PH. (818) 886-3755
SALES@THERMOMETRICSCORP.COM

Live chat by BoldChat

  • Type K Thermocouple: -454 to 2501 °F (-270 to 1372 °C)

    Composed of a positive leg which is iron and a negative leg which is approximately 45 % nickel-55% copper.
    (Note - Constantan is Copper-Nickel.)

    This is the most common thermocouple type that provides the widest operating temperature range. Type K thermocouples generally will work in most applications because they are nickel based and have good corrosion resistance.

    Composed of a positive leg, which is approximately 90% nickel, 10% chromium and a negative leg, which is approximately 95% nickel, 2% aluminum, 2% manganese and 1% silicon.Type K Thermocouples are the most common general purpose thermocouple with a sensitivity of approximately 41µV/°C, chromel positive relative to alumel. It is inexpensive, and a wide variety of probes are available in its -200°C to +1260°C / -328°F to +2300°F range. Type K was specified at a time when metallurgy was less advanced than it is today, and consequently characteristics vary considerably between samples. One of the constituent metals, nickel, is magnetic; a characteristic of thermocouples made with magnetic material is that they undergo a step change in output when the magnetic material reaches its Cure Point (around 354 °C for type K thermocouples).

    Deviations in the alloys can affect the accuracy of thermocouples. For type K thermocouples the tolerance class one is given as ± 1.5 K between -40 and 375 °C. However, deviations between thermocouples coming from the same production are very small and a much higher accuracy can be achieved by individual calibration.

    Metallurgical changes can cause a calibration drift of 1 to 2°C in a few hours, increasing to 5 °C over time. A special grade of Type K is available that can maintain special limit accuracy up to ten times longer than the regular grade.

    TYPE K CHART °F TYPE K CHART °C

    Type K Thermocouple Notes

    1. Chromel® is 90% nickel and 10% chromium and Alumel® is an alloy consisting of 95% nickel, 2% manganese,
         2% aluminum and 1% silicon.
  • 2. Type K is one of the most common general purpose thermocouple with a sensitivity of approximately 41 μV/ ºC.
  • 3. The Chromel® is positive relative to Alumel®.
  • 4. It is inexpensive, and its potential range is -270 °C to +1372 °C (-454 °F to +2501 °F) and is relatively linear.
  • 5. The nickel constituent is magnetic and, as other magnetic metals, will undergo a deviation in output when the     material reaches its Curie point which occurs at around 350 °C (662 °F) for type K thermocouples. The Curie point     is where a magnetic material undergoes a dramatic shift in its magnetic properties and causes a drastic shift to     the output signal.
  • 6. It may be used in continuously oxidizing or neutral atmospheres.
  • 7. Most usage is above 538 °C (1000 °F)
  • 8. Exposure to sulphur contributes to premature failure.
  • 9.Operation at certain low oxygen concentrations causes an anomaly called preferential oxidation of chromium in     the positive leg which causes a condition referred to as ‘green rot’ which generates large negative calibration     drifts that are most serious in the 816 to 1038 °C (1500 to 1900 °F) range. Ventilation or inert-sealing of the     protection tube can prevent / mitigate this condition.
  • 10. Cycling above and below 1000 °C (1800 °F) is not recommended due to alteration of the output from hysteresis       effects.