Editing Thermocouple (section)

===Reference junction===

[[File:Cold Junction Compensation with Thermistor to measure the junction temperature..jpg|thumb|right|Reference junction block inside a Fluke CNX t3000 temperature meter. Two white wires connect to a [[thermistor]] (embedded in white thermal compound) to measure the reference junctions' temperature.]]

To obtain the desired measurement of <math>\scriptstyle T_\mathrm{sense}</math>, it is not sufficient to just measure <math>\scriptstyle V</math>.
The temperature at the reference junctions <math>\scriptstyle T_\mathrm{ref}</math> must also be known.
Two strategies are often used here:
* "Ice bath": The reference junction block is maintained at a known temperature as it is immersed in a semi-frozen bath of distilled water at atmospheric pressure. The precise temperature of the melting point [[phase transition]] acts as a natural [[thermostat]], fixing <math>\scriptstyle T_\mathrm{ref}</math> to 0&nbsp;°C. 
* Reference junction sensor (known as "{{visible anchor|cold junction compensation}}"): The reference junction block is allowed to vary in temperature, but the temperature is measured at this block using a separate temperature sensor. This secondary measurement is used to compensate for temperature variation at the junction block. The thermocouple junction is often exposed to extreme environments, while the reference junction is often mounted near the instrument's location.  [[Silicon bandgap temperature sensor|Semiconductor thermometer]] devices are often used in modern thermocouple instruments.

In both cases the value <math>\scriptstyle V + E(T_\mathrm{ref})</math> is calculated, then the function <math>\scriptstyle E(T)</math> is [[root-finding algorithm|searched]] for a matching value. The argument where this match occurs is the value of <math>\scriptstyle T_\mathrm{sense}</math>:
:<math>E(T_\mathrm{sense}) = V + E(T_\mathrm{ref})</math>.