I have searched a lot of forums with recommendations, but I have not found anything that states direct answer.
How to choose the amperage for Current and voltage sensor?
I know if You select too large amperage, it reduces the precision, but if you select too small, it will burn the device.
Sow how it is, is it he ESC max amperage + 10A for security? Or there is another formula?
Hi
I heave read that you simply add up the ESC max amps and then add a little for safety. So if you are flying a quadcopter with 20A ESC, you should get a current sensor that can handle about 90A (20A x 4 + 10A)
However I have not found much details on this either. As I have used the APM power module (max current of 90A) with no problems with 6x 20A ESC. I think this is to do with the voltage scaling of the sensor to 3.3V which increases the maximum current you can measure.
Do you have any other links with more details and maybe we can figure this out?
Hi.
I studied a bit through books, and talked to electronics teacher in our university.
He confirmed that if the ESC ar in parallel the amperage should be summed up afterwards adding all servos, FC, etc. basically everything that draws energy. But he was not sure, because, he needed more info about how ESC worked and how the meter is working in this particular case, as he has not worked with multicopters. Because he didn’t think that the ESC constantly draws 70 amps, and I believe ESC don’t do that.
So because I’m building large multicopter 70A ESC with 8 of them, I need a pretty dam big meter about 600A 
But I’m pretty sceptical about this(thats a VERY big meter required) so I will continue research and I will replay once I get this clear.
Sounds good, and I do agree that we are missing something as I doubt 600A will be flowing through as you would need very thick wires to deal with that sort of current! 
I will also look around some more to see if I can get to the bottom of this.