Thermocouple Catalog (North America) - English - Pyrotek

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GENERAL TECHNICAL REFERENCES AND TABLES LETTER OF CALIBRATION Thermocouples are classified by calibration type because they have differing EMF (electromotive force) versus temperature curves. Some generate considerably more voltage at lower temperatures, while others do not begin to develop a significant voltage until subjected to high temperatures. Calibration types are designed to deliver as close to a straight line voltage curve inside their temperature application range as possible. This makes it easier for an instrument or temperature controller to correctly correlate the received voltage to a particular temperature. 80 Thermocouple Millivolts / Temperature Curves 70 60 50 J K N Millivolts 40 30 20 R S B 10 0 0 1000 2000 3000 4000 5000 Temperature (°F) BASE METAL TYPES Type K Type K is used extensively at temperatures up to 2300°F (1260°C). This type works in most applications since they are nickel based and have good corrosion resistance. It is the most common sensor calibration type providing the widest operating temperature range. Type N This nickel based thermocouple alloy is used primarily at high temperatures up to 2300°F (1260°C). While not a direct replacement for Type K, Type N provides better resistance to oxidation at high temperatures and longer life in applications where sulfur is present. Type J The Type J may be used, exposed or unexposed, where there is a deficiency of free oxygen. For cleanliness and longer life, a protecting tube is recommended. Since JP (iron) wire will oxidize rapidly at temperatures over 1000°F (540°C), it is recommended that larger gauge wires be used to compensate. Maximum recommended operating temperature is 1400°F (760°C). Type J is the second most common calibration and a good choice for general purpose applications where moisture is not present. NOBLE METAL TYPES Types S, R, B Maximum recommended operating temperature for Type S or R is 2640°F (1450°C). Type B is recommended for use as high as 3100°F (1700°C). These thermocouples are easily contaminated. 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. PYROTEK INC. Page Revision: OCT-13-EL-1128 www.pyrotek.info/thermocouples • email: info@pyrotek.info Page 34
GENERAL TECHNICAL REFERENCES AND TABLES TABLE 1 - TOLERANCES ON INITIAL VALUES OF EMF VS TEMPERATURE FOR THERMOCOUPLES NOTE 1: Tolerances in this table apply to new essentially homogeneous thermocouple wire, normally in the size range 0.25 to 3 mm in diameter (No. 30 to No. 8 AWG) and used at temperatures not exceeding the recommended limits of Table 2. If used at higher temperatures these tolerances may not apply. NOTE 2: At a given temperature that is expressed in °C, the tolerance expressed in °F is 1.8 times larger than the tolerance expressed in °C. Note that wherever applicable, percentage-based tolerances must be computed from temperatures that are expressed in °C. NOTE 3: CAUTION—Users should be aware that certain characteristics of thermocouple materials, including the EMF versus temperature relationship may change with time in use. Consequently, test results and performance obtained at time of manufacture may not necessarily apply throughout an extended period of use. Tolerances given in this table apply only to new wire as delivered to the user and does not allow for changes in characteristics with use. The magnitude of such changes will depend on such factors as wire size, temperature, time of exposure and environment. It should be further noted that due to possible changes in homogeneity, attempting to recalibrate used thermocouples is likely to yield irrelevant results, and is not recommended. However, it may be appropriate to compare used thermocouples in-situ with new or known good ones to ascertain their suitability for further service under the conditions of the comparison. THERMOCOUPLE TYPE T J E K or N R or S B TEMPERATURE RANGE °F °C 32 to 700 32 to 1400 32 to 1600 32 to 2300 32 to 2700 1600 to 3100 0 to 370 0 to 760 0 to 870 0 to 1260 0 to 1480 870 to 1700 TOLERANCES-REFERENCE JUNCTION 32°F (0°C) Standard Tolerances °F °C (whichever is greater) Note 2 ±1 or ±0.75% ±2.2 or ±0.75% ±1.7 or ±0.5% ±2.2 or ±0.75% ±1.5 or ±0.25% ±0.5% C 32 to 4200 0 to 2315 Note 2 ±4.4 or 1% -328 to 32 T A K A -328 to 32 E A -328 to 32 -200 to 0 -200 to 0 -200 to 0 ±1 or ±1.5% ±1.7 or ±1% ±2.2 or ±2% Special Tolerances °F °C (whichever is greater) Note 2 ±0.5 or 0.4% ±1.1 or ±0.4% ±1 or ±0.4 ±1.1 or ±0.4% ±0.6 or ±0.1% ±0.25% A Thermocouples and thermocouple materials are normally supplied to meet the tolerances specified in the table for temperatures above 0°C. The same materials, however, may not fall within the tolerances given for temperatures below °C in the second section of the table. If materials are required to meet the tolerances stated for temperatures below 0°C the purchase order must so state. Selection of materials usually will be required. B Special tolerances for temperatures below 0°C are difficult to justify due to limited available information. However, the following values for Types E and T thermocouples are suggested as a guide for discussion between purchaser and supplier. Type E: - 200 to 0°C ± 1°C or ± 0.5% (whichever is greater) Type T: - 200 to 0°C ± 0.5°C or ± 0.8% (whichever is greater) Initial values of tolerance for Type J thermocouples at temperatures below 0°C and special tolerances for Type K thermocouples below 0°C are not given due to the characteristics of the materials. B B B PYROTEK INC. Page Revision: OCT-13-EL-1128 www.pyrotek.info/thermocouples • email: info@pyrotek.info Page 35
Page 2 and 3: Table of Contents Introduction.....
Page 4 and 5: SELECTION GUIDE FOR ALUMINIUM SMELT
Page 6 and 7: I1 SERIES - BASE METAL AND NOBLE ME
Page 8 and 9: IP SERIES - METAL ALLOY PROTECTION
Page 10 and 11: I3 SERIES - ANGLE BASE METAL TC OR
Page 12 and 13: I5 SERIES - STRAIGHT MgO, BASE META
Page 18 and 19: T1 SERIES - THERMOCOUPLE PROTECTION
Page 20 and 21: M1 SERIES - MINERAL INSULATED THERM
Page 22 and 23: M3 SERIES - MINERAL INSULATED ELEME
Page 24 and 25: P1 SERIES - GENERAL APPLICATION DIE
Page 26 and 27: P3 SERIES - ARMOR ADJUSTABLE BAYONE
Page 28 and 29: A1 SERIES - THERMOCOUPLE ACCESSORIE
Page 30 and 31: THERMOCOUPLE PROTECTION TUBES Plain
Page 32 and 33: THERMOCOUPLE PROTECTION TUBES Clay
Page 36 and 37: GENERAL TECHNICAL REFERENCES AND TA
Page 44 and 45: GLOSSARY OF TERMS Fahrenheit Scale:
Page 46: Our mission is to provide innovativ

Thermocouple Catalog (North America) - English - Pyrotek

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