I'm not sure how they work either, but as long as they work...
I did tell my employees about the testers not working in relationship to moisture.
One of my men was working outside the other day and sweating. He also keeps his GB "ticker" clipped to the inside of his T-shirt. He said when he was working outside that day he couldn't get the tester to work reliably. Thanks for sharing the information guys, it may save someone some day.
I always tell my guys that the testers always tell you if the power is on but not necessarily if the power is off...use a meter.
Also, I know that if you are under high-tension / high-voltage wires that if you hold your tester in the air it will beep like there is constant voltage.
