Labview for linux

LabVIEW 6i: An impressive tool for data acquisition

The latest version of National Instruments' LabVIEW graphical programming language for building on-screen "virtual instruments" is faster, more feature-laden, and prettier to look at. It is also Webfriendly. Quality control and process control specialists will benefit the most. I had a chance to look at the final pre-production code in July, just before press time.

At its most basic, LabVIEW is a graphical programming language. You use its symbolics to map out a process and build an on-screen "virtual instrument" (VI) to monitor and control external data acquisition or processes. NI says most of its sales are to production environments, where LabVIEW can configure, say, testing of cell phone circuits at the end of the line. LabVIEW can also monitor lab-level experiments, or mile-long chemical plants.

I last ran across LabVIEW in a professional setting, where it was used to control production in a bench-sized chemical plant making coatings for strain sensors. The software first shipped in the mid-80s. NI, among others, supplies plenty of instrumentation that can hook to standard computers and feed a LabVIEW built virtual instrument. For the review, NI sent along one of its DAQCard-1200 PCMCIA cards and a function generator to make my Windows 98 laptop think it was connected to a bunch of external sensors.

There is no practical limit, aside from power of the computer it runs on, to the complexity of processes or the amount of data LabVIEW 6i can control. But there is a limit to how complex a system anyone might want to build using pre-designed blocks. This latest version pushes the limit quite far. After quickly determining that the interface is quite responsive on my test machine - with a modest 450-MHz Pentium III and 64 MB of RAM - I spent more time checking points at which users could be led astray.

How easy is it, for instance, to build an instrument that records all incoming data but flags transmission lapses and discards startup resonance and repetitive zeros, and spans for calibration? Can all or almost all of the data processing be done within LabVIEW, or do you have to risk exporting the data to another package to run the stats or draw a nice chart? How good is the array of signals LabVIEW can send out to tickle a circuit being tested? How easily does LabVIEW share data with the rest of the enterprise?

In a word, LabVIEW 6i was impressive - on all counts. There may be better packages for running predictive mechanical simulations and for handling "fuzzy" data (economic data, for instance). But in its broad niche, LabVIEW 6i is a robust, mature package that won't steer you wrong. This latest version, for instance, has a new "digital I/O" virtual instrument display to represent timing data and digital patterns. That's an easy way to handle zeros and spans-you define the time segments to ignore. The tutorials, wizards, and help files are detailed and easy to navigate, and include AVI animations with sound.

As you might expect these days, you can also stream LabVIEW-generated data across the Web, and read it on LabVIEW built virtual instruments. The VIs display on your browser once you download the free plug-in from www.ni.com/labview. You do not need LabVIEW running on the same machine as the browser, either. I didn't test the idea, but it seems almost trivial to split up a large stream of, say, ten measurements and send two or three to each of a half-dozen specialists around the world in real time as data are gathered. There's an ActiveX development system for this, so use Internet Explorer, not Netscape.

Once you design your software in LabVIEW 6i, you compile it - LabVIEW is a true 32-bit compiler. You can create executables and shared libraries (DLLs in Windows-speak). Compiled programs run faster. VIs developed on older versions run fine in 6i. Visual Basic is a nice match for LabVIEW developers. The links to Java are still being developed. The latest version offers fast Fourier transform routines that are fast indeed - NI says they are 20 to 30 times faster than in earlier versions - and that can also be nicely deconstructed.

LabVIEW 6i comes in three versions the base package, full development system, and professional development system. There are add-ons for datalogging and alarm triggering, machine vision and image processing, SQL, Internet functions, process control, PID and fuzzy logic, system simulation and design (linear and nonlinear systems), sound and vibration, signal processing (including wavelet), and optical character recognition. Prices start at $995. Expect to spend $2,000 or so for everything you need. Upgrades from older versions are $395.

LabVIEW runs on many platforms, including any computer that supports Windows 9x or NT, Power Mac OS '7.6.1 or later, UNIX, and major Linux distributions.

For details and ordering information, visit www.ni.com/labview/.