VISA Package by Vendor

[nonomiya]

Hiall,                                                                                                                                                                                                                        I am bit confused why different Vendor need to provide their own VISA Library, sych as NI, Agilent, Tektronix, and so on..., the vendor create side-by -side mode to compliant with default visa32.dll, But I have no idea why they need to implement the same library. I think it should be similiar with IVI C-Shared component to be a common recousce, right?                                                                                                                                                  Thanks

[Matt_S.]

Hi,

VISA is just a standard set out in the VXI-PNP consortium. Each company simply chooses to develope its own implementation to match with its software and programming model. This also allows different side applications (like NI-SPY) to work slightly differently from company to company.

Hope this was helpful. For more information, look up more info on the VXI-PNP consoritium.

-Matt S.

[Makoto]

Although NI-VISA can be downloaded freely, it is not a free software.  Basically only NI product users have the valid end user license for NI-VISA.  This point is very different than IVI shared components that are completely free.  Therefore other vendors may need to provide their own VISA to solve the license issues.

[nonomiya]

Hi everybody,

After check, I found Ni-VISA cost about 400 U.S. dollars.. god

1) As I known, VISA defines six resource classes as follows:
    INSTR/INTFC/MEMACC/BACKPLANE/SERVANT/SOCKET

    so, that mean different VISA library provider will implement the subnet or fullset, right?
2) if I have NI-VISA and Agilent VISA, if they all support INSTR class,
    that mean no matter which one I use as "visa32.dll" will be fine and compatible, right?

thanks all!

Thanks!

[JoshuaP]

Most VISA vendors charge for their VISA product if you are not using any of their other products. In National Instruments case, if you are using LabVIEW/CVI or any of NI hardware you have a valid license for NI-VISA and no additional fees are required.

Here is the official license policy for NI-VISA.
http://www.ni.com/visa/license.htm

-Josh

[Makoto]

> that mean different VISA library provider will implement the subnet or fullset, right?

Depending on VISA vendors, subset or fullset resource types are implemented.
I believe the latest NI-VISA implements all.

> if I have NI-VISA and Agilent VISA, if they all support INSTR class,
> that mean no matter which one I use as "visa32.dll" will be fine and compatible, right?

Basically every VISA32.DLL shows the same behaviour for the same resource type
even if VISA vendors are different.  However, there may be some minor differences
between VISA implementations. For better application quality, you should test your
app operation with all the VISA libraries on which your app may operate.

makoto