Barometric pressure difference
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I never find the same atmospheric pressure value between what my Suunto Race displays and my barometer present in my house. The latter is always consistent with the different weather sources. And my watch is always much lower despite the altitude accuracy.
Are others in the same situation?
Is there an offset that could be adjusted?
Does my sensor have a problem despite the fact that the altitude is correct most of the time (I’m not talking about the elevation gain which is overestimated most of the time).
Today exemple:
Watch : 984hpa
House Baro : 1017hpa
Weather source : 1017hpa
Altitude : 569mThank you in advance for your feedback.
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@Chris_Dx Could you check the barometric sensor temperature value? When worn on the wrist, it’s usually around 30°C. A temperature sensor malfunction might be causing the discrepancy.
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the weather sources give the atmospheric pressure values at sea level, while your watch shows the pressure at your current altitude which should be around 948hPa, assuming the reference 1013 hPa at sea level (since 1hPa ~ 8.78m at low altitudes)
for a sea level air pressure of 1017hPa, you should read 951 hPa
you can check it here https://www.mide.com/air-pressure-at-altitude-calculator
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@Stefano-M64 From Suunto website: “A barometer watch continuously measures absolute air pressure using the built-in pressure sensor. Based on this measurement and reference values, it calculates altitude (altimeter, or alti) or sea level air pressure (barometer, or baro).”
My understanding is that the watch always displays the recalculated sea-level air pressure value. This makes sense—otherwise, the barometric trend would be useless for tracking weather trends during mountain hikes or similar activities. My watch is accurate; it currently shows 1026 hPa, matching the 1026 hPa reported by my weather source (explicitly stated as pressure reduced
to sea level), while I’m at an elevation of 289 m.a.s.l. -
@inkognito a barometer can only measure the absolute air pressure, it can be used to derive the correct altitude or sea level pressure only if properly calibrated (“reference values”), for example by the GPS during an activity.
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@Stefano-M64 I fully agree…
OP’s watch shows incorrect barometer value (that should imho report sea-level pressure, at least mine does and Suunto webpage also indicates this) but correct altitude. So, there is either a problem with the temperature sensor (since temperature correction is also used in the calculation) or something else (like if sensor reports wrong absolute value thats used for calculation)…
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@inkognito currently temperature shows on the watch (on the wrist) is exactly at 30°C and the watch pressure indicate 986hpa (for 973m of altitude which is the correct one).
And my house barometer indicates 1019hpa for 1018hpa by weather sources.
Comparing to the previous information given in my first message, seems to have an offset of -33hpa.I had one Ambit 3 Peak and one 9 Peak Pro in the past and pressure indicated by these watches was always matching the house barometer.
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@Chris_Dx that is your problem. Does the watch altitude change when you shake the watch ? IT can be dirty sensor
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@Dimitrios-Kanellopoulos No altitude is stable and sensor is clean.
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@Chris_Dx what is your town / location ? and what reading does the watch have atm ?
PS. no need for personal data, just a coarse location somwhere (town/ nearby town etc)/. So I can lookup the sea level pressure there
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@Chris_Dx said in Barometric pressure difference:
pressure indicate 986hpa
btw pressure indicate 986hpa looks bad for 973m of altitude
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Also note:
Relative pressure is the atmospheric pressure corrected to sea-level conditions.
To compare pressure conditions from one location to another, meteorologists correct the measured pressure (referred to as absolute pressure) to sea-level conditions. Because the air pressure decreases as you rise in altitude, the sea-level corrected pressure (the pressure your location would be at if located at sea-level) is higher than your measured pressure if you live above sea-level and lower than your measured pressure if you live below sea-level.
Relative pressure is larger than absolute pressure unless you live at or below sea-level.
