27-09-2012, 04:46 PM
VISA Structure:
visa.docx (Size: 154.62 KB / Downloads: 21)
VISA (Virtual Instrument Software Architecture) is a standard I/O language for instrumentation programming. By itself does not provide instrumentation programming capability. It is a high-level API that calls
into lower level drivers. The hierarchy of NI-VISA is shown in the below.
VISA is capable of controlling VXI, GPIB, or Serial instruments and makes the
appropriate driver calls depending on the type of instrument being used. When
debugging VISA problems it is important to keep in mind that this hierarchy exists. An
apparent VISA problem could in reality be the results of a bug or installation problem
with one of the drivers into which VISA is calling.
VISA PROGRAMMING:
VISA is an object-oriented language. The most important objects in the VISA language are known as resources. In object-oriented terminology, the functions that can be used with an object are known as operations. In addition to the operations that can be used with an object, the object has variables associated with it that contain information related to the object. In VISA, these variables are known as attributes. A simplified outline of the internal structure of the VISA language is shown below.