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Oscilloscope memory depth: when bigger is not always better

Travis Wheeler — Wed, 14 Mar 2012 18:28:11 +0000

Oscilloscope memory depth is an often misunderstood concept. In fact, many designers don’t even know how much memory their scope has. This article discusses what oscilloscope memory is, why it is important and the benefits and trade-offs of memory in different oscilloscope architectures. In the end, the truth is that all memory is not created equally.

How much memory does the digital oscilloscope on your bench have? Not sure? Don’t feel bad; most people don’t know. But when it comes to oscilloscope memory depth, bigger is always better, right? As with many things, the answer isn’t as straight forward as it may seem.

Let’s start with what oscilloscope acquisition memory is, and why it is important. In an oscilloscope’s simplest form, they are made up of a front end for acquiring the analog signal; that signal is then passed on to an analog to digital converter where the signal is digitized. Once it is digitized, that information has to be stored in memory, processed and plotted/displayed. The oscilloscope memory is directly tied to the sample rate. The more memory you have, the higher you can keep the oscilloscope’s sample rate as you capture a longer period of time. The higher the sample rate, the higher the effective bandwidth of the oscilloscope.

So as we said before, the deeper the memory, the better the oscilloscope, right? In a perfect world, the answer would be yes. Let’s compare two oscilloscopes with similar specifications outside of memory depth. One is a 1 GHz scope with 5GS/s sample rate and 4,000,000 points of acquisition memory (we’ll call this a “MegaZoom Architecture”). The other is a 1 GHz scope with 5GS/s sample rate and 20,000,000 points of acquisition memory (we’ll call this a “CPU-based Architecture”). Table 1 shows common time base settings along with the sample rate. There is a simple calculation to determine the sample rate given a specified time base setting and a specific amount of memory (assuming 10 divisions across screen and no off-screen memory captured):

Deep memory is clearly beneficial when it comes to sample rate, but when would it not be advantageous? When it makes your oscilloscope so slow that it is no longer helpful in debugging a problem. Deep memory puts a larger strain on the system. Some scopes are setup to handle that well and remain responsive with a fast update rate; others attempt to make it a banner specification when it isn’t really usable and slows the update rate by orders of magnitude (see What is Update Rate? for a discussion on update rate).

Full article by Richard Markley, TM World

Aeroflex rolls out trio of broadband signal analyzers

Travis Wheeler — Wed, 22 Feb 2012 18:33:35 +0000

Three low-cost broadband signal analyzers from Aeroflex locate, record, and analyze complex communications signals for commercial, military, and aerospace applications. Comprising a portable instrument and two rack-mount units, the analyzer family is said to reduce the average cost of signal analysis by 55%.

The Scout CS1104 portable signal analyzer provides RF coverage from 20 MHz to 3 GHz with instantaneous bandwidth of 40 MHz. It also packs 8 Gbytes of signal-capture RAM and a 1-Tbyte removable data-storage disk to allow you to record and analyze while stationary or mobile.

The Hunter CS1207 and Explorer CS1247 rack-mount signal analyzers let you search for a specific signal, hone in on a narrower frequency range around that signal of interest, and analyze it. Hunter’s RF coverage extends from 10 MHz to 6 GHz with 70-MHz instantaneous bandwidth. Explorer combines Hunter’s narrowband capability with additional wideband capability. It provides RF coverage from 10 MHz to 6 GHz with user-selectable instantaneous bandwidth of 70 MHz or 400 MHz. Both Hunter and Explorer have a 32-Gbyte signal-capture RAM and an 8-Tbyte removable data-storage disk.

All three instruments are compatible with Aeroflex BSA modular software. Standard software modules supplied with each analyzer include BSA Basic (spectrum and spectrogram waterfall plots), BSA Modulation Domain (calculates and displays AM, FM, and PM waveforms), and BSA Scanning Spectrum Analyzer (to view any range of spectrum instantaneously). A GPS hardware module is standard on Scout and can be ordered as an option for Hunter and Explorer.

Full article on Test & Measurement World

Technical Communities Breaks Sales Records for 2011

Ali Cheung — Tue, 10 Jan 2012 23:33:49 +0000

Technical Communities, Inc., the company technical organizations who sell to the government rely for proven contracting, marketing and sales solutions, broke its all-time annual sales record in 2011.

All Technical Communities’ revenue categories achieved record results, including test, laboratory, medical, information technology and direct marketing. This is the eighth of the past nine years where the company showed year over year sales growth.

The privately held company also now has a record number of partnerships with 120+ technical companies. In addition to service offerings, the company holds and manages multiple federal, state and local government contracts. It is owner and operator of industry leading online marketplaces that focus on the U.S. government agencies, military organizations and prime federal contractors. They include ecommerce sites gsamart.com and testmart.com and the govcontractsmagazine.com government-focused content network.

“We are very excited to announce these results for 2011. It was Technical Communities’ focus on our partners’ needs, expertise in reaching government customers and successful management of multiple GSA Schedules that helped us achieve record sales and partnerships,” said Peter Ostrow, Technical Communities, Inc. President and CEO.

Technical Communities continues to add partners, product lines and services that solve problems and focuses on government customers. The company regularly sells to more than 1,400+ U.S. government, military and prime federal contractor buying organizations and has reach into the 1+ million prospects in its proprietary database.

For the fourth year in a row, Technical Communities was named to Inc. Magazine’s list of the fastest growing private companies in America.

How a standard defines a voltage or current pulse greatly influences wave shape

Travis Wheeler — Sat, 17 Dec 2011 18:02:39 +0000

Electronic products must pass some level of immunity tests when subjected to conducted or radiated energy. Some of those tests include subjecting the equipment under test to electrical impulses–short duration single events using defined voltage and current waveforms. Engineers also use impulse tests to verify electrical spacings on PCBs and to periodically check motor-insulation.

Several international standards define impulse waveforms, but only at certain points in how a voltage or current will rise and fall. The waveform shape, peak voltage, impedance, and application of the pulse varies among standards. The test pulse you use depends on the standard you apply because standards define impulses differently.

Waveform Definition

The IEC (International Electrotechnical Commission) has at least two standards that define impulse tests and their waveforms. Use IEC 60060-1, “High Voltage Test Techniques” when testing insulation systems and use IEC 61000-4-5, “Testing and Measurement Techniques – Surge Immunity Test,” for switching and lightning-transient tests. Many standards that define testing of specific products reference either of these two standards because these two standards.

In some end-use Standards, both the insulation system of the DUT (device under test) and the ability of the device to withstand lightning and switching transients are important. The requirements of IEC 60060-1 and IEC 61000-4-5 are different, so the authors of the end-use standard must decide which standard to reference. A relevant example is IEC 61730-2, the Standard for photovoltaic (PV) panels, which references IEC 60060-1 as its impulse standard definition, which is applicable to insulation systems. In the PV standard, the authors note that the test is “To verify the capability of the solid insulation of the module to withstand over-voltages of atmospheric origin. It also covers over-voltages due to switching of low-voltage equipment.” While this scope would be closer to that of IEC 61000-4-5, the authors elected to conduct the test under the requirements of an insulation impulse test, which they deemed a better definition of their test program.

Full article by Jeff Lind, Test & Measurement World

Gigahertz RF measurements can be accurate

Travis Wheeler — Sat, 19 Nov 2011 18:18:11 +0000

Extremely high frequency, which can be defined as the frequencies between 30 and 300GHz, remained relatively undeveloped for many years, except for somewhat esoteric applications such as radio astronomy and remote atmospheric sensing.

That is because this frequency range is highly susceptible to atmospheric attenuation – when resonance of the oxygen molecule attenuates the signal, or when rain absorbs the signal, reducing signal strength.

But with spectrum scarcity in the sub-10GHz band, applications for millimetre-wave systems are found in consumer and non-consumer communications, security, imaging and radar. In particular, with increasing demand for multi-gigabit-per-second communication created by the likes of high-definition (HD) and 3D video, it was soon recognised that the 7GHz of unlicensed bandwidth available around 60GHz was a big opportunity.

So, for several years, the extremely high frequency region has become an area of intense development, with several applications actually being able to capitalise on its signal attenuation characteristics.

Wireless HD

Among the many short-range communications standards that have appeared in the 60GHz frequency range is WirelessHD, a media standard for video in the home that effectively untethers the TV from other home video and audio devices.

Conceived as an in-room, point-to-point, non-line-of-sight standard that uses the band between 57GHz and 64GHz, it is capable of transmitting HD video images and the first products have a limited range of up to10 metres, pleasing copyright owners.

The increased signal attenuation at high frequencies is due to the very small wavelengths generated.

So WirelessHD antennas use various beamforming techniques to concentrate power in the direction of the receiver and bounce signals off nearby objects, using both direct and reflected signals to achieve a stronger, more stable signal.

As you move into higher frequencies and the wavelength size decreases, so the physical structure of devices also comes down in size. This can increase cost dramatically because of the machine costs related to making smaller components. The tolerances involved become much greater too.

Instrumentation can also prove more expensive at higher frequencies, because the frequencies and modulation bandwidth are outside the range of most standard test equipment. One reason for the cost increase is economies of scale.

SiGe and CMOS transistors that can run fast enough for circuits in the millimetre-wave region are a relatively recent arrival, so the growth in millimetre-wave applications has created a correspondingly recent demand for millimetre-wave instrumentation for device specification verification.

Costs can be trimmed by using a down converter module to convert the 60GHz signal to lower frequencies that can be analysed on standard equipment. But there is a risk when using a downconverter or harmonic mixer that the mixing produces multiple image frequencies unsuitable for spurious measurements.

Waveguide flange

Users of harmonic mixers would also need to take account of the waveguide flange, requiring a further conversion to 1.85mm coax to interface with the DUT.

Any additional hardware will also add measurement uncertainty into the signal observed. So it is advisable to use millimetre-wave test equipment that allows measurements to be performed directly on the signal.

When calculating uncertainty in RF measurements stemming from voltage-standing-wave-ratio mismatch, it is important to recognise that uncertainties increase as the frequency rises. So although many spectrum analysers have good power measurement capabilities, a dedicated RF power meter provides better accuracy and impedance matching – critical at higher frequencies.

Precise calibration

It has been said that a vector network analyser (VNA) is only as useful as its measurement accuracy. So to get the best out of a high-frequency VNA, precise calibration is vital. Sources of error come from less than perfect input impedance at the RF receiver and/or output impedance by the RF source, as well as wear and tear to cables and connectors.

Things are further complicated when measurements cannot be made easily at the coaxial connectors, for instance on wafer devices. Calibration won’t fix every error, but you can minimise them by choosing a VNA with good raw system performance and unique calibration techniques.

Full article by Jamie Lunn, ElectronicsWeekly

Manufacturers test new distribution channels

Travis Wheeler — Mon, 07 Nov 2011 18:09:36 +0000

Prominent manufacturers of test equipment, who have historically sold directly to their customers, have begun exploring new sales channels and are now offering a wider variety of products through distributors, franchisees, and online stores. And what may be even more surprising is that their use of these new channels is not limited to low-end instruments. In fact, manufacturers are working more closely than ever with distributors to coordinate both sales efforts and technical support.

“Over the last five years, we’ve seen a major broadening of the channel in terms of the types of equipment that’s resold and the level of sophistication,” said Mike Stonebraker, director of worldwide indirect channels in the Electronic Measurement Group at Agilent Technologies.

Two of the most dominant test-and-measurement companies, Agilent and Tektronix, have both increased sales through distribution. Agilent has honed its distribution strategy over the last two years, a move that appears to be working out well for the company. “It’s been a major trend in our business and a strong contributor to growth as well,” said Stonebraker. Indeed, 25% of the company’s orders come from indirect channels today, compared to only 8% two years ago, according to a company spokesperson.

Stonebraker gave credit to Tektronix and Fluke for pioneering the use of distribution for low-end equipment years ago. Agilent took note of their success, he said, realizing that its customers also likely wanted a more-efficient purchasing process. “Engineers don’t necessarily need to see another engineer to make a decision on what piece of test equipment to buy,” Stonebraker explained. “When a customer wants to buy their 10th scope and it’s exactly like the previous nine, all they want is the quickest and simplest way.”

Tektronix also has expanded its use of indirect channels. The company has used distributors for more than 20 years, but lately has started selling higher-end equipment through the channel. Late last year, Tektronix announced new distribution agreements with Allied Electronics, Entest, Newark, and TestEquity, authorizing those firms to carry higher-performance oscilloscopes, signal generators, spectrum analyzers, logic analyzers, and bit-error-rate testers. And this year, Tektronix, which is a subsidiary of Danaher, inked similar agreements with several European distributors.

Vendors are using specific channels to meet particular needs. Some high-end products are still only available directly from the manufacturer, such as the Tektronix DSA8200 digital sampling oscilloscope, which requires custom configuration, said Gina Bonini, technical marketing manager at Tektronix. On the other hand, some of the company’s distributor partners are beefing up their technical chops and building their own applications teams, she added.
Tektronix direct and indirect sales people frequently work together on sales opportunities, said Faride Akretch, also a technical marketing manager. “We don’t see it as either [a direct sale or an indirect sale]. We see it as a combination of the two.”

Full article by Tam Harbert, Test & Measurement World

High growth market for modular instruments

Travis Wheeler — Thu, 20 Oct 2011 21:34:24 +0000

In industries ranging from aerospace to white goods, the complexity of devices under test (DUTs) is rising, with the devices becoming faster, smaller, and cheaper. This greater product sophistication, along with the incorporation of radio frequency (RF) in an increasing number of devices, is compelling engineers to change their test strategy and adopt modular tools that are flexible enough to be customized to their testing needs. Continued innovations by market majors are helping vendors of modular instruments increase the capabilities of their offerings, thereby driving demand.

Apart from changing the way devices need to be tested, Moore’s Law is improving the functionality of modular instruments. For instance, while RF with PXI was almost an impracticable concept a decade ago, today, RF instrumentation in a small form factor offers very high performance – almost the best in its class. PXI instrumentation has strongly benefitted from technology innovation in semiconductors and more specifically, processors, field-programmable gate arrays (FPGAs), and data converters. Advancements in FPGA capabilities are extremely useful in test and measurement applications, wherein customers need highly deterministic and fast processing capabilities.

Although these product improvements bode well for the modular instruments testing market, manufacturers will be challenged to replace the traditional instruments. While users are expected to gradually shift to modular instruments, they still primarily use traditional rack-and-stack instrumentation due to product familiarity and ease of use. Another important reason for the slow migration is that customers have a wide array of modular instruments to choose from, while with traditional devices, the decision making is far easier as they are closed systems. In 2010, traditional instruments accounted for almost 85 percent of the total market revenue for general purpose test equipment worldwide. Even though its revenue share is decreasing, it will remain a prominent revenue generator in the total market for the next five years.

Increasing automation, superior DUTs, and the hectic pace of research and development (R&D) will swing the revenue balance in favor of modular instruments over time; nevertheless, it will be critical for market participants to educate potential customers about the key benefits of modular instruments over traditional instrumentation.

Full article from Business Wire

Moderate growth predicted for signal generator market

Travis Wheeler — Mon, 10 Oct 2011 18:23:14 +0000

The next 10 years will be a “wireless decade,” as products offering 3G, 4G, and WCDMA wireless interfaces will proliferate. We will see different types of wireless devices beyond the traditional ones, and their fast development and implementation will be the key factor driving the demand for signal generators. It will be imperative for manufacturers of signal generators to adapt their products to comply with evolving wireless standards.

Although the signal generator market has bounced back from the economic crisis of 2009 and is surpassing the levels of 2008, caution and uncertainty continue to restrain end users from making capital expenditures. The industry is demanding products that offer higher performance and higher functionality, yet at a lower cost. In the Asia-Pacific region, the manufacturing base has been increasing and the focus on production has created a much more cost-sensitive environment, boosting the market for signal generators.

Higher bandwidth is the number-one requirement for end users. A greater number of digital modulations transport more data in the same bandwidth, making the modulations more likely to generate imprecise levels of transmissions and phase angles. Signal generators, therefore, play a critical role in test systems. As Bob Buxton, marketing manager in the general-purpose business unit at Anritsu, said, “a signal generator is the heartbeat of the test system; power level is the strength of the heartbeat, accuracy of the instrument is the heart rate, and the quality of the signal is the profile of the heartbeat.” A key driver for vendors of signal generators will be the ability to provide higher frequencies and lower phase noise in their products.

During the economic downturn of 2009, the global revenue for both RF and microwave signal generators declined by an average of 22%. According to Frost & Sullivan’s analysis, the RF signal generator market held the largest market share at 57.3% and is projected to reach $365.8 million in 2011, while the microwave signal generator market accounted for 42.7% of the market and will reach $273.1 million in 2011.

Overall, Frost & Sullivan believes that the signal generator market will experience moderate growth during the forecast period. The compound annual growth rate for RF and microwave signal generators from 2011 to 2015 is estimated at 3.2% and 3.4%, respectively.

Full article by Fernando Nara, T&M World

Keithley enters power-supply market

Travis Wheeler — Sat, 24 Sep 2011 17:53:38 +0000

Keithley Instruments, known among engineers for its precision measurement instruments and source-measure units, has entered the bench power-supply market. The company’s new 2200 series consists of five linear power supplies with power outputs from 86 W (72 V, 1.2 A) to 150 W (60 V, 2.5 A). Dual displays on the instruments provide programmed and measured voltage and current. When using remote sensing, the instruments display voltage at the sense point.

You can program the power supplies from their front panel or with SCPI commands through their GPIB or USB interfaces. Like other instruments from Keithley, the 2200 series can store seven 80-step sequences that you can step through using software or an external hardware trigger, thus saving a host computer from programming the instrument for each setting. The power supplies can also store up to 40 settings that you can recall from the front panel or through programming commands. A front-panel lock-out function lets you disable the front panel when you don’t want operators changing settings. Programmable limits prevent the instrument from potentially damaging a device under test with excessive current.

Basic DC accuracy is 0.03% for voltage and 0.05% for current. Programmable resolution is 1 mV and 0.1 mA. The supplies have front and rear outputs for use on the bench or in a rack, plus rear-panel status and control lines.

Full article by Test & Measurement World

Fluke instruments speed field calibrations

Travis Wheeler — Thu, 22 Sep 2011 17:20:09 +0000

Engineers and technicians can use Fluke’s new 750 series of calibrators to calibrate temperature, pressure, voltage, current, resistance, and frequency. In addition, these rugged handheld instruments offer three operating modes—measure, source, and simultaneous measure/source—enabling technicians to troubleshoot, calibrate, or maintain instrumentation with just one tool.

The Model 753 and Model 754 feature a menu-driven display that guides users through tasks. Programmable calibration routines let you create and run automated as-found/as-left procedures to ensure consistent calibrations. Recorded results can be downloaded to a PC via a USB port.

The graphic display of the calibrators is bright enough to be read in any light condition, and a multilingual interface displays instructions in English, French, German, Spanish, or Italian. Units also have a rechargeable Li-ion battery pack that provides power for an entire shift and can be charged from within the calibrator.

The 750 series comes standard with three sets of stackable test leads, three sets of TP220 test probes with three sets of extended-tooth alligator clips, two sets of AC280 hook clips, a soft case, Li-ion battery pack and charger, USB communication cable, and HART communication cable (Model 754 only). Both models come with a NIST-traceable certificate of calibration.