BME280/BME680 Pressure Readings

[WoHo]

I have a BME280 and a BME680 sensor and get reasonable readings for temperature and humidity (and gas). But the pressure is always around 955 hPa; +/- 2 hPa. Both, BME280 and BME680, measures always the same constant pressure (only the decimal place differs).

I use the official examples, also the BSEC example. Tried also some Python examples from the web, same result. Temperature, humidity (and gas) are ok, pressure always constant.

I have no clue why only the pressure is not valid, e.g. constant. What do I wrong?

Appreciate any help, hint, …

Thanks in advance

WoHo

[shellywang]

Since both pressure sensors measured the same value, the value is exactly the current environmental pressure. Also, the unit is hpa, so the changes in decimal places are acceptable.

[BrynParrott]

Well I have something similar.

I have BME680 purchased in the form of a Seeed Studios Grove style sensor board, supported by a Arduino MCU.
my temp and RH readings look OK, and agree with data published by the weather bureau. But pressure differs.
weather bureau say it us 1020 hPa /mBAR, but my device says its 1001 hPa. The difference in values is more or less consistent.
My altitude is 96 metres above mean sea level, I do not know if this would account for the difference.
What formula can I use to compensate for altitude and temperature ?
Is there another source of error ?
Could my device be faulty ? (I see no similar complaints on Seeed forum).

[handytech]

It is common to observe an "absolute offset" after assembling/mounting the pressure sensor. Such offsets are typically stable over time, which seems to match your observations. Therefore such offsets may be compensated by a one point calibration method (use a calibrated reference device in a stable environment right next to the sensor to estimated your offset, then subtract it from future pressure measurements). Using a calibrated reference device is strongly advised above weather station data to prevent any local weather or altitude changes to influence the measurements.

[BrynParrott]

Thanks for your response.

I found that if I use the DFROBOT Library (containing BME680 Library), it provides a more expensive set of functions for the BME 680.  I am able to provide an altitude to calibrate a Sea Level function, and then Fetch pressure compensated for Altitude, and its reasonably accurate.  However when I tried to integrate the DFRobot library into my own sketch, I have run into problems with compilation, the subject of a separate message on this board.