Higher analogue bandwidth, higher sampling rate, higher memory points and faster response are the biggest trends seen in oscilloscopes. But inbuilt support for connectivity to a computer or the network is the key specification that will drive the next-generation scopes
SHWETA DHADIWAL BAID
Equipment vendors had foreseen that test and debug engineers would need to connect their equipment to the computer. Connectivity through various standards and modes has thus become the biggest trend in oscilloscopes today. As the computers continue to deliver higher performance and speed, they have become an attractive option for higher deliverables in test and measurement.
According to a Frost & Sullivan report, the oscilloscope market is primarily driven by constant technology innovations in the communication and computer industry. In 2009, the world oscilloscope market generated revenues of $987.7 million, which is expected to reach $1513.4 million by 2014 as the demand for new products with enhanced features like PC connectivity along with Internet support increases.
The transition from analogue to digital in the communication and computer industry has given rise to the need for high-performance RF test tools, which has accelerated the demand for digital as well as PC-based oscilloscopes or digitisers. Users demand connectivity not only for waveform data transfer but also for control and remote access of the equipment. Thus Ethernet, universal serial bus (USB) and general-purpose interface bus (GPIB) have become key specifications in next-generation oscilloscopes.
Modularity and virtual instrumentation is another technology trend seen in oscilloscopes, where the computer becomes the front-end screen while PXI or LXI ports enable the connectivity of oscilloscope hardware.
The phase of change
Oscilloscopes are the basic test and debug equipment found in every phase of electrical or electronic development. As consumer and industrial products become more intelligent with advanced embedded electronics, vendors aim at providing more and more features that are vital to supply products which are based on the new standards.
“Oscilloscopes have evolved from the traditional analogue scopes to high-performance digital oscilloscopes. Today, oscilloscopes have extremely high-speed analogue-to-digital converters (ADCs) and a huge memory of nearly 2 giga-points,” informs Sanchit Bhatia, digital applications’ consultant, Agilent Technologies. They have unprecedented analysis capabilities and more and more automated compliance software.
“Deeper memories, higher sampling rates, colour TFT and LCD wide-screen displays, and built-in options like function generator, DSO demonstrator and multichannel logic analyser are the major technological developments seen in oscilloscopes,” shares Chandeep Singh, CEO, Silicom Electronics.
In addition to the internal technology of the device, the development and enhancement of the probes play a very important role. Naresh Narasimhan, pacific technical marketing manager, Tektronix, says, “The highest-bandwidth oscilloscope is of little use to the user if the signal cannot be tapped and directed to the device.”
Connectivity to PC
Computer has become an inseparable part of test and measurement instrumentation. Digitisation has made it easier to take the oscilloscope signal on a PC. Bruce Tulloch, director-software development, BitScope, believes, “Products that leverage power of personal computers, netbooks and tablets are expected to become even more common. These are generally more useful than traditional standalone oscilloscopes because they can be produced at lower cost, are more flexible in use, and can meet or exceed the specifications of many standalone solutions.”
“In earlier days, analogue oscilloscope required single-shot external signal out and a special camera was required to capture the image. With the advent of digitisation, the same signal is captured in the memory and can be seen on the digital storage oscilloscope (DSO) screen or taken to a PC via USB, RS-232, GPIB, LAN, etc,” shares Neelam Kumar, executive director, Aplab.
“The scopes come with USB host feature, so the waveform image can be captured directly onto a USB flash drive without the need of PC,” adds Kumar.
“Analogue scopes have also entered the area of Ethernet connectivity and multi-location applications,” informs J.K. Baldua, director-technical, Scientech Technologies.
High-speed interface for data transfer
Oscilloscopes help capture signal waveforms and analyse them for performance. The increasing complexity of the signals and the challenges associated with signal integrity and high-speed data acquisition have stirred up the performance requirements of digital scopes.
Bhatia shares, “The oscilloscope market is now witnessing increasing adoption of high-speed serial data bus technologies like PCI Express, serial advanced technology attachment (SATA) and HDMI. As the memory depth of digital storage oscilloscope has increased to 2 giga-points, these interfaces facilitate faster data transfers.”
GPIB phases out, USB takes in
USB has almost replaced GPIB in instrumentation control. The plug-and-play capability of USB is widely used in many form factors in oscilloscopes. Today, users demand performance along with ease of operation. As USB is the most commonly adopted standard in the PC world, you do not have to write the code or install drivers separately while connecting a hardware using USB port to your computer.
USB PC-based oscilloscopes eliminate the need for an external power supply and can be conveniently used with a laptop or notebook computer. Standalone box oscilloscopes offer more than one USB port for connectivity to other equipment as well as computer.
Bhatia shares, “In some of the older aerospace and defence applications, when the automated test algorithms for controlling the overall system use GPIB for control, you may require a USB-to-GPIB converter if you use a latest oscilloscope with USB port.” Many companies including Agilent and National Instruments provide USB-to-GPIB and GPIB-to-high-speed-USB connectors.
Although USB offers all the flexibility and ease of operation, there are some issues around it. Nandini Subramanya, marketing communications manager, National Instruments, informs, “USB 2.0 does not necessarily mean high speed as USB standards provide different data rates. When a device is called USB 2.0-compatible, it supports the low- (1.5Mbps) and full-speed (12Mbps) transfer rates. To ensure greater transfer rates, you should purchase an instrument with high-speed USB (480Mbps).
“There are two types of USB ports. Type A ports are flat and elongated. Normally found on computers, these are typically used to save data to USB memory sticks and not for instrument control. For controlling your instrument through a PC, you need Type B device port, which is more like a square shape.”
Connecting scope in network
When it comes to automated test applications, Subramanya cites, “Oscilloscopes are just one of the many instruments required to enable the multiple types of measurements needed to verify the functionality of today’s units under test.” Engineers demand high-performance, modular, flexible systems, with easy upgradeability to the latest commercial-off-the-shelf (COTS) technology and reusability along with the option to control remotely.
LAN eXtensions for Instrumentation (LXI) based instruments come in compact, flexible packages with high-speed capabilities and reliable measurements. Bhatia shares, “Ethernet LAN enables wired as well as wireless connectivity to the equipment in the network. The major advantage of LAN Ethernet port is the complete support for remote control of the instrument including viewing of waveform data and transfer of the data and set-up files from any location. LAN also leverages the Internet, allowing you to access the equipment in India from anywhere in the world.”
Explaining the way it works, Bhatia shares, “LXI instruments have a Web server on the equipment itself. Once you connect it in the network, an IP is assigned to it. You can open any Web browser like Internet Explorer to control the oscilloscope in your network.” The benefit is that all the equipment are interconnected and you can plan an event based on triggers from other equipment and monitor them remotely.
You can also file transfer protocol (FTP) into a digital storage oscilloscope (DSO) in the network to grab the data from its memory.
Virtual instrumentation for customised scopes
As devices become more complex and test times costlier, software-defined instruments offer significant flexibility, integration and cost benefits over traditional architectures based on standalone box instruments. “With digitisers driven by flexible software, test engineers can perform standard oscilloscope measurements and easily build other instruments such as spectrum analysers, transient recorders and ultrasonic receivers,” says Subramanya. Sometimes there is a need of tight synchronisation within the instruments at picoseconds-level accuracy for high-channel-count and mixed-signal applications.
“Replacement of oscilloscopes is not inevitable as these instruments have become reputable solutions for testing, debugging and troubleshooting electrical signals. But with the advent of virtual instrumentation, we may come across new instruments that combine the capabilities of oscilloscope with other test equipment as an all-in-one solution,” shares Narasimhan.
Due to increasing product complexity, shorter times to market, increasing hardware and software abstraction, and reduced budgets, monolithic instrumentation architectures with predefined functionality are unable to meet the current demands.
Subramanya says, “Virtual instrumentation technology has pioneered the concept of user-defined systems to design, prototype and deploy test, control and embedded applications. This strong framework which leverages graphical programming software and modular hardware has helped customers to simplify development, increase productivity and dramatically reduce time to market.”
Talking about modularity, Subramanya shares, “PXI provides a rugged PC-based platform that continues to offer the highest bandwidth and lowest latency. PXI digitisers are optimised for automated test because of their high data throughput, tight synchronisation between channels and ease of integration with other types of instrumentation.”
Oscilloscopes are available in the form of high-speed digitisers. “Digitiser cards have their own attractiveness if users need to combine a few instruments for repeated set of customised testing or for higher vertical bit resolution. Customisation also means the need to invest on software programming efforts. Digitiser cards can replace an oscilloscope in system level to a certain extent if the user uses it just as an ADC to fetch data,” says Appala Srinivasa Rao, area manager-product support and applications, Rohde & Schwarz.
Application software: Key to better user experience
The whole idea of PC connectivity will be bullied if you do not have a good application software. Narasimhan shares, “Many oscilloscope applications need special software applications that make it easier for the user to analyse and evaluate the measurements in an automated way.”
Vendors see a growing need in this area, particularly for mid-range products that can provide performance measurements at an affordable cost. Narasimhan adds, “Newer applications such as automated power measurements, jitter analysis, and low- and medium-speed serial bus decoding are being integrated in the oscilloscope software.” To give a near-PC experience, oscilloscopes have Microsoft Windows—the most common operating system—running beneath.
“With specialised application software functions, users can download the image of a waveform with measurable parameters. It provides the comma-separated variables (CSV) file format so that data points of the sampled signal can be collected to make detailed analysis of the signal like Fourier’s Analysis,” shares Kumar.
Challenges in PC-based scopes
As we talk about the power of PC, it is important to understand the disadvantages as well:
1. Unlike standalone box equipment, you need to install oscilloscope software on your computer to operate the equipment from the computer.
2. The PC will take its own defined time to boot, compared to the instant start-up of a self-contained oscilloscope. However, this distinction is narrowing as the latest scopes too come with a full-fledged operating system like Windows, which may take some time to boot.
3. Multi-threading and multi-tasking on the PC can be a distraction in oscilloscope operation.
4. Oscilloscopes last longer than PCs and hence it may happen that the scope is running an older version of the operating system with weaker protection against virus. If the scope is affected by the virus attack, it may spread the virus throughout the network.
Turn your iPad, iPod, iPhone into the smallest scope
Interesting innovations are happening to support oscilloscope functions on Apple devices working on iOS. A company named Oscium delivers innovative test equipment that leverage the Apple MFi interface. iMSO, an Oscium product, is the world’s first mixed-signal oscilloscope (MSO) for iPod touch, iPhone and iPad. The company focuses on making test equipment more intuitive.
Based on Cypress’s CY8CKIT-023 PSoC 3 device, iMSO is world’s ultra-portable MSO with 2MHz bandwidth and up to 12MSa/s sample rate, ideal for hobbyists, students, and field sales and application engineers.
Innovative ASICs to address key challenges
Measuring instruments are the most complex real-time embedded systems which demand precision, scalability and speed. Vendors are now equally involved in highly innovative semiconductor R&D to come up with application-specific integrated circuits (ASICs) matching their special needs.
A key challenge in using a digital oscilloscope as a debug tool is its blind time. During this time, the user may miss critical signal events at his device under test. Typically, digital oscilloscopes today have a blind time ratio (the ratio of the active acquisition time to the blind time) of over 99.9 per cent.
Rao shares, “Some of the innovative ASICs demonstrate the ability to acquire, analyse and display the signal at a speed of greater than one million waveforms per second. The result is that the blind time between two acquisitions can go below 900 ns in standard operation mode and below 200 ns in segmentation acquisition mode.” It also enables fast detection of rare signal anomalies without the need to make further setting on your scope.
True analogue bandwidth is another key criterion for an oscilloscope. “Bandwidth enhancement techniques like digital signal processing (DSP) boosting and frequency interleaving have many drawbacks like high noise and high total harmonic distortions,” informs Bhatia. The invention of a new semiconductor called indium-phosphide (InP) and 3D Microcircuits Technology have proved to achieve a true analogue bandwidth as high as 32 GHz.
IBM’s silicon germanium (SiGe) is another combination of elements which offers twice the performance of the previous generation along with real-time bandwidth beyond 30 GHz. Narasimhan informs, “The 130nm SiGe bipolar complementary metal-oxide semiconductor (BiCMOS) provides the next-generation, scalable, performance oscilloscope platform.”
The performance level of SiGe is comparable to that of exotic materials like InP and gallium-arsenide (GaAs). High-speed bipolar transistors are present on the same die as the standard CMOS providing large-scale integration along with extremely high performance.
With continuously evolving technology, the key challenge for any test and measurement equipment is to keep up with the change. Bhatia shares, “With the buses becoming faster, chip-size becoming smaller and the quality of digital video becoming better, one thing we should remember is that the expectation from the instrument used to test them is getting bigger!”
“It is difficult to predict what shape will an oscilloscope take in future. It may be a pocket-sized oscilloscope with bare minimum features like a popular multimeter or Jules Verne’s science-fiction oscilloscope. But one thing is sure that higher-bandwidth scopes with more information on rapidly changing waveforms will bring revolution in electronics due to better understanding and analysis of electronic circuits,” says Kumar.
“Modularity will enable addition/removal of channels, upgradation of bandwidth and make the scopes sleeker, lighter and faster,” informs Prabhanjana Rao, regional sales manager-South Asia, Lecroy.
“The oscilloscope would be a display device like a tablet PC with multiple inputs,” adds Singh.
According to Baldua, “It will be smart and handy with big storage capabilities.”
While USB has become the standard today, “In the future, Bluetooth connectivity will also help in quick transfer to mobile devices,” says R.T. Swamy, head-T&M, Yokogawa.
“Oscilloscopes of the future will have tight integration with COTS technology to leverage heterogeneous computing architectures and inclusion of latest technologies like cloud computing,” shares Subramanya. To deliver the ultimate user-experience, they will be highly customised modular equipment which can leverage a personal computer technology and connect to a network for controlled operation.
The author was a senior technology journalist at EFY