If you actually take the fft of that and calculate THD, you will find that it’s not as bad as you interpret it.
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Not the best example, I took a snap while I was just messing around. This is a Multiplus, over a 5Khz range, and greatly zoomed in. I’m using a 9V AC transformer so that it is not directly connected to the grid, so the figures on the screen is somewhat meaningless (eg the 200mV scale). I just wanted to see what it is like. The 50Hz (main frequency) is off to the left, off the scale, and then you can see the third harmonic, the 5th… etc etc basically all the odd multiples of the original (the even ones cancel out), so you see a spike at 150Hz, another at 250Hz, another at 350Hz… and after that there is pretty much nothing left to see.
Doing the same on the grid shows a pretty similar picture.
Pha, Keysite garbage… You welcome to borrow my 1989 vintage Tek 222PS, good up to 600V both channels isolated… No transformer required…
Groetnis: PS no not the scope model, just a friendly jab. Like en Keynote stuff (HP baby)
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I could of course just use the 10x switch on the probe. The scope is limited to 200V peak (which is about half of what I need to measure grid voltage). Also, the one side of the scope is earthed and therefore already at neutral. But I have the old transformer around anyway, and that way I know it is safe 
This is the cheapest Keysight scope you can buy (it’s an educational model). It’s about a third more expensive than the usual hobbyist options, the Rigol DS1052E or the Siglent SDS1202. It comes with very basic decoding support: Serial, i2C… not CAN-bus though, that costs extra. It is heavier than the usual options too, and from reviews I’ve seen, better internal screening. It has USBTMC and VISA support (for doing remote measurements), and a built-in http interface that allows you to make snapshots of what is on the screen.
The main reason I got it was for timing experiments. Using a trigger and measuring how an analog signal responds to that trigger.
It was tongue in cheek, that post thing can do none of what you need, no FFT and no screen printing, you’d have to get a polaroid for that 
Keynote (HP) is super stuff!
Not to go derailing this, back OT.
Groetnis
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Oh I got that… but I really like this scope, I had to brag a little
Not sure what you are trying to say, but that is how you would actually measure THD. Of course, with the correct scales, not like you scaled.
@plonkster I still need to turn your arm 
I got a Nad c546BEE that I replaced the laser but i need to get it on a scope to adjust the optical and you got the rite tool for it.
I just find it fascinating all the areas where the Fourier transform is applicable. Some people in my line of work apply it in time series analysis.
Not sure if you’ve done the mathematics behind it before, but if you want to see an awesome visualisation of how it works, 3B1B has a great video on it. I’ll try to link it below.
Edit: I believe it is this one: But what is the Fourier Transform? A visual introduction. - YouTube
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Giving Richard an example of what an FFT looks like on a scope. Agreed that it needs to be scaled correctly, didn’t have pictures of that floating on my phone though. Pretty much need to scale it only from 50Hz up to 550Hz, maybe. In my case I wanted to see if there are significant higher frequencies… given the 20kHz PWM signal. Doesn’t look like it though.
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Thanks, that makes sense.
The first CD made in 1983 by Philips. (what happened to that company??)
Sony also launched theirs at the same time since it was a joint venture.
PS: On display in an Italian museum. No English version permitted.
This is perhaps a better picture. Span is set to 500Hz, with the center at 250, just to use the screen space effectively. This is a picture of the grid wave (yellow) with the FFT (magenta) overlayed.
The bulk of frequency is at 50Hz (to the left, off the scale, and then every division is another 50Hz, so 100Hz has nothing (it cancels out), and the same for all the even harmonics. The odd ones at 150Hz, 250Hz, 350Hz and 450Hz is visible.
Interesting here, the 5th harmonic is higher than the 3rd. I don’t know enough about this stuff to know if that means anything.
I also have the scale set up for volts rather than dB.
I hope this is not too off-topic, but I think it slides in with the topic of permanently running on an inverter. Your power is probably going to be less clean than a good grid connection.
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