How to measure the digital waveform

[santhanaraj]

Hi,
      iam using USB-6501 Digital I/O and get digital waveform (pulse) but i
can't measure pulseperiod, pulseduration, duty cycle, cycle avg, how to
get this requirment. ihave attached the vi.


Single-input-read.zip:
http://forums.ni.com/attachments/ni/70/7365/1/Single-input-read.zip

[Elizabeth L]

Hello,
 
Keep in mind that the USB-6501 has static digital I/O timing.&nbsp; This means that all of your measurements are software-timed, which is undeterministic.&nbsp; For benchmarks on the performance of software timing with the USB-6501's digital I/O, see <a href="http://digital.ni.com/public.nsf/allkb/376BBB979269F9C5862570F7006A030F?OpenDocument" target="_blank">KnowledgeBase 3TEC9UX6: USB-6501 Benchmarks with NI-DAQmx</a>.
&nbsp;
The VI you posted cannot accurately measure period, pulse duration, or duty cycle.&nbsp; There is no timing information in the digital waveform you are reading.&nbsp; To perform these types of measurements you should be using a counter, not static digital I/O.
&nbsp;
The USB-6501 has only&nbsp;one counter with limited functionality. In your program I notice that you are reading from multiple channels, so it sounds like you need a device that has more than one counter.&nbsp;If you are interested in upgrading to a device with multiple, full-functionality counters, I would suggest that you contact NI for a recommendation of what device will be best&nbsp;for your specific application&nbsp;at <a href="http://sine.ni.com/apps/utf8/nicc.call_me?p_lang_id=us" target="_blank">ni.com/contact</a>.
&nbsp;
There are example VIs that ship with LabVIEW demonstrating how to use counters to make the measurements you want to make.&nbsp; Go to the Help menu in LabVIEW and select Find Examples....&nbsp; This will open the Example Finder.&nbsp; Look in the folder called Hardware Input and Output » DAQmx » Counter Measurements » Period or Pulse Width.&nbsp; The examples found in this folder will allow you to perform the measurements you need using a counter.&nbsp; The following documents explain in greater detail how these measurements are performed:
&nbsp;
<a href="http://zone.ni.com/devzone/cda/tut/p/id/2875" target="_blank">Developer Zone Tutorial: Pulse-Width Measurement with a Counter</a>
<a href="http://zone.ni.com/devzone/cda/tut/p/id/2868" target="_blank">Developer Zone Tutorial: Period&nbsp;Measurement with&nbsp;a Counter</a>
&nbsp;
I hope this helps!&nbsp; Please let me know if you have any questions about the resources I suggested.