Should the LabVIEW program be reduced to the speed of data collection?

[Daniel Unruh]

I'm using a LabVIEW program created by Ocean Optics for a
Spectrophotometer probe with is run through the USB port. The problem
occurs when we attempt to collect data over a time frame of one
second. For some reason the whole LabVIEW program will begin to
operate at the speed of data collection when we try to run the VI with
an integration time of +500 ms. If anyone would be able to offer any
kind of explanation or theory it would be greatly appreciated. Thanks
for any and all help.

Daniel

[waldemar.hersacher]

Dear Daniel,

since LV has no support for USB this must be done through a DLL or Active-X control. A call to a DLL or Active-X method is a synchronous node in LV, that means LV will go on executing when the call completes.

My theory of your problem is that the program makes such a call and it would take that time to collect the data in the DLL or Active-X control. If you have only one loop in the program and do not use dynamic loaded VIs through the VI server than the program seems to hang on each of this calls.

I hope this helps
Waldemar