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Bucking the trend of rising costs, clever test-and-measurement designers have been successfully exploring methods of reducing costs and still providing quality performance instruments. For example, a new market for test instruments is being created by the separation of an instrument’s processing/control and measurement modules. With the accelerated performance of personal computers, it also has proven viable to create PC-driven instruments that interface through high-speed and common platform-interface technologies.

Fig. 1Until recently, there were several technological barriers to using PC-driven techniques for high-performance test-and-measurement instruments. One such restriction was the inability to rapidly transfer data through a common interface platform from a sensor to a PC. Here, speeds had to be fast enough to provide adequate fidelity. Additionally, CPU processing speeds, physical memory, and random-access memory (RAM) were not up to the speed or capacity challenge of handling professional-grade instrument data output. These factors would lead to a large bottleneck as attempts were made to handle the data from the instruments.

In addition, limitations were placed on the processing of data once it was transferred. Another challenge associated with portable platforms was providing enough power for both the test instrument and PC hardware. In the mid-2000s, a few components could use the power and data rates offered by the technology, such as those based on USB 2.0. Yet network analyzers (NAs) or spectrum analyzers (SAs) with enough bandwidth or frequency range to compete with even low-end benchtop instruments were still inconceivable.

To solve many of these limitations with current hardware would require a proprietary interface technology and a specialized workhorse of a computer, mitigating the benefits of a PC-driven computer. In 2008, the USB-IF released USB 3.0, an update to the USB standard that enabled raw data rates of 5.0 Gbps and 900 mA of simultaneous power draw. The PC world adopted USB 3.0 as the standard for the latest computers, laptops, and even several tablet computers. As for its impact on test and measurement equipment, Matt Maxwell, Tektronix’s product manager of spectrum analyzers, notes, “USB-based instruments are no longer limited in terms of performance or analysis capabilities, making them a viable option for much more demanding applications than in the past.”

The low costs and high data capabilities associated with USB have supported the emergence of a variety of different applications. Examples range from USB test instruments to high-definition/high-speed imaging cameras and industrial sensing/control. Maxwell says, “Until the advent of USB 3.0, it simply wasn’t possible to move real-time signal information to a laptop or tablet computer fast enough. With highly capable quad-core processors like the Intel Core i7—along with solid-state drives (SSDs) and fast RAM readily available at affordable price points—today’s USB 3.0-equipped PCs and tablets represent capable platforms for supporting test-and-measurement applications.”

Portable and low-power processing, memory, and storage have all advanced, thanks to the growing demand for portable computers and the Internet-of-Things (IoT) connected environment. Meanwhile, higher-performance and smaller, solid-state memories and CMOS microelectronics have reduced both their size and power draw on computers. In fact, many of the latest laptops/tablets have nearly desktop-equivalent processing capability. The portability of heavy processing has enabled convenient on-site programing, processing, and data storage for large amounts of complex sensor data.

As computers became a standby in every household and office, the number of computer accessories and peripherals also grew. The size of these markets drove computer manufacturers to settle mostly on common interfacing, which has enabled PC-driven test and measurement instruments to advance more consistently. Maxwell says, “Test-and-measurement providers are experts at designing and building the actual signal-acquisition and analysis solution. PC manufacturers are experts at designing and building computer systems, and can do so more cost-effectively than test-and-measurement providers.”

Fig. 2Take the use of commercial-off-the-shelf technology, which is increasingly being used by industrial and military organizations. With computers as well as other consumer products, modular components have decreased in cost and increased in performance at a rapid pace that proprietary technologies could not maintain. “Therefore, it makes economic sense for test-and-measurement companies to take advantage of the advances enabled by the PC industry,” says Maxwell. “By removing the requirement to build a front-end PC, test-and-measurement companies can offer instrumentation at lower price points and bring new products to market faster.” (Fig. 1.)

The benefits of PC-driven test-and-measurement instruments, such as cost, portability, and rich software potential, are attractive enough to encourage early technology innovators. Yet new techniques must be used to shrink the footprint of such high-performance electronics with a limited power budget and the necessary ruggedization. “USB instrumentation needs to be light, compact, and rugged,” explains Maxwell. “This typically requires all new board layouts and potentially new ASICs, along with close attention to heat management while ensuring a clean signal path. While USB 3.0 is fast, bandwidth limitations and power constraints can limit performance.”

Even with USB 3.0’s increased data rate, practical limitations prevent the interface from reaching the maximum 5-Gbps data rate. Practical data rates range to 3.2 Gbps (Fig. 2). Yet Maxwell says, “The bandwidth limitations can be overcome by using a faster interface than USB 3.0, such as USB 3.1, Thunderbolt, or even multiple connections.”

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