This FAQ addresses the following commonly-asked questions about LXI technology:
1) What are the benefits of Ethernet for data acquisition applications?
2) What are the additional benefits of using LXI for Ethernet data acquisition?
The widespread adoption of LXI to replace GPIB is driving the development of high-performance, LXI-based tools for PC-based data acquisition. LXI adds several features on top of the Ethernet standard to specifically address the needs of test and measurement applications, including synchronization, flexibility in form factor, and longevity.
3) What are the performance metrics of LXI data acquisition?
With Gigabit Ethernet connectivity a standard feature of PCs, Ethernet-based data acquisition systems now can deliver sustained throughput of over 100 MB/s, and this will continue to increase as 10 GB Ethernet and future generations of Ethernet become the norm. LXI adds benefits to Ethernet, such as triggering and synchronization as precise as 20 ns over standard Ethernet cables. LXI also adds more precise triggering and synchronization options, as discussed later in this document.
The first byte latency associated with the Ethernet packetization process is often in question for engineers when considering LXI data acquisition. For high-volume production test systems that need to take multiple measurements from multiple instruments in as little time as possible, the overhead of initiating each test step is more important than data throughput in order to minimize test cycle time for each UUT. For a data acquisition system taking data at a prescribed rate, the opposite is true – reliable throughput of data is more important than the relatively small proportion of time spent sending the first byte, because of the need to avoid data loss regardless of how demanding the required throughput. The first byte latency for a Bustec system is on the order of 100 to 150 μs
4) How can I be sure that LXI technology will last over time?
Computer bus technologies – such as ISA, EISA, Micro Channel (MCA), PCI, PXI, PCIe, and PXIe – constantly emerge and subsequently become obsolete without maintaining compatibility with each other, making long-term or lifetime support for existing systems extremely difficult. LXI is based on standard TCP/IP Ethernet, a network bus with long-lasting adoption, millions of users, and performance improvements that preserve backward compatibility.
LXI provides seamless interoperability between vendors, giving users the flexibility to select the most suitable LXI products for their specific application. Plus, the standard complements existing test and measurement systems, working with GPIB, VXI, PCI, and PXI standards.
LXI promotes ease-of-use with easily configurable LAN options, VXI-11 instrument discovery, and connectivity between test and measurement software, including VISA and IVI drivers to instruments. This technology also provides coordination activities using IEEE 1588 and the IVI LxiSync API for managing the arming, triggering, and event functionality of LXI devices.
Because LXI offers numerous benefits as an emerging technology, and will continue to play a role in data acquisition applications where flexibility and seamless integration are critical application needs. Many companies have adopted LXI technology, which has been in existence since 2004. Read about the History of LXI.
5) Common industries where LXI technology is used include:
6) How is LXI different from the traditional PCI- or PXI-based systems?
While there are many viable platform options for data acquisition systems, each with its unique features and benefits, LXI distinguishes itself with its flexibility in size and power as well as accessibility in its use of ubiquitous Ethernet technology.
Because LXI systems are not based on cards that must fit inside a PC, they are not limited by the power and real estate constraints of PCI and PXI-based systems. The ADCs in traditional PCI and PXI instruments do not have optimal headroom for taking accurate 10 V measurements. LXI products, on the other hand, have the real estate to use a 15 V power supply for analog power rails, which allows for more accurate measurements without having to alter the original signal.
With an LXI-based data acquisition system, setup and results data are typically displayed via Ethernet connectivity on the host PC. As long as they include an Ethernet port, LXI instruments have much flexibility in physical size and shape, whereas PCI and PXI boards must fit into standard-sized slots and chassis. Although most LXI devices are designed for rack mounting, some devices may use a smaller form factor to support portable, stand-alone form factors. With Bustec LXI data acquisition systems, signals enter and exit the module from its front panel while connectors for Gigabit Ethernet, power, and trigger cables are found on the back of the module. DUT connectivity is reserved for the front of the module, with line power and the RJ-45 Ethernet port on the rear panel.
Without the need for mainframes or slot-0 controllers, LXI systems can provide considerable cost savings compared to chassis-based platforms. LXI modules feature self-contained power supplies to improve reliability, lower costs, and provide widely distributed system architectures.
7) Why should I use Bustec LXI products for my data acquisition system?
Bustec has a long history in high channel-count data acquisition systems, starting in the 1990s on the VXI platform. With hundreds of deployed systems in critical applications, such as mil/aero test applications and nuclear power plant monitoring and control systems, Bustec continues to invest in R&D to develop new technologies that lower costs and increase performance.
Bustec systems are known for their high throughput, channel density, and accuracy. A system comprised of Bustec ProDAQ 6100 LXI function card carriers can reach up to 100 Mbytes/s throughput for streaming waveform data, with 20 ns synchronization accuracy between separate LXI devices. Their function card line includes 24-bit resolution analog input cards with an absolute accuracy of 50 μV typical for the 10 V range. In addition, over 384 digital I/O channels or 192 analog input channels can fit in 1U of rack space.
For flexibility, Bustec offers data acquisition solutions for LXI and VXI using the same function card modules in carriers for both platforms. The company addresses applications where accuracy is critical, such as those that include static signals (voltage, temperature, pressure, etc.) and dynamic signals acquired at higher speeds, as well as closed-loop control and simulation.
View our complete LXI product line.