488.2 .NET API and data acquisition speed issue

[njn1]

I have a tricky problem which i am unable to solve. I am using an NI PCMCIA GPIB card to talk to an Agilent E4418B/E4412A power meter/sensor using a software written in VB.NET2003. I downloaded the 488.2 .NET API off NI site sometime back. The data acquisition is done in a high speed mode (200 readings/s) as oppsed to the regular speed (20 or 40 readings/s). The fastets speed I can achieve is 50 readings/s with the above setup. The data acquisition loop contains just one call to the instrument and should easily handle 200 readings/s (i'll explain this later).

When I run a similar applicationbut  written in Labview 8.0 program with the same hardware setup, i am getting the 200 readings/s. This confirms that the hardware that i am using is not hindering the download speed. Now this is where it gets complicated - when I go back to the VS.NET2003 application and run it, I am getting the 200 readings/s.!. I will continue to get this so long as i don't reboot the computer. Once i reboot, I fall back to the original low speed - 50 readings/s.

What's in the Labview 8.0 program (that remains in the memory even after the Pabview is shutdown) that makes the data acquision from VB.NET faster? My 488.2 .NET API has installed a NationalInstrumentsCommon.dll Ver 7.0.0.341 in my laptop.

Thanks.

[John E]

Hi,
I have a few questions that may help find the issue:
1) Are you using instrument drivers, for LabVIEW or .NET?
2) Are you using function calls or wrapper calls?
3) It sounds like the above behavior occurs when you run:
     the .NET code (then close it)-> LabVIEW Code (then close it)-> then .NET code.
What happens if you run
     the .NET code (then close it)-> then .NET code.

Finally, I would recommend comparing your LabVIEW and .NET code.  It is likely that some difference between them is causing this behavior.


Regards