Resolver

A position detector that uses a magnetic circuit and is comprised of three components:
1) Iron core to be mounted on rotor shaft,
2) Windings to be mounted on bracket
3) Analog-to-digital converter
The output from the windings is a set of two-phase inductance signals, functions of rotary angle θ, from which the rotor angle is resolved into a digital value in an appropriate number of bits. See the curves below.