USB FFT (Cheap ?)

[Nikon1975]

Do you know any USB oscilloscope that, with a software, can be used also as a FFT ?

Thanks,

Davide

[cliffyk]

Almost any of them, one of the least expensive for audio frequency work would be the Syscomp Circuit Gear CGR-101 ($189 from Saelig, a bit less perhaps elsewhere).

It also uses 10-bit ADCs, for a theoretical 60 dB dynamic range which would get you close to being able to observe 0.1% THD using the FFT analysis. The typical 8-bit scopes with FFT are pretty much worthless for any distortion analysis as their 48 dB range limits distortion analysis to just a bit better than 0.5%.

[star882]

If audio is all you need, you can just use a sound card and Baudline.
baudline signal analyzer - FFT spectrogram

[womai]

I have designed an USB/PC based oscilloscope that can also do real-time FFT. Available as a self-assembly kit or fully built up and tested:

DPScope - A Low-Cost PC-Based Oscilloscope

Regards,

Wolfgang

[Frex]

It seem to be an interesting product, and good value for money.
However, a very important point for an audio instrument is the dynamic range.
I don't have find which resolution allow this instrument. Probably 8 or 10 bits...
Unfortunately, FFT will be not very usable for fine audio investigations.
it's still a very good job !

Frex

[womai]

Resolution is 8 bits as you suspected (except for datalogger mode, where it is 10 bits).

The hardware itself would support 10 bits, although the maximum sample rate would be a bit lower (takes more time to store 2 bytes per sample than 1), but that wouldn't be a big issue - around 200 to 500 kSamples/sec would still be more than enough for audio. 10 bit sampling would need some changes to microcontroller firmware and PC software, but nothing really dramatic.

[ghg]

Hi

10bit and 500ksps would be fine,
just make sure the input conditioning gives the 10bit -> 60dB dynamic range, too.

Please, add a FFT screen pic to your web page.

BR

Gary

[PedroDaGr8]

Originally Posted by womai

I have designed an USB/PC based oscilloscope that can also do real-time FFT. Available as a self-assembly kit or fully built up and tested:

DPScope - A Low-Cost PC-Based Oscilloscope

Regards,

Wolfgang

Well I'll be, I just read your instructable today. I am going to be purchasing one of your kits once I have a job again (anyone want a chemist in San Diego? ).

Nice job on it.

[Nikon1975]

what about this ?

EasySync USA

Davide

[cliffyk]

Originally Posted by Nikon1975

what about this ?

EasySync USA

Davide

I had forgotten about the StingRay. It has been available for several years now, and is 12-bit.

The software is decent, better than many others, and most important to me it let's you change the ghastly black background to something readable on an LCD screen. I am often bemused by how PC instrument manufacturers are so hell-bent on simulating "real" instruments that they simulate the bad parts too--like black background display areas, unnecessary range selection buttons, and the like.