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Barometric pressure and rain gauges

Discussion in 'Embedded' started by Neil Bradley, Apr 24, 2004.

  1. Neil Bradley

    Neil Bradley Guest

    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, Apr 24, 2004
    #1
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  2. What's rain? :cool:

    While we're on the subject, is there a good non-mechanical
    method for measuring wind speed?
     
    Everett M. Greene, Apr 24, 2004
    #2
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  3. A project I worked on once used a two-axis ultrasonic wind
    speed sensor. It cost thousands of dollars, though...
     
    Grant Edwards, Apr 24, 2004
    #3
  4. Neil Bradley

    TheDoc Guest

    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..
     
    TheDoc, Apr 24, 2004
    #4
  5. Neil Bradley

    Clint Sharp Guest

    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, Apr 24, 2004
    #5
  6. Neil Bradley

    R. Martin Guest

    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
     
    R. Martin, Apr 24, 2004
    #6
  7. Neil Bradley

    Robert Scott Guest

    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, Apr 25, 2004
    #7
  8. Neil Bradley

    R. Martin Guest

    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
     
    R. Martin, Apr 25, 2004
    #8
  9. While we're on the subject, is there a good non-mechanical
    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
     
    Bill Ricker N1VUX, Apr 25, 2004
    #9
  10. While we're on the subject, is there a good non-mechanical
    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
     
    Bill Ricker N1VUX, Apr 25, 2004
    #10
  11. Neil Bradley

    CBFalconer Guest

    Stick finger in mouth, extract, and hold up. Wind is coming from
    cool side, and coolness is a relative measure of wind speed.
    Calibration to local conditions is needed :)
     
    CBFalconer, Apr 29, 2004
    #11
  12. Neil Bradley

    Tauno Voipio Guest

    For a professional solution, go to <http://www.vaisala.com/>,
    pick wind sensing and look for WS425.

    Tauno Voipio
    tauno voipio @ iki fi
     
    Tauno Voipio, Apr 30, 2004
    #12
  13. You forgot to mention the Wyoming wind gauge -- a log chain
    hanging from a tree limb. You count the number of links
    standing straight out.

    NCAR may want to consider the chain method. They once lost
    their anemometer after seeing the velocity go off scale at
    125 MPH in one of Boulder's "breezes". [Hurricanes?!?
    Hurricanes are for wimps!]
     
    Everett M. Greene, Apr 30, 2004
    #13
  14. Neil Bradley

    Tauno Voipio Guest

    I'll refer to my earlier response:

    For a professional solution, go to <http://www.vaisala.com/>,
    pick wind sensing and look for WS425.

    Tauno Voipio
    tauno voipio @ iki fi
     
    Tauno Voipio, May 2, 2004
    #14
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