Tiberius
10 kW
Alan B said:Tiberius said:Can I ask again, what resistor precision do you need in the potential dividers?
Nick
Good question.
If we need 0.1V accuracy with 30V full scale that would be 1 part in 300 or 0.3%. Precision resistors have gotten fairly cheap these days. Especially if surface mount is used.
But the real issue is stability. We probably want to calibrate the ADC anyway. So in that case we need stability in the resistors, and calibration will compensate the values for the actual resistances.
If we want to use the differential mode of the ADCs then the resistors will have to be significantly better.
I thought we were talking about much better accuracy than 0.1 V. Also there are two resistors in a potential divider.
And if you are monitoring the top cell, you are measuring the positive and the negative voltage separately, so the errors in each of those measurements add up.
Nick