J Type Vs. K Type Thermocouple: The Difference Explained


In various industries, the functioning of machines and equipment can rely significantly on accurate and precise temperature measurements.

Temperature is an important measurement parameter used in various industries to ensure the efficient operation of machines and equipment. The quality of output and integrity of machines can sometimes be directly proportional to the temperature range. Thus, it is of utmost importance to use the right equipment for accurate temperature readings.

One of the instruments widely used for accurate temperature measurement is the thermocouple. Thermocouples are made by joining together two dissimilar metallic wires to form a junction. A small voltage is created when the junction comes in contact with hot or cold temperature, which is then measured to get temperature readings. The type of wire used determines the temperature range that can be measured and how accurate the readings will be.

In this article, you will learn about the J type vs. K type thermocouple, their capabilities, and their differences.

J Type Thermocouple

The J Type thermocouple is a general-purpose thermocouple with a smaller temperature range. It is most suitable for light industry operations where temperatures range between -346F to 2193F or -210C to 1200C. The J Type thermocouple is made of iron on the live positive leg and copper-nickel alloy on the neutral leg.

Likewise, the Type J thermocouple has a smaller temperature range making it unsuitable for high-temperature operations above 750C (1383F). This is because when iron in the thermocouple comes in contact with oxidizing agents that creeps into the thermowell, the iron goes through an irreversible molecular change which causes the wrong transmission of voltage and affects the accuracy of temperature readings.

Furthermore, the magnesium oxide insulation on the Type J thermocouple cannot tolerate greater temperature readings.

 Advantages of J Type Thermocouple Wire

  • Affordability and accessibility to Varieties
  • General-purpose and versatile
  • Suitable for work operations where temperatures reduce quickly

Disadvantages of J Type Thermometer Wire

  • Unsuitable for higher temperatures, oxidizing environments
  • Small output signals
  • Requires careful calibration before usage
  • Problem with noise.

K Type Thermocouple

The Type K thermocouple has a wire combination of chromel and alumel legs. The wire combination has high corrosion resistance, making it suitable for work operations in an oxidizing atmosphere. Of the four major types of thermocouples, the Type K thermocouple has the widest temperature range between -270C to 1260C.

Additionally, the Type K thermocouple is capable of functioning in various atmospheres and rugged environmental conditions, making it a more preferred choice for industrial workers.

Advantages of Type K thermocouple

  • Wide temperature range
  • Highly durable
  • Fast response
  • Good resistance against oxidation
  • Good linearity of emf to the measurement temperature

Disadvantages of K Type thermocouple

  • It becomes susceptible to drift over time.
  • Less accurate than Resistance Temperature Detector (RTD)
  • Not ideal for reducing atmospheres

Temperature Monitoring with Infra View

 Temperature monitoring spans from using basic types of thermocouples to advanced temperature management equipment. At Infra View, we have a variety of temperature monitoring products suitable for large-scale operations with higher functions and efficiency.

Regardless of the fuel type of facility, temperature requirements, projects, or work application, we can help you find the best temperature monitoring equipment. Kindly contact us today to learn more about our products.

Use our Pyrometer Selector to find the right solution for your temperature monitoring needs and place a request for quote.

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