- Identifying an audio ADC - 1 Update
- tests to do on used oscilloscope? - 1 Update
| bob prohaska <bp@www.zefox.net>: May 11 03:37PM I'd like to find a datasheet for an audio ADC used in an inexpensive USB audio capture "card" so as to better understand how to use it and what it can do as a low-frequency oscilloscope. It came from Amazon, sold under the name "DIGITNOW! USB Audio Capture". It seems to work surprisingly well, working with no issues on a Raspberry Pi 4 using the stock RaspiOS version of Audacity. It also works under the latest (not stock) version of xoscope, which had to be recompiled to obtain ALSA support. I'm inexperienced with both programs, so the behavior is somewhat confusing but it does seem worth exploring further. The seller's tech support carefully misunderstands every question. It's a one-chip dongle, the single IC is marked IS821S SHO3AO9OAGC 1O2DNMO19 All the O characters look the same, so they could be mixed with zeros. Repeated searches using Google and DuckDuckGo have turned up nothing, does anybody recognize at least a manufacturer? Thanks for reading! bob prohaska |
| "jurb...@gmail.com" <jurb6006@gmail.com>: May 10 03:41PM -0700 Need some equipment. I take a DC voltage source and then adjust a square wave generator to that voltage and go up seeing if the amplitude stays with the changing of the V/div. control. And move the position control to see if the waveform is linear at all portions of the screen. Keep going up in frequency, I happen to have a generator that stays stable at any frequency, it is a Wavetek and operates on a different principle than most. Most do keep a square constant, but not necessarily in sine wave. Next you need a freq counter, set the generator accurately to a 1,000Hz square, put the scope on 1mS/div. Adjusting the horizontal position to where the first cycle lines up with the graticule, check the rest. They should also line up and the vertical parts of the square wave should be on graticule lines all the way across. If they run off, the time base or H size is off. To determine which, switch to different frequencies ad time bases, always with the freq counter on it. If they vary it is the time base, if they constantly run off one way or the other it is the H sweep size - or more professionally put - deflection. How accurate you need it depends on price. I got one I don't pay much attention to, the time base or deflection is slightly off but I am not measuring frequency with it. The amplitude reads right and that is enough because I use it for everything. Even DC, it is much quicker because usually I only need to know a source is there. If you need a scope that is totally accurate all the way you need an old Tektronix. |
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