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Thermocouple Reference

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.

TypeUnited States ANSI 96.1United Kingdom BS 1843West Germany DIN 43714France NF C42-323Japan 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 Wire Color Codes

TypeJKT
 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

TypeThermocoupleRTDThermistor
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

T-time

Radiation Error of Exposed Thermocouples

T-exposed