I tested the accuracy of a shunt resistor of 20 μΩ by applying short pulses of 100 A. At lower current levels near 0, I noticed the sensed current had a variation of ±300 mA. I did some research and learned about the thermovoltage effect which I assume is causing this inaccurate readings.
To compensate this effect, I got the Seebeck coefficient of the shunt (1.5 μV/K) and the internal heat resistance (1 K/W). I registered the data for the sensed currents in a table. From what I found online, this is the calculation steps to make:
- Power dissipation of the shunt: P = I2·R.
- Max. temperature between two junctions: ΔT = P·1 K/W.
- Thermal voltage: ΔV = 1.5 μV/K·ΔT.
- ΔI = ΔV/20 μΩ.
- Icompensated = I - ΔI.
I would like to know if these calculations are correct? Should I always substract the thermal voltage or does it depend on whether the sensed current is positive or negative?
