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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

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

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

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.

USB test instruments provide portable modularity

Travis Wheeler — Wed, 24 Aug 2011 19:18:07 +0000

The USB (Universal Serial Bus) provides PC connectivity with many desirable attributes, so it is no surprise that test instruments have arisen that use the USB to link to a host computer. What may be surprising, however, is the range of functions and performance levels available from USB test instruments. Data-acquisition, signal-generation, measurement, and RF instruments are all available with USB connectivity, and engineers can mix-and-match multiple instruments to form a complete test platform.

True to their “universal” name, USB ports have become pervasive, available on virtually every personal and industrial computer in production. Even production-test systems based on the personal computer architecture offer USB ports. And for good reason. A USB 2.0 port (the most commonly available) provides hot-swappable plug-and-play connectivity, transfers data at rates up to 480 Mbps (faster than 100-Mbps Ethernet), offers host power to attached devices, and has the ability to connect 128 unique endpoints to the host through a single port. The new USB 3.0 specification boosts data rates nearly tenfold.

To leverage the availability and simplicity of USB, a number of companies have created test instruments that link through USB to a host PC for processing, control, and display. The most common of these instruments are DSOs (digital storage oscilloscopes) and function generators, many from small companies that specialize in these portable instruments. The Australian company Esis and the UK-based Elan Digital Systems, for instance, both offer the USBscope50—a PC plug-in not much larger than a flash drive that accepts standard BNC probes (Figure 1). The instrument has a 75-MHz input bandwidth and can capture 8-bit samples at a rate of 50 Msamples/s in single-shot capture. For repetitive signals, the instrument provides capture timing equivalent to 1 Gsample/s.

The two companies also offer a 12.5-MHz DDS function generator with 0.2-Hz resolution and ±10-V output, a 100-MHz clock and pulse generator, and a 50-MHz frequency/period counter, all in the same form factor. The modules are stackable to form a suite of interrelated instruments, using an adapter that permits four modules to share the same USB port. Thus, you can provide a test stimulus, measure output frequency, and examine two waveform channels using an ordinary laptop and a collection of modules that could fit into a shirt pocket.

The USB test-instrument market is not limited to specialty companies, either. Both Agilent Technologies and National Instruments offer numerous USB-based test instruments. NI, for instance, has more than 50 different USB instrument modules, including 6.5-digit DMMs (digital multimeters), RF power meters, data-acquisition units, thermocouple signal conditioners, and DSOs. Agilent has many similar types of instruments along with unique functions such as a 4×8 two-wire switch matrix and source-measure units with four-quadrant operation.

The USB instruments from both companies can operate as stand-alone devices or can be plugged into a chassis that aggregates several instruments into a test-equipment platform. The chassis enables triggering and synchronization of module operation as well as aggregating the command and data transfer for multiple instruments onto a single USB port. Further, chassis mounting helps ruggedize the USB modules, providing added protection against field hazards. NI offers four- and eight-slot USB module enclosures and has recently introduced a one-slot CompactDAQ enclosure for USB, Ethernet, or wireless connectivity. Agilent has a chassis capable of handling six modules (Figure 3).

The use of a chassis to combine multiple USB modules into an integrated test platform can push the bus to its limits. While a USB port can supply power to the attached instrument, for instance, that power is limited to 500 mA at 5 V. As a result, chassis systems must use an external power “brick” rather than drawing from the host, and then supply power to the plug-in modules from this external source.

Full article by Richard A. Quinnell, T&M World

Agilent’s T&M ‘Dreamliner’ hits the road

Travis Wheeler — Fri, 24 Jun 2011 18:40:29 +0000

A luxury transport truck carrying more than $4-million worth of test and measurement equipment is making its way across North America this spring/summer, as Agilent Technologies Inc. brings its Innovation Tour to major high tech hubs in Eastern Canada.

With 17 stops in total, the ‘Dreamliner’ brings the T&M leader’s latest technology innovations directly to the electronics design communities in Toronto, Montreal, Ottawa and Waterloo ON.

“We get lots of engineers, technicians and design managers on-board to see our extensive set of test solutions that include LTE, LTE-Advanced, MIMO, RFID, WLAN and others, says Brian Withnell, account manager of Agilent Canada’s electronic test and measurement products. “We try to show the test equipment and systems that are ahead of the technology wave, which helps participates get firsthand experience in an informal environment that they might not otherwise have an opportunity to see.”

The roving display, which has traveled to date 6,973 miles, includes a broad mix of technology, including everything from handheld, low-cost scopes, digital multi-meters and more high end products such as signal sources and generators, 32GHz real-time oscilloscopes.

Full article at Electronic Products and Technology

Acceptance of USB power meters continues to grow

Travis Wheeler — Wed, 18 May 2011 22:01:15 +0000

In the past, traditional power meters were the de facto standard for performing power measurements. In market terms, power meters are a mature and stable segment. With capital expenditure being a major concern for many companies, however, end users are requesting more cost-effective alternatives, and USB power meters have made significant inroads in the market. The lower cost of USB power meters compared to traditional devices plus their ease of use and portability drive demand for such instruments.

There is definitely a trend toward the use of more USB-based technology. Several leading companies in this market, such as Anritsu and Rohde & Schwarz, made the decision to focus on USB power meters. But the huge existing installed base of traditional power meters is projected to delay the growth in the USB power meter market in the short and medium terms.

With $77.4 million in revenues, traditional power meters represented the majority of the total market revenues for all types of power meters in 2010, a 75.2% revenue market share, and companies such as Rohde & Schwarz currently witness nearly as much revenue from traditional power meters as from USB power meters. Yet, the traditional power meter segment is a declining market, as projected revenues are expected to fall to $72.6 million in 2017.

The trend is shifting in favor of USB power meters. USB power meters have been undergoing increasing growth with revenues reaching $25.5 million in 2010. It is estimated that increasing revenue growth rates will translate into sizable revenues of $43.1 million by 2017, or 37.3% of the total market revenues.

Further analysis performed on the market in 2010 indicates that 70% of the revenues from USB power meters were generated from the communications end-user segment, and the other 30% came from the aerospace and defense industry. The market share of aerospace and defense, however, is expected to increase over the forecast period (2011 to 2017). This is mainly due to capital expenditure from governments.

The defense sector is expected to play a key role in enhancing the market share of USB power meters in the future. Moreover, the market is seeing increased adoption of higher-frequency and higher-speed measurements in aerospace radar signal applications that will be key drivers for USB power meters in the forecast period. The use of USB power meters is likely to accelerate, due to their ability to provide precision and affordability, which address end-user demands more effectively than their traditional counterparts.

Full article By Mariano Kimbara, T&M World

Agilent aims waveform generator at military scenarios

Travis Wheeler — Mon, 28 Feb 2011 16:53:04 +0000

Agilent is aiming an arbitrary waveform generator at radar, satellite and electronic warfare device designers to make reliable, repeatable measurements and create highly realistic signal scenarios to test their products.

Precision arbitrary waveform generation is required for realistic testing of low-observable aircraft systems and for high-density communications used in satellite communications systems.

The M8190A arbitrary waveform generator delivers simultaneous high resolution and wide bandwidth along with industry-leading spurious-free dynamic range and very low harmonic distortion. The instrument’s 2-GSa memory allows designers to create longer test scenarios that are more realistic.

“The M8190 AWG allows engineers to approach reality when they create test scenarios,” said Jürgen Beck, general manager of Agilent’s digital and photonic test business, in a statement.

The M8190A has 14 bits of resolution and up to 5 GHz of analog bandwidth per channel simultaneously.

A proprietary digital-to-analog converter designed by the Agilent Measurement Research Lab and fabricated with an advanced silicon-germanium BiCMOS process yielded a DAC operating at 8 Gsamples/s with 14-bit resolution and at 12 Gsamples/s with 12-bit resolution. At 8 GSa/s, the Agilent DAC delivers up to -80 dBc SFDR, an industry-leading specification.

It was this technology breakthrough that eliminates the trade-off between high resolution and wide bandwidth so measurements are more reliable and repeatable and engineers are less likely to misinterpret glitches in the waveforms as analog output.

The M8190A runs on an AXIe modular system, which is designed for high-performance instrumentation. It can be used with either a 2-slot or 5-slot chassis.

Full article by Nicolas Mokhoff, EE Times

New GSA Schedule Top Deals: Technical Equipment

Mark Howe — Wed, 19 Jan 2011 18:42:34 +0000

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Analyzer Scours Spectrum To 7 GHz

Travis Wheeler — Mon, 09 Aug 2010 16:14:55 +0000

The N9342C is a handheld spectrum analyzer from Agilent Technologies for analysis of signals from 100 kHz to 7 GHz, although it is tunable to 9 kHz. Ideal for field testing and signal surveillance, it includes an integral 7-GHz tracking generator, option for a GPS receiver, and optional 8-GHz antenna for signal tracking.

According to Brian LeMay, General Manager of Agilent’s Chengdu Instruments Division, the portable spectrum analyzer is “Specifically designed for the field, the N9342C HSA is extremely easy to use and brings RF field test efficiency to a new level.” The analyzer provides simple-to-use, one-button measurements for a wide range of popular parameters, including adjacent-channel power, occupied bandwidth, and channel power. An optional three-in-one backpack provides comfort and hands-free operation in the field. The analyzer includes USB and Ethernet ports for connection to a personal computer (PC), and is shipped with free N9342C HSA PC software.

Full Article By Jack Browne, Microwaves & RF