What hardware do I need to monitor the signal from an incremental encoder?

Question

We are trying to implement a feeding
solution for one of our cutting machines and I’m not quite sure how to proceed. 
I have attached a document from the NI website that outlines exactly what we are
trying to do but does not go into detail on any of the concepts like programming
and implementation.
1.) We have a NI DAQPad-6015
connected to a SC-2345 which has one SCC-CTR01 module installed.  Which this
configuration can we read the incremental encoder signal and use to setup our
cutting machine as outlined in the attached document?  If not what is the
minimum amount of hardware we need to sample the signal from the incremental
encoder and obtain both the direction and magnitude of the
movement?
2.) If we wanted to use the
information obtained from the encoder and subsequently send a signal to a
stepper motor controller or perhaps a PLC what additional hardware would be
needed.
Thanks,
Chris  
Attachments:
Incremental Encoder Example.pdf ‏94 KB

Answer 1

Hi Chris,
For quadrature encoder measurements your
hardware is not the ideal equipment. The 6015 doesn't provide X4
decoding. That means, that the board counts only one raising edge of
one phase. Still, if you connect phase A and B to the counter inputs,
it will count up and down, depending on the direction of the axis, but
as already mentioned, you will loose 75% of the available resolution. Here is some more information about this topic.
The document that you are referring to recommends a PCI-6624
and this is in fact a much better option. This board provides X4
decoding and isolated inputs not only for phase A and B but also for
the Z-index (not available for the 6015).
If you need a USB-solution and if you can work with TTL voltages, you might have a look at the USB-6218, that provides isolated I/Os.
For motion control there are various options. E. g. you could use an NI motion control device like the PCI-7332,
but there are also options to communicate with external motion
controllers through CANopen, RS232 or various fieldbusses. Depending on
the solution that you choose, you may need a bus interface that
provides support for your programming software.
I hope that helps,
Jochen KlierNational Instruments
Message Edited by Jochen on 09-24-2008 09:24 AM