How to measure main AC 240V?

[harrychoo]

Hi all,

Can I know the way to measure main AC (240V)?

If i using multimeter, can i randomly put the + and - probes on the neutral and live line?

If i want to see the main waveform, what device should i use? If normal oscillocope able to do this without burning it? Or i need some special device or probes?

Thanks

[Staigen]

Hi

A little warning here! If you connect the common ground to the AC Neutral you can get a ground loop, and if you dont do that, you dont measure the true AC line! Also, if you accidently connect the oscilloscopes common ground to the AC live terminal you get a short! This will probably lead to destruction of the oscilloscope! To avoid this, use an insulation transformer between the mains and the input to the oscilloscope. And, for safety of the scopes input stage, use a high voltage probe, some scopes can not handle the peaks on the mains!

//Staigen

[harrychoo]

If i using transformer to step down the main voltage, will the output AC waveform exactly same as the input AC from main??

I heard that floating can be done on the oscilloscope in order to probe the 240VAC main. Another method is using differential probe.

Am i right? How to do the both methods above?

Thanks