# acceleration output interpretation

I'm using LSM9DS1 accelerometer which I configured with 16g range.

I left the device without movement and I got following accelerations

x : 0

y : 0

z : 1300

the device is subjected only to gravity, hence the positive value got in Z

my question is what's the origin of the value 1300, the earth gravity acceleration is 9.81 m/s²

• normally it is calibrated for 1g =0 not freefall (0g) – Tony Stewart Sunnyskyguy EE75 Sep 21 '16 at 14:52
• sorry I don't get you, if 1g = 0, so do you mean that 1300 = 1300 g?? – Makhlouf GHARBI Sep 21 '16 at 14:54
• The resolution is probably mili g, though the datasheet should tell. – Bence Kaulics Sep 21 '16 at 14:57
• What if you flip it? – Eugene Sh. Sep 21 '16 at 14:57
• 1300 exactly? I would guess your reading method is wrong – Eugene Sh. Sep 21 '16 at 14:59

Maybe it would help to read the part of the datasheet where it tells you the output units?

From page 12 of the datasheet: Linear acceleration sensitivity FS = ±16g 0.732mg/LSB

So take the reading, multiply by 0.732 and then divide by 1,000 to get the acceleration in g.

1340 * 0.732 / 1000 = 0.981g

edit - Note that is 0.981g NOT 9.81m/s, it's 20mg off, well within the margin of error of the sensor, that the value happens to be the same digits as 1g measured in m/s is just a confusing coincidence.

You choose +/-16g range for full scale then follow calibration methods to get 0 output at rest, if that is what you want, otherwise compute mg sensitivity.

• also facing true north for mag.