Bosch Sensortec Community

    cancel
    Showing results for 
    Search instead for 
    Did you mean: 

    BMP280 - vibration drift

    Highlighted
    New Poster

    BMP280 - vibration drift

    I am using a BMP280 as altimeter in an experimental aircraft.  The sensor does experience some vibrations.  The first BMP280 installed had a small offset, well within the specs.  After ~30 hours of flight, I noticed a sudden increase in measured air pressure.  Going from a correct altitude of 840 ft, to around 500 ft.

    Gradually it got worse, after another few hours of flight, the error was now more than 600 ft in altitude, sitting at airport elevation with no engine running -- no vibrations.  I replaced it with a second BMP280. Again, initial installation was within specs for the surveyed elevation.

    Now, after ~20 hours of flight time, I notice an offset of about 70 ft. Again, the measured air pressure is higher than the surveyed elevation.

    The sensor reading is identical (short term)  whether exposed to vibrations or not.

    Are these sensors drifting this much because of vibrations? The data sheet does not specify tolerance against vibrations.   Are they meant to be installed only in benign environments like cell phones?

    Thank You.

     

    4 REPLIES 4
    Highlighted
    Community Moderator

    Re: BMP280 - vibration drift

    Tolerance against vibrations is indeed not specified, but I would have a few questions about your design.

    Since the sensor outputs absolute atmospheric pressure (in Pa), could you please share what is the sensor output at the different stages of your tests (rather than the converted altitude)?

    Also I would like to ensure that you are somehow compensating for weather changes when calculating altitude based on absolute pressure? You would typ. need some reference of real-time 'ground pressure' (or local sea-level pressure) if you want to compensate of that.

    Finally it is not totally clear to me yet whether the offsets are observed during the stress only, or if the offsets persist then forever?

    PS: please keep in mind that Bosch Sensortec offers sensors for the consumer goods industry(Consumer Electronics application), and thus shall not be used in any safety-critical applications.

    Highlighted
    New Poster

    Re: BMP280 - vibration drift

    Thank you for your response. Yes, the absolute pressure reading is converted to a pressure altitude, using standard atmospheric calculations. And, yes 😀 I do correct for local altimeter setting.

    As I mentioned, initial installation outputs correct altitude (within max 30'), which is then zeroed out in software as a fixed offset. This results in a reading that ALWAYS match the local FAA approved official altimeter setting, located 200m from my location. This is the scenario before the drift occurs.

    Once the drift starts creeping in, it is permanent. The drift is always in one direction -- too high pressure (too low altitude reading). Under stress or not, the reading is identical.

    I am aware of the wording "not for use in safety-critical applications".  Should I look for another vendor?


    Thank You.

    Community Moderator

    Re: BMP280 - vibration drift


    @Burt_N wrote:

    Thank you for your response. Yes, the absolute pressure reading is converted to a pressure altitude, using standard atmospheric calculations. And, yes 😀 I do correct for local altimeter setting.

    As I mentioned, initial installation outputs correct altitude (within max 30'), which is then zeroed out in software as a fixed offset. This results in a reading that ALWAYS match the local FAA approved official altimeter setting, located 200m from my location. This is the scenario before the drift occurs.

    Once the drift starts creeping in, it is permanent. The drift is always in one direction -- too high pressure (too low altitude reading). Under stress or not, the reading is identical.


    This is not an expected behavior in our experience. Our sensors are for example used in several drones, for which we have not observed such persistent offsets. In my opinion, some other leads should be investigated. Is the altitude correction a one-time offset compensation only? If so the offset will change over time based on weather conditions, and should be updated live or frequently enough. If weather compensation is not relevant, is it possible that the harsh conditions are creating some permanent stress in your system(e.g. bending of the PCB)?


    @Burt_N wrote:

    I am aware of the wording "not for use in safety-critical applications".  Should I look for another vendor?


    Only you can tell from your usage of the sensor and if you are within the product's terms of use!

    Highlighted
    New Poster

    Re: BMP280 - vibration drift

    The one-time offset is a compensation for the initial installation error, and would probably be accurate for that pressure altitude only.  This fixed offset is in the order of < 1hPa.

    The airport has a calibrated Automated Weather Observation Service, reporting the current "Altimeter Setting". This is actually the air pressure at MSL.
    My application has a graphic display and corresponding adjustment, and when adjusted correctly for the local altimeter setting, the altimeter reads the field elevation.  The reported setting here in the US is inches of Hg, with a precision of 0.01".  Each 0.01" (~0.34 hPa) is approximately 10ft in elevation at these elevations (~1000 ft).

    Before any drift had occurred, my altitude reading was always accurate within 10ft.

    Temperature wise, it is not exposed to any extremes. Outdoor temperature swings around here is between -10C through +35. Mechanically, I am actually using a breakout board since I am not confident in soldering techniques for such a small part.

    This is the board, that is then mounted on my main board. It would not experience any undue stress, IMO.

    https://www.amazon.com/HiLetgo-Precision-BMP280-3-3-Atmospheric-Pressure/dp/B01ICN5QPU

    After the first sensor failure, I thought I maybe had a counterfeit product. Possible?

     

    Icon--AD-black-48x48Icon--address-consumer-data-black-48x48Icon--appointment-black-48x48Icon--back-left-black-48x48Icon--calendar-black-48x48Icon--center-alignedIcon--Checkbox-checkIcon--clock-black-48x48Icon--close-black-48x48Icon--compare-black-48x48Icon--confirmation-black-48x48Icon--dealer-details-black-48x48Icon--delete-black-48x48Icon--delivery-black-48x48Icon--down-black-48x48Icon--download-black-48x48Ic-OverlayAlertIcon--externallink-black-48x48Icon-Filledforward-right_adjustedIcon--grid-view-black-48x48IC_gd_Check-Circle170821_Icons_Community170823_Bosch_Icons170823_Bosch_Icons170821_Icons_CommunityIC-logout170821_Icons_Community170825_Bosch_Icons170821_Icons_CommunityIC-shopping-cart2170821_Icons_CommunityIC-upIC_UserIcon--imageIcon--info-i-black-48x48Icon--left-alignedIcon--Less-minimize-black-48x48Icon-FilledIcon--List-Check-grennIcon--List-Check-blackIcon--List-Cross-blackIcon--list-view-mobile-black-48x48Icon--list-view-black-48x48Icon--More-Maximize-black-48x48Icon--my-product-black-48x48Icon--newsletter-black-48x48Icon--payment-black-48x48Icon--print-black-48x48Icon--promotion-black-48x48Icon--registration-black-48x48Icon--Reset-black-48x48Icon--right-alignedshare-circle1Icon--share-black-48x48Icon--shopping-bag-black-48x48Icon-shopping-cartIcon--start-play-black-48x48Icon--store-locator-black-48x48Ic-OverlayAlertIcon--summary-black-48x48tumblrIcon-FilledvineIc-OverlayAlertwhishlist