ADC resolution questions

Discussion in 'General Electronics Chat' started by maxpower097, Jan 15, 2011.

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  1. maxpower097

    Thread Starter Well-Known Member

    Feb 20, 2009
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  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Nope, the bits go in powers of 2. 12 bits is 4096 steps of resolution. 24 bits is more than it is possible to distinguish.
     
  3. tom66

    Senior Member

    May 9, 2009
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    It is a binary relationship.

    A 10-bit ADC has 1024 steps and a 12-bit ADC has 4096 steps; the number of bits has increased by two, which means the number of steps has quadrupled.

    With a 24-bit ADC you would have 16,777,216 steps.

    You could probably pick up what the neighbours were saying with such a sensitive button. It would sense the slightest change in the midatlantic ocean currents. The wind outside would be a scream to it.

    Thing is, making such an ADC isn't impossible. In fact for just a few thousand US$ you can buy a 28-bit ADC, which has 268,435,456 steps. I think you could eavesdrop on the ISS with that. ;)

    However, as you hit such a high resolution costs massively increase. So do sampling rates. That 28-bit ADC can do a maximum of 14 samples per second. A common microcontroller ADC can do more than 500,000 samples per second.

    Which is one reason why most digitising oscilloscopes are 8-bit only - it is easier to make a 1 GS/a ADC with 8-bit resolution. It is not easy to make a 12-bit ADC go so fast without a hefty price premium. And you need fast in video games.

    Then again, why would you need so much resolution, even 1024 steps? Even 16 steps would probably be good enough for most people. Such resolution is a marketing gimmick, in my honest opinion.
     
  4. timrobbins

    Active Member

    Aug 29, 2009
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    1024 = 12 bit
    2048 = 13 bit
    4096 = 14 bit
    .....

    However you then need to determine whether you anaolg input can resolve to that resolution. For example, a wirewound pot wiper touches one or a few turns of resistance wire, but there may only be 500 turns in the pot, so the effective resolution (the wiper voltage output) may jump around a bit as the wiper contatcs different turns. You also need to have a supply voltage to the pot that has noise/hum level better than resolution, or filter before the adc, as it will cause digital jitter, which you can also digitally filter, but you don't want to eat in to the max dV/dt you want from the game controller (which goes to the 'speed' of the ADC and whether it can accurately track a fast change of controller - a point that you need to get a handle on if you want to go to higher resolution ADCs.)

    Tim
     
  5. tom66

    Senior Member

    May 9, 2009
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    Actually 1024 = 10 bit, 2048 = 11 bit and 4096 = 12 bit.
     
  6. timrobbins

    Active Member

    Aug 29, 2009
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    Further to above comments - you need a video screen with equal to or more resolution than 1024, or 2048 pixels to see the movement you're trying to make. And the 'resolution' of the video game software (which is what really counts) is unlikely to be more than the highest screen resolution the game can be configured for.
     
  7. maxpower097

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  8. maxpower097

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    Last edited: Jan 16, 2011
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