Accurate Voltage Reference

Discussion in 'Electronics Resources' started by Syniva, Jun 27, 2010.

  1. Syniva

    Thread Starter New Member

    Jun 21, 2010
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    Anyone know where I can find an accurate voltage reference, better than 1%?

    I'm using the LM335 temperature sensor, which outputs 10 mV per 1 degree Kelvin. So, at 20 degrees Celsius, it outputs 2.9315 volts, or since it is accurate only to 1 degree, it actually outputs something between 2.9215 and 2.9415 volts. Supposedly it is more accurate if calibrated, but I have yet to try that since I don't have a reference voltage accurate enough to use it at its uncalibrated accuracy. (Nor am I sure I have a thermometer accurate enough, but that's a different problem.)

    The best voltage reference I've been able to find outputs 5 volts to an accuracy of 1%, or between 4.95 and 5.05 volts. If I use this as the reference voltage for my ADC, then the readings from the ADC will be in error by 1% as well.

    At 2.93 volts, a 1% error turns into 29 mV, which generates an error of 2.9 degrees on top of the 1 degree error the LM335 already comes with. So at 20 degrees Celsius, I would read anything between 16.1 degrees and 23.9 degrees. That's a range of 61 to 75 fahrenheit. I imagine I could guess the temperature and be just as accurate.

    I tried making my own reference (which wouldn't be absolute voltage accurate, just accurate to itself over time) and, while I came up with something that performed a lot better with varying input voltages than zener diodes and 7805 regulators, it was still really temperature-sensitive. I guess the next step would be to wrap it in styrofoam and heat it to a constant temperature, but I'd really rather just buy something, assuming I can find something, and it isn't crazy expensive.
     
  2. sceadwian

    New Member

    Jun 1, 2009
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  3. Syniva

    Thread Starter New Member

    Jun 21, 2010
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    That would be one. Apparently I'm incompetent at searching, or just unlucky, but I swear I searched for hours one day.

    Thanks for your help.
     
  4. sceadwian

    New Member

    Jun 1, 2009
    499
    37
    Searching is a fine art, and results are a fickle mistress. Often you just have to change terms, problem is they're generally the terms you're NOT thinking about at the time.
     
  5. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
    16
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