IEEE 1588 supports distributed test systems
By Martin Rowe, Senior Technical Editor -- Test & Measurement World, 10/1/2006
Engineers often develop centralized measurement systems when they need precise timing across dozens or even hundreds of channels. When used in large applications such as aircraft wing measurements, centralized systems need long wires. Of course, long wires are likely to pick up interference, which reduces measurement accuracy. Decentralized, or distributed, systems can use shorter wires but can suffer from synchronization errors.
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Two computers use IEEE 1588 interface cards to synchronize their measurements. |
To compare centralized and distributed systems, Alex B. McCarthy, senior product marketing manager at National Instruments, conducted an experiment using a rotating shaft. McCarthy used three shaft encoders that produced 2500 ticks/revolution to measure shaft rotation. The centralized system used one PC that contained three counter cards to count encoder pulses. The distributed system used two PCs, one with one counter card and the other with two. Each PC in the distributed system contained an IEEE 1588 interface card. At 2160 rpm, the encoder’s tick period was 11.1 µs. Synchronization error in the distributed system was just 230 ns, which was insignificant in this application.
To learn more about McCarthy’s application, you can download a zip file that contains his paper, “LXI uses IEEE 1588 PTP to Simplify Large-Scale Measurement Systems.” The zip file contains LabView code used in the IEEE 1588 example as well as links to related articles about IEEE 1588.
