Relation between sampling & resolution

Discussion in 'Homework Help' started by amit.31, Sep 5, 2011.

  1. amit.31

    Thread Starter New Member

    Aug 29, 2011
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    Hi,

    how increase in sampling rate reduces resolution?

    Any help would be greatly appreciated and thanks in advance.
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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  3. hgmjr

    Moderator

    Jan 28, 2005
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    Increasng the sampling rate suggests that you are taking samples more often. That would in turn improve resolution.

    Perhaps what you intended to state is that increasing the time between sample taking. If so, then that would result in a decrease in resolution.

    hgmjr
     
  4. Georacer

    Moderator

    Nov 25, 2009
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    The sampling rate is the number of measurements per time unit. The resolution is the quantity of data in each sample.

    Those two quantities aren't directly linked to each other, so increase in one, doesn't mean reduction in the other.

    However, their product equals the current data send rate, and if this has a maximum (bandwidth), further increase in one quantity must be accompanied with reduction in the other, otherwise the data will be skewered (skewed?).
     
    amit.31 likes this.
  5. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    you could run into problems if your sampling rate is faster than the controllers ability to handle it. An ADC greater than 8 bits into an 8 bit controller for instance. Another problem could be the need for smoothing algorithms if your sampling a jittery line, resulting in processing overhead. Although sampling speed does not imply resolution as mentioned, in practicallity, it could.
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Increasing the sampling rate does not necessarily improve the resolution.
    Increasing the sampling rate increases the maximum frequency that can be recorded. Since any proper sampling system requires an anti-aliasing filter, the input is already band limited. Hence increasing the sampling rate adds no new frequency information.

    The amplitude resolution is improved if more samples are recorded and then averaged. But an improvement in resolution is achieved only if there is random noise in the signal.
     
  7. amit.31

    Thread Starter New Member

    Aug 29, 2011
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    Well, thanks to u all....

    Actualy i m working on an sigma delta ADC.
    n i studied about dithering yesterday....basically i was having a doubt like "how this(dither) noise inserted at the input imoproves the overall SNR of the ADC?"

    thanks in advance again....
    with regards.
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    This is because of quantization effects. Imagine if you took repeated samples of a constant noise-free voltage. You would get the same answer and no improvement is obtained by averaging. When you add random noise whose amplitude is large enough to cross several quantization steps, you will get different results. When these are averaged you will enhance the resolution of your ADC.
     
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