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VISA COM INSTR command return two answers for each instrument

Question asked by oferoded on Dec 21, 2014
Hi:
I’m writing some API for Keysight scope MSO9404A using C#. My platform is Windows 7 32 bit.
I installed the IOLibSuite_17_0_19013 library using side by side mode because I have another non Kesight instrument connected which uses NI VISA.
My instruments are connected via the USB port.
In my C# project I added a reference to VISA COM 5.2 type library.
I’m using this code to scan for connected instruments:

                ResourceManager resourceManager = new ResourceManager();
                String[] sResources = resourceManager.FindRsrc("?*INSTR");
And I got two answers even if I have one instrument connected:

"USB0::2391::36877::MY51500146::0::INSTR”
"USB0::0x0957::0x900D::MY51500146::INSTR”

Please notice that the VID and PID in the address line are the same in the two lines but in different format:
2391 = 0x0957
36877 = 0x900D

I investigated for a while and noticed that in the directory c:\Windows\System32\ I have two dll’s:
agvisa32.dll
visa32.dll

When I rename agvisa32.dll to another name and run again my code I got only one line in the answer:
"USB0::0x0957::0x900D::MY51500146::INSTR”

Just to be clear:
The problem occurs only if Kesight Visa is installed as secondary Visa at Side by Side mode.

Any idea how to solve the problem?

Thanks,

OFER ODED  

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