Virtual Instrument Software Architecture
Encyclopedia
Virtual Instrument Software Architecture, commonly known as VISA, is a widely used I/O
API
in the test and measurement (T&M) industry for communicating with instruments
from a PC.
VISA is an industry standard implemented by several T&M companies, such as Rohde & Schwarz
, Agilent Technologies, National Instruments
, Tektronix
and Kikusui.
The VISA standard includes specifications for communication with resources (usually, but not always, instruments) over T&M-specific I/O interfaces such as GPIB and VXI.
There are also some specifications for T&M-specific protocols over PC-standard I/O, such as VXI-11 (over TCP/IP) and USBTMC (over USB).
The VISA library has standardized the presentation of its operations over several software reuse mechanisms, including through a C API
exposed from Windows DLL, visa32.dll and over the Microsoft COM
technology. Although there are several VISA vendors and implementations, applications written against VISA are (nominally) vendor-interchangeable thanks to the standardization of VISA's presentation and operations/capabilities. Implementations from specific vendors are also available for less common programming languages and software reuse technologies.
Input/output
In computing, input/output, or I/O, refers to the communication between an information processing system , and the outside world, possibly a human, or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it...
API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
in the test and measurement (T&M) industry for communicating with instruments
Measuring instrument
In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the process of measurement gives a number relating the item...
from a PC.
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
VISA is an industry standard implemented by several T&M companies, such as Rohde & Schwarz
Rohde & Schwarz
Rohde & Schwarz is an independent group of companies specializing in electronics. Well known as a manufacturer of electronic test equipment, they also manufacture equipment used for broadcasting, radiolocation, and radio communications...
, Agilent Technologies, National Instruments
National Instruments
National Instruments Corporation, or NI , is an American company with over 5,000 employees and direct operations in 41 countries. Headquartered in Austin, Texas, it is a producer of automated test equipment and virtual instrumentation software...
, Tektronix
Tektronix
Tektronix, Inc. is an American company best known for its test and measurement equipment such as oscilloscopes, logic analyzers, and video and mobile test protocol equipment. In November 2007, Tektronix became a subsidiary of Danaher Corporation....
and Kikusui.
The VISA standard includes specifications for communication with resources (usually, but not always, instruments) over T&M-specific I/O interfaces such as GPIB and VXI.
VXI
The VXI bus architecture is an open standard platform for automated test based upon VMEbus. VXI stands for VME eXtensions for Instrumentation, defining additional bus lines for timing and triggering as well as mechanical requirements and standard protocols for configuration, message-based...
There are also some specifications for T&M-specific protocols over PC-standard I/O, such as VXI-11 (over TCP/IP) and USBTMC (over USB).
The VISA library has standardized the presentation of its operations over several software reuse mechanisms, including through a C API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
exposed from Windows DLL, visa32.dll and over the Microsoft COM
Component Object Model
Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages...
technology. Although there are several VISA vendors and implementations, applications written against VISA are (nominally) vendor-interchangeable thanks to the standardization of VISA's presentation and operations/capabilities. Implementations from specific vendors are also available for less common programming languages and software reuse technologies.
History
VISA was originally standardized through the VXIplug&play Alliance, a now-defunct T&M standards body. The current standard, "VISA Specification 5.0", is maintained by the IVI Foundation.See also
- Interchangeable Virtual Instruments (IVI)
- SICL
- Standard Commands for Programmable Instruments (SCPI)
- Instrument DriverInstrument DriverAn Instrument Driver, in the context of Test & Measurement application development, is a set of software routines, which simplifies remote instrument control. The specification of instrument drivers is defined by the IVI Foundation....