DC current sensing with INA219B

Other Hardware Sensors
1

Hi, I need to measure currents in a PSU between 0 and 3A with at least 10mA accuracy. I thought an ACS712 Hall sensor would do it but there I barely get 185mV/A, insufficient to get any decent measurement out of the ADC on an Arduino Uno.
I may go with opamps to amplify the sensor output but then I also amplify noise and measurement errors.

As an alternative I am considering a INA219B sensor that uses simple shunt resistor to sense the current.

Question: can I set the shunt resistor in the negative supply line and at the same time supply voltage for the controller (Pro Mini) from the positive from the PSU and the negative from a slightly higher (1 to 2V) potential then the one used to sense the current?

Reading from the datasheets this looks acceptable but I want to make sure from this forum.

I will not use the voltage measurement feature of this chip.

2

Common mode range, according to the datasheet, is -0.3 to +26volt.
But I see these chips always used high-side. Any reason you can't you use it this way.
A shunt in the + wire could be less problematic than a shunt in the ground wire.
Don't understand the 1-2volt part. Shunt voltage loss could be 0.3volt if a 0.1ohm shunt resistor is used.
Leo..

3

Hi Leo. A shunt on the positive rail, but what with the GND: there are 40V between + and - and I need to power the controller with GND is negative reference. What now?

4

INA169.

No onboard A/D. Just current to voltage that the Arduino A/D can measure.
Leo..