LXI Devices can circumvent network and controller latency. Though Real-Time Operating Systems (RTOSs) can improve timing variability by limiting latency, they still introduce uncertainty, and delays are still present. Windows-based controllers commonly cause several milliseconds of variable delay. This controller and its operating system can cause variable delay in the trigger because of latency and variable delays. IEEE 1588 timing is more accurate and consistent and can avoid the message-based triggers issued from a controller at time-sensitive moments. Prior to LXI, test and measurement instruments typically relied on PCs and an active Internet connection for the time check, which created opportunities for inaccuracy. In addition to this feature, the LXI standard introduces time-based triggers. Even if the time "known" by the system is wrong relative to the physical world, instruments still agree on the timing and perform the various functions required in the correct sequence at the correct interval. The IEEE 1588 scheme ensures that instruments agree on the correct current time, leveraging a master clock located within the system. These features allow devices to execute trigger functions and, for the first time, standardize a method for executing triggers in a system based on knowledge of common system time reference to an accuracy not achievable before the advent of IEEE 1588.Ĭlass B LXI Devices provide timing and synchronization between the various components based on a common reference clock without requiring a controller (PC) to be the origin of time information. Class B instruments provide LAN and Web server functionality with the addition of a synchronization API and support for the IEEE 1588 precision time protocol. The Consortium is now witnessing the emergence of Class B instruments. These LXI Devices allow users to build quick and easy-to-manage test systems that can be remotely controlled, as shown in Figure 1. Web services are used to gain access to LXI Devices and achieve immediate control over their configuration, making them easy to set up, configure, and debug.
Some of these Class C instruments include features associated with Class B or Class A LXI Devices but not the complete set of features required to declare class compliance.
All major instrument functionalities are accessible through the Web server, which simplifies software development, system commissioning, troubleshooting, and maintenance. These instruments incorporate the key features attributed to LXI-compliant instruments, built-in Web servers so that users can monitor and control the system using Ethernet, and any standard Web browser. Since the release of the LXI standard, most instruments have been certified as Class C. The trigger functionality is broadly equivalent to the backplane triggers of modular instruments in card cages (though cable lengths might be longer than backplane trigger lengths) and the ad hoc point-to-point trigger systems used on bench instruments. The wired trigger bus provides a standardized capability for supporting trigger events between devices whose timing accuracy is limited by cables and LXI Device hardware. The Class B interface allows devices to execute triggered functions equivalent to those available over the General-Purpose Interface Bus (GPIB) with similar or better timing accuracy.įunctional Class A LXI Devices provide a standardized LAN interface, synchronization API, IEEE 1588 operation, and a wired trigger bus interface.
This class includes physically small products (such as sensors) that use battery power or Power over Ethernet and devices with key attributes including a simple architecture, low cost, and small size.įunctional Class B LXI Devices provide a standardized LAN interface, synchronization API, and IEEE 1588 timing support. These devices, which are not required to support either the wired trigger or IEEE 1588 timing aspects, are particularly suited to applications where non-LXI products have been adapted to the standard. Classes of LXI productsįunctional Class C LXI Devices provide a standardized LAN and Web browser interface conformant with the LXI standard. The class succession from C to A provides progressively more functionality and gives instrument designers the ability to incorporate the precise functionality required for their instruments and intended applications. The LXI standard identifies three functional certification classes: Class C, Class B, and Class A.