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Found 2 results

  1. I have a requirement that I thought would be SIMPLE, but can't get it to work. I have a 9205 card in a little 9174 cDAQ USB chassis. My *intended* behavior is to wait (block) at the DAQmx Trigger/Start Analog Edge on, say channel ai1, until I get a falling edge thru, say, -0.050V. So I have a little vi (that contains 2 parallel loops) that I want to sit & wait for the trigger to be satisifed. I'm doing "routine" voltage measurements in another AI loop on a different channel. I want this vi to run separately from my "routine" voltage measurements because I want the app to respond "instantly" to input voltage exceeding a limit to prevent expensive damage to load cells. I was afraid that if I used either Finite or Continuous sampling to "catch" an excessive voltage, I might miss it while I'm doing something else. Yes, yes, a cRIO real-time setup would be better for this, but this is a very cost-sensitive task... I just want to "Arm & Forget" this process until it gets triggered, whereupon it fires an event at me. SO... I'm also reading the same voltage on channel ai0 for regular-ole voltage measurements, and just jumpering them together. I did this because I read somewhere that you can't use the same channel for multiple DAQ tasks - I *thought* I would need to set up the tasks differently. {but now that think about it, the setups can be the same...}. I've set up the DAQmx task the same as shipping examples and lots of posts I've seen. I'm supplying a nice clean DC voltage to a 9205 card using a high quality HP variable power supply. Using NI-MAX, I've verified that my 9174 chassis & 9205 are working properly. THE PROBLEM - When I run it, the vi just sails right through to the end, with no error, and an empty data array out. No matter WHAT crazy voltage I give the "DAQmx Trigger.vi" (set up for Start Analog Edge), it never waits for the trigger to be satisfied, just breezes on through as if it weren't there. If I set the Sample Clock for "Finite Samples", the DAQmx Read fails with timeout - makes sense, since the trigger wasn't satisfied. What could I possibly be doing wrong with such a simple task??????? So my fundamental misunderstanding still vexes me - does the DAQmx Trigger vi not block and wait for the trigger condition to be satisfied, like the instructions state - "Configures the task to start acquiring or generating samples when an analog signal crosses the level you specify"? I stripped my requirement down to the bare essentials - see the 1st snippet, the 2nd is my actual vi. Any ideas, anybody?
  2. I have a problem I was hoping you might be able to help me figure out. I need to be able to create 6 analog output channels that will have separate data files loaded into them. These channels will be started individually in a timed sequence. I am having trouble getting the analog DAQ tasks created. LabVIEW is complaining when I try to set them up as individual tasks in the same routine. I used a for loop on an array of data files and an array of channel names. The error code is suggesting that I set the channels up under one task. But the problem with that is that I don’t know how to get individual channels of that one task started. I created the initial for loop in Main.vi. This gives me error -50103. My single instance is in Main_1.vi. I am trying to use a PXI-6363 card initially because that is all I have now. But I will try to upgrade to a PXI-6733 when I get ready for the test. Is there something with the 6363 that doesn't allow for multiple tasks on the same card for the same function? Thanks for your help. Joe Main.vi Main_1.vi
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