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

[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.

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)

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

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.

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.

[Fungus]

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.

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.

[Zero999]

That is precisely what I want to check. Pure sine waves, or modify ones.

What about connection to the secondary of transformer?

A transformer can change the shape of the wave. The most accurate way is with a 100x probe... or make a box with a resistor divider in it.

Yes a transformer will distort this signal a little, but not enough to be visible on an oscilloscope at mains frequencies, you'll still be able to distinguish between a modified and pure sine wave. Most of the distortion will occur at higher frequencies, so there might be some ringing on the modified sine, but it should be fairly obivous.

[juan3211]

Even for compare several "pure" sine waves between them, or several modified sine waves between them ?

Do you think tha transformer will not modify enough the waves? May be only a very high frequencies?

Thanks.

That is precisely what I want to check. Pure sine waves, or modify ones.

What about connection to the secondary of transformer?

A transformer can change the shape of the wave. The most accurate way is with a 100x probe... or make a box with a resistor divider in it.

Yes a transformer will distort this signal a little, but not enough to be visible on an oscilloscope at mains frequencies, you'll still be able to distinguish between a modified and pure sine wave. Most of the distortion will occur at higher frequencies, so there might be some ringing on the modified sine, but it should be fairly obivous.

[tggzzz]

Even for compare several "pure" sine waves between them, or several modified sine waves between them ?

Do you think tha transformer will not modify enough the waves? May be only a very high frequencies?

You have to define what "compare" and "modify enough" means. That implies you have to define your objectives.

Other snippets from your posts....

I haven't still recieved it but two different YouTubers have confirmed me that they have already measured 230VAC mains waves.

Youtubers also confirm the world is flat, that 5G causes cancer, and that the world is run by giant reptiles living under a mountain.

Given that, what's your point again?

That is precisely what I want to check. Pure sine waves, or modify ones.

As others have stated, to check that you don't need to make a physical connection - just hold a probe near the output and capacitive coupling will show you enough to distinguish that.

So if I want to check my home circuit (ground +neutral+phase, generally neutral is connected to ground in grid's substation) how do I need to connect transformer secondary outputs ? What is the correct option?

The correct option is to read and understand the references in https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/ There are many obvious and subtle ways in which a beginner or experienced professional can damage themselves or scope or UUT.

[juan3211]

Thanks a lot. I must admit that my posts are not clear enough.

Now I know that these two YouTubers how review the 1013D don't know a lot about it or about electronics in general.


I want to test several inverters and signals. All 230VAC RMS.
My goal is to check if it is pure sine or not, and this is very easy.

But also, I am asking myself if there are also differences among pure sine waves , and among modified sine waves.

I am sure that they are.

The Fnirisi 1013D has a FFT (Fourier) to see harmonics of a signal, and may be I could compare this data among pure sine to see the quality of them. Probably main's harmonics will be different than an cheap Chinese inverter.

I dont need to compare them with high detail, but yes basics.

May be I have explained (with my words) better.

Thanks a lot guys!
 

[wasedadoc]

You are overthinking this.  Just get started by holding the probe near an insulated output from the inverter.  No connection needed.  There is a good chance that will tell you all you want to know.  If not, you can proceed to a more advanced method.

[joeqsmith]

...
Now I know that these two YouTubers how review the 1013D don't know a lot about it or about electronics in general.
...

Rather than place the blame on the YouTubers,  maybe consider the SISO factor (Shit In = Shit Out).   Asking better questions may yield better results.

DDS (DIY Domótica Solar) 21 hours ago
​@joe smith  hi , in order to measure a 50-60hz sine wave to check some inverters, main grid,... modified or pure sine, armonics, .... Is it good to use a step down transformer ? For example, from 240vac to 24vac. Or it (transformer) will distrub, smooth, .... signal ?

joe smith13 hours ago
 @DDS (DIY Domótica Solar)  It depends what you are after.   Anything you use will cause some error.   Not all transformers will have the same response.  Of course, you don't want to apply any DC to a transformer.  Following videos show a simple transformer / LEM used to measure AC power with my scope. 

[tggzzz]

Asking better questions may yield better results.

Just so.

General truism: it is easy to answer a question correctly, but it is more difficult to know the correct question to ask.

[JeremyC]

I want to test several inverters and signals. All 230VAC RMS.
My goal is to check if it is pure sine or not, and this is very easy.

But also, I am asking myself if there are also differences among pure sine waves , and among modified sine waves.

juan3211, keep in mind that 230V RMS = 650Vpp. You should buy a high voltage differential probe like the Miscig DP10013.
Sample link:  https://www.amazon.com/Micsig-DP10013-Differential-Attenuation-Tektronix/dp/B074K4XPW3

[shapirus]

high voltage differential probe

High voltage yes, but it doesn't have to be differential. Inverters are floating, because they are battery-powered. They don't have any connection to ground.

[JeremyC]

high voltage differential probe

High voltage yes, but it doesn't have to be differential. Inverters are floating, because they are battery-powered. They don't have any connection to ground.

OP mentioned that he may need to check mains in his house

So if I want to check my home circuit (ground +neutral+phase, generally neutral is connected to ground in grid's substation) how do I need to connect transformer secondary outputs ? What is the correct option?

[juan3211]

Thanks, he is my brother in law, I am helping him by posting here. I will check the videos myself and try to explain him, thanks

[juan3211]

Yes, that is why the best option could be a simple step down transformer. As I have read all of you, it will not disturb the wave form a lot, so for a no-precise job, it may work

high voltage differential probe

High voltage yes, but it doesn't have to be differential. Inverters are floating, because they are battery-powered. They don't have any connection to ground.

OP mentioned that he may need to check mains in his house

So if I want to check my home circuit (ground +neutral+phase, generally neutral is connected to ground in grid's substation) how do I need to connect transformer secondary outputs ? What is the correct option?

[joeqsmith]

Thanks, he is my brother in law, I am helping him by posting here. I will check the videos myself and try to explain him, thanks

...
Now I know that these two YouTubers how review the 1013D don't know a lot about it or about electronics in general.
...

Rather than place the blame on the YouTubers,  maybe consider the SISO factor (Shit In = Shit Out).   Asking better questions may yield better results.

You posted the comment blaming YouTubers, not your brother in law.  Now you blame him.   I may not know a lot about electronics in general but I'm mature enough not to blame others for my shortcomings. 

[juan3211]

Sorry, I am not speaking about you. I was speaking a out two YouTubers that said that the Fnirisi 1013d was capable of measuring 230vac with 10x and that they already had done it.

Sorry if have written something that you feel bad.

Sorry.

Of course it is not general, I am more confident with this forum, not YouTube. My brother in law has get that answer from 2 YouTubers. NOT YOU

Sorry again for misunderstanding.

Thanks a lot for all your help.

Thanks, he is my brother in law, I am helping him by posting here. I will check the videos myself and try to explain him, thanks

...
Now I know that these two YouTubers how review the 1013D don't know a lot about it or about electronics in general.
...

Rather than place the blame on the YouTubers,  maybe consider the SISO factor (Shit In = Shit Out).   Asking better questions may yield better results.

You posted the comment blaming YouTubers, not your brother in law.  Now you blame him.   I may not know a lot about electronics in general but I'm mature enough not to blame others for my shortcomings.

[juan3211]

Thanks a lot for your videos.

They are quite complicated for me, but this is my fault, not yours. I am newbie. I can see that you measure the wave form after a transformer with little distortion in it.

As I understand, in this videos you are not comparing the wave before and after the transformer, are you?  I have tried to searched a video with this comparation but I can not find anything similar.

Anyway, thanks a lot. I think that I can go on using an step down transformer

Thanks a lot guy and sorry again for my words, I didn't want to create polemic.

...
Now I know that these two YouTubers how review the 1013D don't know a lot about it or about electronics in general.
...

Rather than place the blame on the YouTubers,  maybe consider the SISO factor (Shit In = Shit Out).   Asking better questions may yield better results.

DDS (DIY Domótica Solar) 21 hours ago
​@joe smith  hi , in order to measure a 50-60hz sine wave to check some inverters, main grid,... modified or pure sine, armonics, .... Is it good to use a step down transformer ? For example, from 240vac to 24vac. Or it (transformer) will distrub, smooth, .... signal ?

joe smith13 hours ago
 @DDS (DIY Domótica Solar)  It depends what you are after.   Anything you use will cause some error.   Not all transformers will have the same response.  Of course, you don't want to apply any DC to a transformer.  Following videos show a simple transformer / LEM used to measure AC power with my scope. 

[joeqsmith]

..They are quite complicated for me, but this is my fault, not yours. I am newbie. I can see that you measure the wave form after a transformer with little distortion in it.

As I understand, in this videos you are not comparing the wave before and after the transformer, are you?  I have tried to searched a video with this comparation but I can not find anything similar.
..

Unlike you, I provided a plethora of information about my goals.   I mentioned what I showed was just for fun.  I based my criteria from IEC 6100-3-2 which calls for 40 harmonics.  Living in the USA, I used a fundamental of 60Hz,  or 2400Hz for the upper end.  To improve my scope's limited vertical resolution, I set the sample rate (after filtering and decimation), of 3X over the 40th harmonic (7200Hz). 

I stated that ANY measurement will have errors and that transformers are not all the same.   I've shown using/designing transformers well into the MHz on this forum.  I mentioned that I had no idea what that transformer I used for these two videos was.  It is very old and possible an audio transformer from a tube amplifiers.   To get some idea of how it behaved I swept it from 10Hz to 200KHz and we were not close to the 3dB point.   I then overlaid the primary and secondary along with the LEM at 100kHz using basically a resistive load (PF=1).  It was far beyond what I needed to meet my goals.   

You shouldn't expect what ever E core you find to yield the same results.  Still if you needed to measure MHz on your AC mains, I made a few videos walking through the calculations for a couple of diff probes I cobbled together.   With diff probes being so cheap, it's nothing I would recommend building.   

[Zero999]

I haven't read the entire thread in detail. It's now too long and filled with fluff it's completely unreasonable to expect anyone to read thoroughly.

Briefly: yes it's possible to measure the mains with a standard x10 probe, if the neutral is connected to mains earth. Just connect the probe to the phase conductor and it will work. Obviously don't connect the neutral of the grid to earth, as the only the distributor is allowed to do that. In the case of an inverter: check the resistance with a multimeter, when it's connected up, but switched off. It's generally a good idea to earth the neutral of an inverter to prevent it from floating at high voltages. Read the manual. If in doubt, use two x10 probes: one on the live and the other on the neutral and the math/differential function.

As mentioned above, a small mains transformer is also a decent option. It won't introduce any noticeable distortion on a pure sine wave, but perhaps a little on the modified sine wave. A toroidal transformer is better. I've found small mains transformers are generally good up to 10kHz, but obviously the losses will be higher with increasing frequency. I'm purely referring to using one for voltage measurement, but to power anything.

[juan3211]

Thanks a lot for this answer !

I haven't read the entire thread in detail. It's now too long and filled with fluff it's completely unreasonable to expect anyone to read thoroughly.

Briefly: yes it's possible to measure the mains with a standard x10 probe, if the neutral is connected to mains earth. Just connect the probe to the phase conductor and it will work. Obviously don't connect the neutral of the grid to earth, as the only the distributor is allowed to do that. In the case of an inverter: check the resistance with a multimeter, when it's connected up, but switched off. It's generally a good idea to earth the neutral of an inverter to prevent it from floating at high voltages. Read the manual. If in doubt, use two x10 probes: one on the live and the other on the neutral and the math/differential function.

As mentioned above, a small mains transformer is also a decent option. It won't introduce any noticeable distortion on a pure sine wave, but perhaps a little on the modified sine wave. A toroidal transformer is better. I've found small mains transformers are generally good up to 10kHz, but obviously the losses will be higher with increasing frequency. I'm purely referring to using one for voltage measurement, but to power anything.