Why don't these products show 100% humidity?

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  • Updated 3 years ago
Why don't these products show 100% humidity?
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Posted 3 years ago

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Photo of George D. Nincehelser

George D. Nincehelser

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The type of technology being used just isn't accurate enough to warrant that kind of precision.

Here's a performance chart from Sensirion, maker of the SHT21 chip used in the 5n1.  (Sensirion also provides chips for other brands of personal weather stations)

Note that after 80% RH the tolerance for error goes up to as much as +/- 5 percentage points in the worst case.  Typical accuracy being +/- 3 percentage points.   So being able to display "100%" isn't terribly meaningful.

Note the same accuracy issue also exists below 20%.   Some weather stations don't even bother with RH below 16%, which annoys some desert dwellers.

So as a basic-rule-of-thumb, RH values in the upper and lower 15 or 20 percent bands should be taken with a grain of salt.  They have a larger margin of error than the middle values.
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AcuRite Kevin

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George has covered this very well.  Thank you!