I understand a clamp meter works by measuring the magnetic field generated by current flowing through a wire.
It's well known that clamping 2 wires carrying the same current in opposite directions will show a null reading because one magnetic field is cancelling the other.
What I find surprising though is that if the second wire carrying the opposite current is placed immediately outside the clamp, it has no measurable effect. I was expecting its magnetic field to couple with the clamp to some degree but that seems not to be the case. Why?