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The Preferred Method for Electronic Test

Wed, 08/06/2014 - 9:40am
Lindsay Hock, Managing Editor

With oscilloscope technology developing at a fast pace, vendors try to keep up with the common trends.

Advancements in high-sensitivity current probes, like Keysight’s N2820A, allow designers to see both a zoomed in and out view of the devices.Oscilloscope technology is developing at a fast pace with more features packed into smaller and less expensive packages, providing engineers with more choices in the expanding marketplace. Recent market analysis from TechNavio notes the global oscilloscope market will grow at a 20% CAGR through 2016.

Engineers see the advantage in working with companies, such as Rigol Technologies, Pico Technology, Teledyne LeCroy and Keysight Technologies, that can quickly adapt to new standards and requirements they face more frequently in completing their projects. With the advancements in field-programmable gate arrays (FPGA) technology and power over the past five years, users no longer have to wait for new ASIC designs or repackaged products. Development of new oscilloscope capabilities and value can now quickly leverage the newest available hardware components and the refinements of a multi-generational user interface faster.

Once digital oscilloscopes became established as the tool of choice for electronics system designers, manufacturers raced to deliver oscilloscopes with increasing bandwidth and higher timing resolution. “These products enabled the first phase of the ‘digital revolution’,” says Trevor Smith, business development manager, Pico Technology, Cambridgeshire, U.K.

Today’s digital oscilloscopes are pushing the envelope in terms of bandwidth. In serial data applications, a rule of thumb is oscilloscope bandwidth should be at least five times the fundamental frequency of the signal being measured. “A PCIe Gen 1 signal at 2.5 Gb/sec has a fundamental frequency of 1.25 GHz,” says David Maliniak, technical marketing communications specialist, Teledyne LeCroy, Chestnut Ridge, N.Y. “Thus, a 6-GHz oscilloscope would be required to accurately display the signal.”

Early digital scopes had 6-bit analog-to-digital converters (ADCs) in the data acquisition front end. After a few years, 6-bit ADCs gave way to 8-bit ADCs. ADCs have resolution of 2N bits. “So for a 6-bit scope, that meant 64 discrete levels of vertical quantization,” says Maliniak. “When they moved up to 8-bit ADCs, users got a four times boost in vertical precision with 256 discrete levels.” Most oscilloscopes have relied on 8-bit ADCs for decades now.

In the interim, oscilloscope vendors have tried to mimic higher levels of vertical resolution with software-based workarounds, including averaging of multiple acquisition and what they’ve called “enhanced resolution” or “high resolution” modes. Both of these techniques have their places and come with limitations and/or tradeoffs. However, ADC technology has advanced. In Teledyne LeCroy’s HDO Series of 12-bit high-definition oscilloscopes, the 12-bit front end means 4,096 discrete levels of vertical quantization. This is about 16 times better than the standard 8-bit instruments.

Debugging and troubleshooting requires fast update rates, which is how fast the scope can trigger, process the information and plot it to the display. The faster the scope can do that, the more likely users can find infrequent problems that are keeping a design from working properly. Having a scope with an uncompromised update rate is important, as scopes that vary their update rate based on what other features are turned on can hide issues.

The way customers interact with oscilloscopes has become more important. Vendors are leveraging advancements in touchscreens and the increasing adoption of tablets and smartphones by users. “There are some capabilities (like zone triggers) where touch naturally lends itself to that a traditional knob and button don’t,” says Richard Markley, product manager, Keysight Technologies, Santa Clara, Calif. “But just putting a touchscreen in isn’t the answer, you need the graphical user interface to be designed for touch to make it truly useful.” In additional, implementing a technology like voice control can take a frustrating experience and simplify it.

From analog to digital, or mixed
Analog oscilloscopes were known for their ability to see things early digital oscilloscopes hid due to their slow update rate, or dead time. Creating oscilloscopes with uncompromised update rates and hundreds of levels of intensity grading helps bridge the gap between the benefits of analog scopes and the benefits of digital scopes. The same is true with high-resolution ADCs. “Having an ADC that runs at 40 GS/sec and 10 bits allows much better measurements across a broad set of bandwidth points assuming the entire signal path has been designed to take advantage of the extra resolution,” says Markley.

The increasing embedded capability of digital storage scopes is bringing opportunities for engineers to learn more about their devices without constantly offloading data for analysis. Higher-resolution screens mean ADCs can be combined with advanced averaging and filtering techniques to show more detail and signal fidelity. “Color depth on the displays also enables scopes to show additional information, including intensity, glitch detection, pass/fail or even normalized RMS differences between waveforms,” says Chris Armstrong, director of product marketing and software applications, Rigol Technologies, Beaverton, Ore. “Flexible high-speed ADCs have made advanced averaging, fast Fourier transforms and digital triggering easier than ever.” Making complex data more accessible to researchers is critical to the continued development of labs, both in university and commercial research areas.

And while digital scopes may dominate the marketplace, mixed signal oscilloscopes are in demand because they show time-correlated waveform data from analog and digital elements of a circuit. High-resolution scopes are gaining popularity for working with new sensor technologies that are appearing on the market, according to Smith. Users are demanding improved analysis tools which enable waveform data to be viewed at higher levels of abstraction to make searching for anomalies and glitches easier.

Deep-memory oscilloscopes such as the PicoScope 6000 Series use hardware acceleration to provide fast display update rates. The raw samples are stored in the oscilloscope, but advanced signal processing acceleration is used to quickly form and transfer the data image to the display. The PicoScope 6000 Series hardware acceleration engine can process up to 5 billion samples per second, which is approximately two-orders-of-magnitude faster than the raw samples that could be processed in a typical CPU.

Size, portability matters
Today’s researchers and engineers face increasingly complex and critical troubleshooting tasks. Designs that work fine in the laboratory can sometimes fail in the field, causing customer dissatisfaction, lost production, expensive repair bills and safety concerns. So, engineers need lightweight, compact, but powerful tools on-site to validate device functionality, identify failures and trace the root cause by capturing waveform errors such as timing faults, crosstalk, transients and other issues.

Along with the importance of on-site analysis capabilities, the size of the scope’s display is of importance. Some users prefer larger displays, while other prefer a small form factor. The nature of display preferences may also change with user’s age. An older generation of researchers tend to prefer larger displays and box instruments, while the younger generation typically prefers small form factors, handheld or iPhone-like displays. Also the integration of additional tool sets is also important to size and portability of the devices. An oscilloscope is often the center piece of an engineer’s tool bench, and having integrated capabilities, like digital channels or arbitrary function generators has several benefits. One is saving space and money. But the second, according to Markley, is not as obvious. “If the additional features are truly integrated, versus just included in the same frame, there are new measurement capabilities opened that weren’t available before in a single instrument,” he says.

Probing solutions
A key user trend revolves around power. Vendors typically see two key users of oscilloscope technology: the power producers and the power consumers. “The power consumers have unique needs from the producers, and the number of people with these needs is growing as more devices are developed that stress battery life,” says Markley.

As part of this, designers need the ability to measure current from micro-amps to amps, with a broad dynamic range. Advancements in high-sensitivity current probes, like Keysight’s N2820A, allow designers to see both a zoomed in view for when a device is sleeping, as well as a zoomed out view for when the device wakes up. In addition, custom software allows measurements to be made across both of those views so designers can optimize their device’s power consumption.

Measurement fidelity begins at the probe tip, so the choice of test accessories can be as important as the choice of test equipment. Pico Technology offers a range of oscilloscope probes and sensors: passive and active probes up to 1.5 GHz, high-voltage and high-bandwidth differential voltage probes, current probes, thermocouples, accelerometers and pressure transducers matched to their oscilloscopes that enable accurate measurement of a wide range of parameters. For maximum versatility PicoScope users can define a custom probe with a linear equation, or refer to a lookup table for user-defined parameters and measurement units. This enables any probe or sensor, from any supplier, to be used and scaled appropriately within PicoScope.

Probes and inputs continue to evolve for specific applications. New requirements for differential signaling in data transmission require differential and active probe capabilities. Current probes have become critical to many emerging power supply and battery maintenance applications as consumer electronics continue to drive toward smaller and more efficient power modules and systems. One result of this continued trend, according to Armstrong, is more sources for these tools and accessories than a decade ago. This has driven down cost and helped to create customer value even in high-performance applications where a few years ago there weren’t many options available for engineers to consider.

Pushing the speed barrier
With the emergence of technologies pushing to 50 Gb/sec and beyond, there’s a need for high bandwidth. Agilent offers real-time oscilloscopes over 60 GHz with sample rates up to 160 GS/sec. However, bandwidth is only a portion of the story, according to Markley. Low noise and low jitter measurement floors make that bandwidth useable. Deep memory (up to 2 Gpts) maintains that sample rate. And having the ability to combine up to 10 oscilloscope frames together allows precision measurements across multiple channels with 150 fsec precision. All of this combines to provide a complete solution for users who require advancements in bandwidth and sampling speed over the past few years, according to Markley.

Ultra-high-performance measurement instruments have paved the way for significant improvements in component technology, which have led, in turn, to increased demand for higher-performance, general-purpose instruments that enable deployment of those new technologies. For engineers working on high-speed serial communications, interconnects, backplane and PCB design, Pico Technology has a range of sampling oscilloscopes up to 20-GHz bandwidth and with TDR capability for mainstream signal integrity (SI) measurements. PicoScope 9300 Series sampling oscilloscopes have the same PC-based design concept as other PicoScopes, taking advantage of modern PC performance that provides great measurement and processing capability and can be upgraded whenever the need arises.

Improvements in FPGA and DSP technologies over the past few years continue to drive improved waveform update rates for oscilloscopes. This is important because while sample rates are limited by the ADCs used, the update rate dictates the amount of dead time in measurements, according to Armstrong. Reductions in dead time means less time hunting for intermittent issues for engineers and translates directly into increased productivity in the hands of a savvy engineer.

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