Sorry for the newbie questions, but I'm not familiar at all with
relative humidity, dew points, and temperature, or they they
correlate. I've tried wiki-ing it, but have not found the answer.

I'm trying to find very accurate hygrometers (perhaps a chilled-mirror
hygrometer) but the RH accuracy listed for these high end hygrometers
are listed like "0.5C", which I believe is the dew point. How can I
use this number to find the RH accuracy in RH% units? I'm guessing the
temp factors into it, but I need the most accurate hygrometer for an
indoor room that could be anywhere from 0-120 F, but in real life the
temp will be between 60 and 80 F.

Also, can anyone recommend a very accurate hygrometer?

Thanks!

On Sat, 1 Mar 2008 16:45:22 -0800 (PST),
Karl , in
wrote:

+ I'm trying to find very accurate hygrometers (perhaps a chilled-mirror
+ hygrometer) but the RH accuracy listed for these high end hygrometers
+ are listed like "0.5C", which I believe is the dew point. How can I
+ use this number to find the RH accuracy in RH% units?

Why do you want a relative humidity value? you do realize that RH% is
almost a totally *worthless* number?

http://einstein.atmos.colostate.edu/.../Humidity.html

If you simply must have RH%:

http://en.wikipedia.org/wiki/Dew_poi..._approximation

RH = 100 - 5(T - Td)

RH is in percent, and T and Td are in degrees Celsius

+ I'm guessing the temp factors into it

What is it, exactly, that you're trying to do? and what sort of
accuracy do you really require?

It may be that the chilled-mirror hygrometer is overkill for your
purpose, and that a less expensive alternative may be exactly what you
want.

--
Consulting Minister for Consultants, DNRC
I can please only one person per day. Today is not your day. Tomorrow
isn't looking good, either.
I am BOFH. Resistance is futile. Your network will be assimilated.

What is it, exactly, that you're trying to do? and what sort of
accuracy do you really require?

It may be that the chilled-mirror hygrometer is overkill for your
purpose, and that a less expensive alternative may be exactly what you
want.

Well, I'm building a walk-in humidor for cigars and I want to be able
to control the humidity levels to more than 1% RH accuracy. +/- a
couple of % in the RH affects the smoking experience and taste. RH is
used when storing and aging cigars.

Thanks

On Mon, 3 Mar 2008 14:38:47 -0800 (PST),
Karl , in
wrote:
+ What is it, exactly, that you're trying to do? and what sort of
+ accuracy do you really require?
+
+ It may be that the chilled-mirror hygrometer is overkill for your
+ purpose, and that a less expensive alternative may be exactly what you
+ want.
+
+ Well, I'm building a walk-in humidor for cigars and I want to be able
+ to control the humidity levels to more than 1% RH accuracy.

Well, then you should probably start with something like this

http://bcspecialties.com/cigarasp/500U.asp

or ask cigar and/or HVAC knowledgable folks about suitable hardware.

--
Consulting Minister for Consultants, DNRC
I can please only one person per day. Today is not your day. Tomorrow
isn't looking good, either.
I am BOFH. Resistance is futile. Your network will be assimilated.