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Spikes in the LIS2DH12 accelerometer raw data

soundarya1
Associate II

‎2024-04-21 11:45 PM

Spikes are present in the data coming from the LIS2DH12 accelerometer when placed in a casing, but when it is in the open there are no spikes. Attached is an image of the 3 axis data plotted from the accelerometer when placed on the table with casing and rotated. I have also added another plot of the same device on air (no movements). Please advice how to mitigate this issue. Thanks.

 

Axis_Plot_closed_and_zreversed.png

 

Axis_Plot_in_air.png

 

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7 REPLIES 7
Federica Bossi
ST Employee

‎2024-04-24 02:57 AM

Hi @soundarya1 ,

Welcome to ST Community!

Can you give us more details about your casing? Is it possible that it is in contact directly with the top of the LIS2DW12?

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soundarya1
Associate II
In response to Federica Bossi

‎2024-04-25 03:27 AM

Hello @Federica Bossi,

The casing/enclosure has no direct contact with LIS2DW12. It only encompases the entire device. There is nothing else placed above LIS2DW12. 

 

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soundarya1
Associate II
In response to soundarya1

‎2024-04-25 04:16 AM

Also, the casing is ABS casing, there is 5mm+ of space present between the casing and LIS2DW12. 

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Federica Bossi
ST Employee
In response to soundarya1

‎2024-04-26 12:04 AM

Can you send me a picture to better understand? It is definitely casing related since without it no spikes can be observed...

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soundarya1
Associate II
In response to Federica Bossi

‎2024-04-30 06:14 AM

I have added a picture of the sectional view which shows the casing for your understanding.

The green in the image is the pcb where the accelerometer in mounted. 

Please note that there are 2 fastener at around 1-2 cm on either side of the accelerometer. Also, there is 5mm+ of space present between the casing and the pcb. 

 

Artboard 4-100.jpg

 

 

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Federica Bossi
ST Employee

‎2024-05-02 02:12 AM

Hi @soundarya1 ,

When you put the LIS2DH12 in the casing and it doesn't rotate, what do you see? can you share a graph?

In addition, can you write me your settings? ODR, FS, BDU...

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unsigned_char_array
Lead

‎2024-05-02 02:28 AM - edited ‎2024-05-02 02:46 AM

Could be vibration. Have you rotated at different speeds? What is the spectrum of the spikes? Perhaps the enclosure has a certain resonance frequency that causes issues.

Also the data looks like it's a modulo of the real data. It overflows/wraps around. You can see that around t=1250 the x and y values slowly cross the boundary and then wrap around. If you remove the overflows from the data does it still have spikes? Or is it bouncing around 0.0/0.8?

Can you attach a csv file of the raw data? (integer not floating point)

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