Emulation extends the life of ATE systems

Most companies know the production of one product won't last long—many products are manufactured for less than a year before the next generation hits production. In this environment, test engineers must design test systems that are flexible enough to handle an ever-changing product lineup.

Aerospace and defense companies have a different problem. Many aerospace and defense systems remain in service for 20 years or more. The problem for test engineers in this world is to ensure that the ATE that supports these systems also remains in service.

One obstacle to keeping older ATE systems working is the age of the computers that run the systems. Many of these computers are 10 to 20 years old, and finding replacement parts is difficult at best. While you can find companies that specialize in selling replacement parts, what you're usually purchasing are parts scavenged from computers taken out of service, so you can't depend on the replacement parts to last very long.

Older computer systems also use obsolete storage devices and media. According to David Dunn, northeast regional manager for Arraid (Phoenix, AZ; www.arraid.com), "The disk drives and tape drives that came with these computers were never expected to last this long. These devices have the most moving parts and they are the items hardest to find parts for."

Even if you can find these storage devices, maintaining them can be problematic. They require regular adjustment and calibration, and finding personnel with the expertise needed to keep them running can be challenging. Dunn expects this problem to get even worse as years pass, and these skilled people retire.

It is also difficult to find the disk packs or floppy disks that older storage devices use. In 2002, for example, the last remaining manufacturer of 1/2-in. magnetic tape discontinued production.

Since computers and storage devices are so cheap these days, a natural question is, "Why not just replace the darn things?" The answer is that hardware is only part of the ATE equation.

ATE systems contain both hardware and software, and most older ATE systems used computers that were not PC compatible, such as Hewlett-Packard minicomputers. Replacing these dinosaurs with more powerful PC hardware is just not possible without rewriting the software.

The cost of rewriting the software is just too high. Estimates range as high as $1 million. If the system is near the end of its usable life, rewriting the code obviously makes no sense. And the ATE system may have to be re-certified if the design is significantly modified.

Perhaps the best option for addressing the problem of aging computers and storage devices is to replace them with new units that emulate the older systems. Several companies make units that use new hard disk drives but that appear to the ATE system controller as though they were the older drives. They are plug-compatible, too, meaning that they use the same connectors as the drives they replace. You should be able to simply unplug the old drive and plug in the new one.

Two companies manufacture systems that emulate HP hard disk drives, which are popular in older ATE. For more information on these manufacturers, see the facing page.

While obsolete computers and storage devices are the biggest problems facing test engineers who must keep older test systems alive, the test instruments can pose problems, too. Instruments can fail, and if they're not repairable or if the cost of repair is too great, then the test engineer must find a suitable replacement. Often, the manufacturer has discontinued that instrument, so a new replacement is not readily available.

According to Mark W. Morris, VP of sales and marketing for ZTEC Instruments (Albuquerque, NM; www.ztec-inc.com), the problems that test engineers face when replacing instruments are much the same as when they need to replace computer systems. You can't simply replace an aging instrument module with one that has similar or better analog specifications.

"When an instrument becomes obsolete," Morris says, "you are not looking at a $15,000 problem, but at a $500,000 problem." The instrument hardware may only cost $15,000, but modifying and integrating the software that controls that instrument may cost as much as $500,000, especially when you consider the cost of software validation.

Fortunately, several vendors make instrument modules that are plug-compatible replacements for some of the instrument modules that the major manufacturers have made obsolete. As shown on the facing page, you can now buy modules that emulate pulse generators and DSO modules from HP/Agilent, Wavetek, and Tektronix.

If you are responsible for keeping an older test system alive, plan for the day when one or more of the components will fail. One way to prepare for that day is to build up an inventory of replacement parts. Another, less expensive, approach is to keep handy a list of vendors that can supply the plug-compatible parts you'll need. You'll find three such vendors in the chart on the next page.