I am attempting to make an optical chilled mirror dew point hygrometer, and
then a full weather station to accompany it, anybody built similar items?
TIA

TOC

Tom,
No, I havn't built such a hygrometer, but would be very interested to hear
how you get on, and details of your design, if you are willing to divulge
them. It is an idea I have been toying with in the past.
Regards
--
Bernard Burton
Wokingham, Berkshire, UK.


Satellite images at:
www.btinternet.com/~wokingham.weather/wwp.html
"Tom @ HollyLodge" wrote in message
...
I am attempting to make an optical chilled mirror dew point hygrometer,
and
then a full weather station to accompany it, anybody built similar items?
TIA

TOC

I am attempting to make an optical chilled mirror dew point hygrometer, and
then a full weather station to accompany it, anybody built similar items?

Doing it the hard way, then! I would have thought the most important
thing would be to have a very smooth highly polished surface on a piece of
copper that is as thin as possible, say about 10 thou or 0.25 mm. It might
buckle if you bash it, though. Brass would be nearly as good, and easier to
work.
What liquid are you going to use? Petrol would be OK - very volatile,
but it will become a little less effective each time as you blow off the
volatiles, but cheap enough. I use it to top up a Tippex bottle. Pongs a bit
but the volatility is right.

Best of luck - Tudor Hughes, Warlingham.

"Tom @ HollyLodge" wrote in message m...
I am attempting to make an optical chilled mirror dew point hygrometer, and
then a full weather station to accompany it, anybody built similar items?

Is this any use ?

http://www.generaleastern.net/pdf/DEW_10.pdf

Paul.

On Mon, 11 Aug 2003 17:48:42 +0100, "Tom @ HollyLodge"
wrote:

I am attempting to make an optical chilled mirror dew point hygrometer, and
then a full weather station to accompany it, anybody built similar items?
TIA


In a previous working life I was involved in evaluating and building
dewcells, as they are called.

The biggest problem used to be contamination of the mirror surface
IIRC.

This Irish scheme looks interesting:

http://www.irishscientist.ie/ITDTL107.htm

JPG






TOC

"TudorHgh" wrote in message
...
I am attempting to make an optical chilled mirror dew point hygrometer,
and
then a full weather station to accompany it, anybody built similar items?

Doing it the hard way, then! I would have thought the most
important
thing would be to have a very smooth highly polished surface on a piece of
copper that is as thin as possible, say about 10 thou or 0.25 mm. It
might
buckle if you bash it, though. Brass would be nearly as good, and easier
to
work.
What liquid are you going to use? Petrol would be OK - very
volatile,
but it will become a little less effective each time as you blow off the
volatiles, but cheap enough. I use it to top up a Tippex bottle. Pongs a
bit
but the volatility is right.

Best of luck - Tudor Hughes, Warlingham.

What is the easy way then??

What is the easy way then??

Whirling psychrometer.

TH

While optical detection of water adsorption is certainly the
most common, may I mention acoustic detection ?

If you are versed in RF electronics (and actually not much is
needed nowadays with monolithic amplifiers provided by Minicircuits
and Macor), you can go for a cheap Rayleigh mode Surface Acoustic
Wave filter. These are used as RF bandpass filters: the propagation
of the Rayleigh acoustic wave is strongly attenuated by the
adsorption of water. By gluing a small thermocouple on top of the
SAW device, you just have to cycle the temperature of a Peltier
module on which the SAW device is fixed, and log the temperature for
which the acoustic wave propagation disappears.

I build such a system for fun during my PhD, although I didn't do
any calibration on it (others have). As mentioned, the contamination
of the surface is a major issue for more than in-lab use.

Jean-Michel

On 12 Aug 2003 02:31:52 -0700, Paul wrote:
"Tom @ HollyLodge" wrote in message m...
I am attempting to make an optical chilled mirror dew point hygrometer, and
then a full weather station to accompany it, anybody built similar items?

Is this any use ?

http://www.generaleastern.net/pdf/DEW_10.pdf

Paul.

That one only seems to go to 90%. is there an electronic/automatic one
that goes to 100%?
--
John - http://www.reiteration.net/~jfm
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