Real Traditional Instruments vs. Virtual Instruments:
Having it Your Way

By Jonathan Tucker
Data Acquisition Product Marketing Manager
Keithley Instruments, Inc.

There is a school of thought today that computer-based virtual measurement systems are the best solution to solve your measurement problems. Yes, the computer has become extremely powerful, able to control measurement instrumentation, analyze data, automate industrial processes, and communicate data across networks, including the Internet.

So much is being said these days about 'virtual instruments.' Virtual instruments are computer-based measurement systems using a graphic interface that makes programming the real, traditional instruments easier for people who are not software or computer experts. The role of software is that of an enabling tool, as it controls the operations of the measurement process. But it is important to realize that traditional instruments make the demanding electrical measurement, not the software. Thus we cannot overlook the importance of the traditional instrument. They are not a thing of the past and will continue to evolve.

As the demand for smaller and low power consumer devices increase, buyers of test and measurement equipment are demanding changes in the measurement hardware they need for their emerging measurements. Test and measurement companies need to design products with form factors and functionality that their customers demand. That's why you are going to see more hybrid products in the future. For example, Keithley Instruments recently developed the SourceMeter product line after extensive customer research. This specialized hybrid instrument combines a separate current and voltage source with a precision DMM to create a 60-watt ATE system in one box. Traditional DMMs are now being redesigned by Keithley and other manufacturers to accommodate special switching cards to create very powerful data acquisition systems that are based upon traditional instrumentation architecture.

Let's look at an example application using a traditional instrument: testing of a cellular telephone. Cell phone manufacturers are requesting specialized test equipment that can power the phone, act as a battery simulator, and can also measure the low current that the phones draw from batteries. The solution is a hybrid precision readback power supply that acts like a battery simulator. This type of instrument comes in the traditional rackable or benchtop form factor due to the need to source or sink substantial levels of current and to dissipate heat. This new power supply design prevents accidental phone shutdown during test that normally can occur with standard power supplies. When the cell phone is switched from standby mode to the full power mode, the current draw on a normal power supply can change by as much as 100 percent. This results in a voltage droop where recovery time can take milliseconds, possibly shutting off the phone. But like any GPIB instrument, this new power supply can be controlled from your computer.

Traditional instrument manufacturers are hard at work developing new hybrid solutions to meet the needs for new demanding measurements. On-board microprocessors and DSP systems in the traditional instruments offer the capability to perform complex measurement algorithms without the intervention of the PC. Technology will continue to advance and make traditional instruments smaller, faster, but also more complex. The elegance of the new traditional instrument hybrids will still provide the solution for the types of measurements that customers demand.

As new, hybrid traditional instruments become more complex, the need for the virtual instrument becomes more apparent. The new, hybrid instruments require more time to learn in order to take advantage of the advanced feature sets they offer. Virtual instrumentation is designed to simplify the development of the measurement application using complex programmable measurement hardware. This is where the virtual instrument becomes invaluable. Vendors of traditional instruments now provide drivers and library tools based upon graphical programming environments and ActiveX controls to simplify the programming of the traditional instrument.

Thus the virtual instrument and real, traditional instrument will complement each other. Both are required to solve the demanding measurement problems that just cannot be accomplished with general-purpose digital measurement systems. It's not a question that's as simple as always virtual and always traditional, regardless of what manufacturers may attempt to imply.

Jonathan Tucker is the Data Acquisition Product Marketing Manager for Keithley Instruments in Cleveland, Ohio. He has been in the Test & Measurement industry for 15 years with experience in benchtop/rack and stack instrumentation, and data acquisition hardware and software. Jonathan holds a Bachelor degree in Electrical Engineering from Cleveland State University, and a Masters in Business from Kent State University. He can be reached at Keithley Instruments, 28775 Aurora Rd., Solon, OH 44139-1891. Tel: 440-498-2718.

(This article appears here by permission of the publishers of testandmeasurement.com, where it was published on November 3, 1999)