Why Voltage Dividers Are Not Just About Ratio
A voltage divider looks like one of the simplest analog circuits.
Vout = Vin * R2 / (R1 + R2)
Two resistors in series, a midpoint into the ADC, and a high voltage becomes a lower voltage. Battery voltage, button ladders, external inputs, and NTC dividers often use this pattern.
But many field problems start here too. The ratio is correct, but the ADC value is not. Large resistors save power, but readings jitter. Connecting the next stage pulls the voltage down. Moisture makes the divider drift. Input overvoltage creates more protection current than expected.
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