Need clarification on LIS2DW12 Sensitivity/Resolution Specification

[anonymous.8]

Posted on October 23, 2017 at 20:22

Hi, the datasheet for the LIS2DW12 3-axis accelerometer specifies a typical sensitivity of 1.952 mg/digit.

What does that mean exactly? What digit are they talking about. The output is contained in two 8 bit registers to make a 16 bit value. Are they talking about 1.952 mg/bit instead? Or else what format is the 16 bit output number (digit?) presented in?

Also it does not state what the actual bit depth is. OK, so the output is contained in a 16 bit number, but is the resolution 10, 12, 14 or 16 bits?

[Legacy member]

Posted on October 23, 2017 at 21:50

Hello,

it is supposed to mean 1.952 mg/LSB (the least significant bit). The output value of the accelerometer is stored as a 16 bit number in two's complement format.

Please note that if you multiply the sensitivity [mg/LSB] by the lowest and the highest value stored in a 16 bit number (-32 768 to 32 767), you get a higher value than the actual resolution found in the datasheet [+/- 2 , +/- 4, +/- 8 or +/- 16 g] of the sensor. Performance outside these boundaries is not guaranteed.

David

[anonymous.8]

Posted on October 23, 2017 at 22:08

Thanks for that clarification. I found the way that Bosch presents their sensitivity much easier to understand i.e. 512 bits/g. When you do 1000mg/512 it works out to 1.953 so I think that is what STM mean when they say it is 1.952mg/LSB. So for the +/- 16 g range (for which the sensitivity is 1.952mg/LSB) there is +/- 16g * 512 bits/g or +/- 8192 which is a 14 bit resolution.

Now wouldn't it have been much easier for everyone to understand if their datasheet had just come out and said it has a 14 bit resolution to start with?