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Point-by-Point Analysis and Array-Based Analysis in LabVIEW

LabVIEW 2013 Help

Edition Date: June 2013

Part Number: 371361K-01

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The approach used for most point-by-point analysis operations in LabVIEW remains the same as array-based analysis. You can use filters, integration, mean value algorithms, and so on, in the same situations and for the same reasons that you can use these operations in array-based data analysis. In contrast, the computation of zeros in polynomial functions is not relevant to point-by-point analysis, and point-by-point versions of these array-based VIs are not necessary.

The following table compares array-based LabVIEW analysis to point-by-point analysis.

Data Analysis Technology
Array-Based Analysis (traditional paradigm)
  • Prepare a buffer unit of data.
  • Analyze data.
  • Produce a buffer of analyzed data.
  • Generate report.
Point-By-Point Analysis (newer paradigm)
  • Receive continuous stream of data.
  • Filter and analyze data continuously.
  • Generate real-time events and reports continuously.

The following table presents other comparisons between array-based and point-by-point analysis.

Characteristic Array-Based Analysis Data Acquisition and Analysis with Point By Point VIs
Compatibility Limited compatibility with real-time systems Compatible with real-time systems; backward compatible with array-based systems
Data typing Array-oriented Scalar-oriented
Interruptions Interruptions critical Interruptions tolerated
Operation You observe, offline You control, online
Performance and programming Compensate for startup data loss (4-5 seconds) with complex “state machines” Startup data loss does not occur; initialize the data acquisition system once and run continuously
Point of view Reflection of a process, like a mirror Direct, natural flow of a process
Programming Specify a buffer No explicit buffers
Results Output a report Output a report and an event in real time
Run-time behavior Delayed processing Real time
Run-time behavior Stop Continue
Run-time behavior Wait Now
Work style Asynchronous Synchronous

When you perform point-by-point analysis, keep in mind the following concepts:

  • Initialization—You must initialize the point-by-point analysis application to prevent interference from settings you made in previous sessions of data analysis.
  • Reentrant Execution—You must enable LabVIEW reentrant execution for point-by-point analysis. Reentrant execution allocates fixed memory to a single analysis process, guaranteeing that two processes that use the same analysis function never interfere with each other.
    Note Note   If you create custom VIs to use in a point-by-point application, be sure to enable reentrant execution. Reentrant execution is enabled by default in almost all Point By Point VIs.
  • Deterministic Performance—Point-by-point analysis is the natural companion to many deterministic systems, because it efficiently integrates with the flow of a real-time data signal.
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