HOW TO DETERMINE TEMPERATURE BY MEASURING THE OUTPUT MILLIVOLTAGE OF A THERMOCOUPLE SHREVEPORT ENGINEERING DEPARTMENT DOCUMENT

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1 Page 1 of 41 HOW TO DETERMINE TEMPERATURE BY MEASURING THE OUTPUT MILLIVOLTAGE OF A THERMOCOUPLE SHREVEPORT ENGINEERING DEPARTMENT DOCUMENT THERMOCOUPLE REFERENCE TABLES The N.I.S.T. (National Institute of Standards and Technology) is the U.S. standards setting agency. They have determined the output millivoltage of all type thermocouples, at all temperatures, within their range. The resulting tabulations are called Thermocouple Reference Tables and the thermocouple output millivoltage is shown for each degree of temperature. Tables based on both C and F are provided in this document for each type thermocouple commonly made by Delta Controls. The junction of each type thermocouple produces a specific millivoltage across it at a specific temperature. A thermocouple consists of two junctions connected in opposition. One is the measuring junction and the other is the reference junction. V D is the millivoltage resulting from the difference between the millivoltages generated by the two opposing junctions. V D is the millivoltage read when a meter is connected across the thermocouple as shown below. MEASURED TEMPERATURE REFERENCE TEMPERATURE MEASURING JUNCTION THERMOCOUPLE + VM - IM IR LEADWIRE + 1 VD MILLIVOLT METER (MEASURES VD AT REFERENCE JUNCTION) REFERENCE JUNCTION (USUALLY AT OR NEAR AMBIENT TEMPERATURE) HOW TO DETERMINE THE MEASURING JUNCTION TEMPERATURE (1) Measure the V D millivoltage as shown above. (2) Measure the actual temperature of the reference junction with a thermometer. (3) Go to the table for the thermocouple being used and look up the millivoltage produced at that temperature. (4) Add that millivoltage to the millivoltage measured as V D to get a total. (5) Find that millivoltage total in the reference table. The corresponding temperature is the temperature of the measuring junction. Example #1 Type T Thermocouple Measured V D = 3.41 mv Reference Junction Temperature = 22 C (71.6 F) (1) From the table: 22 C = 0.87 mv. (2) Adding 0.87 mv to 3.41 mv = 4.28 mv. (3) Finding 4.28 mv In the table, the corresponding temperature is 100 C (212 F) and is the temperature of the measuring junction. Example #2 Type T Thermocouple Measured V D = 4.47 mv Reference Junction Temperature = -5 C (23 F) (lower than the table reference of 0 C) (1) From the table; 5 C = mv (2) Adding mv to mv = mv (3) Finding 4.28 mv In the table; the corresponding temperature is 100 C (212 F) and is the temperature of the measuring junction Metric/English Scale Conversion C = F F = 1.8 C + 32

2 Page 2 of 41 ANSI & ITS-90 THERMOCOUPLES USABLE MEETING POINT ANSI TEMPERATURE LEG METALLIC COMPOSITION LETTER RANGE (LONG TERM) P PLATINUM + 30% RHODIUM 400 TO 3050 F B N PLATIMUM + 6% RHODIUM 200 TO 1680 C P (TUNGSTEN + 5% RHENIUM) 30 TO 4200 F C * N (TUNGSTEN + 26% RHENIUM) 0 TO 2300 C P CHROMEL, -300 TO 850 F E N CONSTANTAN -200 TO +450 C P IRON 30 TO 700 F J N CONSTANTAN 0 TO 400 C P CHROMEL, -300 TO 1800 F K N ALUMEL, -200 TO 1000 C P NICROSIL 30 TO 1800 F N N NISIL 0 TO 1000 C P PLATINUM + 13% RHODIUM 400 TO 2700 F R N PURE PLATINUM 200 TO 1500 C P PLATINUM + 10% RHODIUM 400 TO 2700 F S N PURE PLATINUM 200 TO 1500 C P COPPER -450 TO 400 F T N CONSTANTAN, -270 TO 200 C * Not an ANSI symbol, but is commonly used as a designated name; also sometimes referred to as a Type W. Trademark of Hoskins Mfg P=Positive Leg N = Negative Leg TOLERANCES (THE GREATER OF BASE OR PERCENT READING) F C ** STANDARD PREMIUM REFERENCE TABLE PAGE 0.5% NOT SET 3 NOT ESTABLISHED 1.7 C OR 0.5% 2.2 C OR 0.75% 2.2 C OR 0.75% 2.2 C OR 0.75% 1.5 C OR 0.25% 1.5 C OR 0.25% 1.0 OR 0.75% N.A C OR 0.4% 1.1 C OR 0.4% 1.1 C OR 0.4% 1.1 C OR 0.4% 0.6 C OR 0.1% 0.6 C OR 0.1% 0.5 C OR 0.4% ** Standard grade wire is sufficiently accurate for most applications. The purity and composition of premium grade wire is more closely controlled, and its millivoltage output is closer to the NIST standard chart and therefore reads somewhat more accurately than the standard grade does. NOTE: Individual T/C units may be calibrated by measuring their output at several known temperatures and preparing an error correction chart. This chart is used to eliminate any deviation from the standard output millivoltage versus temperature readings inherent in this particular thermocouple. The result is known as an NIST traceable thermocouple. N.A. N.A. 20 N.A MAXIMUM RANGES OF STANDARDIZED THERMOCOUPLE TYPES (EACH WIRE IS MADE OF A PARTICULAR ELEMENT OR METALLIC ALLOY) *SHORT TERM ONLY! See Table Above for Usable Ranges When Put Into Claus Reactor and Industrial Process Services

3 Page 3 of 41 In accordance with Reference Table for Type B Thermocouples

4 Page 4 of 41 Reference Table for Type B Thermocouples

5 Page 5 of 41 Reference Table for Type B Thermocouples

6 Page 6 of 41 Reference Table for Type B Thermocouples

7 Page 7 of 41 Reference Table for Type B Thermocouples

8 Page 8 of 41 In accordance with Reference Table for Type R Thermocouples C

9 Page 9 of 41 Reference Table for Type R Thermocouples

10 Page 10 of 41 Reference Table for Type R Thermocouples

11 Page 11 of 41 Reference Table for Type R Thermocouples

12 Page 12 of 41 Reference Table for Type R Thermocouples

13 Page 13 of 41 In accordance with Reference Table for Type S Thermocouples C Reference Table for Type S Thermocouples

14 Page 14 of

15 Page 15 of 41 Reference Table for Type S Thermocouples

16 Page 16 of 41 Reference Table for Type S Thermocouples

17 Page 17 of 41 Reference Table for Type S Thermocouples

18 Page 18 of 41 In accordance with Reference Table for Type T Thermocouples C

19 Page 19 of 41 Reference Table for Type T Thermocouples

Temperature Sensing MI Cable Thermocouple Assemblies. Series TCM Multipoint Thermocouple Assemblies. View Product

Temperature Sensing MI Cable Thermocouple Assemblies. Series TCM Multipoint Thermocouple Assemblies. View Product Series TCM Multipoint Thermocouple Assemblies Multipoint Thermocouples are used in a broad range of processes and installations to monitor the temperature in multiple positions or elevations. These sensors