LIS2DH12 16G full scale goes up to 24G?

[IC.1]

Hi, this is a question about LIS2DH12.

I've been puzzled over the full scale settings for this sensor.

As it says in the datasheet, the ranges are ±2g/±4g/±8g/±16g, yet when I am set at 16g, I am able to obtain a max range of -24656, +24384.

I am using low power mode, and calculating the ranges by hand, here are the ranges I get:

(-24656, 24384) 16G

(-8192, 8128) 8G

(-4096, 4064) 4G

(-2048, 2032) 2G

Since at low power mode, the accelerometer only outputs a byte of data, and accounting for a signed integer, the max positive value would be 127 multiplied by whatever the mg/digit is.

In the case of 16G, it would be 127 * 192 = 24384, yet for the other configurations the max value remain near their thresholds.

Therefore, is there something I am misunderstanding about 16G mode, or is there something wrong with the datasheet?

Thanks for your time,

Isaac

[Eleon BORLINI · Accepted solution]

Hi Isaac @IC.1​ ,

Your calculation is correct: in the 16g case, in every mode, the mechanical full scale is not coincident with the digital full scale (so, basically, the 0xff output).

In other words, you are actually able to detect shocks / vibrations higher than 16g (in the FS 11 case), but after this value the relationship with is no more linear, so the simple multiplication is no more effective after 16g (i.e. about dec125).

And this is true not only for the LIS2DH12 product, but also for some other old accelerometers.

My suggestion for you is to work just up to 16g and discard the higher values.

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