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GeneralInformation

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Type E

What letter of calibrationshould I use?

The Type E thermocouple is suitablefor use at temperatures up to 900°C(1650°F) in a vacuum, inert, mildlyoxidizing or reducing atmosphere. At cryogenic temperatures, thethermocouple is not subject to corrosion. Thisthermocouple has the highest EMF output per degree of allthe commonly used thermocouples. Type K thermocouples usually workin most applications since they arenickel based and have goodcorrosion resistance. It is the mostcommon sensor calibration type providing the widest operating temperature range. Type J Type J is the second most commoncalibration and a good choice forgeneral purpose applications wheremoisture is not present. The Type J may be used, exposed orunexposed, where there is a deficien-cy of free oxygen. For cleanliness andlonger life, a protecting tubeis recom-mended. Since JP (iron) wire willoxidize rapidly at temperatures over540°C (1000°F), it is recommended thatlarger gauge wires be used tocompensate.Maximum recom- mended operating temperature is760°C (1400°F). Type K Due to its reliability and accuracy,Type K is used extensively at tem-peratures up to 1260°C (2300°F). It’sgood practice to protect this type ofthermocouple with a suitable metal or ceramic protecting tube, especially inreducing atmospheres. In oxidizingatmospheres, such as electricfurnaces,tube protection is notalways necessarywhen otherconditions are suitable;however, it isrecommended for cleanliness andgeneral mechanical protection.Type Kwill generally outlast Type J because the JP (iron) wire rapidly oxidizes,especially at higher temperatures. Type N This nickel-based thermocouplealloy isused primarily at high temperatures up to 1260°C (2300°F). While not a direct replacement for Type K, Type N provides better resistance tooxidation at high temperatures and longer life in applications wheresulfur is present. It also outperforms Type K in K’s aging range. Type T This thermocouple can be used ineither oxidizing or reducing atmos-pheres, though for longer life, aprotecting tube is recommended.Because of its stability at lowertemperatures, this is a superiorthermocouple for a wide variety ofapplications in lowand cryogenictemperatures. It’s recommendedoperating range is -200°to 350°C (-330°to 660°F), but it can be usedto -269°C (-452°F) (boiling helium). Types S, R and B Maximum recommended operatingtemperature for Type S or R is1450°C (2640°F); Type B isrecommended for use at as high as 1700°C (3100°F). These thermo-couples are easily contaminated. Reducing atmospheres areparticularlydamaging to the cali-bration. Noble metal thermocouples should always be protected with a gas-tight ceramic tube, a secondary tube of porcelain, and a silicon carbide or metal outer tube as conditions require. Type C (W-5 Percent Re/W-26Percent Re) This refractory metal thermocouplemay be used at temperatures up to2315°C (4200°F). Because it has noresistanceto oxidation, its use is restricted to vacuum, hydrogen orinert atmospheres. 16