DC motor feedback methods and options

Hi all,

I am making a DC motor control board and want to add more than one motor feedback method to increase its usefulness. At the moment I have added the quadrature encoder option.

What are other popular methods ? Do people use stuff like 4-20mA current loops ?
What are other options that might be useful?

Regards

A little more complicated but back emf sensing is often used because there is no sensor needed.

Back EMF sensing would allow you to measure speed, while current sensing would allow you to measure load

Thank you ronv and schmitt trigger for your replies... they were very helpful !!!!!!!!!!!!!!!!

Shaft angle/rotation rate indicators (e.g. Hall effect, reluctance, optical) providing non-quadrature output pulses might also be used.