any element is crucial for the manufacturing of all temperature related products.
Thermocouples are designed to measure temperature; they are an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage which is interpreted to measure temperature. Commercial thermocouples are inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In contrast to most other methods of temperature measurement, thermocouples are self-powered and require no external form of excitation
Thermocouple Type R: Types R thermocouples, (Platinum vs. 13% Rhodium/Platinum), are usable up to 1480°C (2,700°F).
They are extremely stable but reducing atmospheres are particularly damaging. This type should be protected with a gas-tight ceramic tube and a secondary tube of alumina, aluminous porcelain, silicon carbide, or metal outer tube, as conditions require. Type R can deliver 15 percent more millivolt than Type S.
Thermocouples using noble metals are commonly employed in high temperature measurement and control, particularly for temperatures of 1093°C (2000°F) and higher. Type R thermocouples cover similar applications as Type S, but offer improved stability and a marginal increase in range. Consequently, Type R tends to be used in preference to Type S.
In general, thermocouples employing platinum in combination with platinum-rhodium alloys, gold, or palladium, have been found to be the most reproducible of all the various types. They are resistant to oxidation in air and, because of their high melting points, can be used up to very high temperatures.
Some typical applications for type R are: heat treating and control sensors, semiconductor industry, glass manufacturing, ferrous and non-ferrous metals.
Noble metal sensors are very costly. Elemental hydrogen, sulphur, and some other atomic contaminants must be excluded from type R. If these contaminants are not totally excluded, then significant calibration drift, embrittlement, and failure of the thermocouple wire will occur. In addition, certain elements act as catalysts and must also be excluded from the vicinity of the thermocouple wires.
Low sensitivity and high cost makes them unsuitable for general purpose use.
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