Yes, properly zeroed. And, yes, with the same wire it reads opposite sign with direction changed. Checked it with a Fluke, an Extec, and an Amprobe meter, and I get the same results from all of them. I just tested all three meters-the whole system against my power supply. I used a 25 ohm resistor, set 25VDC. The power supply read 1 A, all three meters read 1 A on either lead, then clipped the meters straight onto the camera power and got the same 'different' readings between + and - leads. So I tested the camera power cable on the power supply with the resistor, got the expected 1A readings. Tested another camera power cable, with the same results.
Amprobe LH41A, Fluke 325, Extec EX613, Vishay Dale 25Ω 25W 1% wirewound, Sony Venice camera (with several attached accessories). Anton Bauer VCLX battery (NIMH). Power cable is 14AWG wire for both wires-essentially lamp cord, that I split apart to get the clamp around the individual wires.
It should read the same amperage whether on positive or negative, right? Or is that wrong? The people who lent the other meters are electricians, and did their own readings with their own meters.