Thermocouple Reference     RELATED PAGES: Temperature Sensors Thermocouple Wire Color Codes Color codes have been adopted by various national and international standard agencies for identification of thermocouple wire and thermocouple products. In the United States, thermocouple-grade wire normally has a brown overall jacket. For Types B, R and S, the color codes relate to the compensating cable normally used. Type United States ANSI 96.1 United Kingdom BS 1843 West Germany DIN 43714 France NF C42-323 Japan JIS C1610-1981 E Purple    + Purple – Red Brown    + Brown – Blue Black    + Red – Black – Purple    + Red – White J Black   + White – Red Black    + Yellow – Blue Blue    + Red – Blue Black    + Yellow – Black Yellow    + Red – White K Yellow   + Yellow – Red Red    + Brown – Blue Green    + Red – Green Yellow    + Yellow – Purple Blue    + Red – White N Orange   + Orange – Red – – – – B Grey   + Grey – Red – Grey    + Grey – Red – Grey   + Red – White R Green   + Black – Red Green    + White – Blue – – Black   + Red – White S Green   + Black – Red Green    + White – Blue White   + Red – White Green    + Yellow – Green Black    + Red – White T Blue   + Blue – Red Blue    + White – Blue Brown   + Red – Brown Blue    + Yellow – Blue Brown    + Red – White Thermocouple Reference Type J K T Material Iron (+) vs. Constantan (-) Nickel (10%) Chromium (+) vs. Nickel (5%) Aluminum Silicon (-) Copper (+) vs. Constantan (-) Temperature Range 0°C to 760°C 0°C to 1370°C -160°C to 400°C Comparison of Temperature Transducers Type Thermocouple RTD Thermistor Advantages • Self-powered • Simple, rugged • Lower cost • Wide temperature range • Most stable • Most accurate • Better linearity • High output • Fast Disadvantages • Nonlinear • Low voltage • Least stable • Least sensitive • Reference required • Expensive • Current source required • Small resistance change • Low absolute resistance • Self-heating • Nonlinear • Limited temperature range • Fragile • Current source required • Self-heating Time Contraints The time constant of any sensor is defined as the time required for that sensor to respond to 63.2% of its total output signal when subjected to a step change. The step change can be either an increase or decrease in the parameter being measured. Five constants are required for a sensor to reach 99% of its total change. The graph to the right illustrates this relationship. Time Constant of Exposed Thermocouples Time Constant as a Function of Wire Size for Exposed Wire Thermocouples in Air T=200°F Radiation Error of Exposed Thermocouples Radiation Error as a Function of Wire Sizes for Thermocouples in Air at 2000°F, at 1 Atmosphere and Mach 0.3 [Top of page | Reference | Thermocouples]

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