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Adafruit BMP280 faulty barometric pressure
Moderators: adafruit_support_bill, adafruit

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Re: Adafruit BMP280 faulty barometric pressure

by emilsjoeholm on Thu Aug 20, 2020 11:08 am

And as we are operating from diffrent runways we always enter current altitude. We need ground barometric pressure when operating.

so should they not show the same when entering the same altitude?

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Re: Adafruit BMP280 faulty barometric pressure

by adafruit_support_carter on Thu Aug 20, 2020 11:54 am

Pressure nomenclature can be confusing.

The pressure measurement from the BMP280, returned by readPressure(), is local static pressure at your location - the actual pressure of the air around the sensor. That can be used to compute altitude, but there are details. This guide tries to cover those:
https://learn.adafruit.com/clue-altimeter/overview

From what I can tell, the Kestrel does not display local static pressure (what the Kestrel calls "station" pressure) . It does an internal computation similar to that guide and then displays local (computed) sea level pressure (what the Kestrel calls barometric pressure).

Set the Kestrel to a given ALTITUDE. Then, for the BMP280, use the seaLevelForAltitude() method and give it that same altitude:
Code: Select all | TOGGLE FULL SIZE
float SLP = bmp280.seaLevelForAltitude(ALTITUDE, bmp280.readPressure());

Compare SLP from that to the "barometric pressure" from the Kestrel.

General summary:
  • Kestrel "station" pressure (inaccessible) = bmp280.readPressure()
  • Kestrel barometric pressure (displayed) = bmp280.seaLevelForAltitude() (assuming same altitude)

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Please be positive and constructive with your questions and comments.