Re: Resolvers & Encoders

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mina Aboul Saad"
<minaf@l...> wrote:

> Hi group,
>
> Could someone explain the difference between encoders and resolvers

(basic

> info.) for a newbie who wishes to learn?
> Thank you.
>
> Mina F.

A resolver is in essence a rotating transformer. A known Sine wave
signal is applied to one set of coils and the inducted output read
from the other. As the shaft of the resolver rotates the phase
relationship changes based on the amount of rotation. External
circuitry is use to measure the phase difference between the two
signals. Very small offsets can be measured. Resolvers require a lot
of external circuitry that has to be calibrated and adjusted from
time to time.

An encoder is basically a digital device that uses a light source
(usually an LED) and two or more sensors with a "shutter" mechanism
that interrupts the light as the encoder is moved. The light
interruptions are counted and the pulse count is used to determine
position. Encoders are largely self contained (little external
circuitry) and interface easily with digital controllers. Digital
encoders have improved in resolution and accuracy and the cost has
dropped so that most new designs using encoder feedback now use the
encoder approach.

There are many other technical aspects about encoders and how to use
them that others may wish to share with you but those are the basics.