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JScot.1
Visitor II
January 10, 2020
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How to convert 14-bit acceleration data from AIS1120SX and AIS2120SX to units of G

  • January 10, 2020
  • 3 replies
  • 1323 views

Hello all!

I'm attempting to convert the 14-bit acceleration data from the AIS1120SX/AIS2120SX. I'm successfully retrieving the data from the part with an acceleration command, and I'm able to view the value returned, but I don't understand how to convert the value to G.

There is a table (Table 39 - Acceleration data example from section 5.1.1) in the documentation which contains examples of conversions, but the examples aren't helping me.

0690X00000BvosLQAR.png

Are some number of the bits fractional? If so, which bits? How is it that a value of 120.4 Gs is represented by b'01111111111111? The 0.015 G value almost makes sense if D0 (the least significant bit) represents 2^-6, but that is the only case in which that makes sense; it doesn't make sense for the other values.

Thanks for any help you can provide!

JD Scott

    This topic has been closed for replies.
    Best answer by AK A.1

    Hi,

    Full range of the accelerometer is -120g to +120g. Hence, sensitivity is calculated as

    240 / (2^14) = 0.0146 g/LSB

    So, to compute the acceleration value in g, multiply the decimal value read from the register by the above computed sensitivity.

    Ex: In the 1st case in the table above, the decimal value is 8191.

    Acceleration in g = 8191 * 0.0146 = 119.6 g which is almost near to the value computed in the table.

    Hope this helps.

    Akshay

    3 replies

    A
    AK A.1Answer
    Visitor II
    January 10, 2020

    Hi,

    Full range of the accelerometer is -120g to +120g. Hence, sensitivity is calculated as

    240 / (2^14) = 0.0146 g/LSB

    So, to compute the acceleration value in g, multiply the decimal value read from the register by the above computed sensitivity.

    Ex: In the 1st case in the table above, the decimal value is 8191.

    Acceleration in g = 8191 * 0.0146 = 119.6 g which is almost near to the value computed in the table.

    Hope this helps.

    Akshay

    J
    JScot.1Author
    Visitor II
    January 10, 2020

    Akshay,

    Thanks for your help, I very much appreciate it. I was able to convert the values using the info you gave me.

    JD Scott

    D
    DDale.1
    Visitor II
    August 26, 2020

    Hi,

    About AIS2120SX chip, can you tell me how to initialize it?

    That is, the acceleration from being charged up to being able to read the X and Y axes.

    What is the entire SPI operation?

    It's very difficult to use this chip.

    I tried to initialize the chip, but failed.

    Thanks for any help you can provide!

    D
    DDale.1
    Visitor II
    August 26, 2020

    Hi,

    About AIS2120SX chip, can you tell me how to initialize it?

    That is, the acceleration from being charged up to being able to read the X and Y axes.

    What is the entire SPI operation?

    It's very difficult to use this chip.

    I tried to initialize the chip, but failed.

    Thanks for any help you can provide!

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