Need of VISA driver

[AnandR]

Hi All,

We have following driver for following devices.

DAQmx driver : DAQmx devices

NI-488.2 Runtime : GPIB devices

NI-DMM: NI DMM devices.

can anyone let me know why we need VISA library when we have above device drivers.

Regards,

Anand

[crossrulz]

VISA is an abstraction layer for instrument communications over Serial (RS-232, RS-422, RS-485), Ethernet, GPIB, USB, and possibly other buses that I am not currently aware of.  This makes drivers reusable by having a single set regardless of which of these buses you are talking over: the only thing to change is the initialization.

[RTSLVU]

NI-VISA lies between software (like LabVIEW) and hardware (instruments) and handles all of the interface specifics.

With a properly written program using VISA you can take an instrument that was connected using an RS-232 serial port and move it to GPIB, LXI, USB, or any other interface without having to change anything in your program.

This is very handy when you have several "test racks" full of various instruments and need to swap out a failed instrument or replace an old one.

[AnandR]

Hi,

Can you please elaborate this.

With a properly written program using VISA you can take an instrument that was connected using an RS-232 serial port and move it to GPIB, LXI, USB, or any other interface without having to change anything in your program.

As per my understanding , VISA will be used to communicate with instruments ,The instrument will be either connected via serial, or GPIB or Ethernet port etc.

Regards,

Anand

Regards,

Anand

[RTSLVU]

Well for instance we have several Yokogawa WT230 power analyzers in our lab. Some of them have GPIB and some of them have RS-232 interface.

Using NI-MAX I create a VISA alias called "Yokogawa" that points to the serial port or GPIB address the power analyser I am using is plugged into.

In my LabVIEW program the VISA Resource for the power analyser will simply be "Yokogawa". (not ASRL1::INSTR or GPIB::3::INSTR)

Now I can swap out the Yokogawa for one that uses serial or GPIB (or any other interface) and I only have to update the VISA alias in NI-MAX.

No changes at all need to be made in the LabVIEW code, because VISA takes care of all that.

[crossrulz]

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@RTSLVU wrote:

This is very handy when you have several "test racks" full of various instruments and need to swap out a failed instrument or replace an old one.

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My prime example is when we decided to design a whole new rack for a new system, it was decided to eliminate GPIB and go to LAN (mostly for cost).  The same models were being used, just with LAN instead of GPIB.  All of my power supply, oscilloscope, DMM, etc. drivers that used VISA had no changes necessary and just ported over without a problem.

[RTSLVU]

Also this might help explain where and how VISA fits in. 

This is a diagram of the Validation Test Platform I wrote for our test lab.