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ADC over sampling

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djs

Electrical
Mar 21, 2001
719
Does anyone have any hands on experience with this concept. An explanation can be found attached to this post. I am looking into an application where I will need 12 bits of resolution and most microcontrollers have only a 10 analog to digital converters.
 
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Yes, this works great. As long as you can spend the time to take extra samples, and your noise is truly random, it works great. I've oversampled a 1-bit A/D (comparator) and gotten 12-bit resolution (lots of samples!). Coincidentally, this was on an ASIC designed by Atmel too!

John D
 
Assuming your noise is Gaussian... if it's not, well, you'll need to take that into account.

Dan - Owner
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I was thinking about applying a controlled ramp signal mainly because I am not sure that the noise level in the signal I will be measuring will be large enough. BTW the signals will be amplified pH and ORP signals. So time is not that important in this application.
 
Huh? You don't think the noise in the signal will be large enough? Isn't that a good thing?

You can add in "controlled" noise, but that's to account for non-linearities in the lower bits of an ADC and has nothing to do with noise in the signal. I see no use in applying a "controlled ramp", whatever that may be.

Dan - Owner
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Perhaps I did not explain it well enough. Please look at the bottom of page three of the document I supplied a link to. Noise at the input of the ADC must be at least 1 LSB which for the Atmel chip is about 2.5 mv. I fully expect that the noise level to be much lower than that level. For this reason I will probably need to use the technique called "dithering" in the attached document. Dithering is shown in more detail on page six.
 
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