level detection PXI 6624

[LrnnLV]

Hi all,

I am trying to find out some details about the level detection in PXI 6624.I have a very simple timing measurement to perform. Start trigger at P1@9V and stop the trigger when P2 @-9V and measure the time elapsed( expected time is 1-1.4sec)

How to configure the CounternGate  Signal in level detection mode? The UserManual says it is possible. I need help figuring this out.I see there is optical isolation for the inputs and I would think the inputs are only Supply/Gnd referenced.

Appreciate any help.

Neha 

[GarPar]

Hi Neha-

     I found some documentation in the LabVIEW 2009 Help file that explains how to configure your device for level trigger detection in software.  It contains an explanation of the VI to use, how to configure it, and points out where to find an example in the NI Example Finder.  It can be found here.

     Look through this document and the LabVIEW example and let me know if you have any further questions.

     Best of luck with your application!

[GarPar]

Hi Neha-

       I was looking a little further into your question and I made some assumptions in my previous post that I should clarify/possibly retract.  The 6624 is a counter/timer card.  In the user manual it clarifies that digital low is anything below 0.8V and high is guaranteed anything above 4V.  So, in reading your first post over, I assume that you are reading two square waves that jump from 0-9V, correct?  One on P1 and the other on P2, with one line inverted?  Then it sounds like you want to measure the time between the 9V on P1 and the -9V on P2, correct?

     If my understanding is now correct, then you should not use the level trigger detection example in LabVIEW, since it is for one signal on an analog line.  Instead, what you should use is two-signal edge-separation, which measures the time between two different edges of two different signals.  Using the timebase, this measurement begins counting on the first active edge on the AUX line and latches the count into memory on the first active edge of the gate.  What occurs internally is that a pulse is created with the first active edge of the AUX line and ends on the first active edge of the gate.  The counter then performs pulse width measurement on this created pulse.

     Here is a link to a page on our website that will help you with this task:

KnowledgeBase 2D9G49EV: How Can I Measure the Time Between the Rising Edges of Two Digital Signals?

     If, however, you are measuring two analog signals, you will need to get a DAQ card with analog inputs.  If this is the case, I will refer you to our technical sales department at  (800)-433-3488. 

     I apologize for any confusion, and hope this clarifies what you need!

[LrnnLV]

Thanks Gary,

You are right I need a card with analog inputs. So the PXI-6624 doesnot serve my purpose. Appreciate your effort.