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Measuring Mains with Rigol DS1052E

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logicnibble:
Hi!
It's dangerous to measure mains voltage directly with an oscilloscope but since I've read many guys have done it, I'd like to know about the Rigol DS1052E and if there are any tips & tricks, like:

-Not connecting Rigol earth ground.
-Using diferential reading between channel 1 and 2 and not using the common aligator from both probes.

Thanks

mikeselectricstuff:
If you have to ask this you probably shouldn't be doing it at all.
Lifting the scope ground is a very BAD idea. Diff probes often don't have sufficient range and/or common-mode rejection.
The normal way to do it is power the device under test from an isolating transformer so you can then ground the circuit ground (seperate ground- don't rely just on the scope probe ground).
Make sure your probes are suitably rated- you'd normally want a x100 probe for mains use. 100 probes are also handy to have for probing high impedance circuits like 32K watch crystals.

Kiriakos-GR:
I think that logicnibble had set one interesting question.

And no it does not limited to the Rigol product range.

As a electrician I would like to have on screen other than volts and the wave form too.
So to be able to see and tell how perfect or clean is the AC wave at 220 or even at 380V.
Or even, to be able to check DC/AC inverters and see how they respond against a specific load.

Some people they do complains that the low quality DC/AC inverters cause noisy operation on small motors, usually small pumps.
I like to be able to see of what is happening with the wave forms.

If there is a tool capable to help me out there, I need to know which one is capable for the task.


   

ejeffrey:
What are you trying to measure?  You can measure phase-to-ground and neutral-to-ground with an ordinary high voltage probe.  For phase-to-phase or phase-to-neutral measurements, hooking up two probes and doing math A-B on the scope has terrible common mode rejection, but it might be OK at 50 Hz.  Simply doing separate measurements of phase-ground and neutral-ground may be the most illuminating -- the neutral-to-ground voltage is indicative of the current.  Not enough for a true measurement, but if you turn on a reactive load you will probably see an out-of-phase voltage pop up on the neutral line.

If you just want to see the AC waveform, see if you can find a small AC output wall transformer with <24VAC output and measure the secondary voltage.  High harmonics will be filtered by the transformer, but if you purpose is to look for garbage on the mains caused by other devices you can still probably see plenty.

logicnibble:

--- Quote from: ejeffrey on August 02, 2011, 03:33:03 pm ---What are you trying to measure?

--- End quote ---
I'm trying to measure a uC circuit which is powered by a capacitive (transformerless) power supply.
This means all circuit is LIVE.
I also would like to measure a dimming circuit, which is LIVE too.


--- Quote from: ejeffrey on August 02, 2011, 03:33:03 pm ---...an ordinary high voltage probe.

--- End quote ---
Does Rigol DS1052E have one?

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