Type K and Type N thermocouples are popular temperature sensors, but they have different characteristics, advantages, and limitations. Here’s a detailed comparison to help you understand the differences between the two and how to choose the best one for your specific application:

1. Materials

• Type K:
  • Positive leg (Chromel): A nickel-chromium alloy.
  • Negative leg (Alumel): A nickel-aluminum alloy.
  • Type K is widely used due to its cost-effectiveness and versatility in many industrial applications.
• Type N:
  • Positive leg (Nisil): A nickel-silicon alloy.
  • Negative leg (Nisil): A nickel-silicon alloy.
  • Type N thermocouples use a more stable alloy combination, which offers better performance in certain environments than Type K.

2. Temperature Range

• Type K:
  • Temperature range: -200°C to +1372°C (-328°F to +2502°F).
  • Type K is suitable for both low and very high-temperature applications.
• Type N:
  • Temperature range: -200°C to +1300°C (-328°F to +2372°F).
  • Type N has a slightly narrower temperature range than Type K but still covers a wide range for many industrial applications.

3. Accuracy

• Type K:
  • Accuracy: Typically ±2.2°C or 0.75% of the reading (whichever is greater).
  • Type K has lower accuracy, especially at higher temperatures, compared to some other thermocouples.
• Type N:
  • Accuracy: Generally better than Type K, typically around ±1.0°C or 0.5% of the reading (whichever is greater).
  • Type N is known for its better accuracy at high temperatures and overall better stability over time.

4. Stability and Durability

• Type K:
  • Type K thermocouples are generally stable at lower to mid-range temperatures but can experience drift and degradation over time, especially at high temperatures (above 1000°C).
  • The alumel leg can oxidize at high temperatures, affecting accuracy.
• Type N:
  • Type N thermocouples are more stable than Type K, especially at high temperatures. The Nisil alloy is resistant to oxidation and offers better long-term stability, making it more reliable in extreme environments.
  • Type N thermocouples are particularly known for their high-temperature stability and can last longer under harsh conditions, even in oxidizing environments.