High Altitude Altimeter

[lavila540]

I need to build an altimeter that has the capability of detecting 100,000ft apogee. I want to program the altimeter to detect a specific altitude and give off an electrical charge to ignite the deployment system of my rocket. I also want to make the altimeter programmable to detect apogee , lets say if it was previously set to deploy at 50,000ft and the rocket does not make it to that altitude , i want it to detect apogee<50,000ft and deploy upon descending.
If any one has any ideas that may help please share them with me.
Thanks , Louis

 

[daddles]

The logic part of the task can be done with something like a PIC microcontroller.

If you want to relate pressure to altitude, you have some design work to do first. Go find the ICAO standard atmosphere equation that relates height above ground with air pressure. Then match those pressures with a suitable pressure sensor. How close you want to be to a particular height will drive what kind of resolution you need from the pressure sensor. Finding a light weight sensor with good resolution will probably be a challenge. At 32 km, the pressure is about 9 mbar, so you'll need to find a sensor that can resolve, say, 1 to 0.1 mbar. It also needs to measure absolute pressure, not gauge pressure (unless you set your firmware to read atmospheric pressure and elevation immediately before launch). The electronics should be relatively straightforward once you find a suitable sensor.

 

[poor mystic]

Motorola are reputed to have the best pressure sensors and a quick google of "motorola pressure sensor" might help. I see they have a special range of low pressure sensors.