In the days of DC servos, resolvers were used because of their resitance to noise, the down side was low resolution and were usually geared up, They have resurfaced now being used for commutation on sinusoidal AC servo systems, the resolver is fed into the drive first for commutation and then the result is electronically multiplied and a psuedo encoder signal complete with marker pulse is fed from drive to controller, this can usually be resolution selected by dip switch.
For the commutation, the resolver has two phases out, the third is artificially produced from a vector of the other two.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.