I'm making a battery voltage meter with a Wemos D1 Mini. The Analog input has a Vref of 3.2v. The battery that i will measure is a Lithio one of 72v, minimal 68V to max 84V, the Analog Input of the Wemos give to me (3.2v / 1024) of precision and i need more precision because with a resistor divisor i have a range from 0-90v but i will not use 0-60v, so my question is if with a OpAmp (i have a LM324) and some resistors i can map 60v-90v to 0v-30v and then use resistor divisor to down to 0-3.2v and get more precision with the ADC. The resolution that i want get is aprox 3mV-5mV
And used proteus to simulate the circuit of positive m and negative b
Like you see Vref' not is same (even closed) to calc and Vout is outside 3.1v range of calc... what I'm doing wrong here?