BME280, 680 pressure and altitude

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s0050506
 
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Joined: Tue Dec 19, 2017 8:47 am

BME280, 680 pressure and altitude

Post by s0050506 »

Hello, for Bosch BMEx80 sensors is stated

" ±1 hPa absolute accuracy, and temperature with ±1.0°C accuracy. Because pressure changes with altitude, and the pressure measurements are so good, you can also use it as an altimeter with ±1 meter or better accuracy"

Please what is wrong with this calculation:
1.2 (kg/m³) * 9.87 * Altitude (meters) = ±100 (Pa)
Altitude = approximately 100 / 12 or ±8 meter accuracy

Worsening at higher altitudes (lower densities).

Thank you, regards

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adafruit_support_carter
 
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Re: BME280, 680 pressure and altitude

Post by adafruit_support_carter »

See the "Relative accuracy pressure" value in Table 3 of the datasheet:
https://cdn-shop.adafruit.com/datasheet ... 001-10.pdf
This is the value that relates to altitude sensitivity, which is ~0.12hPa. Work backwards from that and you should get ~1 meter.

Note that there is a difference between absolute and relative. Absolute would be if you are standing at 1000 meters, it should report 1000 meters. Relative would be if you move up 1 meter, it should report a change of 1 meter (even if the absolute number is wrong).

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