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    BMX 160 Electrical Specification Questions

    MarleyRun
    Occasional Visitor

    BMX 160 Electrical Specification Questions

    Hello Everyone,

    I am working with the BMX160 for a project and have some questions regarding its internal timer and the sensitivity spec on the gyro and magnetometer. Further explanation into any one of these would be appreciated.

    Timer
    1. What is the accuracy of the internal timer? In 2.3 it mentions the sensor time as having a resolution of 39 us, but never specs the accuracy of the timer (in ppm or % for example).

    Gyro
    2. Can I expect the gyro sensitivity error to be consistent across each axis on one particular chip? Or is the sensitivity error unique per axis?
    3. Can I expect the gyro sensitivity errors to be comparable for all chips from the same production lot?
    4. Does gyro sensitivity change due to anything other than temperature/voltage? We would like to model the sensitivity error for better results.
    5. Does the relative sensitivity change with different dps ranges? Do we need to calibrate for every combination of dps-range and axis?

    Mag
    6. Can I expect the mag sensitivity error to be the same across each axis on one particular chip? Or is the sensitivity error unique per axis?
    7. Can I expect the mag sensitivity errors to be comparable for all chips from the same production lot?
    8. Does mag sensitivity change due to anything other than temperature/voltage? We would like to model the sensitivity error for better results.

    Gyro sensitivity error means how much the chips deviates from the ideal degrees-per-sec per LSB. Could be % or offset.
    Mag sensitivity error means how much the chips deviates from the ideal uTeslas per LSB. Could be % or offset.

     

    Tags (3)
    2 REPLIES 2
    BSTRobin
    Community Moderator

    Re: BMX 160 Electrical Specification Questions

    Hello MarleyRun,

    Please refer the following reply.

    1.What is the accuracy of the internal timer? In 2.3 it mentions the sensor time as having a resolution of 39 us, but never specs the accuracy of the timer (in ppm or % for example).

    Reply: Any data out of datasheet, and website document, need NDA
    2. Can I expect the gyro sensitivity error to be consistent across each axis on one particular chip? Or is the sensitivity error unique per axis?

    Reply: different for every chip and axis and temperature .... but in application user can look the sitivity error of each axis consistent in constant condition
    3. Can I expect the gyro sensitivity errors to be comparable for all chips from the same production lot? 

    Reply: not correct. please consider the characters in datasheet and sensitivity error in spec.
    4. Does gyro sensitivity change due to anything other than temperature/voltage? We would like to model the sensitivity error for better results.

    Reply: Mainly bu not only temperature and voltage, for example the bending ...A better model will improve the sensitivity performance.
    5. Does the relative sensitivity change with different dps ranges? Do we need to calibrate for every combination of dps-range and axis? 

    Reply: Of cause different range has different sensitivity, I guess you talk about rel. sensitivity error ?
    6. Can I expect the mag sensitivity error to be the same across each axis on one particular chip? Or is the sensitivity error unique per axis?.

    Reply:  No. but in application. look axis sensitivity error constant in constant condition. should be in spec.
    7.Can I expect the mag sensitivity errors to be comparable for all chips from the same production lot?

    Reply:  In datasheet characters description about sensitivity error
    8.Does mag sensitivity change due to anything other than temperature/voltage? We would like to model the sensitivity error for better results.

    Reply:  Mainly but not only. a better model can improve performance. but there is not available in API or driver

     

    Could you refer these replies and give further feedback if you have?

    imubeagle
    Member

    Re: BMX 160 Electrical Specification Questions

    "Reply: Of cause different range has different sensitivity, I guess you talk about rel. sensitivity error ?"

    I don't think you answered the intended question.  If the true/measured gyro sensitivity @ FS=500 is 68.6 lsbs/dps (which means its above the typical 65.6 by ~4%), does that imply that @ FS=1000, the sensitivity is also ~4 % above the typ (which would be about 34.3 lsbs/dps).  Or is there a totally different error for each of the FS settings?  Otherwise you would have to measure at the four different settings in case you want to use them in the future.  Seems reasonable to just measure the error at one FS and use that correction to correct all four sensitivities.

    The datasheet does not clarify this, it just has the ranges for each FS.

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