A

#### Andy Hendershot

I am trying to come up to speed on encoders and have not found any good descriptions of some of the terminology. My motion controller documentation refers to encoder cycles per revolution and quadrature counts where the quadrature count is 4 times greater than the cycle count. Most quadrature (CHA, CHB) incremental encoder resolutions are listed as pulses per revolution (PPR), are these quadrature counts? In other words if I have 1000 PPR do I have 1000 quadrature counts per revolution and 1000/4=250 cycles per revolution? It sounds that simple, I hope it is. Can any one suggest a good source of information on encoders?
All help greatly appreciated Thank You.

T

#### Tom Gianni

I've seen PPR (pulses per rev) used frequently by Europeans. I'm very sure that, for example, a 2000 ppr encoder means 8000 counts (quadrature). So, PPR refers to pre-quad or what we typically call lines/cycles in the U.S.
In other words, a TTL encoder channel high and low period = 1 pulse = 1 line/cycle = 4 counts or edges (AqB).

D

D

#### Donny

I have just completed a motion project using quadrature encoders and high speed counter cards. I can configure the counters as X1,X2,or X4.

X1 means one count up everytime phase A is rising, which would mean I would get 1000 counts in one revolution on a 1000 PPR quadrature encoder.

X2 means one count up everytime phase A is rising and one count up everytime phase B is rising, which would give you 2000 counts in one revolution on a 1000 PPR quadrature encoder.

X4 means one count up on Phase A rising; one count up on Phase B rising; one count up on Phase A dropping; and one count up on Phase B dropping, which would give you 4000 counts in one revolution on a 1000 PPR quadrature encoder.

It will depend if your counter can be configured to do this, otherwise you are probably stuck with X1 (Counts per Rev. = Pulses per Rev.).

D

#### Donny

<PRE>
________
Phase A | |
_________| |____________________

_________
Phase B | |
___________| |____________________

</PRE>

J