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Electronics => Beginners => Topic started by: catcream on June 17, 2024, 11:16:55 pm

Title: SDS1104X-E FFT: Help explain noise floor
Post by: catcream on June 17, 2024, 11:16:55 pm

Hello, I tried using the FFT function on my SDS1104X-E to measure a 1kHz+5kHz sine signal from my Dayton Audio DATS v3 for any distortion. I see the noise floor decreasing as frequency increases, and also noise between the two spikes (1k-5k) often sit at -40dBV but sometimes drop to -50dBV at certain frames.

My guess is that the DATS has a THD less than measureable by 8 bit and I'm only seeing the oscilloscope noise floor, however I'm still curious as to why it looks like this, especially the -40 to -50 dBV thing. Can anyone explain this?

Also, can I use my Scarlett 2i2 gen 4 for audio measurements? (+0.1x or something-resistor voltage divider for amplified signals). I'd like to see THD and also make bode plots for op amp based filters/crossovers. Thanks!

Title: Re: SDS1104X-E FFT: Help explain noise floor
Post by: aliarifat794 on June 18, 2024, 07:16:49 am

 The fluctuation between -40 dBV and -50 dBV could be due to various factors such as environmental noise, slight variations in signal input, or the oscilloscope’s internal noise characteristics.