11 years on and you're still the best and electronic master. Just to let you know:- One of the finest videos you made was on the CMOS Phase Locked Loop, (CD 4046). That was truly a master class! Thank you Mr. Wolfe!

Your videos are all top quality. There are so many utubers who just do so much hand waving and yabba-dabba, on EE subjects. I produced an FFT programs a few years back. I took the code from Frank Press's book "Mathematical Algorithms" and got it working on a PC-104 486 board connected to a quarter res LCD. I used a DOS graphics library I had developed earlier. I really like the MDS4000 scopes. One company I worked for put one on my desk. I used it a lot and left a write-up on one of their products, complete with signal graphs. I wish I could afford one.

That explanation of a window function is golden. I came thinking “I know how to use the FFT - I’ve done it before, but this is good television”, but even in that regard I learned oodles about the parameters. I’d pay out of pocket for another degree if you were on teaching staff.

You really explain things the best way. Anyone who takes the time to actually draw on paper with a pencil deserves a big thumbs up. Those 4 morons who did not like this video should be ashamed!

Love your demos/videos very much! Whatever I didn't completely understood I now understand. Thank you again!

Thank you for putting out this very helpful tutorial. The basic idea of how FFT would have been contemplated by early thinkers is clear now.

Thanks for a superb demonstration of FFT for audio frequencies. I've only recently upgraded from an old analog CRO to a DSO. I design, build & repair valve (tube) guitar amplifiers and was particularly interested in FFT for audio and your excellent, detailed demonstration has nailed it for me. Thanks again.

Well I never really understood what FFT was, so thank you very much for that. A picture paints a thousand words.

Excellent video as usual! Thanks! I can see using FFT on a digital scope to sound proof a room or reduce sound as well as wear and tear in a machine.

Hey Alan, Excellent Explanation. Thank you very much for your time and efforts.

Thanks a lot sir. Your videos are really easy to understand and helps me get the concept really fast. Really appreciate the practical nature of the demo. Thanks again!

As a recent EE grad, I could only wish my instructors taught as well as you. Thanks for taking time to explain these fundamentals.

Great job, and very interesting as always. It's always a nice day to see that you've posted a video, even if it doesn't even remotely apply to me.

Thank you! Just got a second hand R&S scope for the sole purpose of having frequency distribution from DC to 9 kHz, and couldn’t get the span narrower than 10 MHz. Though I had made a mistake. Seeing your vid made it all work out as expected. TY!

That was very helpful, thank you for you time on this topic.

Thanks I have struggled in this fft, but after seeing your video I understand how it works

I don't know how to thank you for all the good videos!! Thanks you so much!!!

Very Excellent explanation well done and well presented. Learned something new Great Job

Thanks for posting. You have done a great job explaining things.

Excellent introduction, thanks!

This video was indeed very helpful. Thanks!

That makes so much sense!!! And, THANK YOU SO MUCH!!! You've just been put on my "best friends forever" list! Lemme go try this! thanks again! I have Native Instruments Reaktor to check this on, so it's pretty much like programming, but with modules and in real time.

Thanks good man. Great tutorial as always.

Awesome video. Video instructors like yourself are a godsend & especially to people like me who are trying to modify and build amplifiers with no electrical engineering background or former electronics education other than what we have been able weave through on the internet. Thank you very much! Still trying to decide whether to purchase a used but working/calibrated analog scope (I lost a bid the other day on a GW 20mhz semi-modern analog scope w/digital buttons for $42 lightly used *sigh*😣) or one of the modern cheap digital units that does a simple 100khz or similar simply for the math and fft functions like in the video. Im torn lol i like the simplicity and real time accuracy of the analogs ive seen...but i also really want to be able to have fft capability as well as the simplified time saving math functionality. Oh, plus at this very minute my budget is limited to maybe slightly over $100 (the biggest handicap of the matter 😅) to spend on such - so used is thr only real option 😬

awesome video and explanation as always, thanks.

Thanks for this great tutorial on fft. I am taking a receivers class this semester and I need to know how all this works.

Now that is how to teach! I wish this guy had been one of my tutors.

Excellent video!

Thank you for your effort and sharing this interesting information!

Very nicely presented!! Thank you!

That was solid and comprehendible.

Sorry for popping up randomly in the comments of your old videos, but I recently discovered your channel and I wish I had discovered it earlier, it's awesome, thank you. One question on the video: can you actually determine the rpm of the drill, maybe form the lowest frequency peak ?

Great idea!!!! Let's take your scope to a hardwarestore to examine the "noise"of your soon to be new drill

Thanks, this was a very good refresher. Very clear and concise. Of course you would use a better microphone with a known frequency response if you really wanted to measure accurately.

I still vividly remember how I struggled to understand all that. I hope I have given you some clues that point you in the right direction.

Very nice explanation

I can't be the only one who winced at the thought of a drill so close to that scope!

It is worth to note the dynamic range of the measurement. Pending on scope settings, the spurious dynamic range is only about 40 to 50 dB. Most oscilloscopes are limited by a 8 bit analog-to-digital converter. However, the scope may show a noise floor well under 50 dB with erroneous harmonics.

Nyquist limit applies to every frequency in the signal you're examining, not just the ones you're interested in. Those high-frequency components you don't care about will still give you aliases. In this case though I imagine the speaker is rolling off the higher frequencies pretty well.

Hi Alan, Thanks for the video, I am using a similar oscilloscope to the one in the video (Tektronix DPO400 series) and trying to measure values between 30Hz-150kHz using the FFT mode. When comparing the results of the measurements at two test frequencies (120Hz and 125Hz), I noticed significant difference in FFT max value vs. the Vrms value of the time domain signal at the same input value.. At 120Hz, I'd see 6.35Vrms for both FFT and time domain Vrms. At 125Hz, I'd see 5.39Vrms for FFT and 6.35Vrms for time domain. I'm assuming this has to do with what you were describing when talking about windowing and the signal beginning and ending at the same value. How would I go about solving this issue in this case? Thanks, Jadon

First of all let me take a pleasure to appreciate this video. I am neither designer or musician, I am engineering student struggling with my Digital signal processing(DSP) course. Everything seems perfect in theory class but I am still doubtful as to how I am gonna use this in my project that aims at building voice controlled security system, recording particular voice in say more noisy region. (thinking of this for my final year project). I need some help in visualizing all these DSP tools...

Love your vids! Thx!

Great video, thanks.

Oh! I looked at that video a while back, now it makes more sense. Thank you so much. I was sweeping the frequency of a bandpass filter instead of a the frequency of a sinewave. *facepalm*

Excellent, does is need a 1k Ohm resistance on the cables between the sound card and the computer or oscilloscope with FFT function? Thank s

Very Good! Even an entry-level hobbyist like myself understood that entire video! I wish I knew why I understood it now, but when I read about the FFT function, I thought to myself "...I must be dumber than a box of hammers because I have no idea what I just read..." Thanks for the video and the reaffirmation in my own mind that I may not be as stupid as my dad (rest his soul), said I was, lol. Rich

If you can, could you explain how FFT works? I've been trying to wrap my head around the windowing methods. like, how it figures out each of the frequencies. If you could, that'd be great! Thanks again!

hey, guess its kindda ages after you have posted this video... but a really good job giving the bacics of FFT..i really wud love to find some more stuff on FFT can you refer me to some of that? Thanks

thanks you that's a good video you made

Very good video

Good stuff. Thanks.

Hi , I would like to know if it is possible to measure in a specifit frecuency the exact value of the ohms in a crossover 2nd order ? thank You

I have 3 scopes with this feature and now I know how to use them.

You are also getting the magnetic field inductively, mixing into the signal. The effect of that may (or may not) be quite significant.

I can't find much by googling about the window factors involved in frequency resolution mentioned in this video (freq res = w.f. / t_duration), only about window correction factors to correct amplitude or power of peaks for different window functions. e.g. for Hamming 1.85 for amplitude and 1.59 for power. Are they the same thing?

Thank you sir!

Thanks for the video Alan, I have a question, how do I measure the dynamic range of a signal with the FFT function in the scope? How do I know where is my noice floor and how to improve it?

Concerning the negative value: the phase could be 180 degrees off. In fact to correctly do an FFT you not only need to multiply it with a sine, but have to do the same again with a cosine (something I had omitted because explaining an TTF in 500 chars is a bit challenging :)). These two values then make x and y values of a vector where the the angle is the phase, and the magnitude is the signal strength of that frequency.

Cool, I'll check them out as well!

I'm also thinking of incorporating a audio sweep generator into along with fft from my scope. What sort of things would you see ? What would you need to consider ? What if you were to use a noise generator ? N6GRG

can you please recommend a book on exploiting an oscilloscope for its functions including that of a FFT

can u make a video on how a to d and d to a "audio" converters work???

Nice video. In Acquisition Mode 9:19 what is the difference between Hi Res and Average?

I've written a couple of introductory FFT blogs at Scope Junction...may be of use.

we bought a oros nvgate for vibration and noise measurement, in the manual i saw selections such as rms, max, or min, are these the time domain displayed signal? how can i get these from the original value? and the frequency domain has inst. spectrum and avg. spectrum, are these the same?

thanks very helpful

Never thought about the "audio quality" of my drills before. 🤯🤣

Nice explanation of using FFT on a scope. Just a couple of questions, Is the window effectively a built in apodization function? I always looked at the FFT as capturing the frequency content of a time domain signal at a specific instant in time. I am curious when we look at the audio spectrum as typically 20 Hz - 20 kHz, if we take a sample longer than 50 microseconds don't we begin losing resolution of the signal at high frequency since the signal is possibly changing this quickly? What I guess I am getting at is that if we sample at more than double the Nyquist frequency for the frequency band in question, and we capture 400 ms of samples the FFT could change dramatically over that time with a complex audio (music) signal, so is the oscilloscope just averaging all of these samples? Thanks for your instructive demo!

Thanks man. If it was not you. I would no longer high marks on this

Allen, is it possible to use the FFT to measure phase noise in 1 Hz bandwidths of a oscillator or transmitter?

Thank you sir..

Thank You !!

👍Thank you sir.

Thanks for your great video. Question: Why is it so difficult to find a "swept-tuned" frequency analyzer for audio? My scope does FFT, but I would like to use swept-tuned. It seems they all want to start at 9KHz and go up, not down. (I'm guessing cost is a factor, but why?)

Hey Alan! This might be a dumb question; but can you do a bode plot using FFT? If so, can you show us how. Thanks!

Would you be able to upload your Notes to this video? Thank you so much for your Videos!

Thank you so much!!! :D

HI there, this was very interesting for a novice. I use a scope in automotive applications but I'm not expert. I am however trying to work out if I can use the FFT function to detect a momentary frequency drop out in a constant frequency signal. My expectation is that I would see a spike at the low end of the spectrum? Appreciate your thoughts. Alex

Fantastic

PS: That's one reason why complex numbers are often used in DSP: one complex number can hold both the phase and the amplitude. You have to envision a complex sine wave as a spiral going along the time axis. Another advantage is that you can define both positive and negative frequencies (going clockwise or counterclockwise). E.g. doing AM demodulation of a signal using complex numbers is trivial: you just take the amplitude of each complex sample and you're done! Try that using just real numbers.

It's almost as though you knew what you were talking about! LOL Good show!

Can an oscilloscope with FFT do a spectrum analysis for power frequency voltage and currents? I am typically interested in analyzing motor currents(50Hz) to look at components of 2x, 3x, 4x and other higher-order harmonics.

I would like to see how you find the spatial resonant frequency of a inductor using the fft function of the oscilloscope.

why were my tutors so bad? Wish they had been as good as you!

The windowing is not essential to the FFT, it is the method for 'cutting' a piece of signal out of a continuous stream. See it like a fade in/fade out. One important property that enables Fourier analysis is that if you take two sine waves, multiply them, and then integrate the resulting signal, you get 0 if the two frequencies are different. This is easy to check e.g. with a spreadsheat (make two columns with sine wave values, multiply the columns and sum the results).

A speaker works as a microphone but not "just as well." The inertia and spacial extent of the cone attenuates high frequencies and the coil couples directly to the motors' changing magnetic fields.

Great video but I can not see difference in spectrum of drills.

I used to do this in the lab

Hi allen. Why do you need a spectrum analyzer-If we can get the spectral components through FFT. How is spectrum analyzer better than FFT ?

The guy is Mr. Wizzard!

So, it looks like: if waveform = the sinewave frequency, the value < 0. I'll study this thoroughly tonight until my brain is full, then I'll get brainwashed for a couple of hours and catch up on movies I never got to see. Thanks again! So, to make a spectrum analyzer, I'd need to sweep the frequency of the sine wave instead of the filter frequency? then of course, read it in, read it out to a scope, right? I'll give it a shot to see what happens!

Can the fft function be used like a spectrum analyzer? For RF?

Thanks

Thumbs up.Thanks

Where does the scale and reference come from on the FFT?

I was talking about qwaqwa1960. But okay. kool. thanks!

Thank you thank you & thank you ^_^

Can we see original Signal power on FFT in the oscilloscope.i see DB but i must see dbm

I definitely find that the Dewalt has a smoother top end and more pronounced mids than the Sears. Just kidding, GREAT video. Very useful...

Nice. A drill is likely to have lots of ultrasonic energy though. I wouldn't use less than 100kSa/s. OK...maybe not with that transducer!!! :-)