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NPoth.1
Associate
March 19, 2021
Solved

Do you know the following characteristics (typical values) on the gyroscope and accelerometer of LMS6DSM : - Scale factor - Axis misalignment - Bias stability ?

  • March 19, 2021
  • 2 replies
  • 3090 views

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Best answer by Eleon BORLINI

Hi @NPoth.1​ ,

yes, I can share you some characterization / bench measure data -especially on the last two parameters-, since they are not in the datasheet:

  • Scale factor: the LSM6DSM is digital, so the exact conversion factor from voltage to digits depends on the internal ADC. However, the sensitivity -that depends on the selected Full Scale-, is defined in the datasheet, p.23: for the accelerometer, (milli)g stands for 9,81m/s^2 (/1000), the Earth gravity acceleration, while dps stands for degree per second. For example, in the FS=2g case the accelerometer sensitivity is 0.061 mg/LSB, meaning that a variation of 1 bit in the data output refers to an increase of 0.061 milli-g sensed.

  • Axis misalignment (i.e. "cross axis" parameter, or non orthogonality):
    • For the accelerometer (X to Y, X to Z, Y to Z):

0693W000008xXpIQAU.png

  • For the gyroscope (Pitch to Roll, Pitch to Yaw, Roll to Yaw):

0693W000008xXsGQAU.png 

  • Bias stability:
    • For the accelerometer:

0693W000008xXyxQAE.png

  • For the gyroscope:

0693W000008xXz9QAE.png 

If my reply answered your question, please click on Select as Best at the bottom of this post. This will help other users with the same issue to find the answer faster. 

-Eleon

2 replies

Eleon BORLINI
Eleon BORLINIBest answer
ST Employee
March 22, 2021

Hi @NPoth.1​ ,

yes, I can share you some characterization / bench measure data -especially on the last two parameters-, since they are not in the datasheet:

  • Scale factor: the LSM6DSM is digital, so the exact conversion factor from voltage to digits depends on the internal ADC. However, the sensitivity -that depends on the selected Full Scale-, is defined in the datasheet, p.23: for the accelerometer, (milli)g stands for 9,81m/s^2 (/1000), the Earth gravity acceleration, while dps stands for degree per second. For example, in the FS=2g case the accelerometer sensitivity is 0.061 mg/LSB, meaning that a variation of 1 bit in the data output refers to an increase of 0.061 milli-g sensed.

  • Axis misalignment (i.e. "cross axis" parameter, or non orthogonality):
    • For the accelerometer (X to Y, X to Z, Y to Z):

0693W000008xXpIQAU.png

  • For the gyroscope (Pitch to Roll, Pitch to Yaw, Roll to Yaw):

0693W000008xXsGQAU.png 

  • Bias stability:
    • For the accelerometer:

0693W000008xXyxQAE.png

  • For the gyroscope:

0693W000008xXz9QAE.png 

If my reply answered your question, please click on Select as Best at the bottom of this post. This will help other users with the same issue to find the answer faster. 

-Eleon

NPoth.1
NPoth.1Author
Associate
March 23, 2021

You answered my questions concerning axis misalignment, thanks a lot !

Regarding the bias stability, can you tell me the observation time (period) ?

Regarding the scale factor, I'm interested in the accuracy of the scale factor (not of the scale factor value itself). Do you have typical values of the accuracy (precision) of the scale factor for gyroscope and accelerometer (in ppm or %) for FS=+-8g and for FS=+-2g?

Thanks again, you are very helpful.

Eleon BORLINI
ST Employee
March 23, 2021

Hi @NPoth.1​ ,

you are welcome.

For the bias stability, the observation period is 72h.

For the accuracy/precision parameter, I can share you the sensitivity error in non linearity:

0693W000008xhrwQAA.png0693W000008xhZoQAI.png-Eleon

NPoth.1
NPoth.1Author
Associate
March 24, 2021

For the bias stability, I expected an "observation time" in second. For me, the "observation time", is the value on the x-axis (tau) where the Allan variance is smaller.

0693W000008xmReQAI.png 

For the accuracy/precision parameter of accelerometer, thanks, you answer my question.

What about the accuracy/precision parameter of gyroscope ?