I use a handheld "clamp-on" AC ammeter for this purpose. To separate out the hot wire (cannot get a reading by clamping around the bundled cable), I also purchased a $15 accessory that simply has an AC plug on one end, and a jack at the other, and in between it routes the wires separately through a plastic cage thing for clamping purposes. One side of the cage thing can be clamped-to for direct reading, the other side gives a more sensitive 10X reading when clampled onto. Very useful that.

Cheers