Icons Simplify Programming Of Data-Acquisition Software

Using a personal computer to control laboratory instruments and automate data collection is like many things in life-- there are trade-offs. On the positive side, computerized data acquisition is usually more accurate, more consistent, and less consuming of technicians' time than are manual methods. On the other hand, someone has to set up the system. In the past, this often meant hiring a person with computer experience--a trade-off too costly for many labs. Vendors of data-acquisition software understand that most scientists are not computer programmers. Since the late 1980s, following the lead of Cupertino, Calif.-based Apple Computer Inc.'s user-friendly Macintosh, these software developers have used computer graphics to simplify instrument control and data acquisition. Setting up an automated data-acquisition system--in applications ranging from basic research to quality control--is no longer a job for computer experts only. Data Translation Inc. 100 Locke Dr. Marlboro, Mass. 01752-1192 (508) 481-3700 Fax: (508) 481-8620 DOS: Global Lab $995 (add-~on packages for Global~ Lab-- Statpack $695;~ Graphpack $595)~ Data-acquisition hardware~ also available. Keithley ASYST Software Technologies Inc. 100 Corporate Woods Dr. Rochester, N.Y. 14623 (716) 272-0070 Fax: (716) 272-0073 DOS: Easyest LX $995; Easy-~est AG $395; ViewDAC~ $2,495; ASYST $2,295 Windows 3.0: Snap-Master $995~ Data-acquisition hardware~ also available. Laboratory Technologies Corp. 400 Research Dr. Wilmington, Mass. 01887 (508) 657-5400 Fax: (508) 658-9972 DOS: Labtech Notebook $995; Labtech Notebook/XE $2,495; Labtech Acquire $195~ Macintosh: Chrom/RT $2,495~ Windows 3.0: Labtech Note~book $1,495; Labtech Note~book/XE $2,495; Chrom/RT $2,495 National Instruments Corp. 6504 Bridge Point Pkwy. Austin, Texas 78730-5039 (512) 794-0100 (800) 433-3488 Fax: (512) 794-5794 DOS: LabWindows $695; Measure $495; NI-DAQ for DOS--Free with board pur-chase Macintosh: LabVIEW $1,995;NI-DAQ for Macintosh--Free with board purchase Windows 3.0: NI-DAQ for Win~dows--Free with board pur~chase~ Data-acquisition hardware~ also available. Strawberry Tree Inc. 160 South Wolfe Rd. Sunnyvale, Calif. 94086 (408) 736-8800 Fax: (408) 736-1041 DOS: Workbench PC $995;~ QuickLog PC--Free with~ board purchase ~Macintosh: WorkbenchMac~ $995; QuickLogMac--Free~ with board purchase~ Data-acquisition hardware~ also available. "The great thing about this software is you don't have to be a programmer to use it," says Douglas Stahl, a biomedical engineer at Beckman Research Institute in Duarte, Calif. "You can sit down, look at the manual, flip through the examples, and set up an experiment in a very short amount of time." Stahl used a Macintosh II computer and a program called WorkbenchMac from Strawberry Tree Inc., based in Sunnyvale, Calif., to automate a capillary high-pressure liquid chromatography system linked to a mass spectrometer. Used in analyzing proteins and peptides, the computer coordinates the actions of various pumps and valves, delivering minute quantities of reagents at the desired pressure into the capillary columns. "Our Workbench-controlled system shows less run-to-run variability than the earlier manual system," Stahl says, adding that the manual system required technicians using stopwatches to switch the valves at appropriate times. The automated system, he says, "is now used on a routine basis to perform separations on protein samples in the 10- to 20-picomole [10-12 mole] range, and, on several occasions, it has enabled us to analyze protein samples in quantities as small as 0.5 picomole." Using WorkbenchMac, Stahl found he was able to create a working model of the system in about two weeks. "Of course, each time we got the computer to do one thing, we thought of something we'd like it to do, too. If you had to write the programs for all of this, it would take months," he says. Writing Programs With Pictures The trick to simplifying the setup of a data-acquisition system is the use of pictorial representations of functions, or "icons." The more advanced data-acquisition programs available today use icons to replace lines of computer code. Here's the old way: To connect an analog device, such as a temperature sensor, to a PC, someone had to write a software routine that told the computer how to deal with the voltage information coming from the sensor. This was usually done in the C language or BASIC, giving the computer such instructions as which port to monitor for voltage data (converted to digital format by an analog-to-digital converter); how often to check that port; where to store values found there; how to display them; when to start monitoring; and when to stop. With icon-based data-acquisition software, this is how much easier it is: The user selects an icon with the computer mouse that represents temperature (analog) input and drags it onto a blank workspace. To display temperature readings on the screen, the user brings a second icon representing a chart or graph to the workspace, then draws a line between it and the first icon. That's all that's required. Temperature readings are displayed on the screen. Similarly, storing the readings on a disk is done simply by drawing a line connecting the disk icon to the temperature icon. Drawing a line to connect two icons replaces the majority of the programming needed to set up a data-acquisition system the old way. However, it's true that there is a bit more to the process. For analog input, such as voltage information coming from a temperature sensor, a menu is used to specify the voltage range and the sampling speed and resolution of the data-acquisition interface board. Entire data-acquisition setups are put together in much the same way that a draftsman would create a block diagram on a drawing board. Here, the drawing board is the computer screen, the pen is the mouse, and the ink is the set of icons--which represents various functions used in data acquisition and instrument control: analog and digital inputs and outputs, data loggers, chart recorders, and so on. And in some more advanced packages, like Austin, Texas-based National Instruments Corp.'s LabVIEW, computer programming concepts--such as specifying execution order, repetitive operations, and branching routines--are handled graphically. Icon-based data-acquisition systems are easier to set up and modify than are those created with traditional programming languages. Some packages even have behind-the-scenes capabilities, such as the ability to survey the computer's hardware to see where plug-in analog-to-digital conversion boards are currently installed, how many channels the boards have, and so on. These packages further simplify setup by presenting only valid options in the menus displayed to the user. Graphical data-acquisition packages are also easier to use than are programs that require the user to enter precisely formatted typed commands, making it possible for people with a wide range of skills to operate them. Many users report that technicians usually need less training to be able to operate these icon-based systems, and when it's necessary to swap one technician for another, there's less of an impact on the consistency of an experiment. Not all data-acquisition software for PCs is icon-based. Data Translation Inc. of Marlboro, Mass., for instance, offers Global Lab, which is menu-driven and allows users to set up a data-acquisition system by making selections from a variety of lists. A menu-driven system isn't as intuitive to program as one with icons, but it still beats writing computer code. Packed With Power Because icon-based programming is so simple, or perhaps because icons are kind of cute, people might assume that PC- based data acquisition is useful only for simple applications. This is not necessarily the case. True, some PC-based data- acquisition packages are better suited for simple applications, but these are the inexpensive ones, or those that come free with the purchase of a data-acquisition board. These low-end software packages are designed primarily to acquaint users with computerized data acquisition. With LabVIEW, "you can do anything that you can do with any other programming language," says Nicolas Groleau, a graduate student at the Massachusetts Institute of Technology Center for Space Research. There, scientists are using LabVIEW to create a data-acquisition system for use aboard the space shuttle. Scheduled to fly aboard the July 1993 shuttle flight, this LabVIEW-based system will acquire and analyze the responses of astronauts to an experiment called "the rotating dome," which has flown on three earlier shuttle missions. The rotating dome experiment investigates changes in how humans orient themselves in zero gravity. The astronaut is shown a rotating stimulus occupying the full visual field. The astronaut's brain's interpretation is that he or she is rotating in the direction opposite the visual stimulus. However, proprioceptors, as well as sensors located in the subject's inner ear, correctly assess the subject as stationary. The resulting conflicting sensation of motion and immobility is called paradoxical vection. The LabVIEW system collects data from five input signals. The first, a tachometer attached to the dome, tells researchers when the dome begins turning, its speed, and which direction it is turning. The second input signal comes from a joystick operated by the astronaut subject, who moves it in the direction he or she perceives his or her own body to be moving. Third is a bite board located in the astronaut's mouth. "Humans have a natural reflex that makes them want to right their head with perceived vertical," says Groleau, who programmed the system. "There is a gauge bridge built into the bite board. Its signal is positive or negative, proportional to the amount of torque the subject gives it." The last two signals are electrodes that measure muscle activity on the left and right sides of the neck. Between each 20-second trial is a 10-second rest interval, during which raw data are analyzed, and both raw data and calculated values are stored on the computer's disk. Eight values are calculated, including onset of vection, average vection, maximum vection, and four indices of head movement based on bite board and electromyography data. Because the rotating dome experiment has been performed previously in shuttle experiments that did not involve LabVIEW, a second computer using different software will be used to control the movements of the dome during the shuttle flight. "We could have used LabVIEW to control the dome, too, but we have to use the other computer to replicate previous experiments," says Groleau. "For on-the-ground trials here, we use LabVIEW. It sends a voltage signal to activate the motor that turns the dome and can also control the lights and a visual target inside the dome." This LabVIEW application is part of a larger artificial intelligence system called Astronaut Scientific Advisor, also referred to as PI (Principal Investigator)-in-a-Box. The aim of the project is to put the knowledge of the experiment's principal investigator into the on-board computer so astronauts are less dependent on earth-bound support. "This is looking longer-term, toward a space station," says MIT's Groleau. Groleau is no stranger to computers or data acquisition. The project is tied to his dissertation for his doctorate in computer science. He chose LabVIEW over writing the code himself because that would have taken longer, he says, and would not have looked as nice. Regardless of the sophistication of the application, the ease of use of the icon-based data-acquisition software is a plus for scientists. Says Stahl of the Beckman Research Institute: "If you want to set something up really quickly and get results, or if you have a lot of ideas about experiments you'd like to try, this software lets you throw an experiment together in just a couple of days and try it." Caren Potter is a freelance writer based in Trinidad, Calif.

Icons Simplify Programming Of Data-Acquisition Software

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