Thermocouple Measurement and Reference Junction Temperatures

Thermocouple Measurement and Reference Junction Temperatures

Calculate the amount of voltage “seen” by the voltmeter given the following measurement and reference junction temperatures:

• T1 = 589 ^oF ; T2 = 63 ^oF ; T3 = 70 ^oF ; Vmeter = __________ mV
• T1 = 821 ^oF ; T2 = 69 ^oF ; T3 = 73 ^oF ; Vmeter = __________ mV
• T1 = 1524 ^oF ; T2 = 91 ^oF ; T3 = 105 ^oF ; Vmeter = __________ mV
• T1 = 1922 ^oF ; T2 = 102 ^oF ; T3 = 135 ^oF ; Vmeter = __________ mV

Answer :

All answers based on ITS-90 thermocouple table values:

• T1 = 589 ^oF ; T2 = 63 ^oF ; T3 = 70 ^oF ; Vmeter = 0.463 mV
• T1 = 821 ^oF ; T2 = 69 ^oF ; T3 = 73 ^oF ; Vmeter = 0.953 mV
• T1 = 1524 ^oF ; T2 = 91 ^oF ; T3 = 105 ^oF ; Vmeter = 3.378 mV
• T1 = 1922 ^oF ; T2 = 102 ^oF ; T3 = 135 ^oF ; Vmeter = 5.294 mV

Note: all temperatures at T2 are irrelevant because this is a junction between similar metals (type B wires connecting to corresponding type B wires). The reference (cold) junction is where the type B wires connect to copper, at temperature T3.