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How to check a 230VAC sine/modified wave with an oscilloscope (FNIRISI 1013D)

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juan3211:
Yes, I understand that. I can't touch, just in case, even the BNC connector of the probe without disconnecting the mains source in the circuit. I need to connect/touch everything before switching on the circuit.

May be anyone could share us her/his experience.

Thanks for yours.


--- Quote from: Fungus on March 20, 2023, 08:42:55 am ---
--- Quote from: juan3211 on March 20, 2023, 06:50:44 am ---Hi, what do you think is better ?
Make my own 10x divider with 10 X 1 Mohm resistors and use the 10x probe (total 100x, and I don't care of I measure 232 or 235 because of different values in resistors)

--- End quote ---

I would use 200k resistors so your 'scope doesn't affect the circuit so much.


--- Quote from: juan3211 on March 20, 2023, 06:50:44 am ---I hope you understand that I don't want to buy an expensive 100x probe afte buying a cheap oscilloscope, and only for a few test.

--- End quote ---

Just don't cheap out on the precautions. Be aware of polarities, etc. It might even be wise to measure across a resistor in the middle of the chain so there's always a megaohm or so between you and the electrons. Everything else should be in a box with just that one resistor exposed.

--- End quote ---

Fungus:

--- Quote from: juan3211 on March 20, 2023, 09:44:55 am ---Yes, I understand that. I can't touch, just in case, even the BNC connector of the probe without disconnecting the mains source in the circuit. I need to connect/touch everything before switching on the circuit.

--- End quote ---

If you're measuring a resistor in the middle of the resistor chain then no matter how you connect things there's still a megaohm or so between you and the real power. Max current will be lass than a milliamp.

juan3211:
What about P4100 100:1 probe ?

https://a.aliexpress.com/_EHZzXD5

May be the best option is a "small transformer block to step-down to a safe voltage" method? does it disturb signals?

wasedadoc:
Depending on your definition of "small" I can confirm from my own practical observations that what Fungus already wrote that transformers can distort the waveform is true.  However if you are merely interested in sine versus multilevel approximation and if the latter seeing how many levels, then any of the several methods already suggested to you would have had the job done days ago.

adam4521:
I understand earlier in the thread we do not know whether the inverters will be earth referenced, neutral referenced (if UPS), or floating.

That being the case the most flexible and safe ‘low cost’ measurement is to use the transformer method. The wave ‘shape’ on the secondary will be close enough to the primary.

Agree with everyone — get the live conductors into an enclosure. OP, if that is too much hassle you might find you already have an enclosed plug-top transformer in your house, like this one I kept from an old Netgear router. While AC-AC transformers are not common for new kit now, you can still find inexpensive ones sold in a case as ‘doorbell transformers’.

I would test your inverter output with a small resistive load (eg tungsten desk lamp) to get some current flowing.

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