I'm doing my first project on my Raspberry pi with analogue signals, using the PCF8591 ADC.
I managed very easily to measure 0 - 5 V with the chip, connecting the Reference Voltage (VREF, pin 14) to VDD (5V).
How can I change the range to some mV? Can I just apply, let's say, 20mV to VREF, and 20mV on my analogue input will be digitised as 256 (8 bit)?