Bill, I will address the one question you asked, which was why would Fluke show a clamp-on being used clamped around a hot and a neutral (ungrounded and grounded conductors) if it was always going to read zero?
This is what I do all the time when I am called in to trace the source of net current magnetic fields in circuits. If you clamp around a hot and neutral and get a reading (usually a half an amp to many amps) that means one of two things, usually:
1) Some of the neutral that should be balancing out the hot is traveling in another path, either a separate grounding path, or to another neutral. This would indicate a wiring error that needs to be corrected.
2) There is excess neutral, coming from another circuit. This also would be an error.
The follow-up measurements would be to measure the hot and neutral separately to see what the situation is. This is often done in the panel box.
Since we are not dealing with micro-amps we don't have to be worried about the absolute accuracy of our ammeters. We are seeing symptoms which lead us to the cause of the disease.
If it is said that the conductors you are measuring are going to a completely isolated appliance, and there is no equipment grounding conductor, then the reading should be zero. If it is not, either the meter is at fault or the appliance actually is not isolated and you need to investigate further.
Bill, I would suggest that if you have any more to say about instruments, you should start a new thread purely about instruments and their accuracy and tolerances.
This thread may have run itself out, but if you have anything more to say about the cause of net currents, let's hear it. I believe you have been told that any parallel currents flowing on insulation would not show up as net current.
Karl