ACS712 Arduino Current Sensor

ACS712 Arduino Current Sensor is a hall effect current sensor. Hall effect will convert the magnetic field created by the current that flows through the sensor to voltage directly proportional to it and makes this sensor able to generate voltage linearly with the current that flows through this sensor.

ACS712 has 3 types according to the maximum range of the current measurement. The first is 5A, then 20 amp max, and for 30A max.
So you can choose which is the best sensor for your project. Which range of current do you want to measure? And if you measure a pretty small current like below .4 amp. I don’t recommend using this sensor. Get a shunt current sensor for DC measurement or CT type for AC measurement instead. Because they will have more sensitivity for small currents. It is really difficult to sense a small current using this sensor.