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Re: GPS and Barometric pressure sensor recommendation please

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Vaisala radiosonde might be what you are looking for.  It contains
temperature (two of them),  humidity and barometric sensors.  RS80 variety
also comes with 8 channel GPS transiever (it transmits Doppler shifts, so
you'd need to figure out how to obtain the position from them).  They are
quite cheap on ebay, around 10 quid.

The links to check:

http://www.google.co.uk/search?q=vaisala+rs80+radiosonde
http://www.zfx.de/sonde /


   Vadim

Re: GPS and Barometric pressure sensor recommendation please

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Please note that the sonde requires a special receiver/processor
to decode the downliked position and weather data. The GPS receiver
in the sounding system is able to resolve movements, but not
absolute position, which is not needed in its primary purpose.

The budget permitting, I think that the solution is a credit-card
GPS module. They are available from most primary GPS manufacturers.

There is one more point to take into account, if the altitude is to
be measured with a pressure sensor: the reference pressure must
be set to match the current weather situation (called QNH or QFE).

Tauno Voipio
tauno voipio (at) iki fi



Re: GPS and Barometric pressure sensor recommendation please

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So what you are telling me about the pressure is that I have to
calibrate the barometric pressure sensor every time before I use it to
take into account the weather changes? Interesting.

I did not think that was necessary for my application. I want to know
the altitude of each point in relation to each other and not against a
reference (i.e. sea level), unless the weather changes in between
readings I think I'll be ok without calibration, don't you think? I just
don't want to complicate my life if I don't have to. Please advise.

Re: GPS and Barometric pressure sensor recommendation please
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Yes,  this is standard procedure for mountaineers, who often use barometric
presure an hight indication. 19th century technology, no batteries needed,
smaller and lighter than GPS.

Wim



Re: GPS and Barometric pressure sensor recommendation please

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Right.

A rule of thumb at low altitudes is 27 feet / millibar, or 8 meters /
hectopascal.

Tauno Voipio
tauno voipio (at) iki fi



Re: GPS and Barometric pressure sensor recommendation please

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http://home.germany.net/100-173822/d_logg2_engl.htm
Circuit Cellar had an article about an altimeter datalogger in their February
2001 issue.
It won 3rd prize in their Design2K contest.
http://www.circuitcellar.com/design2k/winners/third.htm


Good luck with your project.

Regards
David.


Re: GPS and Barometric pressure sensor recommendation please
Hi,
is anybody of you be able to decode rs80 signal??
I have tried with the "famous" german sheets intructions but i don not
understand how to use the calibration coefficients.

For example if these are the frequencies:

F1 = 9690 Hz for the first coefficient
F2 = 7665 Hz for the second coefficient
FT = 8876 Hz for the temperature sensor


Which is the temperature? if you try to calculate let me know!!

thank you for help.

enrico

Re: GPS and Barometric pressure sensor recommendation please
On Tue, 31 Aug 2004 17:42:41 +0100, Clint Sharp

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I suspect this one: http://www.zfx.de/sonde /

   Vadim

Re: GPS and Barometric pressure sensor recommendation please
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The old link is disappeared but fortunately I had saved the pdf file
so now look at http://prohu.altervista.org/convert.pdf

Let me know.

greetings

enrico

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