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    Data sheet clarifications needed

    Data sheet clarifications needed

    rozerinaktas
    Member

    Dear Team, 

    I am writing my master thesis in a company on aerospace and its applications. We are currently working on MEMS sensors and I have a tool to run the performances of MEMS sensors based on the specifications and a model that has been developed. I am currently on analysing the performance of Bosch accelerometer and gyroscope products.

    Based on my model and definitions, I am currently having a few confusions with the data sheets for the sensors. I will ask for both accelerometer and gyroscope. They will be like in the following;

    Questions for BMG160 gyroscope;

    1) I see on the data sheet that the ‘senstivity’ value has a unit of LSB/°/s. Is this parameter corresponding to scale factor, as an effect on the input/output ratio of the device? If so, how can I convert this to a unit of %(divide by 8 maybe?)? If not, which parameter value shall I use as a scale factor for my calculations available in the data sheets?

    2)I see ‘cross axis sensitivity’ parameter. Is this parameter the same thing with the non-orthogonality of the 3-axis? If not, can I have a detailed definition for that parameter?

    3)On the data sheet, I can’t see the misalignment error of the sensors(3 gyroscopes). Is this error considered on the model or is it given as a different parameter or calculated differently? My main consideration is to distinguish the non-orthogonality of the 3 axis measurements and the misalignment of the 3 different sensors because I have different parameters for both in my model.

    Questions for BMA400 accelerometer;

    1)Similar to the above case, which parameter shall I refer to as the scale factor?

    2)What exactly is the ‘Alignment Error’?

    3)Why is the unit for the non-linearity ‘%’ ? Shouldn’t it be a function of the true acceleration?

    4)Also similarly to the above case, is there a term for the misalignment of the sensors (with respect to each other) in the sheets?

    The documents I am referring are BST-BMG160-DS000-09 revision 1.2 and BST-BMA400-DS000-02 revision 1.1 .

    Thank you for your time and I am looking forward to hear from you soon.

    Cheers,

    8 REPLIES 8

    Hi! Thank you so much for the information provided. On the datasheet I had, the min and max values were not available but now it looks ok. However, can you tell me which IMU model of Bosch you have provided in this table? Because the one I have has from 3g to 24g. 

    clipboard_image_0.png
    By bias instability, I meant the instability that is caused by the flicker noise which also gives a change to the bias over time. In other words, the colored noise of the sensors. Do you have such information or are you interested in such a parameter in your measurements? 

    Thank you and best regards, 

    Hi rozaerinaktas,

    So many questions in a single post. If data is not published in the datasheet, then it is not publicly available.


    I see on the data sheet that the ‘senstivity’ value has a unit of LSB/°/s. Is this parameter corresponding to scale factor, as an effect on the input/output ratio of the device? If so, how can I convert this to a unit of %(divide by 8 maybe?)? If not, which parameter value shall I use as a scale factor for my calculations available in the data sheets?
    Sentivity in LSB/dps = scale factor

    2)I see ‘cross axis sensitivity’ parameter. Is this parameter the same thing with the non-orthogonality of the 3-axis? If not, can I have a detailed definition for that parameter?
    No. Cross axis sensitivity is for example, output on the X axis from stimulus in the Y axis.

    3)On the data sheet, I can’t see the misalignment error of the sensors(3 gyroscopes). Is this error considered on the model or is it given as a different parameter or calculated differently? My main consideration is to distinguish the non-orthogonality of the 3 axis measurements and the misalignment of the 3 different sensors because I have different parameters for both in my model.
    non-orthogonality is part of cross axis sensitivity. Misalignment error refers to the plastic package vs sensing axis.

    Questions for BMA400 accelerometer;

    1)Similar to the above case, which parameter shall I refer to as the scale factor?
    see above
    2)What exactly is the ‘Alignment Error’?
    see above.
    3)Why is the unit for the non-linearity ‘%’ ? Shouldn’t it be a function of the true acceleration?
    The unit is % of full-scale range. In this case, in 2G range, 0.005 * 2G = 10mG. This means that the sensor output will never be further than 10mG away from a straight line between the output at 0G and the output at 2G.
    4)Also similarly to the above case, is there a term for the misalignment of the sensors (with respect to each other) in the sheets?
    see above

    Your last answer was totally unnecessary because your colleague had already replied them. If all of your data is not publicly available and you have many ambiguities, then maybe you can indicate better quality information in your datasheets so that people are not being misleaded. And these forums are to clarify questions from people, does it REALLY matter how long one post is? That is purely ridicilious. Your attitude is very rude and ignorant.  

    Hi rozerinaktas,
     

    Thanks for your comment and feedback. We appreciate every question and recommendation regarding our products, tools and documentation. Our intention is always to provide the best answers as possible. Unfortunately if some information is not available in our datasheets, it typically means such information is either not known or not publicly available, which was the case for your last request. Of course if further clarification of the available information (or its meaning) is needed, please let us know.

    Best regards.

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