RE: [Paparazzi-devel] High precision pressure sensors.

[Gisela Noci]

Please note the ABSOLUTE accuracy - @ temp range of 0 to 50deg C (a typical operating range for non-frozen countries) the accuracy is 4mbar (plus/minus 2mBar) this equate to approx 32meter accuracy. If you 'zero' the sensor reading @ ground level and work in delta to ground level, then autoland becmes possible, with some provisors:

 

Wind shear on the ground (wind speeds around 5m/s)can create up to 0.5mBar pressure diff easily, compared to 20meters above the ground.

 

Changing weather conditions easily cause 0.5 to 1mbar delta over 30 to 40minutes period.

 

You should have a reference sensor on ground, and zero both the Aircraft and ground sensor together, and then update the Aircraft pressure value with the delta on ground, during the landing approach. Beware that if the pressure change on ground is significant,  the Aircraft needs to handle the resultant altitude jump gracefully. A 0.5mBar diff is a 4 meter jump in altitude...  That why Real Pilots don't land on altimeter only.....

 

It can be done with proper harmonising between ground pressur sensor, Airborne sensor, and sensible vertical guidance control loops.

 

 

Have fun

Joe

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From: paparazzi-devel-bounces+address@hidden [paparazzi-devel-bounces+address@hidden on behalf of Francois ALIBERT address@hidden
Sent: Friday, July 16, 2010 10:08 AM
To: address@hidden
Subject: [Paparazzi-devel] High precision pressure sensors.

Hello.

    I recently found on the web that Intersema made new high precision static and dynamic pressure sensors with digital (both SPI and I2C) outputs. They also have a fast conversion time (< 1 ms).

For static pressure sensing:

http://www.intersema.ch/products/guide/calibrated/ms5801-01ba/

http://www.intersema.ch/products/guide/calibrated/ms5803-01ba/

 

For dynamic pressure sensing:

http://www.intersema.ch/products/guide/calibrated/ms5701/

 

    Does anybody ear about those sensors? What about using them on Paparazzi? If the performances Intersema announces correspond to the reel ones, would a 10 cm altitude precision, refreshed at high frequency, could solve some problems for automatic landing?

 

    Regards