encoder counts and pulses

[whatsthis4]

Just a quick question to make sure I understand how quadrature encoders work.

On the encoder disk, we have channel A and B.

Now if I have an encoder with 2000 counts per revolution does this mean that:

1) every rising and falling edge of channel A and B represents one count of motion?

2) there are 500 cycles/rev and this number represents the limit of the encoder as an external clock source since program AND/OR logic cannot be used to combine edges (and therefore have a clock source based on individual counts), unless an external decoder circuit is built?

Thanks a lot

Chris

[JB]

Physically, the disk of an encoder with 2000 counts/rev has 2000 lines for channel A and 2000 lines for channel B.

There are 3 encoding modes :

1) X1 encoding --> only rising edges of one channel --> 2000 counts/rev

2) X2 encoding --> rising and falling edges of one channel --> 4000 counts/rev

3) X4 encoding --> rising and falling edges of both channels --> 8000 counts/rev

See also pages 3-18 to 3-20 in the user manual of the PCI-660X.