Technologies used in the Test & Measurement Industry - A quick perspective
There are controllers and there are instruments. The Test & Measurement industry has created a good number of PC-based and embedded products (over 1000 to be sure) that have been based on a few industry standards. This document is an attempt to provide an introduction to some of the technologies used in this area – particularly GPIB and VXI.
Instruments can measure analog and digital inputs, and also generate analog or digital output, driving relays or creating waveforms. The concept is not limited to test & measurement, but also extends to data acquisition and control. The common configurations make use of PCI add-on cards to a PC, with software running on Windows (sometimes Solaris/HP-UX). The add-on card can connect to multiple instruments (housed in a chassis for example), or even other cards each connecting instruments/sensors etc.
To enable instruments from various vendors inter-operate or replace one another, physical bus standards were introduced. One is GPIB (General Purpose Instrument Bus – also known as IEEE 488.2) and the other is VXI (VMEbus extensions for Instrumentation). Standard command sets were defined to be sent over the bus, so instruments could be replaced with similar ones from another vendor, and one instrument could talk to another.
