INA219B current measurement

[earckens]

I need to measure the outgoing current on a PSU and am considering an INA219B.
Can I place its shunt resistor in the negative supply line yet connect it to a controller (Atmega328) supplied with the positive fixed voltage rail from the PSU (output is 40V so I use reference voltage zener and resistor), and the negative from the common negative supply line?


Looking at the spec sheet it seems ok but I want to make sure from this forum. i will not use the voltage measurement feature of the chip.

Thank you.

 

[ronsimpson]

Absolute max voltage on the + & - inputs -0.3V.
Common mode range includes 0 but not negative. (working range)
I think one of the inputs would work at -0.05V but the data sheet said no.

Because you are measuring "bottom side" the load side of the resistor is positive. If you connect "ground" for the INA219B to the battery (-) then the resistor will give a positive voltage. This will meet the data sheet requirements.

 

[earckens]

Hi ronsimpson, sorry for the inconvenience but the thread I started here now leads a simultaneous life here: https://www.electro-tech-online.com...-0v-lowest-voltage.148899/page-3#post-1274431
For your reply here: I meanwhile changed my design to high side measurement because that is what this chip is designed for, plus some other issues related to the specific circuit where it is to be used.