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In message <[email protected]>, Ron Bean writes:

>And since this is time-nuts: Measuring humidity accurately is tricky. 
>According to people who have tested them, commercial electronic humidity 
>sensors, when tested in a lab, have never come anywhere close to the 
>accuracy claimed in the data sheet.

The main problem in measuring humidity is physical gradients:  It is
incredibly hard to create a volume of homogenous humidity on a planet
which has gravity, and for that reason, a lot of labs are not anywhere
near as accurate as they think they are.

>The exception is the "cold mirror" type of sensor, which measures the 
>dewpoint by cooling a mirror and bouncing a light off it to sense the 
>temperature where dew condenses on it. Those are expensive, and they 
>require maintenance to keep the mirror clean.

And they are comparatively slow, last I saw one it could only do
a measurement every second minute.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Never attribute to malice what can adequately be explained by incompetence.
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