ies5:
This isn't Fritzing. It's Paint.Arduino is powered via USB.
5 volt battery is a Anker 13000. They in fact do exist.
Are you saying I should connect sensor ground to only the Arduino?
Same difference.
Ok.
That's not a battery. It's a powerbank.
A battery with a boost converter that automatically turns off below a certain power draw.
What else is powered from that powerbank.
And why didn't you power the sensor from the Mega's 5volt pin.
Is the sensor some distance from the Arduino (if so, how far, and what kind of wire).
Sensor ground must be connected to Arduino ground.
Your picture is not showing that.
Leo..