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Amateur oscilloscope / USB generator (sound chip)

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  • #2
    wesoly wymiatacz
    Level 10  
    Value for money just great. Congratulations on a very successful construction.
  • #3
    katakrowa
    Level 21  
    Cool cheap and looks effective. I had this Hantek so I suspect yours works better - maybe not this range, but still :-)

    However, I have a question, what is the use of an additional amplifier before entering the sound card?
    Could you please share the source code of your application - I saw that you were doing this in visual studio c ++?
  • #4
    meraks
    Level 1  
    I would like to say hello to everyone (first post).
    I have some doubts about the method of simplified calibration.
    The AC voltmeter shows the effective voltage.
    We calibrate the amplitude. It seems that only after taking into account the coefficient ?2
    we will get the correct calibration. Maybe I was wrong, so please explain.
    It is possible that the calibration procedure takes this fact into account.
    Best regards,
    SM
  • #5
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  • #6
    cefaloid
    Level 32  
    goreckidiy wrote:
    Device parameters:
    Frequency: 20kHz


    At what sampling rate is the above true? Because at 44.1kHz you are not completely able to judge the shape of the 20kHz signal because that gives 2 samples per period. At 192kHz (if the card has one) I can believe it.

    goreckidiy wrote:
    Sound card selection:
    In principle, you can use any. However, it is worth bearing in mind that the one with which you can remove the DC component filter, both on the microphone input and on the headphone output, is better. The DC component filter causes that the input cannot be given DC voltage. As a result, the rectangular graph will not resemble it at all, the sine wave will have characteristic "spouts" at the top, and the triangle will lie on the right side.


    A very valid comment. However, it is not only about the DC component but also filters that cut the band to 20kHz. For example, a 1kHz square wave signal from a sound card where the bandwidth is limited to 20kHz will look like this:
    Amateur oscilloscope / USB generator (sound chip)

    The reason is nicely explained here .

    I hope that at 192kHz the filter of such cards is set to around 100kHz, so its operation can be omitted.

    Generally, looking at the charts from Hantek: good job for this money, and this Hantek is not worth PLN 10. You did not mention that the FFT analysis from the sound card (16 bit or 24 bits) will be reliable and the Hantekt (which is probably 8 bits ...) will be a worthless slug.
  • #7
    pawel-jwe
    Level 30  
    What about phase inversion of the signal through the sound card (MIC input)? I had this problem myself and it is quite common (supposedly it is a software issue - drivers, but I did not study this topic).
    In addition, in cheaper cards, the phase likes to break at the band boundaries, which additionally "spoils" the charts.
  • #8
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  • #9
    cefaloid
    Level 32  
    R-MIK wrote:
    At 44kHz sampling, "digital" 22kHz "analog" band, max 1..2kHz (10..20 samples per period), real 100..200Hz (100..200 samples per period). What can such an "oscilloscope" be for. Only to find the ripple of the linear power supply.


    Therefore, 192kHz sampling can and must be used. Then it starts to make sense and you can analyze something.

    Let it be for 10 - 20 PLN and even fun :)

    R-MIK wrote:
    Better to buy a used oscilloscope and generator.


    The problem is that you can buy an analog oscilloscope for a small amount of money. And this one in the era of microprocessors is in my opinion of little use.

    Digital ones, again below PLN 2,000, are basically toys. With the one used for PLN 1000, it is appropriate to have an analog one next to it, because something like this in audio measurements means a toy and not an oscilloscope:

    Amateur oscilloscope / USB generator (sound chip)
    Because what does this +/- 1 bit noise mean? That for stupid audio we need not 8 but 12 bits of resolution + "digital phosphor" and that costs money.

    So I would criticize the fact that it costs PLN 20 and not 2000.
  • #10
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  • #11
    Freddy
    Level 43  
    Stop hanging the dogs on @goreckidiy :)

    According to the PWN dictionary: an oscilloscope is an instrument for the observation and measurement of electrical waveforms

    According to the wiki: Oscilloscope - an electronic device used to observe, imaging and study the dependence waveforms between two electrical quantities or other physical quantities represented in electrical form

    So no matter if the bandwidth is 20kHz or 10GHz - this is an oscilloscope
  • #12
    cefaloid
    Level 32  
    goreckidiy wrote:
    Does the talk about 8/12-bit resolution somehow relate to my project? - not really.
    Comparing an oscilloscope for> PLN 2,000 to a sound card is also pointless, because it's like comparing a 40 'Full HD LCD TV to a Rubin ;)

    My friend COMPLETELY did not understand my speech. Totally.
  • #13
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  • #14
    cefaloid
    Level 32  
    There has been a misunderstanding ... With this digression I wanted to make all the critics realize how much would cost what they criticized in your appetizer. I wanted to show that even these super "oscilloscopes" for over PLN 1000 (Siglents, Rigoles, Owons) have a lot of problems. And here the cost is at PLN 20. No cost. If you turn up the sampling to 192kHz (is it possible?), This band should be interesting and not so much can be previewed. And not super precisely? In 90% of cases, the idea is to view the chart for an overview.
  • #15
    wesoly wymiatacz
    Level 10  
    Hey, not everyone can afford a device worth 1000+, and here it is cheap, simple and that it has disadvantages, as even super expensive gems will have them and that's it. After all, you can see a lot with the oscilloscope described above. And everyone can afford it.
  • #16
    kassans
    Level 31  
    Cool design! Can you describe how you removed the filters on your soundcard and where less were they?
  • #17
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  • #18
    kassans
    Level 31  
    I just have a stationary machine, I was thinking about a PCI sound card and they are more susceptible to modifications :)
  • #19
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