Author Topic: Calibrate Relative Pressure using a Raspberry Pi computer  (Read 511 times)

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Offline gszlag

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Calibrate Relative Pressure using a Raspberry Pi computer
« on: February 15, 2021, 03:21:03 PM »
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.
Ecowitt GW1000/GW1100
Ecowitt WS68: Anemometer, UV/solar
Ecowitt WH40: Rain gauge
Ecowitt WH32E: Outside T & H sensor
Ambient Weather WS-2000
Stratus Rain Gauge (manual)
Raspberry Pi 3B+ (WeeWX/CumulusMX)
Raspberry Pi Zero 2W WeeWX/MQTT/Belchertown)
---
http://weather.glenns.ca (pwsdashboard - live)
http://weewx.glenns.ca
http://glenns.ca/cumulusmx2/index.htm
---
WU: ITEHKUMM2
PWSweather.com: MBAYWX1
AWEKAS:id=15920
WINDY: Michael's Bay, Manitoulin Island
WOW: Michael's Bay

Offline KC5JIM

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Re: Calibrate Relative Pressure using a Raspberry Pi computer
« Reply #1 on: March 31, 2022, 05:53:45 PM »
Thanks for the tip. I just received my BMP390 and calibrated.
Ecowitt Wittboy| FOSHKplugin on Pi 4


Offline gszlag

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  • Posts: 246
  • ..have you calibrated your barometer today?
    • Michael's Bay - Manitoulin Island weather
Re: Calibrate Relative Pressure using a Raspberry Pi computer
« Reply #2 on: March 31, 2022, 06:05:32 PM »
Thanks for the tip. I just received my BMP390 and calibrated.
Glad to help!
Just curious, what software program did you use? When I bought the sensor, I couldn't find anything to run it so I tried every BMP388 (Adafruit says they are pretty much the same) program on github. Similar - but not the same(chip register differs by one digit) and finally got it to work. Max sampling rate works best.
I see Bosch has something on github that you can compile. haven't tried it.
Unfortunately getting the pressure readings into WeeWX is beyond my limited skill set. Would be nice though!
Ecowitt GW1000/GW1100
Ecowitt WS68: Anemometer, UV/solar
Ecowitt WH40: Rain gauge
Ecowitt WH32E: Outside T & H sensor
Ambient Weather WS-2000
Stratus Rain Gauge (manual)
Raspberry Pi 3B+ (WeeWX/CumulusMX)
Raspberry Pi Zero 2W WeeWX/MQTT/Belchertown)
---
http://weather.glenns.ca (pwsdashboard - live)
http://weewx.glenns.ca
http://glenns.ca/cumulusmx2/index.htm
---
WU: ITEHKUMM2
PWSweather.com: MBAYWX1
AWEKAS:id=15920
WINDY: Michael's Bay, Manitoulin Island
WOW: Michael's Bay

Offline KC5JIM

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  • Posts: 188
    • KC5JIM Weather
Re: Calibrate Relative Pressure using a Raspberry Pi computer
« Reply #3 on: March 31, 2022, 07:26:55 PM »
I used CircuitPython
Ecowitt Wittboy| FOSHKplugin on Pi 4