Does load change if we use 30 or 20A ACS712 Current Sensor?. and what will be the changes in the program? Thank you.
ACS-712-Sample-Project.pdf (174 KB)
That can only be answered by consulting the documentation for the sensors.
That pot might be rated for 3A but that is for the whole track. The way you have it wired it will burn out when the resistance is small because then only a very small part of the track will take all the current.
Hi,
This is your attachment, school practical?
The sensor has nothing to do with the current passing through it.
What does change is the output of the sensor for the same amount of current flowing.
The 30A unit will produce maximum output for 30A
The 20A unit will produce maximum output for 20A.
So if your current is 10A, the 20A sensor will give a higher output than a 30A sensor.
Tom... 
The title of this thread and what you ask in your first post do not match, what do you want to know?
The range of the sensor is set by the manufacturer, it cannot be easily changed by the user. The potentiometer in the circuit will vary the load on the power supply, and therefor the current through the sensor. According to the Sparkfun datasheet for the 5 Amp sensor shown in the schematic, a current of 3.16 Amps will produce an output of 584.6 millivolts (185mV per Amp) from that sensor. For the same current the 20 Amp sensor produces an output of 316 mV (100 mV per Amp), and the 30 Amp sensor give a 208.56 mV output (66mV per Amp). The difference in the sketch will be the scaling of the reading of the Arduino analog input to get a display in Amperes. These are Hall Effect sensors and will not change the load.
As a side note the MingHe B3603 has a maximum output current of 3 Amps, which is lower than what is shown (3.16 A) on the drawing. It would be overloaded.
0712.pdf (682 KB)