encoder vs resolver

Encoder versus Resolver Encoder versus Resolver Encoder is an optical device consisting of a translucent di sk, scored with lines and 2 sets of LED and Photo Di ode, each time a mark passes between the optical link, it is broken generating a sign al, the signals are 90=B0 apart, generating the data for the A/B channel s of the encoder. There is usually a Z mark once a rev as well. Usual ly the encoder is mounted on the back of the motor. Resolver is a magnetic device consisting of 2 static coi ls 90=B0 apart and one rotating one. The rotating coil is fed with a sinusoidal current, and the induced current in the static coils are measured. The relative intensities of the signals gives you the position. Usually the resolver is part of the motor. The encoder is used for most appli cations except the following: 1) Hard radiation (fogs the translucent disk) 2) Very high accelerations (damages the coupling) 3) Very high vibrations (damages the coupling, vibrates the disk) 4) Very high temperatures (damages the disk) 5) Very high resolution (optical resolution) The resolver is not used in the fol lowing cases: 1) Cost factor 2) High speed applications (the lag through the position decoder means loss of accuracy)

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5/8/2018 Encoder vs Resolver - slidepdf.com

http://slidepdf.com/reader/full/encoder-vs-resolver 1/3

Encoder versus Resolver

Encoder is an optical device consisting of a translucent disk, scored with linesand 2 sets of LED and Photo Diode, each time a mark passes between theoptical link, it is broken generating a signal, the signals are 90=B0 apart,generating the data for the A/B channels of the encoder. There is usually a Zmark once a rev as well. Usually the encoder is mounted on the back of themotor.

Resolver is a magnetic device consisting of 2 static coils 90=B0 apart and onerotating one. The rotating coil is fed with a sinusoidal current, and the inducedcurrent in the static coils are measured. The relative intensities of the signalsgives you the position. Usually the resolver is part of the motor.

The encoder is used for most applications except the following:

1) Hard radiation (fogs the translucent disk)2) Very high accelerations (damages the coupling)

3) Very high vibrations (damages the coupling, vibrates the disk)4) Very high temperatures (damages the disk)5) Very high resolution (optical resolution)

The resolver is not used in the following cases:

1) Cost factor 2) High speed applications (the lag through the position decoder means loss of accuracy)

5/8/2018 Encoder vs Resolver - slidepdf.com

http://slidepdf.com/reader/full/encoder-vs-resolver 2/3

Resolvers and Encoders are vastly different though they serve the same purpose in many applications. In rotary applications, both of them areused to sense the speed, direction and position of a rotating shaft. Theyfunction as transducers by transforming mechanical motion intoelectronic information. This electronic information is feedback to

electronic devices controlling the mechanical motion. Feedback is thevital link that closes the control system loop to improve the motionsystem performance.

For many years now, the dominant trend in feedback devices has beenaway from contacting toward non-contacting methods. The wear associated with contacting brushes and wipers reduces longevity andreliability. A brushless resolver uses a second set of rotor and stator coilscalled the transformer to induce rotor voltage across an air gap. Opticalencoders use a rotating shutter to interrupt a beam of light across an air gap between a light source and a photodetector.