LIS3DSH Sensitivity

[FF1]

Posted on January 08, 2018 at 12:53

Dear All,

about this device I'm try to better understand the sensitivity parameters, from the datasheet, using the device at ±2.0g (FS bit set to 000) we must have a Sensitivity of 0.06 mg/digit, hence the number of digit should be: ±2.0/(0.06*10^-3)=±33333.3 practically I suppose ± 15 bit, I'm right?

From this I try to understand the Terminology at the device datasheet page 17/58:

'Sensitivity describes the gain of the sensor and can be determined, for example, by

applying 1 g acceleration to it. As the sensor can measure DC accelerations this can bedone easily by pointing the axis of interest towards the center of the Earth, noting the outputvalue, rotating the sensor by 180 degrees (pointing to the sky) and noting the output valueagain. By doing so, ±1 g acceleration is applied to the sensor. Subtracting the larger outputvalue from the smaller one, and dividing the result by 2, leads to the actual sensitivity of thesensor. This value changes very little over temperature and also time. The sensitivitytolerance describes the range of sensitivities of a large population of sensors.'

may be I've not correctly understanded this sentence, if the device will be thoretically then ideal with this measumerement step I shold see exactly 1 g, any difference should be about non ideality the mechanical error, electrical offset and so on, could you explain a little bit more why with this procedure I can calculate the device sensitivity, I think better the zero error instead, I'm a little confused at this point.

Could you please let me point in right direction?

Best regards

Fabio

[Miroslav BATEK · Accepted solution]

Posted on January 08, 2018 at 16:35

Using the mentioned procedure you can calculate both the sensitivity and offset.

The output of the accelerometer is defined as out = sensitivity * acceleration + offset.

If you do the procedure you will get two values (out1, out2) for two accelerations (+1g, -1g) so you have two equations with unknowns. Both unknowns can be then calculated: sensitivity = (out1 - out2)/2 and offset = (out1 + out2)/2.

Btw. the typical sensitivity is specified in the datahseet so you don't have to any procedure, you just multiply the raw data from the sensor by the typical sensitivity value and you will get the acceleration in g unit.

[FF1]

Posted on February 12, 2018 at 13:14

Hi Miroslav,

well is true I've missed the point, is just a linear system in two equations:

out1=sens *(+1g)+offset

out2=sens*(-1g)+offset

where out1 is the output value measured when applied +1g on the observed axes and similary out2 with -1g applied; of course the offset is supposed constant over the two measurements.

Solution of this system is simple (by using the summing member a member and subctrating member a member way) will give:

offset=(out1+out2)/2

sens=(out1-out2)/2

I've just rewritten it in more expanded way for anyone need it in future.

Thanks!

Fabio

[chaitanya chippada]

Posted on July 06, 2018 at 15:43

Hi ,

I am using LIS3DSH for my project, there is any way to increase data samples per second ,more than 1600 samples per second by increasing I2C clock from 100kHz to 400 KHz. or we can use SPI for for getting more data samples.

I am having one doubt like we can interface two LIS3DSH sensors we can interface on I2C simultaneously with raspberry 3b plus board,if we can do ,how to do ?

waiting for your reply,

Regards,

chaitanya.