Measure an AA battery? If I'm going to measure an AA battery (about 1.5 v) with a USB-powered Arduino, I will connect the battery's +ve terminal to the A0 pin. Shall I connect the -ve terminal to the gnd pin too?
Yes you could although this means you're measuring in relation to the Arduino's logic voltage, which is slightly below 5v (due to a diode's voltage drop) or the voltage of vref.