Software
It's a Visual Adventure!
LabView National Instruments 6504 Bridge Point Pkwy. Austin, TX 78730-5039 800-433-3488; 512-794-0100; 512-7948411 (fax);
[email protected] (e-mail) Version 3.01; $1995
LabView is a graphical programming system based on displaying and collecting icons into a parallel program display to acquire, process, and display data. This visual programming language is available for Sun SPARCstations, Macintosh, HP 9000 Series 700 workstations, and DOS (Windows 3.1 and NT) platforms. Here I review its use on the Macintosh, in 68030, 68040, and power PC in native mode. A novice's first impression of LabView is often how easy it is to assemble the various functional icons and wire them together with the mouse and wiring tool. For applications that require basic data processing, this is true. But this same sense of ease may evolve into frustration as true top-down programming becomes preferred to make the programs function. LabView, icon based or not, is inherently a full-featured programming system that must be taken seriously from the start. All who consider using LabView should be aware that its initial deceptive simplicity is not what makes the effort worthwhile. What LabView does best is to tickle a creative nerve in a way that no code I have used before does. The arrangement of processes within a program in pictorial form that executes the processes in a parallel manner, as opposed to sequentially, occupies, captivates and, given a reasonable attention span, generates more ideas. 34 A
A functioning LabView program can be compiled into a "virtual instrument" (VI) that accomplishes all of the post-acquisition data processing and display. Only the actual data acquisition is done externally to the program by hardware devices. These include National Instruments' own parallel, serial, IEEE-488 (GPIB), or"VXI" boards, and equivalent boards from other vendors. Clearly, one of Lab View's strongest features is its ability to use instrument driver-level software to communicate with and acquire data from various sources. The VI receives the data from the outside and the programmer arranges collections of icons into processing, storage, display, and output functions. LabView is called a lab language for good reason. It is easy to prepare icons and panels of controls and indicators that are direct metaphors for lab instruments and processes. Buttons can be pushed, tanks filled, graphs tweaked, panel meters read, knobs twisted; everything done with a hands-on instrument can be done at the computer with a mouse or keystroke. National Instruments has provided an impressive assortment of sub-Vis that can be incorporated into post-acquisition
tasks as complex as discrete inverse Fourier transformation, cross- and autocorrelation, active filtering, and other kinds of digital signal processing. A completed VI may be easier to read and understand than most lines of code in a nonvisual program. But this is not to say that LabView work can go undocumented. Unless users can understand the reasoning that went into the assembly of the program, it is unlikely that they will understand the program as such, even though its icons are readily recognizable. Before plunging into the details of the language, one must ask, "Is it really worth it, or does using LabView just give us another thing to worry about?" The program requires a fast processor (a 68030 CPU in a Mac at 33 MHz just does it), takes a lot of disk space (a typical LabView folder on a Mac is 10-30 MB), and requires a floating point processor (or its equivalent) and ~ 6 MB RAM to launch. An inexpensive student version that demands fewer resources but has less capability will be released soon. Much of the practical commentary is carried on the Internet (those interested can subscribe via "
[email protected]" and query via
LabView-based fluoride analyzer system performs total fluoride determinations on gas, liquid, and solid samples.
Analytical Chemistry, Vol. 67, No. 1, January 1, 1995
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[email protected]") and in a delightful book, LabView Graphical Programming, by Gary W. Johnson (McGrawHill, 1994). LabView provides opportunities that other languages do not. Yes, it will take time, space, and money to get into the LabView environment. However, that environment is quite complete, and the user will not likely need external signal processing packages to do complete data workups. From my perspective as a teacher, it is the creative spark of discovery inherent in building LabView instruments that decides the issue. What are some of its best features? I think they are the beautiful graphing, data acquisition, data processing, and file handling capabilities. These features have enabled me to access data in a way that made them useful, without hours of effort, and have made my students animated and productive in a single afternoon's lab. Almost any result, experimental or calculated, can be displayed graphically, either as a time series or in true x-y fashion, with remarkable simplicity. All graphs are easily révisable, scaled to suit, and even colored for trace recognition. National Instruments A/D and DIO boards are operated with stunning simplicity by sets of icons provided in the LabView environment, including some called "Easy I/O" that genuinely are. Digital and analog input and output into files and spreadsheets, directly to disk, and directly to RAM all are straightforward. Digital signal processing, a research area in its ownright,is elegantly implemented inrichlydiverse and easily used sets of LabView icons. This includes all of the Fourier and correlation techniques, windowing, digital filtering, full statistics, and regression. Data acquired and displayed can be stored to disk in a variety of forms, delimited or otherwise, with real ease. National Instruments' driver-level software provides routines for real-time, boardcontrolled batch data acquisition under LabView VI initiation, eliminating concerns about real-time data acquisition with
a time-sliced operating system such as that SOFTWARE RELEASED used with the Macintosh. What are some of LabView's worst features? The answer depends on the proDigiSim grammer's skills and available time. For Bioanalytical Systems me, setting up some Vis was difficult. 2701 Kent Ave. Properly "bundling" items into "clusters" Purdue Research Park before graphing the data in an «-dimen- W. Lafayette, IN 47906 sional array took many trips to the highly 317-463-4527; 317-497-1102 (fax) readable manuals to get right. Also, even Version 2.0; $1895 the beta releases of Version 3.1 that I tested do not include an "undo" function. DigiSim is a Windows-based cyclic voltamSlight slips of the mouse, accidental mis- metric digital simulator and tool for alignments of icon sets, or accidentally teaching contemporary electrochemistry. erasing wiring can lead to time-consuming It calculates cyclic voltammograms and rearranging or rewiring. concentration-distance profiles as they I also found that the manuals, albeit change with time for any user-specified well written, presume a technical undercombination of one-electron heterogestanding of some sophistication. For exam- neous andfirst-and second-order homople, LabView did not help me learn digigeneous chemical reactions. Calculations tal signal processing; rather, it helped me are performed using the Rudolph algoimplement what I already knew. Anrithm, which offers unprecedented speed, other problem is related to the number of does not suffer from the limitations versions of the program and the freinherent in other digital simulation methquent updates. Vis may not transfer beods, and removes the requirement for tween versions and may require "convercomputational expertise. Minimum syssion" libraries, unless the versions already tem requirements include Windows 3.1,486 use compatible libraries. DX CPU, a VGA display, and 2 MB RAM. There are two ways to learn LabView. One is the way I did—read the nine volLimsLink umes of instruction manuals and just start Labtronics, Inc. teaching it. The other is to attend one of 95 Crimea St. National Instruments' short courses. The Guelph, Ontario, Canada N1H2Y5 latter way is better. Training videos are 519-767-1061; 519-836-4431 (fax) also available from National Instruments, Version 1.0; $1500 although I have not used them. LabView is a highly successful, wellLimsLink automates data collection from balanced, andrigorousparallel programup to nine RS-232, file, or network sources. ming environment that will be effective in No programming is required. Users can solving instrumental problems at various import worklists, capture instrument data, levels of complexity. It is remarkable that perform calculations, combine data, print something this powerful can be used even reports, and send results to the LIMS. by novices, while still retaining the power Data can be validated before transfer or to handle tasks as complex as reading sent automatically. Sample tables can be hundreds of digital signals or streaming customized and results displayed in real from multitudes of analog inputs directly time. Password and audit trail features to disk. It is a program that deserves the guarantee data integrity. The software can serious attention of all analytical chembe implemented with any LIMS and reists interested in linking instrumentation quires (at a minimum) Windows 3.1, a 486 to laboratory sources. CPU, math coprocessor, a VGA display, Reviewed by John P. Walters, St. Olaf one available COM port, 8 MB RAM, and 10 MB free hard disk space. College, Northfield, MN Analytical Chemistry, Vol. 67, No. 1, January 1, 1995 3 5 A
