Re: [CAD_CAM_EDM_DRO] Jitter in USdigital encoders

Graham Stabler wrote:

>I understand that with rotary vibration of the shaft of an encoder
>errors can result due to dithering or jittering, effectively extra
>pulses that shouldn't be there.
>
>Does the circuitry in a USdigital encoder take care of this? or is
>some external filtering required??
>
>

The encoder counter circuit is required to handle this. Since every

valid transition of a quadrature encoder contains direction information
as well as the fact that one quanta of motion has ocurred, there is no
ambiguity there. Valid transitions are those where only one of the phase
signals (normally called A and B) change state at one time. If two phases
change state at the same time, that is an invalid transition, as
direction of motion
cannot e determined. In general, these transitions are caused by electrical
interference, and will go away after a few sampling cycles, and a valid
transition should follow soon.

Vibration is not required for this position flicker to occur. Whenever
the optical
path of the photosensors is partially blocked by the encoder disc, the
sensor
can be near the transition point, and the normal electronic noise level
in the
sensor electronics can cause it to jitter between the one and zero states.

>
>

Jon