Electronic Design

PC-Based Instruments Reshape The Test Landscape

All types of PCs and traditional instruments take on more of each others' functions to benefit the end-user engineer.

Thanks to advances in microprocessor computing power, a bumper crop of test and measurement (T&M) hardware and software products that use the PC as the host computer is at the ready for engineers. Not to be outdone, manufacturers of traditional benchtop instruments are trying to keep pace. They're harnessing the computational capabilities of the latest microprocessors by embedding them within their products and by simplifying the instrument's interface task to PCs via computer buses.

But flexibility isn't the sole driver of PC-centric T&M product growth. Economics is an overwhelming force, too. Why spend $20,000 to $30,000 for a dedicated piece of test equipment when a $1000 PC can do nearly the same job after adding widely available specific plug-in cards for just a few hundred dollars more?

Test-equipment makers can logically argue that for certain advanced-technology designs—high-speed communication ICs, very complex ICs, and sophisticated DSPs, for example—there's no substitute for a sophisticated piece of test equipment, particularly during a new product's development phase. In fact, many savvy engineers may still be comfortable with their own integral oscilloscopes, spectrum analyzers, frequency sources, and digital multimeters.

Another camp within the traditional T&M industry actually advocates separating instruments from PCs by making the instruments closed systems. This saves the cost of product support, which provides no payback. Agilent Technologies' Infinium line of oscilloscopes, for instance, is designed to run on software expressly written for oscilloscope measurements, not on software of the user's choice.

The lines of distinction between traditional instruments and PC-based instruments often blur. A traditional instrument with a powerful built-in PC can rightly be called "PC-based," as can a PC with built-in T&M functional cards and software. A growing trend has resulted, with both camps joining forces, at least for now, and end users reaping the best of both worlds.

Instruments with PCs inside them aren't necessarily new. Some of the earliest logic analyzers incorporated 8-bit CPUs. Instruments continue to exploit CPU power by including the latest microprocessors, the very devices that are also powering PCs. That fact hasn't been lost on manufacturers of PC-centric T&M hardware and software modules. For over a decade, they've been using the PC on an increasing basis as a platform for T&M functions. National Instruments is spearheading this effort with a broad range of software and hardware products, and so far no challengers exist.

According to Eric Starkloff, platform manager for PXI and Modular Instruments at National Instruments, "On the surface, the approach to T&M being used by those who make PC-centric products like us, and those who make traditional box-type instruments like Agilent (formerly Hewlett-Packard) and Tektronix, may look similar, but they're really two different approaches with distinct differences. You can't upgrade your instrument in the field as quickly as your PC that's being used for T&M functions. An instrument has a typical lifetime of five to 20 years, whereas a PC has a lifetime of 1.5 to two years. Clearly, the PC part of an instrument will deteriorate in performance very rapidly over time compared to the average norm, while PC-centric products will stay in step with advancing PC computational capabilities."

Starkloff adds that "software designed for 20-GHz processors, which we can expect five years from now, is not going to run on processors embedded within a traditional T&M instrument that's five years old."

Traditional T&M equipment makers and PC-centric hardware and software suppliers agree that the application determines the best approach to use. They see the need for a tighter integration of design tools and for application-specific analysis capability. According to National Instruments, research has shown that an engineer rarely uses a single instrument, with an average of five instruments. So coming up with a flexible multimeasurement system would greatly benefit engineers, and few can argue that the PC as a T&M analysis platform is a very powerful tool for this purpose.

COLLABORATION IS KEY
Manufacturers of traditional T&M instruments and those of PC-centric products are finding that working together is better for both, because they're targeting the same end user. Some PC-centric product makers are also joining forces with PC manufacturers, widening the range of T&M capabilities for engineers.

Last year, National Instruments and Tektronix formed a cooperative effort to maximize a design engineer's productivity by delivering National Instruments' LabView software pre-installed on Tektronix's oscilloscopes with Windows platforms. Tektronix also strengthened its foothold into the PC-centric market with the acquisition of Gage Applied Inc., a leader in advanced board-level T&M products for PC platforms.

Other major T&M suppliers have also established working relationships with National Instruments, including Agilent Technologies, Fluke Corp., LeCroy Corp., and Keithley Instruments Inc. In addition, National Instruments announced a partnership this year with Dell Computers. Under the agreement, Dell will preconfigure its PCs with National Instruments' hardware and software products.

National Instruments has also been busy establishing relationships with leading automatic test-equipment (ATE) vendors. It's working closely with large ATE companies like Teradyne/GenRad, Agilent Technologies, Tektronix, and Credence Systems Corp. to advance the functionality of these companies' ATE system offerings.

THE VIRTUAL INSTRUMENTATION CONCEPT
Some 15 years ago, the advent of National Instruments' flagship LabView graphical development environment started the widespread adoption of the virtual instrumentation concept. With LabView's latest version, 6.1, engineers can rapidly create measurement, control, and automation applications using intuitive on-screen graphical aids (Fig. 1). LabView continues to break new ground with such innovations as instant Web-based control, easy data sharing using extend-markup-language (XML) technology, and communications with wireless devices.

LabView has a real-time version and boasts the most software drivers across instrument vendors. Numerous companies have used the environment to significantly reduce the cost of specific testing tasks. In one case, Visteon Corp. used a real-time version of LabView for automotive electromagnetic-compatibility (EMC) testing and cut its testing costs by nearly tenfold.

"Visteon came here and demonstrated this concept to us," says National Instruments' Starkloff. "They had LabView running on a laptop on a PXI chassis and a network connection through Ethernet through their trunk. The chassis acts as if it's a car's cruise-control system and the signals coming out of it are controlling different car attributes like braking and acceleration. You can actually get in the car and work up a new algorithm in LabView for the cruise-control system, download it, and test it immediately, for real-time feedback."

He adds that National Instruments' "ultimate vision is to have an algorithm automatically downloaded into a piece of hardware like an FPGA or an ASIC and create the hardware from the same LabView program."

Engineers need not be software experts to use virtual instrumentation. They can use interchangeable virtual instrument (IVI) drivers, available from PC-centric software manufacturers and traditional instrument companies. Built on the VXI Plug&Play framework, IVI drivers circumvent low-level programming details through intuitive function calls like "Configure Measurement" or "Read Waveform," but at the expense of slower data rates.

THE PXI FACTOR
One key development that has spurred on virtual instrumentation is the PXI standard from the PXI Systems Alliance (Fig. 2). Based on the CompactPCI bus, National Instruments introduced it in 1997. PXI is intended to be midway in complexity and cost between PC-based systems using GPIB and VXI systems (see "A History Of Instrument Interconnect Standards," p. 56).

A great deal of available software runs on the plug-and-play Windows-based PXI system, such as LabView, Lab Windows/CVI, Visual Basic, Visual C/C++, and Borland Turbo C. The advantages of PXI include being able to standardize on card cages and cards and making system configuration easier and more flexible. It also costs less than other approaches like the VXI specification, which supports the VMEbus (although that's only so for midrange channel counts).

But it has drawbacks too, such as limited space inside the card-cage enclosure, limited density for switch cards, and some power limitations. Yet this past March, the PXI Systems Alliance released new PXI specifications that enhance the standard's power requirements. As a result, designers can add more functionality. Moreover, there are provisions for a dual-stack 3U architecture, which enables a 6U chassis to support a greater number of instruments. Geographic addressing was also added for improved slot and hardware identification, and the hardware description framework was enhanced to boost PXI resource management for the configuration software.

AN UNSTOPPABLE TREND
The wide availability of application-oriented software packages like LabView and the more powerful PC platforms appearing every couple of years has made virtual instrumentation irresistible, both on economic and performance grounds. An entire industry making high-performance hardware plug-in cards for data acquisition and control, including National Instruments itself, has emerged with products that meet just about any T&M need (see "Parade of PC-Centric Hardware Products," p. 57). Plug-in card digitizer products using the latest IC technologies like silicon germanium (SiGe) are now available with sampling rates in the range of gigasamples per second (Fig. 3).

PCs are becoming smaller and more powerful, from the desktop, to the laptop, to the notebook, to the palmtop, and next to the tablet format. These products will undoubtedly have a greater amount of hardware and software T&M functionality embedded in them, which will lead to even newer applications in consumer electronics, automotive, industrial, and biomedical applications.

"We've already announced LabView on the chip. We released a pioneer version of it last August called LabView FPGA," says Starkloff. "It allows engineers to create the VHDL code and burn it into an FPGA. That's the ultimate example of how we're deploying these same PC-type technologies down into different sorts of platforms, to allow designers to perform different analysis and control functions at hardware speeds, which is remarkable."

As long as powerful yet low-cost PC platforms continue to become available within shorter life cycles, this trend won't end. This is a case of a powerful PC-centric product industry keeping the pressure on well-established traditional instrument manufacturers to keep honing their product offerings.

So far, both industries have made inroads into satisfying the end user, but the future remains hazy. Some predict they will eventually merge, while others believe one of them may have to ultimately give way. Which outcome will prevail is still anyone's guess.

Need More Information?
Acqiris USA
(845) 782-6544
www.acqiris.com

Advanced Linear Devices
(408) 747-1155
www.aldinc.com

Agilent Technologies
(877) 424-4536; (650) 752-5000
www.agilent.com

Credence Systems Corp.
(510) 657-7400
www.credence.com

Data Translation
(508) 481-3700
www.datatranslation.com

Dell Computer Corp.
(800) 999-3355
www.dell.com

Fluke Corp.
(800) 443-5853; (425) 347-6100
www.fluke.com

Force Computers
(510) 624-8274
www.forcecomputers.com

Gage Applied Inc.
(800) 567-4243
www.gage-applied.com

GenRad
(see Teradyne Inc.)

IOtech Inc.
(888) 714-3272; (440) 439-4091
www.iotech.com

Ixthos
(see Force Computers)

Keithley Instruments Inc.
(800) 552-1115 (U.S.);
(440) 248-0400
www.keithley.com

LeCroy Corp.
(800) 553-2769
www.lecroy.com

Measurement Computing Corp.
(508) 946-5100
www.computerboards.com

National Instruments
(800) 258-7022
www.ni.com

PXI Systems Alliance
(619) 297-1213
www.pxisa.org

Sealevel Systems Inc.
(864) 843-4343
www.sealevel.com

Tektronix Inc.
(800) 835-9433
www.tektronix.com

Teradyne Inc.
(617) 482-2700
www.teradyne.com

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