PXI-6250 Trigger Setup

[RCJ]

I am new to DAQ and need some help.  I am planning on attending NI DAQ training in the future but that will not be soon enough. 

I currently have a Labview program working to monitor 8 sensors (2 load cells, 3 accelerometers, LVDT, strain gauge and a 9 volt trigger I use to trigger the start of my program).  I have them attached to the SCXI-1314 which is mounted to a SCXI-1520 that resides in a SCXI-1000 chassis.  The chassis is connected to a PXI-6250.  So far I have only used the single 6250 because I only have 8 sensors to monitor.

I have received a new requirement to add 2 more sensors to the system and don’t understand how to get them to start gathering data simultaneously.

I have attached the 2 new sensors to the second SCXI-1314 and have the SCXI-1000 chassis attached to both of the PXI-6250 cards now allowing me to monitor up to 16 channels but I can’t figure out how to get both of the 6250’s to read data.

I have tried numerous examples to try and get the cards to both read simultaneously and read some of the tutorials, but to no avail.  When I input all of the pertinent information into the examples and then run the example I never see any sensor data.  It seems like I am not creating a trigger to activate the 6250’s to start taking data.

Any assistance in this matter would be greatly appreciated.  I am new at DAQ but I am familiar with Labview and MAX.

Thanks

[Matthew_W]

Hello RCJ,

There are two options for adding your second SCXI-1520, multiplexed or parallel mode.

 For multiplexed mode you will use one DAQ card to sample both SCXI-1520's. In parallel mode you will have one DAQ per SCXI input card.
 
Here are the steps to add the second SCXI-1520:
  1. Open Measurement and Automation Explorer
  2. Expand the Devices and Interfaces tab then expand the NI-DAQmx Devices
  3. Find your existing SCXI-1000 chassis (if none there, or for new install you would right-click NI-DAQmx Devices and add a new chassis)
  4. Expand the chassis to show the existing card and empty slots
  5. Right click the empty slot that has the card installed, select Insert card. Under Module Array, find your SCXI-1520
  6. Select the Accessory that will be attached to the SCXI-1520
  7. Click the Details tab next to the new card, select Cabling, then pick Multiplexed or Parallel mode along with Communicating card (none if parallel) and Digitizer module (same as first card if simultaneous)
 
I would suggest starting with Multiplexed mode first, be sure you can read from the next SCXI-1520 in MAX. Second, implement the Parallel mode if you'd like, test it again in MAX.
Finally, try the system in your application.

Post back if these suggestions are not sufficient, have a great weekend!!

Best regards,

MatthewW
Applications Engineer
National Instruments

[RCJ]

Thanks for the responce.

I currently have both 1520s and 6250s working and don't have any problem getting both cards to work independently I have a problem when I try to get both cards to work together.  Using some of the examples that should read both channels don't work for me.  I choose my tasks from the drop down box (my tasks use channel a0 on one card and a2 on the other card) then run the vi and usually a timeout occurs and one display has some data but not what I expect.

Thanks

[Matthew_W]

Hi RCJ,


Could you please try the following example and post back what your error is:
                        
    Run the Cont. Acq & Graph - Int Clk.vi from the Example Finder.
          Configure the Physical Channel control; Click Browse in the Physical Channels control on the front panel.
          Expand the SCXI-1520's, they will have theyre MAX alias.
          Hold Ctrl and select ai0 from each.
          Click Ok.
          Run the vi.
          If any errors, please post them back.
 
What version of the DAQmx driver are you using?

 Thanks and have a great evening!

MatthewW
Applications Engineer
National Instruments

Message Edited by Matthew W on 07-23-2007 09:00 PM

[RCJ]

Matthew W,

I ran the Cont Acq&Graph Voltage-Int Clk.vi and configured the Physical Channels as such: SC1Mod1/ai0, SC1Mod2/ai0 and received this error:

200558 occurred at DAQmx Start Task.vi

One task cannot contain multiple inedpendent devices

Create one task for each independent device.

Device: PXISlot11

Device: PXISlot10

Task Name:_unnamedTask<0>

I am running NI-DAQmx Device Driver 8.0.0f0.

Thanks for you help.

Have a nice day.

Robin

[Matthew_W]

 Hi RCJ,

 I'm sorry about the confusion. You are correct, there can only be one DAQ device per task. I was thinking of multiple measurement types per task.

 I'm attaching a screenshot of the continous acquire example, basically it just has a second Analog Input task created for the second DAQ device.

 Try to implement this, if you receive an error code then please post back to this forum. Have a great afternoon!

 MatthewW
 Applications Engineer
 National Instruments

Message Edited by Matthew W on 07-25-2007 10:02 AM

[RCJ]

Thanks,

It looks like this work fine standalone.  Timing looks good also.

I will insert it into my program and see then what the timing looks like.

So-far-so-good.

Robin