Robin2:
The gap between the two readings will always be the same. Whether the pair of readings remains in phase with something that is rotating depends on how you sync the readings with the rotation.
Yes, the gap is same for all the rotations. Thank you. But another problem arrives:
TomGeorge:
Do you have a device to measure rotational position?
Yes, I do have an encoder... incremental rotary encoder attached to a plate with 32 teeth (per rotation, i.e every 11.25 degrees)
TomGeorge:
If so, then measure continuously one sensor and plot it against rotational position, then measure the other sensor the same way.
The problem then still arrives... how to sync the encoder with the piezo sensor correctly, without any lag?? In my case, there is a lag, which keeps on increasing every rotation so the values are not perfectly synced...
I have attached the encoder to digital pins and piezo (currently only 1) to the analog pin and compared the graphs...