virtual instrument software architecture

{{Short description|Test and measurement API}}

{{for|other uses of the term visa|Visa (disambiguation)}}

Virtual instrument software architecture (VISA) is a widely used application programming interface (API) in the test and measurement (T&M) industry for communicating with instruments from a computer. VISA is an industry standard implemented by several T&M companies, such as, Anritsu, Bustec, Keysight Technologies, Kikusui, National Instruments, Rigol, Rohde & Schwarz, and Tektronix.

The VISA standard{{cite news |url=http://www.ivifoundation.org/specifications/default.aspx

|publisher=IVI Foundation |title=VISA Specification}} 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 HiSLIP{{cite news |url=http://www.ivifoundation.org/downloads/Class%20Specifications/IVI-6.1_HiSLIP-2010-06-08.pdf

|publisher=IVI Foundation |title=IVI-6.1: High-Speed LAN Instrument Protocol (HiSLIP)}} or VXI-11{{cite news |url=http://www.vxibus.org/?q=node/206

|publisher=VXI Bus Consortium |title=VXI-11 Bus Specification}} (over TCP/IP) and USBTMC{{cite news

|url = http://www.usb.org/developers/devclass_docs

|publisher = USB Implementers Forum Inc.

|title = USB Test & Measurement Class Specification

|access-date = 2010-04-30

|archive-url = https://web.archive.org/web/20100326005605/http://www.usb.org/developers/devclass_docs/

|archive-date = 2010-03-26

|url-status = dead

}} (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, over the Microsoft COM technology, and through a .NET API. 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 {{Specify|date=August 2015}} are also available for less common programming languages {{Specify|date=August 2015}} and software reuse technologies.