【正文】 thermocouples shows good performance up to +2750 oC. They can be used, for a short period, in temperatures up to +3000 oC. The selection of the types of thermocouple used for low temperature sensing is primarily based on materials of a thermocouple. In addition, thermopower at low temperatue is 4 rather low, so measurement of EMF will be proportionally small as well. More Facts On Various Thermocouple Types A variety of thermocouples today cover a range of temperature from 250 oC to +3000 oC. The different types of thermocouple are given letter designations: B, E, J, K, R, S, T and N Types R,S and B are noble metal thermocouples that are used to measure high temperature. Within their temperature range, they can operate for a longer period of time under an oxidizing environment. Type S and type R thermocouples are made up of platinum (Pt) and rhodium (Rh) mixed in different ratios. A specific Pt/Rh ratio is used because it leads to more stable and reproducible measurements. Types S and R have an upper temperature limit of +1200 oC in oxidizing atmospheres, assuming a wire diameter of . Type S and type R thermocouples are made up of platinum (Pt) and rhodium (Rh) mixed in different ratios. A specific Pt/Rh ratio is used because it leads to more stable and reproducible measurements. Types S and R have an upper temperature limit of +1200 oC in oxidizing atmospheres, assuming a wire diameter of . Type B thermocouples have a different Pt/Rh ratio than Type S and R. It has an upper temperature limit of +1750 oC in oxidizing atmospheres. Due to an increased amount of rhodium content, type B thermocouples are no quite so stable as either the Type R or Type S. Types E, J, K, T, and N are basemetal thermocouples that are used for sensing lower temperatures. They cannot be used for sensing high temperatures because of their relatively low melting point and slower failure due to oxidation. Type B thermocouples have a different Pt/Rh ratio than Type S and R. It has an upper temperature limit of +1750 oC in oxidizing atmospheres. Due to an increased amount of rhodium content, type B thermocouples are no quite so stable as either the Type R or Type S. we will look into some differences between different basemetal thermocouples. Type E (NiCr/CuNi) thermocouples have an operating temperature range from 250 oC to +800 oC. Their use is less widespread than other basemetal 5 thermocouples due to its low operating temperature. However, measurements made by a Type E have a smaller margin of error. 1000 hours of operation in air of a Type E thermocouple at +760 oC, having 3mm wires, shold not lead to a change in EMF equivalent to more than +1 oC. Type J (Fe/CuNi) thermocouples are widely used in industry due to their high thermopower and low cost. This type of thermocouple has an operating temperature range from 0 oC to +760 oC. Links to Related Lessons Temperature Sensors Thermistors Thermocouples LM35s Other Sensors Strain Gages Temperature Sensor Laboratories Return to Table of Contents Experiments With Temperature Sensors Data Gathering Measuring temperature is the most mon measurement task. There are numerous devices available for measuring temperature. Many of them are built using one of these mon sensors. Thermistor Thermocouple LM35 Integrated Circuit Temperature Sensor You can get more information about these sensors by clicking the