Javier Ros Ganuza wrote:

[most of the thread snipped]

>Sorry if it sounds too trivial, but I'm lost, what is the diferencie
>between encoder and resolver. Well, I know what is a encoder, but I was
>thinking that a resolver was in fact a encoder. So what is a resolver (a
>potentiometer?)?
>  
>
A resolver is a different kind of sensor, which detects the rotation of 
a magnetic/electric field.  These are AC excited analog sensors which 
will give you absolute rotation information from 0-360 degrees.  See 
this wikipedia page:  
<http://en.wikipedia.org/wiki/Resolver_%28electrical%29>

An encoder is a digital device, which outputs a code based on position.  
This will either be a binary code giving the absolute position or (more 
common for CNC) an incremental quadrature code based on movement.  See 
this wikipedia page: <http://en.wikipedia.org/wiki/Rotary_encoder>

>>>So in general (just for curiosity), index pulse is always taken from Z
>>>and/or /Z signal from quadrature encoder???
>>>      
>>>
Most incremental encoders with index outputs label the index channel 
"Z".  I think "I" is also used sometimes.

>>Correct. 
>>
>It has been very clarifying  for me.
>
>So, it can be said that: "index pulse" is a concept internally defined
>by EMC and depending on hardware the driver can implement this index
>pulse in different ways. It happens that with the motenc-100 driver, or
>with other divers using quadrature encoders,  the index pulse is defined
>using available Z and/or /Z quadrature signals.
>  
>
No.  Index pulses are not an EMC-specific thing.  Index is a separate 
channel that is used for detecting the orientation of the motor shaft.  
A normal incremental quadrature encoder can only tell you that the shaft 
has moved and in which direction.  The index tells you that the shaft is 
at a certain angle, which people usually define as 0 degrees rotation.

>Do you agree?
>
>Thanks a lot
>
>Javier
>  
>
Good luck
- Steve


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