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Distributed Data Acquisition with ActiveX
Distributed acquisition, analysis, and presentation systems just got easier with ActiveX in LabVIEW 5.0. Historically, the LabVIEW graphical development environment has pioneered data acquisition (DA) ease of use where acquiring data simply meant putting an icon in a window. LabVIEW 4.1 introduced DAQ wizards to generate ready-to-run, custom DA programs from a few mouse clicks. With LabVIEW 5.0, the DAQ wizards have been expanded to include more analog input, analog output, digital I/O, and additional options or combinations to cover the gamut of DA users’ needs.
Occasionally an application involves remote data collection from multiple machines, and the analysis and logging of the collected data reside in a location other than in the acquisition computers. For example, a central application may have to acquire temperature data from sensors connected to individual computers in several different cities, analyze the data, and send them off to another computer dedicated to logging data. If the acquisition computers change on a regular basis, this relatively straightforward problem can become complex, depending on what data the operator needs to collect and where the data are at any given time.
In these cases, the DA engineer not only has to develop the acquisition and analysis programs but also has to learn a networking protocol to properly pass data between applications on different computers. And with the possibility that on some days or hours only an arbitrary subset of the total available acquisition computers would be used, the developer has to create more code to take operator choices into account.
With the ActiveX automation client/server capabilities in LabVIEW 5.0, however, the networking part of the program has been simplified to a few icons that take care of sharing data and controlling applications. The methods and properties necessary to perform these functions are chosen from pop-up menus rather than typed out by the developer. The developer can also change the acquisition of data from a local computer to a remote computer simply by entering the new computer’s name. Finally, LabVIEW 5.0 also acts as an ActiveX container, so developers can embed in LabVIEW other ActiveX controls and documents to present or store the acquired data.
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