Sparkmaster,
By 'the question you asked Larry', I presume you mean
Define "electrical isolation" if I can still get grounded and severely amp-loaded. If I'm getting electrocuted, how is electrical isolation helping me? How exactly is my entire electrocution experience getting all warm and fuzzy and comfortable with this 2nd tranny?
Electrical isolation in this case means that the secondary of the transformer is not 'galvanically' connected to the primary. In other words, there is no flow of electrical current between primary and secondary. Energy flows between the two, by the mutual magnetic coupling, but there is no electrically conductive path from primary to secondary.
This makes the secondary 'ungrounded'. If you were to ground either of the secondary terminals, there might be slight capacitive charging current, but not much current flow. It is only with _two_ ground faults that you would get significant current flow.
Remember that electricity does _not_ 'seek ground', and simply touching an energized conductor is not sufficient for a shock. Electricity 'seeks' to close the circuit, and find a path back to the source.
The power distribution systems that we generally use are _intentionally_ grounded and bonded, meaning that one of the transformer terminals is connected to ground. Because of this, any contact between one of the 'hot' terminals and ground, either directly, or through a load (such as a person) will result in current flow. But with an _ungrounded_ secondary, grounding a lead will not cause significant current flow, because there is no complete circuit back to the source.
Your variac is not isolated. This means that there is a shock risk between the output and _any_ grounded metal. But the step down transformer is isolated, meaning that the only shock risk would require that you contact both output terminals at the same time.
On top of this, the step down transformer means that the maximum output voltage will be perhaps 14V; 5V out of 14V is probably safer and more easily controlled than 5V out of 140V.
WFO,
My guess is that your boss did feel the shock, but was probably ready for it. The current was quite low, intentionally limited by the design of the fence charger. You didn't feel the current passing through you, you felt the spark right at your earlobe.
Your boss could have also done something as easy as holding a bit of metal to your earlobe, say a key or a ring. If he held the metal tightly, he wouldn't feel the arc, but you sure would. I do this when I am getting out of my car on a cold, dry day; I use my key to discharge myself to the car frame.
-Jon
