Here's what I'm talking about. I get readings from my INA219, but I want to make sure they're correct. I'm looking for the total current and voltage drawn by my main circuit.
Nothing wrong with the power connections but you need the other three required connections to +5/SCL/SDA. I have to assume they're in place since you said you got readings. Why do you doubt the readings are correct? If you have a meter, you can certainly verify proper operation.
The ground of the INA219 has nothing to do (does not have to be common) with the circuit being tested. This is quite clear from Adafruit's Fritzing diagram (probably won't hear that too often).
It doesn't have to be but there's no problem if you do connect it, given that the circuit is built correctly.
But I can't figure out how to hook it up to a separate Arduino circuit and use it similar to a conventional multimeter.
The current terminals of the INA219 MUST be WITHIN ground (0volt) and +26volt above ground of the Arduino.Hard/impossible to do so if you don't share Arduino ground with that battery/supply ground.Leo..