Title: 6022BE, Software 1.0.5, Wrong FFT display [Print this page] Author: chenchijungtw Time: 2017-11-19 13:54 Title: 6022BE, Software 1.0.5, Wrong FFT display 6022BE, Software 1.0.5. FFT result is strange. No freq. indication.
Author: amy Time: 2017-11-20 16:59
Sir, You only can calculate by yourself.
FFT frequency calculate：
The frequency of the full screen = sampling rate/2.
For example, in the picture, the sampling rate is 8MSa/s.
The frequency of the full screen should be 4MHz. The frequency of the waveform should be 1MHz.
[attach]1829[/attach] Author: chenchijungtw Time: 2017-11-21 23:47 Edited by chenchijungtw at 2017-11-21 23:59
I'm measuring the 1KHz 2V p-p test signal on scope itself in ch1. I expect to see 1KHz, 3KHz, 5KHz,... harmonics (since it is square wave) but the spectrum is not like that. That's why I say the output is strange.And, how many points for you to calculate FFT? Is it 256, 512 points, 1024 points or?
Is my sample freq. too high? (1MHz. So, FFT bandwidth is up to 500K. If FFT points is too small, we can't identify 1K and it's harmonics)
Author: amy Time: 2017-11-22 16:48
The square from the scope coupling terminal is used to calibrate the probe. The bandwidth of the square is very low. All the other ingredients are filtered.
The fft has 512 points.
What is the frequency of your signal? Author: chenchijungtw Time: 2017-11-22 21:46
I'm measuring 1KHz. When I change the time/Div to 1s, sample freq. will down to 100K samples/s. Than I can see 1KHz and it's harmonics.
Suggestion: Can you display something like frequency for FFT? User must calculate themselves. And, is it possible to measure FFT by cursor?
Can I click the signal on FFT and display the freq/value of that point?
Author: amy Time: 2017-11-23 11:53 Edited by amy at 2017-11-23 12:00
Sir, this is affected by the sampling rate。 When the frequency is low, the sampling rate should be very low.
You can enlarge FFT waveform 10 times, so that you can see more clearly.
[attach]1841[/attach]
And you can use the vertical cursor to measure the time of the frequency point.
The time / (timebase*10) is the proportion of frequency point. You can use multiply it by the frequency of the full screen to get the result.
Author: chenchijungtw Time: 2017-11-24 20:50
The method you said is not user friendly. My suggestion is focus on user friendly point of view. Author: amy Time: 2017-11-25 08:27