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Class B instruments transform test programming
February 27, 2007
The LXI standard requires that Class B instruments include IEEE 1588 precision time protocol capabilities. Already established in the power-generation and IT industries, 1588 is moving into test-and-measurement products with the emergence of the LXI standard. IEEE 1588, or PTP, provides a method for automatic servo-converging of a number of real-time clocks to a master reference clock with accuracies down into the tens of nanoseconds. While such high precision requires special switchgear and highly stable clocks, routine implementations can provide synchronization below a few hundred microseconds using common IT equipment and commodity clocks within a subnet.
Such capability allows event programming to be done on a prescheduled rather than reactive basis. For example, a pulse source can be preprogrammed to output a pulse of one-millisecond duration at 12:00 EST plus or minus 100 microseconds. An interconnected digitizing instrument can also be programmed to collect data at that same time or after a specified interval to achieve desired results. The conventional approach would be to connect the pulse source trigger output to the digitizer input, and then set a delay factor in one or both instruments. The conventional approach might seem easier for simple applications, but for complex pulse trains and other multiphase/multistep applications, programming delays can become a guessing game akin to tuning rather than designing. IEEE 1588 allows test sequences to be preplanned and executed with repeatable execution and results.
Once a critical mass of Class B LXI products is available, we expect test engineers to develop many imaginative programming approaches that will exploit the inherent strengths of common time bases. One application that could benefit greatly would be the study of widely remote geophysical phenomena such as solar flares, earthquakes, and tsunamis. Using a network of time synchronized instruments, data can be collected and accurately time-stamped using GPS time, for example, as the master reference. The collected data could be sent to a common database for correlation and re-assembly into maps and other visualizations with a high degree of time correlation accuracy.--Chuck Cimino, Marketing Director, Keithley Instruments.
Posted by Rick Nelson on February 27, 2007 | Comments (0)
