Angelo

For a project where I need to measure an inductor (detection loop) at 60kHz, I plan to use RMS to DC converters: one to measure voltage across de inductor, and one to measure current across a sense resistor. Then measure phase between voltage...

If encoder is "mechanical", a small R-C filter helps remove the possible oscillations due to bouncing contacts. The classic implementation is a pull-up on the contact side, followed by a R-C. A good explanation I just found...

I have no problem with this. It is totally normal to ask money for your wok. It was only to be clear that you were "advertizing" your product, wich I am not sure it is allowed on this forum.

I used this one: https://www.digikey.com/en/products/detail/recom-power/R-78B5-0-1-0/2256232

You forgot to mention: not free, cost 50$

Test if the Teensy can write a file by itself ? You will know if the problem comes from the SD card, the Teensy or the library.