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NI Vision 2011 for LabVIEW Help

Edition Date: June 2011

Part Number: 370281P-01

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This section describes solutions and suggestions for common errors when using NI Vision with the LabVIEW Real-Time Module.

Remote Display Errors

Why am I unable to display remote images using IMAQ WindDraw?

The Vision Remote Server controls the displaying of images acquired from your remote systems in external windows. If you are unable to display your remote images, press <Ctrl-Alt-Del>, which opens the Windows Task Manager, and confirm that NIVisSvr.exe is running as an active process. If NIVisSvr.exe is not running, close and restart LabVIEW and any open NI Vision applications.

If you still experience errors, contact National Instruments Technical Support.

Why does my remotely displayed image have low quality?

Try these steps to improve your image quality:

  • Ensure that your camera aperture is open to allow the appropriate amount of light for an acquisition.
  • Check your compression settings.
  • Make sure that your display settings in Windows are set to use at least 24-bit color.

How do I select an ROI in an image?

You can you use an Image Display control to select an ROI. Wire your inspection image to the Image Display control on your LabVIEW block diagram to display the image on your LabVIEW front panel.

While your application is running on the RT target, your user can use the ROI tools associated with the Image Display control to select their ROI on the host computer. Use the ROI property node in your application to get the user selected ROI.

You can use the Get Last Event invoke node in your application to determine when a user has drawn a new ROI and to get basic properties of the new ROI. You can also use the Clear ROI invoke node to ensure the Image Display control is not displaying an ROI when your application begins execution. Refer to the Extract file located in <Vision>\examples\vision\2. Functions\Image Management to learn more about using invoke nodes in an application.

You can use the IMAQ Construct ROI VI to allow the user to select an ROI. LabVIEW displays the ROI selection window on the host computer and outputs the selected ROI to the VI running on the RT target. Similarly, you can use the IMAQ WindDraw VI to display the inspection image on the host computer. You can then use the IMAQ WindToolsShow VI to display the tools dialog on the host computer. Your user would then use the ROI tools to select their ROI in the image display window. Use the IMAQ WindGetROI VI to get the user selected ROI for processing on the RT target.

Programming Errors

Why won't my LabVIEW VI run on my RT target?

Your NI Vision VI may not be supported by the LabVIEW Real-Time Module. The following VIs are among those not supported:

How can I make my NI Vision application work on my LabVIEW Real-Time Module system if it contains IMAQ Draw or IMAQ Draw Text?

The IMAQ Draw and IMAQ Draw Text VIs are not supported under the LabVIEW Real-Time Module. However, you can achieve similar functionality by using the Overlay VIs, such as the IMAQ Overlay Rectangle and IMAQ Overlay Text VIs. You also can use the IMAQ Merge Overlay VI to merge your overlay data into your image.

How can I make my NI Vision application work on my LabVIEW Real-Time Module system if the application contains Browser VIs?

If your application uses any of the IMAQ Browser VIs, use the IMAQ ImageToImage 2 VI to embed multiple images within a single image.

Why do I get a File Not Found error from my LabVIEW VI when I run it on the LabVIEW Real-Time Module system?

When you run your LabVIEW Real-Time Module application, your VI is downloaded to your RT target, but your support files—such as images and templates—are not. The File I/O routines in the LabVIEW Real-Time Module and NI Vision always refer to files on the target machine, which is the remote RT target in this case. Use FTP to move your image files to the RT target.

Refer to your LabVIEW Real-Time Module documentation for more information about transferring files to your RT target using FTP.

If you created a VI using NI Vision Assistant, selecting Image File for the Image Source causes your VI to return an error in the LabVIEW Real-Time Module. This is because the File Dialog function is not supported in the LabVIEW Real-Time Module. To avoid this error, select Image Control or Image Acquisition Board as the Image Source.

RT Video Out Errors

Why do I have an invalid Video Out Mode?

To use the RT Video Out functionality with NI Vision and the LabVIEW Real-Time Module, you must have a RT PXI controllers, NI Embedded Vision System device, or NI CVS-1450 Series device that features VESA Bios Extensions 2.0 or later.

If you are using a controller that does not support RT Video Out, consider using Remote Display to display your images.

Why can't I see my images when I use RT Video Out?

Use the IMAQ Video Out Display Mode VI to configure your video mode before you attempt to display your images. This VI allows you to set your refresh frequency, screen area, and color depth.

Note  If you are using a monitor that does not support high refresh frequencies, your images cannot display correctly. Refer to your monitor documentation for information about supported refresh frequencies.


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