0

BME280, 680 pressure and altitude
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

BME280, 680 pressure and altitude

by s0050506 on Tue Dec 19, 2017 9:05 am

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

s0050506
 
Posts: 1
Joined: Tue Dec 19, 2017 8:47 am

Re: BME280, 680 pressure and altitude

by adafruit_support_carter on Fri Dec 22, 2017 10:20 pm

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).

adafruit_support_carter
 
Posts: 9840
Joined: Tue Nov 29, 2016 2:45 pm

Please be positive and constructive with your questions and comments.