Thermoelectric voltages of shunt resistors
By Freddy at may 15, 2014, 17:01:40
Be careful when selecting a resistor for your shunt when low burden voltages are required. Beside the temperature coefficient, the thermoelectric voltages will have its influence in such applications. By the use of different materials whence the shunt resistor is manufactured and the connecion with the PCB, thermocouplers are created. Temperature differences between the terminals cause voltage differences which are the source of offset voltages.
The left resistor has an excelent temperature coefficient, but even a small terminal temperature difference of 5 °C cause a thermoelectric voltage of 200 μV that makes it unfit. The right resistor made by Vishay-Dale has a slightly worse temperature coefficient but a neglectable thermoelectric voltage that makes it very suitable in small burden precision applications.