what are the units of the DAQmx counter?

[dav2010]

Hello,

I created this VI and several similar ones a few months ago, but, I have forgotten some of what I did back then.  I believe that this VI should measure period, using the counter on the DAQ chassis.  Can anyone tell me the units of the period measured?  I think it is seconds, but, I am trying to figure out how to figure that out!  The values of the period are generated by the DAQmx READ function in the WHILE loop.  What units is that function outputting to the array?  What are the units of the array elements, essentially?  See the attached VI.

Also, how do you know?  I opened the DETAILED HELP for the DAQmx Read (Counter 1D DBL NSamp) shown in the VI but, I can't find anything on the units of the data coming out of the terminal labeled DATA with the orange wire, which is actually an array of periods, and we take the average of the most recent 15 or so period measurements.

I had a suggestion months ago for an online NI manual containing a description of Buffered EdgeCounting measurements, but, when I went to find it, the link had been changed by NI, so, I can't find that manual, but, I think the answer is probably there, because I recall that manual being very useful when I did this before.

Thanks for the guidance.

[Chris-NI · Accepted solution]

HI dav2010,

When you create a Virtual Channel, you should specify the units the counter task will use.  There are several options which are listed in the help here:

http://zone.ni.com/reference/en-XX/help/370469AA-01/lvdaqmx/mxcreatechannel/#DAQmxCreateChannel%28CI...

I am not on a computer with LabVIEW right now, but I believe the default should be ticks, which is the number of ticks of your device's timebase.  You can find that information in your hardware specifications.

Regards,

[dav2010]

Thanks, Chris.  I see that by double-clicking the DAQmx Create Channel, the front panel appears, and there is an option for choosing units, including seconds, ticks, and "from custom scale."  I chose seconds.

Thanks,

Dave