ADXL357 output drift in higher frequency than 200Hz

Hi all

I  test ADXL357 output of z-axis 4g acceleration in standard  machine.

Set ODR 4KHz and SPI rate  8MHz. I believe it's fastest data output rate and never missing any data.

Increase the acceleration frequency of machine  step by step, and I get the acceleration value 4g in 20Hz ,4g in 200Hz ,3.7g in 400Hz , 3.5g in 600Hz and 3g in 1000Hz  separately.

So,why ADXL357 cannot sample 4g in higher frequency than 200Hz?

Because ADXL357 can be applied in Structural health monitoring and Condition monitoring according to the APPLICATIONS of  data sheet .

Usually these applications need acceleration of  1kHz  frequency. But ADXL357 cannot measure acceleration of 400Hz frequency?