Difficulty in usage of accelerometer axis limiting?

[SUpen.1]

Hi Sir/Ma'am,

I am using accelerometer LIS3DH for drop test.

I disabled two of axis's x, y and enabled z axis with CTRL_REG1 (20h) .

Threshold 40, ODR 100, Range 2g.

I had varied range from 2g to 16 g.

Even when I dropped from 25 cm and 50 cm height I am not getting any interrupt but when I tilt it in Z->y axis or Z-> -y axis I see interrupt.

Kindly help!!

Thanks and Regards,

[Eleon BORLINI]

Hi @SUpen.1​ ,

You are trying to detect the impact event on the floor (not the free-fall event), right?

If so, suppose that the impulsive event is too short: the issue might be related to a too slow ODR (which might not be able to properly detect the event), and in this case you could try to increase the ODR (e.g from 100Hz to 200Hz or 400Hz). You might also try to change (reducing) the INT1_DURATION (33h) register, i.e. the minimum duration of the Interrupt 1 event to be recognized. As reported in the datasheet, duration steps and maximum values depend on the ODR chosen. Duration time is measured in N/ODR, where N is the content of the duration register.

-Eleon

[SUpen.1]

Hi @Eleon BORLINI​ ,

Free fall event ultimately end up with impact on floor will the both be considered different events?

I am getting same results with increasing ODR to 400Hz and INT1_DURATION is at default is 0 and varying g from +-2 to +-16g.

How do I stop interrupt in case of tilt and only detect impact on floor or free fall.

Thanks and regards,

Swati Upendra

[Eleon BORLINI]

Hi Swati Upendra, @SUpen.1​ ,

you can also detect the free fall (strictly speaking), i.e. the event during which the device is falling (the 3 axis acceleration approximates to 0). See app note, p.26.-Eleon