Hi,
Working with Freescale 56F8037 controller with 12 bit ADC for motor control.
Input voltage range -10V to +10V
ADC High reference = 3.3
ADC Low reference = 0V
ADC values are getting saturated at +9V ( Instead of +10V )
I have computed ADC offset factor and applied but this non linear curve at the edge of range is bothering.
Could the saturation be due to the analogue conditioning (gain, offset) being applied? Reduce the gain, adjust the offset?
If an op-amp is doing the conditioning have you allowed for its ouput not going fully rail-to-rail?
Looking at your table, I see there's a generally steady increase in the error. That suggests to me the op-amp gain is too high. Have you allowed for the op-amp input resistance in calculating the input and feedback resistor values? The op-amp input resistance is effectively in parallel with the external input resistor so will increase the gain over the calculated one.