I have one of these and mine came with a video.
One thing that the video said to do is to connect one wire of the transmitter to a phase and the other to ground not another phase wire. They said that the prefered connection to ground is a water pipe, building steel, a steel door frame or some other metal ground. This keeps the signal from getting interferance and you getting a false reading.

When I got mine I didn't read the instructions or watch the video. I just hooked it up to 2 phases and tried to trace out a panel. I got a wrong reading and shut off the wrong breaker.
Since connecting it as they suggested, it has not failed me yet.

Good tool. [Linked Image]