Accurate Voltage Reference

Thread Starter

Syniva

Joined Jun 21, 2010
25
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.
 

Thread Starter

Syniva

Joined Jun 21, 2010
25
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.
 

sceadwian

Joined Jun 1, 2009
499
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.
 
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