or if you have a 2 channel scope (most are these days) put it in ADD mode with ch2 inverted (this makes it subtract). hook ch2's input to the "hot" ground (do NOT connect the scope ground to the "hot" ground, connect the scope ground to the chassis) and adjust the V/div for full scale deflection. then connect ch1 to the "hot" ground (with ch2 still connected), and adjust ch1's V/div until you get a straight line. once that is done, you can use ch1's probe to see the drive signals, etc on the "hot" side of the supply, and have plenty of isolation to the scope.

most people don't know their scope has this capability, and get an isolation transformer instead. or they more commonly take the dangerous shortcut of cutting the ground pin off the scope's power cord.

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This comes up time and time again - I would suggest using a twin beam scope in that way is probably the most dangerous of all three methods?.

But in all three cases you shouldn't be doing this unless you know EXACTLY why you're doing it that way, and the reasons why it's safe under some conditions, and not under others.

Personally I wouldn't consider using an earthed scope, it's far too dangerous an instrument if you know what you're doing.

For anyone who doesn't know what they are doing, use an isolation transformer - it's the safest method for beginners.

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Sorry maybe I should have made it clear, the inverter is on the same PCB and right next to the secondary side of the SMPSU.



Thanks for the info the ground was a lapse of concentration on my behalf, I will look into getting an isolation transformer .

 

I think we have different ideas of what 'near' means

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