Hand-held computers and PC cards make mobile data acquisition in the factory or field possible -- but be aware of the trade-offs and pitfalls
Claire Tristram
Niels Anderson regularly drives into the heart of the Mojave Desert over unpaved, washboarded tracks that barely count as roads. He travels to the Reaction Research Society rocket-launch site, where he tests rocket engines in temperatures that frequently top 120 degrees F.
Until only a few months ago, Anderson carefully loaded his car with bulky, expensive, and hard-to-transport test equipment before he drove to the site. He just hoped the equipment would survive the trip. But now, thanks to the development of
ruggedized mobile computers
and PC cards for data acquisition, he merely throws his laptop in the backseat
before he heads off.
"I tried everything else, but I still ended up with huge, heavy, problematic equipment that wasn't meant to go over these kinds of roads," says Anderson. "The boards would get unseated on the way, or something would fail when I got there because of the heat. Now I slide a PC card into my notebook. I take a little black bag with me that's smaller than my briefcase. The convenience is incomparable." Still, not just any notebook will survive the demands of field and factory, not every OS provides the no-fail stability required for data acquisition, and matching specialized sensors with the right PC cards can be a job in itself.
All the trends that are revolutionizing desktop computing -- smaller form factors, cheaper components, faster processing, and sturdier designs -- are also making data collection in factory or field environments much easier than ever before. But there are still plenty of chances to stumble when you're putting together a mobile data acquisition plan for yo
ur business.
There are, for instance, "standards" that are less than standard and inflated vendor claims on just how rugged their systems are. You should also watch out for the costs of specialized software development and for peripherals that are available from only one vendor. In fact, for most data acquisition needs, PC-based mobile solutions should still be marked with a big sign that says, "Warning -- Still Under Construction."
The Mobile Revolution
Data acquisition systems -- ways to measure pressure, temperature, or vibration in factory or field settings, or ways to keep track of the movement of inventory or physical assets -- are as old as the industrial revolution. Many companies are still getting by with the same old technologies -- programmable logic controllers embedded into on-site equipment or inspectors armed with a clipboard. Getting factory or field managers to move from embedded, proprietary systems that have worked fine for years to mobile, PC-based so
lutions that are just coming into their own is sometimes a tough sale.
But once managers get used to the idea of mobile data acquisition systems, the advantages of moving are many. Intel-based hardware running DOS or Windows allows for cheaper software development than embedded, proprietary systems. Hand-held or laptop devices are far more flexible, lighter in weight, and easier to move than alternatives, allowing for less equipment redundancy. GUIs boost the ability of field workers to interpret data on-site and to make corrections as needed.
The ability to aggregate data across a shop floor or from multiple geographic locations, sometimes by wireless connections, lets companies improve productivity and lower their costs. "We're hearing from our clients that mobile data collection has improved productivity by as much as 25 percent and has reduced costs by about 25 percent, as well," says Jeff Lohrmann, analyst for the San Francisco office of the research firm World Market Strategies.
Sta
ndard PC technology just doesn't cut it in the mobile data acquisition field, however. General-use laptop designs are not up to the rigors of a shop floor or field environment. Latest-issue CPUs and OSes are also problematic. While ordinary business users can get by with just rebooting when their laptops freeze, that won't wash in a data acquisition system, where the loss of even a few minutes' worth of data can be critical and costly.
Most mobile data acquisition systems, therefore, are based on older CPUs and OSes that are more stable . They use hardware engineered to withstand far more abuse than any general-use laptop and are loaded with applications that are fail-safe.
Desperately Seeking Input
The first link in any mobile data acquisition system is between what's being measured -- be it the number of tablecloths in a storage room or the temperature at the center of a volcano -- and a data acquisition device that can read and interpret the measurement.
Data c
ollection for inventory and asset management technology gives you a range of well-understood choices. Physical assets can be tracked with bar code inputs, RF identification tags, keyboard inputs, or pen-based inputs. The choice you make will depend on how you balance your need for accuracy with your need for flexible input systems.
Bar code and RF identification are close to fail-safe in accuracy, but they require specialized detectors; keyboards and pen-based systems are far more flexible but are also more prone to error. Although none of these technologies offer the ideal solution, each one is appropriate for given applications. All of them have well-understood standards that allow you to mix and match vendor products with a fair degree of ease.
This is not so with the measurement of physical systems, such as temperature, pressure, or vibration, where older sensor technologies such as thermocouples are being wedded to PC acquisition devices, and standards are still far in the future. "Except f
or basic temperature, pressure, and strain sensors, there are massive compatibility issues," says Kevin Sharp, president of the consulting firm Accurate Information. "There are 2200 or more sensor manufacturers, and who knows how many different signal-conditioning circuits. To get a standard output, one that a normal PC card will recognize every time, is still a large, unresolved problem."
Thus, if you plan to use a mobile data acquisition system for collecting physical data, you can't use a standard solution yet. Instead, you will need to work through a reseller or do a lot of homework to find out which sensors work with which boards. "You don't go down to Egghead and buy these solutions," says Sharp. "You'll end up working with a reseller that specializes in a particular vertical market. Before you buy, get a demonstration that proves to you it will work."
The Right Hardware Platform
Once you choose the input technology that's appropriate for your data acquisition appl
ication, you then need to find the mobile computing device that will support that input technology. It must be able to withstand the rigors of your environment.
"If you're dealing with multiple sensor input, by the time you're set up, you're not mobile anymore anyway," notes Sharp. "You'll have 18 to 20 sensors hard-wired to your data acquisition device. In that kind of application, you only need to have a system that's tough enough to survive the rigors of transport while
off
. It's a completely different problem if you need a computer to survive the rigors of a workday while
operating
."
If you're running a typical notebook system and drop it, for example, the disk will tend to twist directly into the read head and destroy your data. Vendors have developed solutions that let you drop your computer with impunity (see the sidebar "Buying Rugged Hand-Held Computers"). However, because increased ruggedness often means compromising on weight, flexibility, or cost, be sure you know y
our needs before you select your hardware.
Some systems, for example, come with shockproof cases, but those systems are so specialized that you need to send them back to the manufacturer if you want to add a board. Other vendors might require that you buy all your peripherals from the same vendor to keep the warranty protection active.
Incredible Shrinking Data Acquisition Cards
Much of the excitement surrounding mobile data acquisition relates to the introduction of PC cards based on PC Card Type II standards, which make the form factor for collecting data smaller than ever. "We're extremely excited about PC Card," says Ed McConnell, marketing manager for
National Instruments
. "Our company has always leveraged off of the PC, where customers can create their own industrial monitoring devices with our tools. But with PC cards, engineers can walk up to a unit anywhere, hook up a couple of probes, and immediately make their tests."
Like everythin
g else in mobile data acquisition, however, the use of PC cards demands a trade-off. Even the most expensive cards top out at a sampling rate of 100 kHz, while a plug-in board can easily provide sampling rates of 1 MHz. The PC Card standard in current use also has yet to provide DMA, and CardBus, PC Card's 32-bit standard, is still part of an unscheduled future plan.
Then there are more mundane issues -- like power. "Some PC cards require more power than portables put out," notes Tim Schmidt, principal for Orlando-based Encore Consulting Group and a specialist in hand-held-computing technologies. "You may have a system that's designed for 7 hours continual use and suddenly find you're getting only half an hour."
Although PC cards themselves are hard to break, add them to a rugged computer and what you get is less rugged than what you had before. "Take a look at the PC cards you're buying," says Schmidt. "Some need antennas or other devices to operate. What happens if these get dropped? Keep in m
ind, also, that you've got 64 little pins on each card. What happens if you need to use three cards in two slots, and you're constantly inserting and removing these cards? Those pins can bend off."
External PC Card slots also add more points of failure to a rugged computer. This requires designers to add waterproof connections (and higher costs) to their mobile devices.
Solutions to these problems are being devised. CardBus will give PC Card the same performance levels as Peripheral Component Interconnect (PCI). The move from a 5.5-V to a 3.3-V standard will ease the power drain (as will the use of lithium-ion batteries.) Until these technologies are standard issue on the mobile computer you choose, however, you'll need to make sure that the current PC Card bus can handle your performance requirements before you commit to a mobile data acquisition solution. And you'll need a backup power supply for even the most simple data collection applications.
You can move acquired data off the hand-
held unit in a number of ways. For example, Norand offers 10Base-T connectivity directly to the network. Wireless units can make wireless network connections, also. One important consideration is the ability to efficiently handle multiple simultaneous downloads from different users (e.g., reporting delivery information). There are
many software solutions
to the data transfer problem. They range from proprietary software to off-the-shelf software to Oracle or Sybase applications.
Keep Software Simple
Some design engineers looking for mobile data acquisition solutions may wonder why they should spend extra money on ruggedized hardware, only to operate that hardware with DOS or Windows 3.1, OSes not known for their crashproof qualities. But there are ways to design your system software so that you get the advantages of easy-to-use development environments, while minimizing the risk.
"To be honest, we don't have too much of a problem with our systems bei
ng DOS- or Windows-based," says Mike Colwell, director of
product marketing at Norand
, a leading manufacturer of hand-held devices. "Most crashes are associated with task switching, and our systems aren't being used in a multiapplication environment. All we're doing is using basic Windows to run a specific data collection application. We find Windows to be quite good in our environment, even though rule number 1 for us is, `don't lose the data.'" Many people choose Windows simply for the ease of using off-the-shelf applications and already-written device drivers.
"In a specific application, it [DOS] can be a stable environment," concurs Schmidt. "The key is to keep users as focused as possible in the specific application they need to do their job. Any time you let users go off and use other pieces of the OS, even to play solitaire, you're creating a lot more support calls."
Choosing DOS or Windows as your OS can help deflate the costs of developing your application, the most
expensive factor in putting a data acquisition system in place. "With desktop systems, there's not much custom development," says Sharp. "But with data acquisition running on remote devices, custom development of software dominates the equation. Remote analysis of geological information isn't going to be available in a $200 software package. You'll need to write it yourself or have someone else write it. Your costs are strongly affected by the availability of standard development tools."
Do You Need It?
Despite plenty of progress, designing a mobile data acquisition system still requires you to test input devices for compatibility, to work with hardware that may spend more time in the shop than in the field, to put up with inadequate power, and to write custom software. In other words, the state of the art in mobile data acquisition systems still leaves a lot to be desired, so much so that some analysts and resellers are advising their clients to forget it and move straight to
emerging wireless technologies to solve the same problems.
"It's not a good business case to go out on-site if you can perform the same function through an automatic process," says Steve Gurley, national director for wireless data at Electronic Data Systems. "In general terms, data collection will be much more cost-effective if done on an automated basis instead of physical inspection. There are wireless alternatives for most applications that lower costs and improve efficiency. I see the trend away from people having to go out on-site as much as possible."
Others dismiss this wireless argument as more infohighway hype and insist that, although there are still problems with hand-held mobile data acquisition systems, none of these problems are insurmountable.
"Why should you run your data acquisition systems on PCs? Because everyone decided that was what a computer looks like," says Ben Bailey,
cofounder of Computer Boards
, which makes PC-based data acquisition
boards and PC cards. "Other solutions, including wireless solutions, get expensive very quickly."
The reality of mobile data acquisition in the next several years is probably evolving to a hybrid system, where companies gain the advantages of on-site mobile data acquisition and use hand-held computers as wireless terminals to relay information to central locations. All vendors of hand-held computers are busy forging deals with wireless LAN and WAN providers.
Their sales pitches to you will no doubt stress the advantages of spread-spectrum technology over infrared, or Cellular Digital Packet Data (CDPD) over cellular circuit-switched data (CCSD) -- or they will tell you the opposite, depending on the alliances they have forged. With such a range of partial answers available to you, it's easy to forget which problem it is you're trying to solve. Don't do that.
"In data collection, stay focused on the process that you're trying to automate," says Sharp. "Don't specify the platform. Specify t
he result. Then look at strategies to accomplish that result. Only then should you decide what technology will give you the results you need."
WHERE TO FIND
Accurate
Information, Inc.
Tucson, AZ
(520) 326-2244
Badger Computers
Tampa, FL
(800) 322-3437
Computer Boards, Inc.
Mansfield, MA
(508) 261-1123
fax: (508) 261-1094
Electronic Data Systems, Inc.
Plano, TX
(214) 604-6000
Encore Consulting Group, Inc.
Orlando, FL
(407) 291-0194
Husky Computers, Inc.
Clearwater, FL
(813) 530-4141
Kalidor
Upland, CA
(800) 252-5436
Microslate
Brossard, Quebec, Canada
(514) 444-8680
National Instruments Corp.
Austin, TX
(800) 433-3488
(512) 794-0100
Norand Corp.
Cedar Rapids, Iowa
(800) 553-5971
Symbol Technologies, Inc.
Bohemia, NY
(800) 927-9626
Telxon Corp.
Akron, OH
(800) 800-8008
Tusk, Inc.
Palm Beach
Gardens, FL
(800) 275-8875
World Market Strategies, Ltd.
San Francisco, CA
(415) 252-8008
photo_link (39 Kbytes)
Badger's GT-110 weighs 30 ounces, uses several battery types, has a PC Card Type I slot, is PC-compatible, and satisfies military specifications for temperature, rain, vibration, and other challenging environments.
photo_link (32 Kbytes)
Computer Boards has a full line of PC cards for data acquisition, including a 16-channel analog-to-digital interface with software-selectable signal gains.
photo_link (27 Kbytes)
Norand's rugged Pen*Key 6600 wireless mobile computer is powerful enough to support advanced graphics displays, runs DOS/Windows, and has two PC Card Type II slots
and one Type III slot.
photo_link (29 Kbytes)
PC cards, such as the DaqCard line from National Instruments, provide data acquisition options in form factors to fit notebook slots. The DaqCard line has a power-down mode to draw less power.
screen_link (48 Kbytes)
Measure for Windows, from National Instruments, is a spreadsheet add-in for direct data acquisition and serial control from Excel. Using Measure, scientists and engineers can take single-point, low-speed readings for temperature and pressure or process monitoring applications using a PC card.
claire@netcom.com
.
Keep The Data Moving
