0-15000 feet (0-4572 meters) altitude measurement with electronic pressure sensor

Which off-the-shelf electronic pressure sensor component (part number) would be used to measure altitude of a baloon starting its journey from sea level
(0 meter) to 15000 feet (4,572 meter) ?
(I assume the pressure sensor outputs analog signal and which will be amplified to be measured by an analog-to-digial converter on a microcontroller)
What is the mathematical/phyical relation (formula) between pressure and altitude?
Daniel
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<Daniel Kolizev> wrote in message

See http://focus.ti.com/docs/mcu/catalog/resources/appnoteabstract.jhtml?familyId42&abstractName=slaa254 for an example.
Dave
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Daniel Kolizev wrote:

That depends on your accuracy requirements. For really inexpensive, fairly accurate for the money sensors I would use a absolute pressure sensor from Freescale semiconductor; they're available from Digi-Key, they don't cost too much, they look like an 8-pin DIP on one side and have a hose nipple on the other -- they're hard to beat. Get one with a range of 0-15psi.

Yes, and I don't think you'll have to amplify it too much.

Findable on the web, I should imagine. IIRC you lose more than 5 psi at 15000 feet, but it's been a while.
--

Tim Wescott
Wescott Design Services
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On 2005-10-25 14:33:43 +0200, <Daniel Kolizev> said:

Hello,
If you want an accurate reading, it would be better to go to the aviation shop and buy an Altimeter. If you need to record the altitude along the flight, you need a barograph, and you can find one at a glider field. By now I think they use GPS with data recording as GPS can deliver an altitude data.
Regards,
MLB
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The relationship between height and pressure is given on this page:
http://en.wikipedia.org/wiki/Atmospheric_pressure
I'm not sure which sensor you need. Use the equation to find out what the range of pressure should be from the given height, then get the sensor which most closely matches that range.
Brent S.
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Daniel Kolizev wrote:

Try http://www.vaisala.com/businessareas/instruments/products/barometricpressure/pmb100
These look they will need a transmitter or something similar in addition to the barometer module.
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Daniel Kolizev wrote:

Additionally, you may want to try a radiosonde or similar instrument. The sondes are already meant to go with a balloon. You will need some sort of receiver however. I am only familiar with the one used by the Navy but I would imagine there are others out there.
http://www.vaisala.com/businessareas/measurementsystems/soundings/products/radiosondes/vaisalaradiosonders80 Just a thought.
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Daniel Kolizev wrote:

P = 1.013 - (1 - (0.0065-h)/288)^5.255
Pressure in Bar, h in metres.
Clifford Heath.
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<Daniel Kolizev> wrote:
| Which off-the-shelf electronic pressure sensor component (part number) would | be used to measure altitude of a baloon starting its journey from sea level | (0 meter) to 15000 feet (4,572 meter) ?
Well, this doesn't exactly answer your question as asked, but it might (or might not) be more useful than actually answering your question. (Which others have done anyways.) And you did ask in rec.models.rc.air, so I'll answer in that context ...
If you're looking to record the altitude over time, and want it small, accurate and relatively cheap, get the RAM2 at http://home.epix.net/~rcbrust /. It costs about $100 and will record 9 hours of altimeter data at one data point/second with a resolution of about one foot. And it only weighs 7.5 grams.
If you're looking to know how high your balloon is and want this transmitted in real time, you may want a variometer. There's several to choose from, but the Picolario at http://www.picolario-usa.com/ is a popular one. Alas, it costs just short of $400. (But there are other options that are cheaper, but have fewer options.) I don't know if these would have 15,000 feet of range, however -- though you might be able to use a scanner and a highly directional antenna to increase the range.
Another option is the Flight Data Recorder at http://www.eagletreesystems.com /, and it can both transmit and record information, and can keep even more information than just altitude. It also has a GPS option that might be useful.
Note that these altimeters give altitude data that is a good deal more accurate than a GPS. You may or may not care, but the difference is there.
Of course, if you want something that you can tie into something else on the balloon, then none of these are likely to be what you want, but you might find them useful as a starting point of something you homebrew.
--
Doug McLaren, snipped-for-privacy@frenzy.com / is the root of all directories.

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