More accurate resolution from the A/d converters

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  1. #1
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    Default More accurate resolution from the A/d converters


    These are not really Picbasic Pro questions, but it's Picbasic Pro I'm using and I don't know where else to ask! Still learning

    Am I right in thinking that if you supply a + and - ref to the RA2 and RA3 pins that the same return count applies to a smaller voltage range therefore making the measurement a higher resolution one and more accurate?

    Can you supply only the RA3+ reference and leave the RA2 nc?

    If I wanted a + ref voltage of 2.5v, would the normal way to do this be by a voltage divider (couple of resistors)?

    What I'm trying to do is get a high resolution and accurate voltage measurement between around 2-4.8volts on a 16f877


  2. #2
    Join Date
    Feb 2004

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    The 16F877 has a 10 Bit ADC (decimal 1024 possible values, 0-1023)
    Your Range is 2.8 Volts (4.8-2)
    The max resolution you can achieve with this range is about 3 mV (2,8V / 1024 = 2,73mV)

    I have not played with different Vref's yet,
    but anyway you will need a well tuned and temperature compensated source for Vref
    to make your ADC conversion result accurate.



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