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finitespace / BME280

Provides an Arduino library for reading and interpreting Bosch BME280 data over I2C, SPI or Sw SPI.
GNU General Public License v3.0
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EnvironmentCalculations SeaLevelPressure #105

Closed Gonzo4 closed 3 years ago

Gonzo4 commented 5 years ago

Hi,

just a question, from where did you get the formula to calculate the EquivalentSeaLevelPressure? The number 5.257 in your formula is always 5.255 googeling around, like in Wikipedia or like here https://www.sparkfun.com/tutorials/253

Eldenroot commented 4 years ago

Bump?

jirkaptr commented 4 years ago

The EquivalentSeaLevelPressure formula was taken from http://keisan.casio.com/exec/system/1224575267. Some sources indicate the constant 5,255, others 5,257. It all depends on what value is used for the vertical air temperature gradient (a), and how accurate is the calculation of the constant M g / R a., where M ... die mittlere moler Masse der Atmosphärengase (0,02896 kg/mol), g ... die Schwerebeschleunigung (9,807 m/s^2), R ... die universelle Gaskonstante ( 8,314 J K^(− 1) mol^(−1) ) The German Wikipedia states: "Für einen Temperaturgradienten von 0,65 K für 100 m nimmt der Exponent den Wert 5,255 an".

finitespace commented 3 years ago

Was this resolved?

Gonzo4 commented 3 years ago

Yes, could be resolved. @jirkaptr has explained it very well, I had thought it was just a typo 👍