December 31, 2013. Microstar Laboratories Inc., maker of Data Acquisition Processor (DAP) systems for PC-based high-performance measurement applications, has released a new Time Base Synchronization module for real-time alignment of acquired data sets at multiple measurement stations using xDAP data acquisition equipment. This software requires no elaborate time protocols or complicated communication stacks. A simple timing pulse stream is sufficient, but better if IRIG-B or GPS receivers are available to provide a time-base signal.
Large distributed data-acquisition applications using multiple measurement stations can either let each station capture data on its own stable but independent time clock or lock the stations to a common time base signal. Either approach presents challenges.
Operating on their own local timing clocks, tolerances of a few parts per million on the sample rates will accumulate over time so that each station captures a different number of samples. Post-processing the discordant data streams to align them for a unified analysis is relatively difficult.
Alignment is assured when every station connects to a common timing source. However, pulse rates for available time base signals often are unsuitable for clocking the data-acquisition sampling directly. For example, IRIG-B delivers highly accurate timing reference pulses at one-tenth-second intervals, but only occasionally is this rate suitable for driving data acquisition. Pure hardware solutions to derive a sample clocking signal from a timing signal are temperamental and expensive.
The Time Base Synchronization Solution
Instead of trying to force hardware synchronization, the Time Base Synchronization module observes the timing reference signal and the measured signals in a common multichannel data stream. It should seem reasonable that when you can see the timing pulses and the data samples together in the same data set, it is clear where they align. Using basic sampling theory, samples that form a valid representation of the signal are sufficient to determine the value of the signal at any point, not just at sample positions. So the Time Base Synchronization module picks the points where you want them, so that they line up with the reference time base, at exactly the sample rate that you want.
Configuring this processing requires two commands: one to perform the timing analysis, and the other to apply the numerical evaluations.
The Time Base Synchronization Module is available with the DAPtools Standard software package, with purchase of an xDAP data acquisition system from Microstar Laboratories, or as a software upgrade. DAPtools Software also provides the DAPL 3000 system, the processing engine that controls all of the real-time processing within the embedded xDAP environment. Also included with DAPtools Standard software are modules for advanced rotating machinery rate analysis and for digital countermeasures to aliasing.
The DAPtools Standard edition software is available now. The one-time license fee for the DAPtools Standard package, including the Time Base Synchronization processing module, is $195.00.