After viewing and interpreting real-time results, what happens to the archived data?

If the original streams were stored on an instrumentation tape recorder, data can be played back as originally recorded through a bit synchronizer and decommutator. Data can once again be viewed, processed, archived to disk, distributed, or sent to strip chart recorders for reports. You can continually repeat this process if you are interested in analysis by inspection. The tape can be replayed multiple times in real time if the ground system components (bit sync, decom, processor, and disk) all support these higher rates.

Another visual analysis technique extracts all instances of measurands for the entire test (hours, even days totaling millions of points) for display in a single window. While this places many instances on a single vertical line, out of tolerance data, whether trends or spikes, is highly visible. You can repeatedly focus in on significant data using a zoom technique until multiple pixels show a single instance. This technique greatly reduces the time required to seek aberrations and review areas of interest (from hours to milliseconds).

In addition to visual analysis, a host of third-party general-purpose analysis and visualization programs can be utilized to evaluate archived data, extract results, and produce reports. Each has its benefits and followers and is available for both UNIX and PC platforms. Some are essentially high-level analysis languages (MATLAB and PV-Wave), while others are GUI-based (Excel, DADiSP). All include a rich set of signal analysis and statistical tools from Fast-Fourier Transforms (FFTs) to t-tests. They may have links to process piped data for near real-time processing as shown in the example below, where MATLAB is used to feed a power spectral density (PSD) graphic from FFT algorithms. Often, scripts are used to create a batch process of reports from an entire test.

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