PCs change quickly; test setups don’t

E-mail

Personal computers have changed drastically since engineers started using them to control instruments. Ten years ago, a typical PC had two serial ports and a parallel port. Today, you may get one serial and no parallel ports. Desktop PCs used to have ISA slots. Now, PCI slots are giving way to PCI Express slots.

Today’s PCs have as many as 10 USB ports and an Ethernet port. If you need a legacy port, you must buy an adapter or use an industrial computer. Of course, test engineers have been adding IEEE 488 ports to their PCs for years. Many test engineers use adapters for older buses, because change comes far more slowly to the engineering community, where test systems may operate for many years.

USB flash drives have become the new floppy disks. Courtesy of SanDisk.

USB gained acceptance as an instrumentation control bus once USB 2.0 ports became available. “For instrumentation, USB 2.0 was essentially USB 1.0,” commented Chuck Cimino, marketing director at Keithley Instruments.

USB flash drives have replaced floppy-disk drives as the easiest way to transfer data between instruments and computers. With capacities up to 8 Gbytes (photo), USB flash drives can handle loads of data, and just about every engineer now carries or wears one.

Ethernet is the other major change in communication ports, and it has created a bit of a gap between generations of engineers. “The new engineers coming out of school understand networking far better than they understand GPIB and SCPI,” said Brian Fetz, program manager at Agilent Technologies. “The industry is already starting to change, and the change will accelerate.”

USB and Ethernet continue to evolve. All new PCs have 100-Mbps Ethernet ports—that’s plenty of speed for test applications—and some network-interface cards offer 1-Gbps speeds. USB 2.0, currently at 480 Mbps, may evolve into USB 3.0 with speeds up to 4.8 Gbps running over an optical link. USB 3.0 was demonstrated at the 2007 Intel Developer Forum, although it will be several years before that port is available on everyday PCs.

In most test applications, current PC bus speeds are adequate. Many instruments perform data reduction for you, so the PC’s processor often doesn’t have to process data. For example, many instruments can perform signal processing by using techniques such as fast Fourier transforms (FFTs). Board-based instruments may contain processors or field-programmable gate arrays (FPGAs) that decimate data down to just the information you need.