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Science Forum Index » Geology - Meteorology Forum » Newbie questions on hygrometers
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| Karl |
 Posted: Sat Mar 01, 2008 2:45 pm |
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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! |
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| Rodney Blackall |
| Posted: Sun Mar 02, 2008 6:23 pm |
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In article
<cc8ad354-8059-45b8-82d6-86dc22393349@u72g2000hsf.googlegroups.com>,
Karl <timmerk@gmail.com> wrote:
Quote: 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?
I think the chilled mirror is probably the most accurate method of getting
dew-point (and hence RH). The probably is no such thing as a very accurate
hygrometer and I doubt that there are many applications where better than 5%
is needed anyway.
--
Rodney Blackall (retired meteorologist)(BSc, FRMetS, MRI)
Buckingham, ENGLAND
Using Acorn SA-RPC, OS 4.02 with ANT INS and Pluto 3.03j |
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| I R A Darth Aggie |
| Posted: Mon Mar 03, 2008 6:34 am |
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On Sat, 1 Mar 2008 16:45:22 -0800 (PST),
Karl <timmerk@gmail.com>, in
<cc8ad354-8059-45b8-82d6-86dc22393349@u72g2000hsf.googlegroups.com> wrote:
Quote: + 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/~mcnoldy/Humidity.html
If you simply must have RH%:
http://en.wikipedia.org/wiki/Dew_point#Simple_approximation
RH = 100 - 5(T - Td)
RH is in percent, and T and Td are in degrees Celsius
Quote: + 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. |
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| Karl |
| Posted: Mon Mar 03, 2008 12:38 pm |
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Guest
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Quote: 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 |
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| I R A Darth Aggie |
| Posted: Tue Mar 04, 2008 6:26 am |
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Guest
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On Mon, 3 Mar 2008 14:38:47 -0800 (PST),
Karl <timmerk@gmail.com>, in
<bd509fea-b918-4e35-ac77-0123d443b39b@e10g2000prf.googlegroups.com> wrote:
Quote: + > 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. |
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