One must be careful here when working with non-isolated equipment such as PFC chargers.
If you want to see/measure the voltage difference between two points both of which are at some potential (not grounded), grounded scope may cause your device blow up as well as ground pin lead. Been there. If the scope is floating (or connected to the mains through isolation transformer and then grounded to equipment chassis) you're OK. You have to know what you're doing. Victor Joe Smalley wrote: > > > What is the point of the power > > com grounding to ground anyway ? > > (first thing we learned at school was to > > take the ground pin off plug of scope) > > The reason one side of the line is grounded is to control the voltage from > line to ground. If one side is grounded, the highest the other line will get > above ground is the line voltage. If neither side of the line were grounded, > the two lines could charge up to several thousand volts before something or > someone brought it back down. > > Removing the ground lug from the scope power cord can put several thousand > volts on the chassis of the scope and shock someone who touches the scope. I > keep my scope grounded. > > I had a long conversation with a Tektronix applications engineer about this > a couple years ago. He had several anecdotes where the ground pin had saved > someone's life and others where the outcome had not been so good. After that > conversation, I got several isolation transformers and stopped considering > disconnecting the ground pin. In his words, "never disconnect the scope > ground pin, a hot chassis can kill you. Always float the equipment. Never > float the scope." > > Joe Smalley > Rural Kitsap County WA > Fiesta 48 volts > NEDRA 48 volt street conversion record holder > [EMAIL PROTECTED]
