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Using the Up/Down Counter of M-Series cards with the DAQ Signal Accessory

Hardware: Motion Control>>Controllers>>PXI-7332

Problem:
I am trying to use the quadrature encoder that is built into the DAQ Signal Accessory to complete the exercises in the Data Acquisition and Signal Conditioning manual.  I am using my Signal Accessory with an M-Series device.  When I follow the instructions in the exercises, however, my encoder doesn't work as described.

Solution:
To count up and down using an M-Series device, you will need to add one external connection and add one function to the block diagram.

To get the up/down functionality of a counter task to work with counter 0 of an M-series device, take the following steps:

1. Externally (physically) connect a wire from the B terminal of the quadrature encoder to the source 1 terminal. (Note that you could connect to any available PFI line. I have chosen source 1 arbitrarily.)
2. Connect internally (in LabVIEW) the Counter 0 B line to the Counter 1 source terminal. (Again this is arbitrary, but needs to match what is physically connected in step 1). For the 6251, you make this connection using PFI 3 and PFI 10. Refer to the image below to see how this could be added to the "count digital events" shipping example. Note that I have connected these terminals using the DAQmx Connect Terminals function.

These modifications are necessary because the DAQ Signal Accessory was specifically designed for E-Series devices.  The default counter pin assignments are not the same for the M-Series devices as they are for the E-Series devices.  Because the DAQ Signal Accessory does not allow access to the pins that are used by default for up/down line for the counters on the M-Series devices, it is necessary to connect the lines as shown above.

Related Links:
Product Manuals: DAQ Signal Accessory User Guide
Products and Services: DAQ Signal Accessory
KnowledgeBase 48IH7V49: Which NI-DAQ Cards Can I Use With My DAQ Signal Accessory?

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Report Date: 04/01/2008
Last Updated: 04/30/2008
Document ID: 4K0FK3Q9

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