LSM6DSV32X Gyroscope Artifacts

[JHenn.1]

We use the accelerometer and gyroscope channels of an LSM6DSV32X for measuring movement parameters of a mechanical system. During some tests we observed artifacts in the gyroscope channel that we cannot explain.

Configuration:

The LSM6DSV32X is connected via SPI and run in Continuous FIFO mode. We have a FIFO Watermark configured and read the entire FIFO whenever its interrupt is detected.

The sensor channels are configured to:

Accelerometer: 3840Hz, +/-32 g

Gyroscope: 3840Hz, +/- 2000 dps

Mechanical Setup:

In order to examine the problem we build a simple mechanical setup and recorded some data with it:

We attached the LSM6DSV32X to a metal bar that pivots around an axle attached to a solid wall. During the recording we lifted the unrestrained end of the metal bar up and dropped it, causing it to hit the wall. After the impact of hitting the wall, the metal bar bounces back and forth a few times.

We repeated this several times over multiple recordings.

This is what the first recording looks like:

Both Signal 2 and Signal 3 look as expected with gyroscope amplitudes of around 400 dps. Here is a close up of Signal 2:

And a close up of Signal 3 (different time scaling in the plot, but very similar to Signal 2:(

However Signal 1 looks completely different. Here the gyroscope amplitudes are close to 2000 dps and the expected patterns of impacts and bouncing back are not visible.

To be sure we did more recordings and while most of the signals looked good, there were several more signals that looked like the example above.

Here is another example:

Question:

For the most part the accelerometer signals look fine, so the problem seem to be in the gyroscope channel only.

During the impacts the accelerometer is almost always clipping (>32G). For our application this is not an issue, however we are wondering if this might cause issues for the gyroscope.

--> Is it possible that we sometimes get artifacts in the gyroscope channel because the accelerometer is clipping?

--> What else could be the problem and cause these artifacts?

Best regards,

Johannes

[PGump.1]

Hi,

I have not looked at the LSM6DSV32X specifically, however, these devices typically use a DSP based on Sampling Theorem for their functionality, and therefore, governed by those limitations.

In your case, Impact analysis can be distorted by low Sample Rates, and DSP’s handling of Overflow arithmetic through filters...

If the front-end of the LSM6DSV32X can be configured for different sample rates or filtering - try there.

I hope this helps.

Kind regards
Pedro