The LXI Standard

The LXI (Lan Extensions for Instrumentation) standard is a new open multivendor standard for automation and control of measurement instrumentation. The initial release of the standard has been published in September 2005. The LXI consortium has spent ongoing effort to advance the standard ever since, with revision 1.3 having been released in autumn 2008.

LXI utilizes the inexpensive physical layer and high bandwidth of Ethernet and extends the Ethernet properties with instrument and application related features needed by the test & measurement community.

• Communication protocols (TCP / IP, UDP, VXI-11)
  
• Communication properties (Web interface, network configuration, behaviour in the network)
  
• Trigger and synchronization capabilities (LXI class A trigger bus, IEEE-1588 timestamping and timebombed trigger etc.)
  
• Physical attributes (connectors, cooling, rack integration, display elements)

By separating computer architecture (PCI, PCI-Express) and instrumentation, the rather long lived instrument hardware is efficiently uncoupled from fast moving computer technologies, therby guaranteeing long term protection of your investment.

The LXI consortium, a non-profit organization, has about 50 member companies, amongst these are the most important and influential instrument manufacturers.

Extract from the members list:

LXI Instrument classes

The LXI standard defines three different classes of instruments. The instrument manufacturer states to which LXI class an instrument conforms. The user can thus easily select the right instrument for a given application. Interoperability with other LXI instruments is being examinated by the LXI consortium or a certified conformance lab prior to market introduction of the instrument.

Today the majority of LXI instruments conform to class C, while many of the instruments that are currently introduced to the market are class B compliant. Some class A instruments are already available as well, mainly covering specific applications e.g. for the Aerospace/Defense industry.

Future LXI class A instruments will define entirely new models of operation with distributed execution of measurements where different instruments directly communicate with each offloading the system controller.

LXI Trigger Capabilities

The LXI standard defines the following capabilities for triggering and synchronization of instruments:

		Standard TTL Triggers : Standard trigger inputs and outputs are used as with legacy instruments: Advantage: Highest performance over short distances
		Lan Trigger and IEEE-1588: The synchronisation of instruments is accomplished via standard LAN (TCP or UDP) packages and the IEEE-1588 precision time protocol. IEEE-1588 triggers are frequently referred to as timebombed triggers as instruments start the measurements based on their internal clocks that are kept in sync by IEEE-1588. Advantage: No dedicated trigger lines needed, good synchronisation over long distances.
		LXI Trigger Bus: Triggers propagate over the LXI trigger bus that is based on differential M-LVDS signals. The trigger bus may also be used for high speed deterministic messaging between instruments. Advantage: Flexible trigger routing with one to many trigger relations is accomplished without complicated wiring between the instruments. Trigger source and destination may vary for different measurements.