NiCr-NiSi/NiAl (Type K) thermocouple finds the widest use in all basemetal thermocouple at temperature above 500℃. The main chemical composition of positive leg NiCr (KP) are Ni≈90% and Cr≈10%; negative leg NiSi (KN) are Ni≈97% and Si≈3%. The operating temperature range is – 200~1300℃(for short term) and 0~1100℃( for long term).

Type K thermocouple has strong resistance to oxidation than other base metal thermocouples. It has high EMF against Platinum 67, excellent temperature accuracy, sensitivity and stability, with a low cost. It is recommended for oxidizing or inert atmospheres, but cannot be used directly in the following cases:

1. Alternatively oxidizing and reducing atmosphere,
   (2) Atmosphere with sulphur gases
   (3) Long time in vacuum
   (4) Low oxidizing atmosphere such as hydrogen and carbon monoxide atmosphere