Re: [CAD_CAM_EDM_DRO] Quadrature?

Scot Rogers wrote:

> So each night (almost) I read my email and this list. Somewhere between 2
> and 7 days a week, someone invarably brings up encoders. Now for the most
> part I understand the basics of encoders and dro's. But one of the things
> that I'm a little fuzzy on is what Quadrature is. I was cruizing ebay and
> ran across some encoders (4) that claim a line count of 2500 and 10,000 in
> (here's that word again) Quadrature.
>
> So, what is it? And how should I approach it when starting to set up a dro?

You would set it up as 10,000 counts per revolution.

Quadrature is misused in this context. Practically all encoders, especially
"incremental" encoders, use quadrature. This refers to a 90 degree phase
shift between two waveforms. The advantage of quadrature is that the
phase shift allows you to determine DIRECTION, as well as distance
moved. What the above 2500 / 10,000 business means is that the encoder
wheel has 2500 stripes around the circle. This produces 2500 cycles
of high-low signals per revolution on EACH of the two encoder channels.
By detecting and counting all 4 edges as they come into the decoder,
you get 4 counts per cycle, thus multiplying the line count resolution
by 4.

Jon