Disable high pass filter when using FFT for predictive maintenance

[JTam.1]

I am using accelerometer IIS3DWB and use MotionSP middleware to write the code for predictive maintenance. I have a 1400 RPM (23 Hz) speed of motor. Could I disable High pass filter (min. cut-off frequency is 33Hz) when using FFT to make frequency domain data? Any concern? Please advise. Thanks 

[Eleon BORLINI]

Hi @JTam.1​ ,

for my better understanding, do you want to avoid the computation made by the function below?

//
  //  @brief High Pass Filter to delete Accelerometer Offset
  //
  //  @param pDstArr: pointer to Accelero Array without offset
  //  @param pSrcArr: pointer to Accelero Array with offset
  //  @param Smooth: smoothing factor
  //  @param Restart: flag to Re-Init internal value
//
 
void MotionSP_accDelOffset(SensorVal_f_t *pDstArr, SensorVal_f_t *pSrcArr, float Smooth, uint16_t Restart)

In this case, you could bypass this function and take the raw data (with offset) from the pDstArr buffer.

You can then apply the FFT process to these unfiltered data.

Is this your case?

-Eleon

[JTam.1]

Hi Eleon,

Would the output of vibration speed data or acceleration data after FFT has DC offset if disable HPF? If I use HPF, that mean I need to change the motor speed to 2800 RPM (46Hz), Right? Thanks!

[Eleon BORLINI]

Hi @JTam.1​ ,

could you be more specific about the FW packages and the hardware you are using?

So that we can be more helpful also in relation to your other post.

-Eleon

[JTam.1]

Hi Eleno, Would the output of vibration speed data or acceleration data has DC offset in the STM32L4+ microcontroller after FFT (if disable HPF of the IIS3DWB vibration sensor)? Please advise. Thanks!

[Eleon BORLINI]

Hi @JTam.1​ ,

yes, it should.

-Eleon