How many bits should be employed to obtain a resolution

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Discussion Overview

The discussion revolves around determining the number of bits required for an A/D converter to achieve a specified resolution of 0.01% with a full-scale voltage of 10V. Participants explore the implications of this resolution in terms of voltage and bits, addressing potential misunderstandings in the calculations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant calculates that to achieve a resolution of 0.01% of 10V, 14 bits are needed, but expresses uncertainty about the correctness of this assumption.
  • Another participant corrects the initial calculation of 0.01% to 0.0001, suggesting that this might lead to a different number of bits required.
  • A subsequent reply questions whether the resolution should be interpreted as 0.01% of the full-scale voltage, proposing that if so, the resolution should be 0.001V, leading to a calculation of 17 bits.
  • One participant highlights the ambiguity in the problem statement regarding whether the 0.01% applies only at the maximum voltage or at other values, such as a 1V reading.
  • It is noted that maintaining units throughout calculations is important for clarity, particularly in understanding the implications of the resolution percentage.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the resolution percentage and its application, leading to multiple competing calculations for the required number of bits. The discussion remains unresolved regarding the correct interpretation of the problem statement.

Contextual Notes

There is uncertainty about whether the resolution of 0.01% applies only to the maximum voltage or to other voltage levels, which affects the calculations. Additionally, there are discrepancies in the interpretation of the percentage calculation leading to different bit requirements.

killersanta
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Homework Statement


An A/D converter is to operate with a full-scale voltage of 10V. How many bits should be employed to obtain a resolution of 0.01%?


Homework Equations


Resolution = Full Scale voltage / (2N - 1)


The Attempt at a Solution



.01% * 10 V = .01/100 * 10 V = .001

.001 = 10 V / (2N - 1)

N = 13.2879 = 14 bits

I am just learning this stuff, but 14 bits seems high to me. I believe the mistake is in the Resolution. I am just assuming they me the resolution is .01% of the full scale voltage, this seems wrong to me.

Thanks for any help!
 
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0.01 / 100 = 0.0001 not 0.001
 
Wow, thank for the quick reply.

I know that, but don't you times it by 10 V? Isn't the units for resolution volts? I assumed when they said "resolution of 0.01%," I assumed this was .01% of the full scale voltage. Is that wrong to assume?
Should resolution just equal .0001? Then N= 16.6 = 17 bits?
 
0.01% of anything is a pretty fine tolerance. 0.01% of 10V is 0.001 V, so the minimum number of bits would be 17, as you calculated. However, the problem statement is not clear if the 0.01% applies only at the maximum voltage. What if you want 0.01% of a 1-V reading?

Note: it's always important to carry the units thru your calculations, so that it's clear thet 0.01% of 10 V = 0.001 V
 

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