LXI – the new LAN standard for networking T&M equipment

The LXI standard is based on Ethernet, the widely used communications standard for LANs. This is just one of the reasons why LXI is widely supported by leading manufacturers of T&M equipment.

The LAN eXtensions for Instrumentation (LXI) standard for controlling T&M equipment and test systems combines the advantages of rack & stack instruments, offering GPIB interfaces and powerful firmware functions, with the benefits of modular, compact VXI/PXI systems (see box on next page). LXI, which is based on the Ethernet standard, defines a uniform, interoperable LAN implementation, allowing T&M instruments to be easily integrated into modular test systems. As the LAN standard is backward compatible with previous versions, it protects existing investments.

Ethernet has a long tradition: At about the same time that the GPIB interface was introduced, Ethernet was developed and also standardized (IEEE 802.3). Unlike the GPIB interface, whose transfer rate is limited due to technological reasons, Ethernet technology could be continuously accelerated. Initially providing a meager 3 Mbit/s,100BaseT and Gigabit LANs are now state of the art – with further enhancements in the pipeline.

The spreading use of the Internet further advanced Ethernet; today, every PC is equipped with a LAN interface as standard. Moreover, the new wireless technologies enhance the LAN capabilities by additional applications.

These are ample reasons for leading manufacturers of T&M equipment to support the new LXI standard. Web servers are integrated in LXI devices, allowing interface and instrument settings to be made simply via a web browser. The programming interfaces for the test software are IVI-C or IVI-COM drivers (IVI stands for interchangeable virtual instrumentation). In addition, the precision timing protocol (PTP) of the IEEE 1588 standard for synchronizing clocks in LAN nodes as well as an eight-channel hardware trigger interface are earmarked for LXI to further expand trigger and synchronization functions. Another future capability is the configuration of hybrid test systems, which will integrate VXI/PXI systems and conventional GPIB instruments via LXI adapters.