Re: [CAD_CAM_EDM_DRO] Encoder Dithering Specs

Tom Hubin wrote:

> Hello,
>
> I am a self-under-employed electrical engineer and was recently involved
> in a discussion about quadrature encoder counting circuit requirements.
> I have no particular equipment in mind. I am just exploring for now.
>
> I have a Sherline CNC mill with stepper motors so this discussion does
> not apply to me yet. But I do expect to graduate to something larger and
> possibly with servos and encoders.
>
> I understand what the counter circuit needs to do in order to count at
> maximum speed in either direction. And I understand what the counter
> circuit needs to do if the encoder dithers as little as one count.
>
> How are the circuits usually specified for dithering less than one
> count. Let's say the encoder A signal is oscillating and the B signal is
> constant.
>

That is dithering by one quadrature count, as opposed to one full cycle
of the quadrature waveform.
AB both high and A low, B high are adjacent states in the quadrature
sequence. So, you count each change as a move, but in opposite directions.
If you define a "count" as moving from one quadrature state to the next,
then there cannot be any dithering of less than one count.

Jon