BME280 on Raspberry showing incorrect values

[robm]

Hello:

I purchased the SparkFun Atmospheric Sensor Breakout - BME280 and is showing me incorrect values for the pressure.
https://www.sparkfun.com/products/13676

The sensor is hooked up with my Raspberry PI 3 using the I2C interface.

I tried several programs:
C program with the official Bosch driver.
git clone https://github.com/BoschSensortec/BME280_driver.git

Python programs:
git clone https://github.com/adafruit/Adafruit_Python_BME280.git
http://www.raspberrypi-spy.co.uk/2016/0 ... -in-python

All of these programs show the same values:
Chip ID : 96
Temperature : 21.02 °C
Pressure : 947.83 hPa
Humidity : 20.53 %

As you can see the pressure is far too low, the correct pressure right now should be around 1022 hPa.

Does anyone has any ideas?

Kind regards,

Rob.

[stlaha2007]

Hi Rob,

Big difference... where's your reference of 1022hPa coming from.

Have nearly the same breakout and mine is close to real, and my BAR500 is mostly far under real (approx 45hPa).

Can't check for now (wires are frozen )

But seems that there are some faulty ones around, as my humidity stays at 100% even last summer.

[bbqkees]

Firstly, this sensor costs less than 4 Euro on Ebay.

Secondly, as you have already tried with multiple methods the sensor seems to work just fine.
Maybe you are living in a high building?

[robm]

I am living near Madrid at an altitude of 625m. The air pressure giving by the sensor is the air pressure at this altitude.
To calculate the air pressure at sea level we must use the formula (see attachment).
So P0 = 1018.70 hPa which makes more sense.

Regards,
Rob

[bbqkees]

If you want the correct value to show up, write a small LUA script with the formula and update a virtual sensor.

[robm]

I added this to my Python code:

Code: Select all

altitude = 625 # My local altitude
pressure_sea = pressure_sensor / pow(1 - (0.0065 * altitude) / (temperature_sensor + 0.0065 * altitude + 273.15), 5.257)