I have been learning about absolute encoders, and am testing a multi-turn absolute encoder (link to datasheet is here). During testing, I realized that after shutting down the power, although the encoder position is saved, the number of turns is not, which means the encoder position is non-volatile, but the number of turns is volatile.
So, forgive me for a lack of fundamental knowledge, but: does there exist a type of absolute encoder that saves the number of turns, even after power is turned off and on again?
I have tried searching for this on stackexchange and on Google, using the search terms "non-volatile" and "multi turn absolute encoder", but I could not find an answer.
EDIT: while searching more about different types of multi-turn encoders, I found a type of encoder that uses what is called the "Wiegand Effect". Wikipedia states "As the encoder revolves, the Wiegand wire core coil generates a pulse of electricity sufficient to power the encoder and write the turns count to non-volatile memory". I have also found an example of this encoder, and this example's datasheet is here. So, I guess I should modify my question as, "Are there any other types of absolute encoders that saves the number of turns, even after power is turned off and on again (other than Wiegand-based encoders)?" I am interested in learning all the different types, if there are any others.