Barometric pressure and rain gauges

I'm currently designing a replacement main board for my Heathkit ID-5001
weather station. I already have replacement relative humidity,
windspeed/direction, and temperature sensors, but I'm looking for a
barometric pressure and and rain gauge sensor solution. By any chance is
anyone aware of an I2C or SPI based device that can provide this
functionality? Or better yet, is there anyone that can point me to how some
of the electronic rain gauges work?

Thanks!

-->Neil

"Neil Bradley" <nb_no_spam@synthcom.com> writes:
> I'm currently designing a replacement main board for my Heathkit ID-5001
> weather station. I already have replacement relative humidity,
> windspeed/direction, and temperature sensors, but I'm looking for a
> barometric pressure and and rain gauge sensor solution. By any chance is
> anyone aware of an I2C or SPI based device that can provide this
> functionality? Or better yet, is there anyone that can point me to how some
> of the electronic rain gauges work?

What's rain?  8-)

While we're on the subject, is there a good non-mechanical
method for measuring wind speed?

In article <20040424.7A2A690.8736@mojaveg.iwvisp.com>, Everett M. Greene wrote:

> While we're on the subject, is there a good non-mechanical
> method for measuring wind speed?

A project I worked on once used a two-axis ultrasonic wind
speed sensor. It cost thousands of dollars, though...

-- 
Grant Edwards                   grante             Yow!  As President I
                                  at               have to go vacuum my coin
                               visi.com            collection!

"Everett M. Greene" <mojaveg@iwvisp.com> wrote in message
news:20040424.7A2A690.8736@mojaveg.iwvisp.com...
> "Neil Bradley" <nb_no_spam@synthcom.com> writes:
> > I'm currently designing a replacement main board for my Heathkit ID-5001
> > weather station. I already have replacement relative humidity,
> > windspeed/direction, and temperature sensors, but I'm looking for a
> > barometric pressure and and rain gauge sensor solution. By any chance is
> > anyone aware of an I2C or SPI based device that can provide this
> > functionality? Or better yet, is there anyone that can point me to how
some
> > of the electronic rain gauges work?
>
> What's rain?  8-)
>
> While we're on the subject, is there a good non-mechanical
> method for measuring wind speed?

Look up "Hot wire anemometer" I have implemented several of these
for both high and low flows.. they can be very accurate.
You will need the temperature, humidity and pressure of the gas ( air )
for the most accurate results..

In message <408a9d89$0$17263$a1866201@newsreader.visi.com>, Grant 
Edwards <grante@visi.com> writes
>In article <20040424.7A2A690.8736@mojaveg.iwvisp.com>, Everett M. Greene wrote:
>
>> While we're on the subject, is there a good non-mechanical
>> method for measuring wind speed?
>
>A project I worked on once used a two-axis ultrasonic wind
>speed sensor. It cost thousands of dollars, though...
>
Everyday and Practical Electronics in the UK published a weather station 
design using an ultrasonic anenometer, check out their web site 
http://www.epemag.wimborne.co.uk for the August and September 2003 back 
issues.
-- 
Clint Sharp

Everett M. Greene wrote:
> 
> "Neil Bradley" <nb_no_spam@synthcom.com> writes:
> > I'm currently designing a replacement main board for my Heathkit ID-5001
> > weather station. I already have replacement relative humidity,
> > windspeed/direction, and temperature sensors, but I'm looking for a
> > barometric pressure and and rain gauge sensor solution. By any chance is
> > anyone aware of an I2C or SPI based device that can provide this
> > functionality? Or better yet, is there anyone that can point me to how some
> > of the electronic rain gauges work?
> 
> What's rain?  8-)
> 
> While we're on the subject, is there a good non-mechanical
> method for measuring wind speed?

Grant mentioned sonic anemometers, but I've seen designs for building
your own that are not as expensive as the examples he mentioned.  In
college my advanced physics lab class built a laser anemometer.  It
used the correlation between the turbulence induced fluctuations in
laser light arriving at the two eyepieces of binoculars to calculate
the component of windspeed perpendicular to the light beam, so you
need two of them to get the total horizontal wind speed (like with
sonic anemometers.  With today's cheap solid state lasers and large-
scale digital ICs, it should be much easier and cheaper to build one
of these than it was 30 years ago.

Cheers,
Russell

On Sat, 24 Apr 2004 20:07:30 GMT, "R. Martin" <russell.martin@wdn.com>
wrote:

>...a laser anemometer.  It
>used the correlation between the turbulence induced fluctuations in
>laser light arriving at the two eyepieces of binoculars to calculate
>the component of windspeed perpendicular to the light beam,..

The sonic ones have the advantage that they will work even in very
foggy weather which will render the laser type useless.


-Robert Scott
 Ypsilanti, Michigan
(Reply through this forum, not by direct e-mail to me, as automatic reply address is fake.)

Robert Scott wrote:
> 
> On Sat, 24 Apr 2004 20:07:30 GMT, "R. Martin" <russell.martin@wdn.com>
> wrote:
> 
> >...a laser anemometer.  It
> >used the correlation between the turbulence induced fluctuations in
> >laser light arriving at the two eyepieces of binoculars to calculate
> >the component of windspeed perpendicular to the light beam,..
> 
> The sonic ones have the advantage that they will work even in very
> foggy weather which will render the laser type useless.
> 

True, but that's a bigger problem some places than others.  I like
the sonic ones, too, but we never encountered heavy enough fog to
prevent the laser system's use.  Of course, we were using it to
measure convergence under sunny conditions. ;-)

Cheers,
Russell

> > While we're on the subject, is there a good non-mechanical
> > method for measuring wind speed?
 
> Look up "Hot wire anemometer" I have implemented several of these
> for both high and low flows.. they can be very accurate.
> You will need the temperature, humidity and pressure of the gas ( air )
> for the most accurate results..

IIRC, calibration at high humidity and/or very high speed can be a problem --
don't you you actually need the both the gas mixing ratio and the liquid water
content as well? A Pacific Cyclone on Guam almost took Mt.Washington's wind
record, but it was determined that the excessive horizontal liquid content
kept the hot wire colder than the "mere" hurricane-strength wind accounted
for.

See also:

    http://www.mountwashington.org/weather/world-record.html

    WIND SENSOR IS AN AN/FPQ13 DIGITAL WIND SENSOR (HOT WIRE 
    ANEMOMETER).  (WINDS ARE GENERALLY ACCURATE AT WIND GUSTS LESS 
    THAN 100 KT OUTSIDE HEAVY RAIN.)
	http://weather.noaa.gov/pub/data/raw/ac/acpq70.pgum.psh.pq.txt

> > While we're on the subject, is there a good non-mechanical
> > method for measuring wind speed?
 
> Look up "Hot wire anemometer" I have implemented several of these
> for both high and low flows.. they can be very accurate.
> You will need the temperature, humidity and pressure of the gas ( air )
> for the most accurate results..

IIRC, calibration at high humidity and/or very high speed can be a problem --
don't you you actually need the both the gas mixing ratio and the liquid water
content as well? A Pacific Cyclone on Guam almost took Mt.Washington's wind
record, but it was determined that the excessive horizontal liquid content
kept the hot wire colder than the "mere" hurricane-strength wind accounted
for.

See also:

    http://www.mountwashington.org/weather/world-record.html

    WIND SENSOR IS AN AN/FPQ13 DIGITAL WIND SENSOR (HOT WIRE 
    ANEMOMETER).  (WINDS ARE GENERALLY ACCURATE AT WIND GUSTS LESS 
    THAN 100 KT OUTSIDE HEAVY RAIN.)
	http://weather.noaa.gov/pub/data/raw/ac/acpq70.pgum.psh.pq.txt