LIS2DH12 giving Z = 0.62g instead of 1g at rest position only when scale is set to 16g

[manjot]

Hi

I am working with LIS2DH12 accelerometer. I want to read and calibrate the raw x,y,z axis data. For the scale level 2g, 4g, 8g, I am getting the accurate readings(At stable position, Z is 1g for above scale levels). But when I change my scale level to 16g, my z-axis is only reading 0.62g value instead of 1g.

Here are the register configurations that I am using:

 /*variables to store values in registers*/

 uint8_t value_ctrl_reg1 = 0x47;  // Turn on the sensor, enable X, Y, and Z, Low Power mode, ODR = 100Hz

uint8_t value_ctrl_reg2 = 0x00; 

uint8_t value_ctrl_reg3 = 0x00;

uint8_t value_ctrl_reg4 = 0x88; // FS = ±8g

/*Read Accelerometer*/

  uint8_t data[6];

  #define Scaling_Fac_ACC 2048

  vTWI_Read(LIS2DH12_OUT_X_L , &data[0]);

  vTWI_Read(LIS2DH12_OUT_X_H , &data[1]);

  vTWI_Read(LIS2DH12_OUT_Y_L , &data[2]);

  vTWI_Read(LIS2DH12_OUT_Y_H , &data[3]);

  vTWI_Read(LIS2DH12_OUT_Z_L , &data[4]);

  vTWI_Read(LIS2DH12_OUT_Z_H , &data[5]);

  x_axis = (float)((int16_t)(data[1] << 8 | data[0]));

  y_axis = (float)((int16_t)(data[3] << 8 | data[2]));

  z_axis = (float)((int16_t)(data[5] << 8 | data[4]));

 /*converting raw data using scaling factor for 16g i.e. sensitivity 2096*/

  x_axis = x_axis / Scaling_Fac_ACC;

  y_axis = y_axis / Scaling_Fac_ACC;

  z_axis = z_axis / Scaling_Fac_ACC;

Please advice me what I am doing wrong in my code to calibrate the raw axis data.

Any help is much appreciated.

[Eleon BORLINI · Accepted solution]

Hi @manjot​ , where did you take this conversion factor for 16g FS?

 /*converting raw data using scaling factor for 16g i.e. sensitivity 2096*/

You can simply multiply the raw value for 192 mg/digit in case of Low power mode.

Regards

[manjot]

Hi Eleon

Thank you for correcting me.

I got that conversion formula from general accelerometer code. But now I followed your advice and it is actually giving the accurate results for all scale levels at low power mode.