FFT from gyro - difference in FFT plot amplitude obtained after switching from Mission Planner 1.3.74 to 1.3.75

ArduCopter Copter 4.0
1

Dear All.
I opened this new thread as suggested by @dkemxr
after this post Issue with FFT in new Mission Planner 1.3.75 build
I executed FFT to the same file (2021-07-31 17-27-12.bin) in Mission Planner 1.3.74 (on saturday July 31) and then after updating to 1.3.75 (sunday, August 01) I found that the vertical axis amplitudes changed.
Does someone know if there has been any change in vertical axis units in version 1.3.75?

I was trying to adjust a Notch filter for Gyro noise. Taking into account the FFT results for 2021-07-31 17-27-12.bin, I selected
INS_HNTCH_FREQ = 100
NS_HNTCH_BW = 50
INS_HNTCH_REF = 0,142915 (equal to MOT_THST_HOVER)
writed parameters to FC and then I executed another AltHold flight, obtaining 2021-08-01 12-04-17.bin (FFT plots of both files using Mission Planner 1.3.75 can be found in the link to the abovementioned thread).
It seems that there is no substantial difference between the signal after and before filter application. I saw in other threads in the blog plots with significative attenuation of the peaks, so it seems something is not working here. I am a novice with Ardupilot, so perhaps I am not considering something. Comments with suggestions are appreciated.

https://drive.google.com/file/d/1UTzNNat1Czz-hxm2iVHII6wQvR8uo26u/view?usp=sharing
https://drive.google.com/file/d/1YlZ65lgbNOJMoZjGfLgmiVxbxtCHzcIj/view?usp=sharing

2

Because you are logging pre-filter data in both logs:
INS_LOG_BAT_OPT,0

Set this to 2 and make another flight. Nothing to do with the version of Mission Planner although the scale has changed as reported in the other thread. This has been true in Beta for awhile. The Y axis scale really doesn’t matter as long as it’s the same analysis pre and post filter.

3

Thank you Dave.
Yes you are right. I missed that step before the execution of the second flight.
I will perform a new flight (I hope next weekend) and then compare the new file with the file 2021-08-01 12-04-17.bin