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How Do I Connect a Quadrature Encoder to NI ELVIS When Using an M Series Device?

Primary Software: Driver Software>>NI-DAQmx
Primary Software Version: 7.0
Primary Software Fixed Version: N/A
Secondary Software: N/A
Hardware: Multifunction DAQ (MIO)

Problem:
I am trying to use two angular quadrature encoders on an NI ELVIS with an M Series device using DAQmx in LabVIEW. The B terminals for the counters are inaccessible because they are set at RESERVED (ctr0) and SCANCLK (ctr1). These lines must be reassigned.


Solution:
It is possible to assign the counter terminals to different lines. To do this:

1. Right click on your block diagram, then select and drop Measurement I/O » NI-DAQmx » Channel Node.
   
2. Place the channel node before the DAQmx Start Task.vi and wire the task and error terminals appropriately.
   
3. Left click on the channel node and select Counter Input » Position » B Input » Terminal.
   
4. Change the terminal to be writable by right clicking on the channel node and selecting Change All To Write.
   
5. Create a terminal constant by right clicking on the input terminal to the CI.Encoder.BInputTerm property and selecting Create » Constant.
6. Finally, choose one of the available PFI lines from the drop down list of the terminal constant.
   

This process can be used to change any of the counter terminals. The final result is pictured below.



Related Links:
KB 318HN20T: Quadrature Encoder with NI ELVIS
NI Developer Zone: Quadrature Encoder With NI ELVIS

Attachments:
b_terminal_encoder.png




Report Date: 11/05/2007
Last Updated: 11/06/2007
Document ID: 4F4IEJQQ

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