Now I'm familiar with current clamp measurement devices like this one:
Clamping it around both the hot and neutral at the same time and their magnetic fields cancel, right?
So today one of our customers told me they were measuring current with this unmarked box that's tied to a 2+ground power cable. The box wasn't surrounding one isolated conductor though. Rather just zip tied to the outside of the entire power cable with both hot/neutral conductors (+ ground).
I put my current clamp meter over the cable and, no surprise, didn't measure anything. Then I put it around the isolated hot wire and measured 7A, the same 7A reading as this thing!
How the hell does this thing work?
There's no markings IDC pins or outward indicators of operation. Just a black plastic box zip tied to a cable. The readings didn't drop when it was pulled away from the wire, just dropped to zero after 3 millimeters or so. I didn't get a chance to change the orientation or anything else.
It has me baffled.
The tech didn't know where it came from, but if I don't figure it out I'm driving the 6 hours back there to find out.