PCMCIA Cards

Acquisition Products Author: Caren D. Potter For nearly a decade, configuring a personal computer for data collection meant opening the cover and plugging a data-acquisition board into an empty expansion slot. But if scientists take to notebook PCs the way the business community has, this may eventually seem as old-fashioned as getting up to change the channel on the TV. Notebook PCs have no expansion slots. To be used for data collection, they must have some other way to get the data-acquisition functions normally provided by add-in boards. (Add-in data-acquisition boards are printed circuit boards that make analog signals from physical events understandable to the digitally minded computer. They provide analog-to-digital signal conversion and often some memory and signal-filtering functions, as well.) Vendors have come up with two main options for adding data-acquisition capabilities to notebook PCs: "cards" that fit into the notebook's PCMCIA (Personal Computer Memory Card International Association) slot, and modules that sit alongside the notebook and connect to its parallel port. Mansfield, Mass.-based ComputerBoards Inc.'s PCM-DAS 16/16 is a good example of a PCMCIA card for data acquisition; the DAQPad-1200 from Austin, Texas-based National Instruments is a parallel port product. A third option, which not as many data-acquisition equipment vendors offer, is a way to connect to the notebook PC through its docking port. By working around the notebook PC's lack of expansion slots, data-acquisition equipment vendors have done scientists several favors. First, they have greatly simplified data acquisition in the field. Now instead of lugging around a bulky PC with its separate monitor and keyboard, all that's needed is the conveniently compact notebook version. Second, by making data-acquisition products that don't require an expansion slot, they've simplified system configuration--for more than just notebook computers. To some extent, these new data-acquisition cards and modules can also be used with bigger PCs. For example, data-acquisition modules that plug into a notebook PC's parallel port can just as easily be plugged into the parallel port of a desktop computer. Data-acquisition cards for the PCMCIA slot are a bit different, since desktop machines don't normally come with a PCMCIA slot, but several companies have already come out with adapters that let desktop PCs accept PCMCIA cards. Branford, Conn.-based CyberResearch Inc.'s CardDock, for example, fits into a desktop PC's expansion slot and accepts PCMCIA cards. For scientists, this hardware mix-and-match is making it easier to move data-collection hardware from one computer to another. It's simply a matter of popping out a card or pulling out a plug and installing the equipment somewhere else. FIELD RESEARCH OF DREAMS: Left, National Instruments' new, smaller-mount veriosn of the PC-LMP-16, a low-power, multifunctional I/O board. Right, IOtech's Wavebook/512, a portable data-acquisition add-on. A third benefit is the ability to collect better data. "The problem with collecting data at the site and then taking it somewhere for analysis is that the sample can change over time," says Don Nuzzio, an adjunct associate professor at the University of Delaware's College of Marine Science. "Bacteria might eat up all the available oxygen, or layers of sediment might mix. Portable systems let you acquire and analyze your data closer to real time, so you get better data." On the market now is the first generation of data-acquisition equipment for portable computers. Like any first-generation products, these have some bugs yet, but they're not so new to the market that scientists have to write their own data-acquisition routines for them. Popular data-acquisition programs such as National Instruments' LabVIEW; LabTech Notebook from Laboratory Technologies Corp. in Wilmington, Mass.; and Snap-Master from HEM Data Corp. of Southfield, Mich., can be used in conjunction with many of these products. These vendors of data-acquisition software constantly add support for additional hardware (printers, circuit boards, and so on) to their packages. Data-acquisition products for portable computers are just more pieces of hardware to support--no big deal, it seems, to them. Still unclear at this point is whether the PCMCIA and parallel port approaches to portable data acquisition will continue to coexist, or whether one will eventually dominate the market while the other dies out. Both approaches have benefits and limitations. PCMCIA is a mouthful of an acronym, but it's part of the jargon of the notebook computer. Not all, but many, notebook PCs have PCMCIA slots, which are subdivided into Type I, Type II, and Type III form factors. A Type I slot accepts PCMCIA cards that are 3.3 mm thick. Cards for Type II slots are 5 mm thick, while those for Type III slots are 10.5 mm (that's still less than 7/16 inch). Whatever the thickness, these devices are small--about the dimensions of a credit card. Specifications for PCMCIA components were established by the Sunnyvale, Calif.-based Personal Computer Memory Card International Association, formed in 1989 by leading manufacturers of computer components. As the association name implies, PCMCIA was initially intended as a standard for removable memory cards, but it soon expanded to include fax, modems, LAN (local-area network) interfaces, and as of last year, data-acquisition interfaces. Most PCMCIA data acquisition cards are the Type II form factor. Because these cards are so small, it is difficult for manufacturers to fit all the necessary components onto them. Also, height restrictions make it impossible for manufacturers to use what is called "through-hole" components such as the integrated circuits and resistors visible on a typical printed circuit board. PCMCIA cards must use surface mount technology in which the components are soldered directly to the board. These factors makes PCMCIA cards more expensive than standard data-acquisition boards. PCMCIA cards run in the neighborhood of $500 to $700, while many add-in boards can be had for half that. To connect PCMCIA cards to the real-world data source, some extra hardware is needed. That includes a cable that plugs into the PCMCIA card and connects it to another device called a terminal block or pod, to which various sensors are connected. "PCMCIA cards are so small, you can't use a screwdriver and hook wires directly to them," explains Ed McConnell, product manager for data acquisition at National Instruments. "The terminal block gives you the space to connect the wires." Terminal block and cable add about another $50 to the price of the PCMCIA-based data-acquisition system. One of the limitations of PCMCIA cards is that they derive their power from the notebook computer. Manufacturers of PCMCIA data-acquisition cards strive to design cards that consume as little power as possible, but even so, the notebook's operating time on the battery is reduced when one of these cards is in use. ComputerBoards Inc. claims to have a power miser of a PCMCIA card that consumes half the power needed by other PCMCIA data-acquisition cards with comparable features. In a test of power consumption conducted by ComputerBoards, a notebook PC alone lasted approximately four hours after a full charge. Adding the company's data-acquisition card reduced operating time to 3.692 hours, but a competitor's board reportedly dropped battery life to 3.33 hours. That's nearly 20 additional minutes of operation from the ComputerBoards product, possibly enough to make a difference to some experiments, the company points out. Some aspects of PCMCIA card operation--data transfer rate, for example--are limited by the host PC's input/output capability. According to Paul Schreier, editor of Rye, N.H.-based Personal Engineering and Instrumentation News, a key part of putting together a notebook PC-based data-acquisition system is finding a suitable computer. In the July 1995 issue (12[7]:23-34), Schreier evaluated six different PCMCIA data-acquisition cards: Sunnyvale, Calif.-based Advantech Inc.'s DACpad 71B; ComputerBoards Inc.'s PCMDAS16S/12; Marlboro, Mass.-based Data Translation Inc.'s PC Card EZ; Taunton, Mass.-based Keithley Metrabyte Inc.'s DASCard 1003; National Instruments' DAQCard-1200; and Akron, Ohio-based Quatech Corp.'s DAQP-12. He reported that not every PCMCIA card works equally well in every notebook computer. "Despite standardization efforts, the [card's support] software doesn't always function identically," he wrote. "Thus, many vendors of data-acq products maintain lists of machines on which they've tested their cards. That's not to say that the cards won't work in others, but a review of those lists is a good place to start when purchasing a system." Schreier's experiences with the different boards brought up another issue that potential users of these systems should consider. Notebook computers usually come equipped with a power-management function that shuts down the computer's central processing unit and peripherals if it senses that the system has been inactive for a certain length of time. This could potentially halt data logging if there are long delays between samples. This is not a problem, however, as long as the user remembers to program the length of the inactive period so that it is slightly longer than the time between samples. In terms of data-acquisition capabilities, how do PCMCIA cards compare with their larger cousins, the add-in boards? "Because of their small size, these cards have limited functionality," says Allen Tracht, principal engineer at IOtech Inc. of Cleveland. "Typically they have eight differential or 16 single-ended analog input channels and a few channels of digital I/O." Some add-in boards, in comparison, can support as many as 64 analog input channels. It is possible to increase the functionality of PCMCIA cards beyond 16 input channels. Some vendors offer external data-acquisition modules that connect to the PCMCIA card via its cable to increase the number of analog inputs to as many as 256. This is a small box that sits next to the notebook PC and contains the more typical add-in data-acquisition boards. While the device offers a solution for those who need more input capability, it does begin to add to the paraphernalia that needs to be hauled around for data collection in the field. Neither the PC nor the PCMCIA card supplies power to the external expansion module, so it must get power from its own battery or power source. A parallel port is the 25-pin connection found on nearly all personal computers and printers. Lately, the parallel port architecture has evolved from the original IBM PC standard parallel port (SPP) to the enhanced parallel port (EPP) that is found on almost all the higher-end notebook PCs. "In several years, the EPP will most likely displace the SPP as the parallel port standard for both desktop and notebook PCs," says IOtech's Tracht. Data-acquisition modules that connect to the parallel port are available in versions that support both the SPP and EPP. These modules are small boxes, usually about the size of the notebook itself, that typically contain two standard-size data-acquisition boards. They sell for between $1,000 and $2,000. These units not only provide data-acquisition capabilities for portable PCs, but also--because they are compatible with any parallel port--are good for doing data acquisition on a desktop PC that has all its expansion slots filled. One drawback of using the parallel port as the data-acquisition interface is that it ties up that port, which is often the connection for the printer. Some vendors, such as IOtech and National Instruments, have configured their external data acquisition modules (the DaqBook and DAQPad-1200, respectively) with a second parallel port where users can connect their printers. This way they don't lose the ability to print while acquiring data. Parallel port-based data-acquisition modules must supply their own power, from either an AC power source or a battery pack, which may be internal or external. The battery run time of these modules is usually comparable to that of the notebook PC. Because these external data-acquisition modules are larger than PCMCIA cards, they offer more data-acquisition capability. SPP-based modules frequently accommodate as many as 256 channels of analog input, four digital inputs, and four digital outputs. EPP-based modules typically don't have more channels than that, but they transfer data faster. Some EPP modules can transfer data as fast as 3 megabytes/second, although the host computer's I/O capability effectively limits the rate to about 800 kilobytes/sec today. The fastest SPP device currently clocks in at about 150 kilobytes/second. Number of input channels appears to be the main difference between parallel port-based data acquisition and PCMCIA data-acquisition cards. Scientists who need to take 50 temperature and pH measurements simultaneously obviously need the parallel port option if using a notebook computer. But many data-acquisition applications do not require many input channels. Flemington, N.J.-based Analytical Instrument Systems Inc. (AIS) builds turnkey analytical systems primarily for analytical chemists. When portability is required, the company configures a notebook with a PCMCIA card. "We build portable spectrophotometers and potentiostats," says Nuzzio, a scientist who started AIS to sell portable data-acquisition systems to other scientists. "The fact the PCMCIA data-acquisition cards have fewer input channels is not an issue for our customers. We prefer to give them the PCMCIA option because there's less stuff to carry around. With a parallel port interface, you've got the additional module, and for our applications a lot of capability that is just wasted." Several vendors offer a portable data-acquisition system consisting of a notebook PC and an external unit resembling a traditional notebook docking station. This docking station is different, however, in that it has been specially configured to hold standard add-in data acquisition boards. Called an expansion chassis, this specially designed docking station connects easily to the notebook PC through its docking port. All it takes is turning a couple of thumb screws. IT'S IN THE CARDS: National Instruments's DAQcard-1200, DAQcard-AO-2DC, and DAQcard-ER-8 kit. Keithley Metrabyte Inc.'s system, DacPac, sells for $1,200 to $1,500. DacPac is compatible with Irvine-Calif.-based AST Research Inc. computers and Japan-based Toshiba Corp.'s T4XXX Series. New Haven, Conn.'s Cyber Research Inc.'s system, NBE Series, works only as a unit consisting of both the company's notebook PC and the expansion chassis. The combination sells for $3,500 to $5,200, depending on the display and processing speed of the notebook computer. Both vendors' products hold two full-size add-in cards. Both provide their own AC power supplies. Keithley's product also includes an internal nickel cadmium (NiCad) battery pack. Notebook computers have been called the second wave of the PC revolution. According to a survey by Dataquest, a San Jose-Calif.-based market research subsidiary of New York-based Dun and Bradstreet, sales of portable PCs may soon exceed desktop sales by as much as 5 million units per year. Scientists will probably account for a good share of those units. "It's logical that scientists will migrate from desktop to portable PCs," predicts Tracht of IOtech. "Benchtop digital voltmeters gave way to portable digital voltmeters in much the same fashion." Does this mean the demise of traditional desktop PC-based data acquisition? Some people think so. " After all, the ISA bus [the expansion slot configuration®MDNM¯ for most desktop PC data acquisition] is 10 years old--a virtual fossil in the land of weekly computer advancements," says Vincent Hebert, marketing communications manager for ComputerBoards Inc. "Customers are hungry for true plug and play. Time will tell if the ISA bus goes the way of the eight-track tape." Caren D. Potter is a freelance writer based in McKinleyville, Calif. (The Scientist, Vol:9, #16, pg.16 , August 21, 1995) (Copyright © The Scientist, Inc.) WE WELCOME YOUR OPINION. IF YOU WOULD LIKE TO COMMENT ON THIS STORY, PLEASE WRITE TO US AT EITHER ONE OF THE FOLLOWING ADDRESSES: garfield@aurora.cis.upenn.edu 71764.2561@compuserve.com The Scientist 3600 Market Street, Suite 450, Philadelphia, PA 19104 U.S.A.

PCMCIA Cards

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