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9403 speed measurement possible?

I'm trying to measure the speed of a shaft using Labview 10, a CDaq-9188, a 9403 module, and a hall-effect prox sensor. While trying to configure the DAQAssistant it says that the 9403 module cannot buffer signals for continuous sampling. Is there a way to measure shaft speed using this setup, or am I going to have to give up one of my 9243 channels and run with AC coupling, as this post suggests;


A snippet of code would help too, I'm learning still.



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The best way to measure shaft speed is to use 2 counters and a digital input.  The 9403 has digital inputs and the the 9188 has 4 counters.  A quick read of the 9188 manual should explain how the counters can be used with a digital I/O module.  A search of should produce several examples of this type of frequency measurement.

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Message 2 of 9

The NI 9403 (along with all other digital modules with more than 8 lines) cannot be used for counter measurements in cDAQ.  The "Digital I/O Considerations for C Series Devices" entry in the DAQmx help breaks down all of the counter and digital I/O capabilities of the various combination of chassis and modules.

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Could he use the PFI 0 BNC input for this and not bother with the digital I/O module?

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Yes, Wayne, the chassis PFI lines should work fine.  To do, this iyeager, you want to specify the internal name of the chassis counter. The problem is that you are using the DAQ Assistant and it won't let you select internal channels.  This is possible to get around and I actually started typing up the instructions before I realized it was rediculous and not worth the effort.  There is a better way.


I recommend starting with one of our examples.  If you want to chose the internal chassis counter name from a list, right click on the physical channel constant/control and select "I/O Name Filtering".  Check the "Internal Channels" box.  In Create Channel, you should use something along the lines of "cDAQ1/_ctr0".  To the right of the create channel, you'll need to insert a DAQmx Channel property node.  Left click on the "property" and select "Counter Input" and then your appropriate measurement type, and then "Input Terminal".  Specify your input terminal as "/cDAQ1/PFI0".




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Here's a little snippet of the code I'm using. When I run it I get error 89120 at the Start It says source terminal to be routed could not be found on the device. I've got the property set to Active Edge counting using a source device of cDAQ-TestLab1 (the name I've given the DAQ I'm hooked to.) The counter channel is set to cDAQ-TestLab1/ctr0. The sample clock source is set to cDAQ-TestLab1/PFI1.


Any help would be appreciated.





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Message 6 of 9

Hi Ian,


Try adding a forward slash in front of the device name. DAQmx terminal names can be fully qualified with a device name (like "/cDAQ-TestLab1/PFI1") or unqualified (like "PFI1"). "cDAQ-TestLab1/PFI1" is an unqualified terminal name that is equivalent to "/cDAQ-TestLab1/cDAQ-TestLab1/PFI1", which does not exist.


This doesn't apply to DAQmx physical channel names, which always must be fully qualified with a device name and thus do not require a leading forward slash.



Brad Keryan
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Message 7 of 9

how can i select the input terminal as u said here ?
thanks alot 

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Message 8 of 9

Eng. Tareq,


I suggest making a new thread with any specific questions you may have.  This thread has been dead for 3 years.


Jon F.
Technical Support Engineer
National Instruments
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