The error in measuring temperature with thermocouples with any instruments is related several factors that combine together to affect the overall accuracy of the measurement:

1.Thermocople wire error:this is the error resulting from the fact that a given sample of bare thermocouple wire will not exactly meet the temperature versus millivolt relationship given the standard tables. The most accurate designation is for Type T thermocouple wire. The errors allowed for T type over the range -40 to 130℃ are 1.0 for standard wire and 0.5℃ for speical limits of error wire.

2.Reference junction error: this is the error in determing the temperature of the reference junction. Sometimes called “cold junction”.

3.Voltage measurement error: this is error in the measurement of the small voltage produced by the temperature difference between the measuing junction and the reference junction.

4.Linearization error: the temperature vs. millivolt relationship for thermocouples is inherently non-linerar. The accuracy of the conversion from voltage to temperature depends on the method that is used to make this conversation. Most commonly there is a fit to standard polynomials or interpolation within the table values. Both of these methods are subjection to some degree of error.

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