Each of the thermocouple types is given a coding letter to denote each of the alloy combinations. The most common code letters are K, J, T and N. Other types include R, S, E, B, C, G and W.
Each thermocouple type has its own alloy pair which are carefully selected and calibrated to meet the international standards to which we must comply. The standard that governs thermocouples in the UK and Europe is BS EN 60584 and covers the characteristics, tolerances and colour coding of the different thermocouple types.
The thermocouple type is suited to different applications and temperature ranges. See the table below for appropriate operating ranges.