LSM9DS1TR gravity expected output

arthur · ‎2017-01-11

Posted on January 11, 2017 at 12:27

Hi, I am using a LSM9DS1TR, with accelerometer scale set to +-16G.

With the device motionless on a table, I read a decimal value of 1360 for the Z axis, and if I flip the board over I read -1360 (give or take a few counts). So, this is obviously measuring gravity.

I would however have expected gravity to be 1G, so I would have expected an output of 1/(16/32768) = 2048, not 1360.

Can anyone explain why I do not see what I expect to see? I've obviously missed something!

Thanks.

Miroslav BATEK · ‎2017-01-11

Posted on January 11, 2017 at 12:42

Please refer to the Table 3 in the datasheet, where you can find accelerometer sensitivity for different full scales. You have to use the sensitivity to convert raw output value from the sensor to acceleration in g unit. In your case (FS=+-16g) the sensitivity is 0.732mg/LSB so 1360*0.732 = 995.52mg = 0.996g ~ 1g. It is expected value.