Express vi's slow down LabVIEW

[Gorman]

I have the PCI 6034e card with a CB-68LP pinout board on a Windows XP computer (2.7 GHz, 512Mb) and LabVIEW 7.0.  When I collect data for only Voltage or only Temperature I like to use the Express Vi's because it is a lot faster and more convinient to add in channels.  However, using all of these Express Vi's has caused all of LabVIEW to basically stop.  Even after I close the vi that I was using LabVIEW still acts very slow.  I have to close all of LabVIEW and then reopen it.  I created the same vi not using as many Express vi's and it runs very smoothly and fast enough where I don't complain about it.  I read something on here about initializing and closing the serial port after each frame, is that the case here?  I am considerably new to LabVIEW and the smooth operating vi was created with help from these discussions, the slow operating vi was mostly my work and could be the reason for the slowness.  I have included the screen shot of the block diagram for the slow and fast operating vi.  Any help would be great.  Thanks.

Bill

[Sandra_T]

Hello Bill,

I see that you are using our PCI-6034E to acquire and record data. There is some overhead involved when choosing to use ExpressVIs instead of using lower level VIs. Express VIs are easy to use, many of the configurations are made for you. The Express VIs are efficient at what they do, but using the lower level functions allow you to optimize. For example, data acquisition can be more efficient if create, configuration and start tasks are outside the while loop, so they only need to execute once.

If you want faster operation, take advantage of lower level vis with their configurability and the multithreading capabilities of LabVIEW.

Let me know if you have any additional questions.

Regards,
Sandra T.

Applications Engineer  | National Instruments