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Calibrate Relative Pressure using a Raspberry Pi computer


Many weather enthusiasts already own a raspberry pi computer to run weewx, Cumulus or other projects. If you can’t afford to buy a Vaisala barometer (approx. $3,000 USD) in order to calibrate your weather station’s barometer, you can probably afford to buy a Bosch BMP390 barometric sensor* (approx. $10 USD or less) for your pi and use the sensor readings to give you a far more accurate Absolute Pressure/Station Pressure reading.

According to the manufacturer: “...sensor’s excellent relative accuracy of ±0.03hPa, which is equivalent to ±25cm difference in altitude.” The data sheet infers that the worst case reading around 25℃ should be ±0.33 hPa.

As a bonus, the Bosch sensor set also includes a temperature sensor that claims an accuracy of ±0.5℃. Bosch seems to be releasing new barometric sensors every year or so. Subsequent releases should be even more accurate.

The Bosch sensor certainly makes things far easier. You no longer have to compare pressure readings with a METAR station or wait for ideal once-a-year weather conditions to compare and calibrate pressure readings. Just enter the sensor’s pressure reading into your personal weather station console as ABS (Absolute Pressure), add the elevation offset for your location and you’ve got the REL (Relative Pressure).

My weather station’s barometric sensor was off by almost 2.0 hPa so having the ability to quickly calibrate or check pressure readings instantly and at any time sure makes things easier.

*NOTE: I bought the Adafruit version of the BMP390 with the Qwiic connectors. The sensor board handles 3.3V or 5V. If you buy a shim and a Qwiic connector cable for just a few bucks, no jumper wires, breadboard or soldering is required.


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