Re: Optical Encoders

Ed Casas (edc@ece.ubc.ca) Mon, 4 Dec 2000 20:01:34 -0800 

Date: Mon, 4 Dec 2000 20:01:34 -0800
From: Ed Casas <edc@ece.ubc.ca>
Subject: Re: Optical Encoders



> The digital outputs on an optical encoder are often grey
> coded. Gray coded means that every time the encoder senses a
> change, the change occurs in any one bit at a time.  Questions:
> If there exists a change, does the encoder scan the change one
> bit at a time from the MSB to the LSB?

No, this would only allow as many changes as there are bits.
Here's an example of the sequence in which a 2-bit gray-coded
output would change:

  00
  01
  11
  10

> and also how fast can the encoder scan the change?

The only limitation would be how fast you could move the encoder
input shaft (thousands of RPM?) and the response time of the
photodetectors (100 ns?).

> Does the encoder scan the change continually or at discrete
> points in time Only?

Continuosly.  As soon as the input angle changes the output also
changes.

-- 
Ed Casas   edc@ece.ubc.ca   http://casas.ece.ubc.ca   +1 604 822-2592