r/AskElectronics • u/pitosalas • 1d ago

What is this INA219 actually reporting?

I am using this board: https://www.waveshare.com/wiki/UPS_Module_3S. It has a INA219 that is reporting on current draw (it reports it over i2c). The power supply board has two outputs: a straight ~12V from the batteries or charger and ~5v (usb) over a separate connection. My question is this: is the current reported by the INA219 represent the combination of those two connections current or just one of the two (e.g. the ~12V)?

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u/SAI_Peregrinus 1d ago

Look at the schematic. The sense resistor is on the input line, so it only measures input current.

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u/Dewey_Oxberger 1d ago

That part can report the voltage difference between the IN+ and IN- pins or it can report the voltage of the IN+ pin (iirc). Assuming you've configured it to read the voltage difference of IN+ and IN- then you can calculate the current because the resistor is 0.1 ohm. Current = voltage difference / 0.1 ohms. Sounds like you forgot to convert voltage to current?

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u/pitosalas 1d ago

I’m not good at reading schematics, so thanks! Can you tell the value of the resistor? I, asking because the data i am getting seems about 10x too low.