Wire for thermocouples

Wire for thermocouples
History of thermocouple wire
How to distinguish chromel from alumel by color
Density and specific heat capacity of alumel, chromel, copel, constantan
Wire for thermocouples from the supplier Evek GmbH

Thermocouple (thermocouple temperature transmitter) - thermocouple used in measuring and transducer devices, as well as in control and automation systems of heating, ventilation and air conditioning.

Advantages of thermocouples

  • Large temperature measuring range
  • High temperature measurement up to 1800 - 2200°C
  • Measurement of low temperatures from -50°C

Disadvantages

  • Accuracy over 1°C is difficult to achieve, resistance thermometers or thermistors must be used.
  • Readings are affected by free end temperatures, for which corrections must be made.
  • Error caused by changes in cold junction temperature
  • Peltier effect (during readings, it is necessary to eliminate the current flowing through the thermocouple, because this current cools the hot junction and warms the cold junction)

Types of thermocouples

The requirements for thermocouples are defined in GOST 6616-94.

  • platinum-rhodium thermocouples - TPP13 - Type R; TPP10 - Type S
  • platinum-nickel platinum-nickel thermocouples - TPR - Type B
  • iron-constantan (iron-copper-nickel) TZHK - Type J
  • copper-constantan (copper-copper-nickel) TMKn - Type T
  • Nicrosil-nisil (nickel-chromium-nickel-silicon) ТНН - Type N
  • chromel-alumel - TXA - Type K
  • chromel-constantane ТХКн - Type E
  • chromel-copper - TXK - Type L
  • Copper-copper - TMK - Type M
  • Silch-silicon - TCC - Type I
  • Tungsten-Tungsten-TVR - Type A-1, A-2, A-3

Comparison of thermocouples

The table below describes the properties of several different types of thermocouples. Within the accuracy columns, T represents the temperature of the hot junction, in degrees Celsius. For example, a thermocouple with an accuracy of B±0.0025G-T would have an accuracy of B±2.5°C to 1000°C.

IEC thermocouple type Temperature range °C (continuous) Temperature range °C (short-term) Accuracy class 1 (°C) Accuracy class 2 (°C)
K (alumel-chromel) 0 to +1100 -180 to +1300 ±1.5 -40 °C to 375 °C ±0.004xT 375 °C to 1000 °C ±2.5 -40 °C to 333 °C ±0.0075xT from 333 °C to 1200 °C
J 0 to +700 °C -180 to +800 °C ±1.5 -40 °C to 375 °C ±0.004xT 375 °C to 750 °C ±2.5 -40 °C to 333 °C ±0.0075xT from 333 °C to 750 °C
N 0 to +1100 °C -270 to +1300 ±1.5 -40 °C to 375 °C ±0.004xT 375 °C to 1000 °C ±2.5 -40 °C to 333 °C ±0.0075xT from 333 °C to 1200 °C
R 0 to +1600 °C -50 to +1700 ±1.0 0 °C to 1100 °C ±[1 + 0.003x (T - 1100)] 1100 °C to 1600 °C ±1.5 0 °C to 600 °C ±0.0025xT 600 °C to 1600 °C
S 0 to 1600 -50 to +1750 ±1.0 0 °C to 1100 °C ±[1 + 0.003x (T - 1100)] 1100 °C to 1600 °C ±1.5 0 °C to 600 °C ±0.0025xT 600 °C to 1600 °C
B +200 °C to +1700 °C 0 to +1820 ±0.0025xT from 600 °C to 1700 °C
T -185 to +300 -250 to +400 ±0.5 from -40 °C to 125 °C} ±0.004xT from 125 °C to 350 °C ±1.0 from -40 °C to 133 °C}} ±0.0075xT from 133 °C to 350 °C}
E 0 to +800 -40 °C to +900 °C ±1.5 -40 °C to 375 °C ±0.004xT 375 °C to 800 °C ±2.5 -40 °C to 333 °C ±0.0075xT from 333 °C to 900 °C

Wire and strip for thermocouples