30 volt analog to digital converter

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ata90

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Assume A/D with below specification:
AVCC: 5V
Resolution: 10-bit

as we know for conversion of max. 5 VDC, the accuracy is 5/1024= 5mV. but for conversion of 30 VDC, we have to decrease 30V to 5V and after conversion, multiply it to 6. therefore the accuracy will down to 30mV.

is there a way to convert 30VDC with above A/D while the accuracy maintains 5mV?
 

You can easily calculate that converting 0 to 30V range with 5 mV resolution refers to 6000 steps, or 13 Bit.
=> Not possible with 10 Bit ADC.

You can restrict the range, e.g. 25 to 30 V.
 

ata90 said:
... is there a way to convert 30VDC with above (10-bit) A/D while the resolution maintains 5mV?
Click to expand...

The simple answer to your question is NO!

To understand the Difference Between Resolution and Accuracy, read this article:
https://www.aspowertechnologies.com...ifference Between Resolution and Accuracy.pdf

However, (as FVM wrote) if you want to measure only a small range (eg from 25 V to 30 V), use a subtractive analog circuit (a simple OPAMP) to convert (transpose) the input range of 25 - 30 V to 0 - 5 V for the A/D.
In this case the resolution remains 5 mV.
 

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