With its triggering and synchronization features, PXI provides an ideal environment for FIUs. And because HIL test systems are commonly architected with PXI-based I/O, PXI also offers close proximity to the signals you need to switch. Such systems are commonly controlled via embedded real-time processing software such as NI VeriStand, so having a PXI-based FIU makes it simple for engineers to programmatically select and control faults from the same interface that is running their model and test sequences.
National Instruments recently released its first FIU, the NI PXI-2510, a 68-channel, 150 V, 2 A FIU designed for use in HIL applications. Each module has 68 feedthrough channels that you can open or short to one or two fault buses. Additionally, each fault bus has a 4x1 input multiplexer, thereby allowing greater flexibility for both the type and number of faults that you can inject via software control.
Figure 6. NI PXI-2510 68-Channel 2 A FIU
In addition to easy integration with HIL test systems, NI PXI FIUs offer the hardware-related advantages of safety, reliability, and connectivity.
Because high voltages and currents are often associated with fault insertion, and reliability is essential for HIL applications, NI takes the utmost care with its FIUs when it comes to safety. Specifically, all NI FIUs are compliant with IEC 61010-1 international standards, and have had their designs verified through third-party agencies such as UL. Finally, each unit is tested prior to shipping to validate both functionality and safety.
Similar to safety, reliability is a key concern for the integrity of long-term tests. Although rated for millions of cycles, electromechanical relays have a finite and relatively predictable lifetime under normal loading conditions. To allow for increased long-term reliability, the PXI-2510 incorporates onboard relay count tracking, which you can use to view the number of cycles each relay has undergone. This helps you determine your maintenance and replacement needs. The PXI-2510 features a user-replaceable relay kit in the event of normal relay failure at the end of its specified lifetime. NI also recognizes that through the course of usage, unforeseen circumstances can result in the accidental damage of relays by exposure to excessive voltages and currents, in which case the user-replaceable relay kit is also valuable. Finally, for mechanical reliability, each FIU design undergoes highly accelerated life test (HALT) screening to ensure mechanical soundness in high-vibration environments, which allows for sustained use in harsh field conditions.
Often overlooked, cabling and connectivity are major concerns for fault insertion applications due to the potentially large number of channels involved as well as the high voltages and currents that you can use. The PXI-2510 offers three connectivity options – screw terminal, bare wire, and DIN connector. Each of these options has been specifically designed to guarantee safety, reliability, and shielding all the way to the signal terminals to provide a full connectivity solution. The result is improved noise and crosstalk in addition to reduced system emissions.
To learn more about connectivity and cabling options for the PXI-2510, visit the “How to Connect Signals to the PXI-2510" tutorial.
In addition to products specifically designed for fault insertion, National Instruments offers a variety of general-purpose switching products that you can use to create custom fault insertion topologies. An example is the NI PXI-2586 10-channel, 12 A SPST module, which you can use to create multiple topologies for fault insertion, including a three-channel, two-bus FIU and a nine-channel, one-bus FIU, as shown in this tutorial.