Electromagnetic position encoder based on the principle of the rotating field that contains a rotor and a stator with a number of windings and with an output voltage that corresponds to the angular position of the rotor.
The stator can comprise three separate windings offset by 120° (synchro) or two windings offset by 90° in relation to each other (resolver) (Figure D 37).
Both are analogue devices that, however, due to their layout are very suitable for digital signal output.
Figure D 37: Selsyn rotary position encoder a) synchro b) resolver