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

Associate II

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ST Employee

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):

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

• Bias stability:
• For the accelerometer:

• For the gyroscope:

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

7 REPLIES 7
ST Employee

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):

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

• Bias stability:
• For the accelerometer:

• For the gyroscope:

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

Associate II

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.

ST Employee

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:

-Eleon

Associate II

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.

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

What about the accuracy/precision parameter of gyroscope ?

ST Employee

Hi @NPoth.1​ ,

ok, I was thinking to the whole acquisition time. Yes, the tau unit measure (average time) is seconds.

>> What about the accuracy/precision parameter of gyroscope?

For the gyroscope I can share you the NL in the +-2000 dps case:

Other questions? 😅 😉

-Eleon

Associate II

😅 😊

So can you tell me the tau value for bias stability of accelerometer and gyroscope ?

Thanks for all !

ST Employee

Hi @NPoth.1​ ,

the cluster time for both accelerometer and gyroscope in the bias stability region of the AVAR plot is about 20s.

-Eleon