Once, combining separate instruments into an integrated test system meant GPIB interfaces. Today, a world of interface options are available, including Universal Serial Bus (USB) and LAN eXtensions for Instrumentation (LXI). Although there’s definitely a role for USB in T&M system integration, from the perspective of a test system integrator, I think LXI offers an edge:
- Many if not most T&M systems can benefit from a common sense of time among all system components. The IEEE 1588 Precision Time Protocol capabilities included in LXI Class B and A instruments simplify the building of systems with tight timing control. The advantages of this include support for measurement data time stamping, synchronization of triggers without the need for hard-wired trigger cables, and the reduction or elimination of system latency effects.
- Although the LXI standard doesn’t require the use of instruments that can be controlled by onboard test scripts, it does enhance scripting capabilities. For example, large test systems can be divided into subsystems coordinated by script-based instruments. This spreads the control and data processing functions across multiple processors, increasing the total processing power available in the system and often improving overall speed and throughput. This division of labor also allows for parallel testing: there’s no need for instruments or subsystems to sit idle while a central controller is busy with another task.
To learn more about the advantages IEEE Std 1588 timing offers for LXI-based test systems, you can download a Keithley white paper: "What IEEE 1588 Means for Your Next T&M System Design.
Todd Hayes is a Sr. Staff Firmware Engineer at Keithley Instruments Inc.