ADC7124 voltage measurement. In applying a precise voltage source on AIN0 and AIN1, I come across a puzzle.
ADC settings: AIN0/AIN1 in bipolair mode; VBias set for AIN2 ; Internal reference enabled, Internal reference chosen in CONFIG0.
Wiring: All AIN's have 220 Ohm protection resistor. AIN0/AIN1 connected to floating voltage source. AIN2 (VBias) connected to AIN1. At that point I measure 1.985V.
Measurements of -2.5V in steps of 0.5V to +2.5V:
From 0 to +1V and 0 to -1V I see differences between my source of <0.002 V. But at 2 and 2.5 V I see measured voltages of 1.708V and 2.038V. At -2 and -2.5V there are similar large differences?
Why is this and what do I have to do to measure over the full range -2.5 to +2.5V?
Your answer is appreciated,