I'm using an arduino due (3.3V) which its power regulator can deliver 800mA of current.
Can I connect a multimeter in series and get a reading of the current my circuit draws, and can i leave it connected so to measure the current in real time?
(I regularly re-program the Due with the circuit connected is there a chance the multimeter can damage the device in this situation?)
Will such a config affect the circuit?
At last should I break the circuit and connect the multimeter to the positive or to the ground connection?
simulate this circuit – Schematic created using CircuitLab
Best Answer
If your DMM is of auto-ranging type, never use it for measurement of current in a low-voltage environment. The auto-ranging DMM will change the measuring resistor (shunt) value in-flight, which will add a varying voltage drop affecting your circuit power supply.
Instead, use a 1% 0.1 Ohm resistor in-line with your power rail (between the regulator and Arduino) as a starting value, and use the milli-voltmeter mode of your DMM to measure the current, I (mA) = V(mV)*10 for a 0.1 Ohm resistor.