EMC Measurement Technology

LangerSX near-field probes enable electromagnetic compatibility (EMC) analyses of interferences emitted by electronic boards, components, and IC pins with high internal frequencies. The SX-R3-1 magnetic H-field probe is designed to detect high-frequency magnetic fields with a high geometrical resolution. The field orientation and distribution can be detected by moving the probe around conductor runs, bypass capacitors, EMC components, and within IC pin and supply system areas. The SX-E03 E-field probe detects bus structures and larger components.

The probes have a 1-to-10-GHz frequency range. Their high resolution (the SX R3-1 achieves 1 mm and the SX E03 covers up to 4 mm × 4 mm) enables them to pinpoint RF sources on densely packed boards or on IC pins. The magnetic-field probe heads are electrically shielded. The probes are connected to a spectrum analyzer input via a shielded cable and SMA connectors during measurement. High clock rates of 2 GHz, for example, may result in fifth-order harmonics of up to 10 GHz. These harmonics are coupled out by RF sources on the board (e.g., conductor-run segments, ICs, and other components). They may stimulate other structural parts of the board to oscillate and emit interferences.

Contact Langer for pricing.

Langer EMV-Technik
www.langer-emv.com

Three Workspaces, Countless Projects

Clive “Max” Maxfield, who received his BSc in Control Engineering from Sheffield Hallam University in England in 1980, began his career designing CPUs for mainframe computers. But he has branched out far beyond that, becoming a prolific writer of engineering books, an EE Times editor, a blogger, and a designer of “interesting stuff,” from silicon chips to Steampunk “Display-O-Meters,” according to his website.

Max, who now lives in Huntsville, AL, recently shared with Circuit Cellar photos and descriptions of some of his ongoing projects and creative workspaces:

I would say that I have three personal workspaces. But before we talk about my workspaces, it might be appropriate to first mention two of my several projects, which vary from artistic to technological.

This is the future home of the Prognostication Engine.

This is the future home of the Prognostication Engine.

One of my projects that is currently in full swing is my Pedagogical and Phantasmagorical Inamorata Prognostication Engine. What do you mean “What’s that when it’s at home?” Isn’t it obvious?

Pedagogical = Educational
Phantasmagorical = It’s pretty darned fantastic
Inamorata = The woman with whom one is in love
Prognostication = Predicting the future
Engine = Machine

The Prognostication Engine is intended to help me predict my wife’s mood. Will the radiance of her smile fall upon me when I return home from work in the evening?

My Prognostication Engine is going to be housed in a beautiful wooden radio cabinet circa 1929. This is going to feature two brass control panels, both of which are going to be festooned with antique knobs and buttons and switches and analog meters (the ones with the black Bakelite bezels). I’m aiming at a Steampunk “look-and-feel” that would not look out of place in a Victorian setting.

One of the tricks I use when working on this type of project is to first create to-scale Visio drawings of all of the knobs, switches, meter, and so forth, and then I create a full-sized card-and-paper mockup as shown below. This makes it much easier to move things around and experiment with different placements so as to decide on the final layout.

The paper and card mockup of the Prognostication Engine's upper and low control panels

The paper and card mockup of the Prognostication Engine’s upper and low control panels

Observe the two small pink dots at the top and bottom of each of the vertically-oriented switches and on either side of the horizontally oriented switches and buttons; also the 16 pink dots around each of the five potentiometers. These are going to be faux mother-of-pearl dots, behind which will be tri-colored LEDs implemented using Adafruit’s individual Flora NeoPixels and NeoPixel Rings, respectively.

Everything is going to be controlled using an Arduino Mega microcontroller development board. Speaking of control, the potentiometers are going to be motorized, so that if an unauthorized operator tries to modify any of the settings, the other potentiometers will automatically change to compensate (later they will all surreptitiously return to their original settings).

Now observe the three black momentary push-buttons located on the lower panel, just under the modestly sized red button (do not press the red button). These equate to gifts of chocolates and flowers and hugs. Judicious use of these buttons increases the chances of happy times; overusing them, however, may trigger the “suspicion of wrongdoing” algorithm. In reality, there’s far too much “stuff” to go into here. Suffice it to say that the large meter in the top right-hand corner of the upper panel will reflect the full range of female emotion, from “Extremely Disgruntled” to “Fully Gruntled” (LOL).

Max has another project, dubbed “BADASS Display,” which was inspired by an item he saw in an electronics boutique-type store—a “really cool 9″ tall, cylindrical Bluetooth loudspeaker, whose outer surface was covered with tri-colored LEDs implementing a sort of spectrum analyzer display.”

While Max wasn’t interested in the $199.95 price, the “seed had been sown,” he says.

Thus was conceived my Bodacious Acoustic Diagnostic Astoundingly Superior Spectromatic (BADASS) display. First of all, I took a look around YouTube to get some ideas. It turns out that there are many different ways to present spectrographic data. For example, check out Gavin Curtis’ “My Big Blue 32 Band Audio Spectrum Analyzer Lady Gaga,”  RGB Styles’s “Coffee Table,” and Techmoan’s “Giant LED Graphic Music Display (DJ Spectrum Analyzer).”

I decided that the first incarnation of my display would boast a 16 x 16 array of tri-colored LEDs. I decided to use Adafruit’s NeoPixel Strips. Once again, I started by creating a cardboard and paper mockup as shown below.

Cardboard and paper mockup of the BADASS Display

Cardboard and paper mockup of the BADASS Display

The NeoPixel strips I’m using have 30 pixels per meter. I’m mounting these vertically, which means the vertical separation between adjacent pixels is 33.33 mm. To provide some visual interest, I decided to make the horizontal spacing between columns 50 mm, which is 1.5 times the vertical spacing.

In the real version, the cardboard will be replaced by plywood stained to look like expensive old wood. Meanwhile, the main display panel and the smaller control panel will be formed from hardboard painted to look like antique brass. In front of each pixel will be a 1″-diameter brass bezel accompanied by a 1/2″-diameter clear Fresnel lens in the center. The hardboard panels are going to be attached to the plywood panel using brass acorn nuts. Once again, the finished unit is intended to have a Steampunk look and feel.

I’m planning on using an Arduino Mega microcontroller development board to drive the display itself. This will be accompanied by a chipKIT Max32 microcontroller board that will be used to process the stereo audio stream and extract the spectrum data.

Max’s three project work areas include his office, his kitchen table, and his garage:

I would say that my first personal workspace is the Pleasure Dome (my office). Why do I think of this as a personal workspace? Theoretically I work out of a home office. In reality, however, I prefer to rent a room in a building belonging to an engineering company called MaxVision (no relation).

When you cross the office threshold, you enter a small corner of “Max’s World” (where the colors are brighter, the butterflies are bigger, the birds sing sweeter, and the beer is plentiful and cold). One of the walls is lined with wooden bookshelves containing an eclectic mix of science books, technical books, comics, and science fiction and fantasy books and graphic novels.

Welcome to the Pleasure Dome (Max's office)

Welcome to the Pleasure Dome (Max’s office)

My office is also the repository for all of the antique knobs and switches and analog meters and large vacuum tubes and such that I collect on my travels for use in my projects. Also, I can store (and present) larger objects in the bay outside my office.

My second personal workspace is the kitchen table in the breakfast nook at our home. This is where I tend to implement the electronics portions of my projects. At the far end of the table in the image below we see the jig I constructed to hold the two brass control panels for my Inamorata Prognostication Engine project. On the floor in the right-hand side of the image is the tool box that contains my electronics tools including screwdrivers, snip, and suchlike. It also contains my test equipment in the form of a cheap-and-cheerful multimeter from Amazon, along with an iPad-based oscilloscope and an iPad-based logic analyzer, both from Oscium.

Max's kitchen table

Max’s kitchen table

Observe the plastic storage box on the nearside of the table. I have a separate storage box for each of my projects. Anything associated with a project that’s currently under construction is stored in that project’s box, including any notes I’ve made, any electronic components and their datasheets, and any mechanical parts such as nuts and bolts.

I tend to gather everything associated with a particular function or sub-unit together into smaller boxes or plastic Ziploc bags. In the case of my motorized potentiometers, for example, I have the potentiometers along with the appropriate nuts, washers, antique knobs and suchlike all gathered together. I cannot tell you how much time and frustration a bit of organization like this saves you in the long run. It also make it much easier to pack everything up when my wife, Gina, informs me that she needs the table cleared.

Below we see another view of the test jig I constructed to hold the two brass panels for the Prognostication Engine. Creating this jig only took an hour or so, but it makes life so much easier with regard to assembling the electronics and accessing everything while I’m in the prototyping and software experimentation phase of the project.

The test jig for the Prognostication Engine on the kitchen table

The test jig for the Prognostication Engine on the kitchen table

Max’s third personal workspace is his garage. When his family’s three vehicles are parked inside, his projects are packed away in a corner, including tools and tiles for a mosaic he is creating that will feature ceramic tiles fired in his recently purchased kiln.

Everything tucked away

Everything tucked away

The shelves covered in plastic sheet to the right are where I place my freshly-rolled clay tiles to gradually dry without cracking. The low-down rolling cabinet in the foreground contains all of my handheld ceramic equipment (shapers and scrapers and rolling pins whatnot) along with general protective gear like face masks and safety goggles. Each of the plastic boxes on top of this cabinet is associated with a currently in-progress project. Behind this cabinet is a red rolling tool cabinet, which contains any smaller power tools, clamps, screwdrivers, wrenches and spanners, and also my soldering station and magnifying lens with helping hands and suchlike. To the right of that tool cabinet is a door (not visible in this picture) to a built-in closet, where I keep my larger power tools such as a diamond saw, desktop grinder, router, and so forth.

On the weekends, Max’s garage space opens up as his stepson drives out in his truck and Max’s wife leaves for her real estate agent’s job. “As soon as she has left, I leap into action,” Max says. “I roll out my tool boxes, set up a folding table and chair, and start work on whatever it is I’m currently working on.”

Another little corner of Max's garage work area

Another little corner of Max’s garage work area

As he works on projects in his garage, Max says he is “happily listening to stuff like Led Zeppelin, Genesis, Pink Floyd, Yes, Supertramp, Gentle Giant, The Moody Blues…”

The image below shows a close-up of the current state-of-play with regard to my BADASS Display. A week ago, I routed out the areas in the big plywood panel that will accommodate the hardboard display and control panels. In this image, I’m poised to mark out the hardboard panels and start drilling the mounting holes along with the 256 holes for the tri-state LEDs.

The BADASS Display

The BADASS Display

What can I say? Working on my hobby projects is a great way to wind down after a hard day at work, and being in any of my three personal workspaces makes me happy.

Max poised to give a presentation at the EELive! Conference in San Jose, CA, earlier this year

Max poised to give a presentation at the EELive! Conference in San Jose, CA, earlier this year

Editor’s Note: To find out more about Clive “Max” Maxfield, read his 2013 interview in Circuit Cellar. You can follow Max on Twitter @MaxMaxfield.

Traveling With a “Portable Workspace”

As a freelance engineer, Raul Alvarez spends a lot of time on the go. He says the last four or five years he has been traveling due to work and family reasons, therefore he never stays in one place long enough to set up a proper workspace. “Whenever I need to move again, I just pack whatever I can: boards, modules, components, cables, and so forth, and then I’m good to go,” he explains.

Raul_Alvarez_Workspace _Photo_1

Alvarez sits at his “current” workstation.

He continued by saying:

In my case, there’s not much of a workspace to show because my workspace is whichever desk I have at hand in a given location. My tools are all the tools that I can fit into my traveling backpack, along with my software tools that are installed in my laptop.

Because in my personal projects I mostly work with microcontroller boards, modular components, and firmware, until now I think it didn’t bother me not having more fancy (and useful) tools such as a bench oscilloscope, a logic analyzer, or a spectrum analyzer. I just try to work with whatever I have at hand because, well, I don’t have much choice.

Given my circumstances, probably the most useful tools I have for debugging embedded hardware and firmware are a good-old UART port, a multimeter, and a bunch of LEDs. For the UART interface I use a Future Technology Devices International FT232-based UART-to-USB interface board and Tera Term serial terminal software.

Currently, I’m working mostly with Microchip Technology PIC and ARM microcontrollers. So for my PIC projects my tiny Microchip Technology PICkit 3 Programmer/Debugger usually saves the day.

Regarding ARM, I generally use some of the new low-cost ARM development boards that include programming/debugging interfaces. I carry an LPC1769 LPCXpresso board, an mbed board, three STMicroelectronics Discovery boards (Cortex-M0, Cortex-M3, and Cortex-M4), my STMicroelectronics STM32 Primer2, three Texas Instruments LaunchPads (the MSP430, the Piccolo, and the Stellaris), and the following Linux boards: two BeagleBoard.org BeagleBones (the gray one and a BeagleBone Black), a Cubieboard, an Odroid-X2, and a Raspberry Pi Model B.

Additionally, I always carry an Arduino UNO, a Digilent chipKIT Max 32 Arduino-compatible board (which I mostly use with MPLAB X IDE and “regular” C language), and a self-made Parallax Propeller microcontroller board. I also have a Wi-Fi 3G TP-LINK TL-WR703N mini router flashed   with OpenWRT that enables me to experiment with Wi-Fi and Ethernet and to tinker with their embedded Linux environment. It also provides me Internet access with the use of a 3G modem.

Raul_Alvarez_Workspace _Photo_2

Not a bad set up for someone on the go. Alvarez’s “portable workstation” includes ICs, resistors, and capacitors, among other things. He says his most useful tools are a UART port, a multimeter, and some LEDs.

In three or four small boxes I carry a lot of sensors, modules, ICs, resistors, capacitors, crystals, jumper cables, breadboard strips, and some DC-DC converter/regulator boards for supplying power to my circuits. I also carry a small video camera for shooting my video tutorials, which I publish from time to time at my website (www.raulalvarez.net). I have installed in my laptop TechSmith’s Camtasia for screen capture and Sony Vegas for editing the final video and audio.

Some IDEs that I have currently installed in my laptop are: LPCXpresso, Texas Instruments’s Code Composer Studio, IAR EW for Renesas RL78 and 8051, Ride7, Keil uVision for ARM, MPLAB X, and the Arduino IDE, among others. For PC coding I have installed Eclipse, MS Visual Studio, GNAT Programming Studio (I like to tinker with Ada from time to time), QT Creator, Python IDLE, MATLAB, and Octave. For schematics and PCB design I mostly use CadSoft’s EAGLE, ExpressPCB, DesignSpark PCB, and sometimes KiCad.

Traveling with my portable rig isn’t particularly pleasant for me. I always get delayed at security and customs checkpoints in airports. I get questioned a lot especially about my circuit boards and prototypes and I almost always have to buy a new set of screwdrivers after arriving at my destination. Luckily for me, my nomad lifestyle is about to come to an end soon and finally I will be able to settle down in my hometown in Cochabamba, Bolivia. The first two things I’m planning to do are to buy a really big workbench and a decent digital oscilloscope.

Alvarez’s article “The Home Energy Gateway: Remotely Control and Monitor Household Devices” appeared in Circuit Cellar’s February issue. For more information about Alvarez, visit his website or follow him on Twitter @RaulAlvarezT.

Test Equipment: What to Consider

Editor’s Note: Ian Broadwell, a postdoctoral fellow at the Department of Chemistry at Ecole Normale Superieure in Paris, wrote the following review of test equipment for circuitcellar.com readers. He is pursuing additional articles about making the right choices in equipment.


Whether you are setting up your own electronics workbench or professional design company, you certainly will be thinking about the test gear you should buy. With big-name brands such as Agilent, Fluke, Keithley, Tektronix, and LeCroy (to name a few) aggressively marketing their latest products, it’s easy to think you’ll have to start earning a pro soccer salary and work until you’re 150 to own some of these high-end products. But this is not necessarily true—if you’re prepared to wait and buy used equipment (I will revisit this point later).

The diverse spectrum of Circuit Cellar readers will have a wide variety of test and measurement requirements. In this first article about “making the right choice,” I want to introduce myself, the variety of test equipment available, and, finally, the rules I follow in buying test equipment for my electronics lab.

Introducing Myself

As a teenager, I had ambitious dreams of setting up an electronics laboratory. My journey started when I became involved with the local ham radio club, G4EKT, in Great Britain’s East Yorkshire County. At 17, I became a fully licensed A-class radio amateur and started to build some of my own equipment, such as a shortwave valve RF power amplifier (a tube amplifier in the US) and a dual-function standing wave ratio / power meter.

After joining G4EKT, I found flea markets and radio rallies a source of electronic and mechanical parts for constructing my own equipment. Money was tight as a teenager, so I could only dream of owning an oscilloscope; having a spectrum analyzer would be like standing on the moon (a very remote possibility). I came to realize it takes years to collect the equipment to set up your lab—and successful people rarely tell you this.

After my schooling, I followed the traditional university route—graduating with a BSc in Physics, MSc in Exploration Geophysics, and a PhD in Physical Chemistry. My professional experience has taken me from being a quality-control technician in an analytical chemistry lab to an offshore field geophysicist in northwest Australia. Eventually, I came full circle—back into academia with several postdoctoral positions in England, China, and now France. The diversity of working environments, locations, and multidisciplinary subjects has provided a unique window for viewing the tools-of-the-trade in different disciplines. My fascination with scientific instruments encompasses all domains.

Currently, I work in the Department of Chemistry at Ecole Normale Superieure in Paris as a Marie Curie Postdoctoral Fellow. My research interests include instrumentation and development of microfluidic tools for use at the interface between physics, chemistry and biology.

A Diversity of Available Equipment

Today we take test equipment for granted. We have testers for just about anything imaginable. Where there is something to be measured, there will be a machine to do so—along with 100 patents claiming rights to all the varied ways to measure what you want to quantify. There has never been a better time to find test equipment in the used market, a result of the global economic slowdown and the turnover and exploitation of new technologies. Consider the computer you bought last year; it’s already old, technologically speaking.

Technological progress has not always been this rapid. Historically, war or military endeavours have driven technological leaps. Remember the Cold War, the nuclear arms race between the US and USSR from 1947-1989? This period of sustained technological development spurred the Internet and the abundance of test equipment we see today. My favorite test-equipment manufacturer was Hewlett-Packard (HP), which produced a vast range of scientific and laboratory equipment from 1939 until 1999, when the company was restructured. Agilent Technologies continues to develop the company’s former test and measurement product lines, while the new HP primarily focuses on computer, storage and imaging products. Most of HP’s equipment is well-documented, with downloadable manuals. Meanwhile, Web-based user groups are continually contributing to online document repositories. And HP’s equipment was built to last, using military-grade components. That is why 20- or 30-year vintage test equipment is often found in working order.

At the high end, test equipment comes in many different forms—from stand-alone, high-precision single benchtop units to dedicated chassis and multifunction rack-mount instrument arrays. HP was one of the first companies to use instrument arrays. This has been further developed by companies such as National Instruments (NI), with its range of chassis and stand-alone data acquisition (DAQ) cards that fit into a desktop PC and form a virtual instrument using NI’s LabVIEW software. Industries often prefer to use modular measurement systems because of the inherent flexibility to tailor the functionality to meet their own specifications. They also conserve space and allow the test stand engineer to automate select tests.

At the low end, every electronics enthusiast should aim to have a basic handheld multimeter and an oscilloscope. This is essential equipment to start your hobby. Fluke, B&K Precision, and Extech Instruments are but a few of the established brands. Although company headquarters are usually located in Europe or the US, many companies have design and manufacturing units in Taiwan and mainland China (Hong Kong and Shenzhen). My experience working in China showed me that the mainland Chinese prefer electronic components and instruments made in Taiwan because of its longer history of Western investment. This is not to say mainland products are poor—Rigol is an excellent brand with top-quality components in its products.

The message is that you get what you pay for. So, whatever basic equipment you intend to buy, try to purchase it from an established brand that you know will provide at least a one-year guarantee and some sort of manufacturing quality control in its products. A Fluke 115 multimeter, for example, has the essential functions you’ll need and costs around $200. For this price, you should feel confident that the meter will last a very long time if used as intended.

Some of the best information sources for those interested in electronics are subscription electronics magazines such as Elektor, Circuit Cellar, Everyday Practical Electronics and Nuts and Volts. Article technical levels vary widely between the magazines, ranging from absolute beginner to seasoned professional. General magazines are a great introduction for beginners and offer a relatively cheap route into the electronics field or more focused areas. Specialized electronics areas such as audio or industrial have their own publications, including audioXpress, IEEE Industrial Electronics, and the free-subscription online EDN Network (www.edn.com).

Speaking to people can be better than wading through magazine pages. Local electronics or ham radio clubs are a rich knowledge source. In fact, they can be more informative than large professional-equipment suppliers who have commercial agreements or little knowledge of different test platforms. In Europe, a number of small equipment brokers survive. They can offer excellent advice on a wide range of equipment issues and projects, because their employees must multitask. Such companies have small profit margins, so their employees often work on projects outside their normal expertise. Brokers also tend to be professionals who have worked in the industry for 20 to 30 years before heading out on their own.

Rules I Use for Buying Test Equipment in My Electronics Lab

After determining your future test equipment needs and drawing up a short list of essential features, it’s time to focus on the brands, models, and vintages that will meet your minimum specifications. Some less obvious things to consider are: the physical volume and weight of the equipment and cooling and power requirements. My lab is situated in a 2-by-3-m room with minimal space and ventilation. Large rack-mounted instruments are heavy and take up a lot of space, which requires careful arrangement to accommodate all the equipment. Additional considerations include: electrical power ratings (daisy chaining too many instruments together from the same socket is a fire risk); sufficient room ventilation to remove hot air from the instruments’ cooling systems; and smells generated by aging, phenolic printed circuit boards.

In recent years, I have been collecting a wide range of instruments. My objective has been to build up a general-purpose electronics lab where overall functionality (i.e., the breadth of measurements I’m able to make) is more important than high resolution and cutting-edge accuracy (this is what calibration labs are for). General-purpose semi-professional labs should, in my opinion, be able to tackle a range of projects—be it RF, audio, or control.

One of the most expensive pieces of test equipment an RF lab should have is a spectrum analyzer. Recently, I spent a lot of time considering spending my money and realized that such a purchase could require remortgaging my house and would, at minimum, need the boss’s (wife’s) permission. In preparation to achieve the “minimum,” I drew up a series of feel good factors” to give weight to my case.

These factors amount to a list of things you should consider before a purchase (see Table 1). They can serve as a yardstick for reviewing a spectrum analyzer or other pieces of equipment.

 

Table 1

Feel good factor Description
a) Space utilization Keithley source meters have five instruments in one unit (i.e., one box replaces four or five boxes of its predecessors). This is efficient space utilization.
b) Connectivity Does the equipment come with all the latest LAN, Wi-Fi, GPIB, USB, and RS-232 protocols as standard?
c) Portability Is the equipment your lab doorstop, or is it small enough to be used in remote locations such as up a cellular phone mast?
d) Ease of use Is the equipment intuitive and easy to use, or do you need the latest version of the user guide and service manual (which may not be available) to get going?
e) Special features and add-ons/expansions Include extended memory depth or high-speed data streaming, automated test stand, hardware upgrades, and powerful proprietary software-analysis functions (i.e., modifications that allow uses with MATLAB or LabVIEW).
f) Resolution/accuracy How much resolution is required and what level of calibration/traceability?
g) Price vs. functionality You are either buying the latest feature-packed instrument or used equipment from a broker or eBay. Generally, money will be tight and buying high-end new equipment isn’t an option. Clearly, the used market can offer some good deals. You find two instruments that have nearly the same functionality and both are tempting. Which do you buy? At first, you may reply the more modern one, as there may be less risk of failure.Let’s now consider buying a 20 GHz vector network  analyzer. The Agilent 8510c is about half the price of the slightly more modern Agilent 8720a.  Both have nearly the same specifications. The 8720a is more compact. The 8510c is definitely larger, more modular (requiring an external signal generator and S-parameter test set), and better built. The latest versions of the 8510c are similar in vintage to the 8720a and differ by only a few years. Agilent repairs are prohibitively expensive for both. The modular nature of the 8510c and abundance of eBay modules translate into increased self-servicing of repairs. If 8510c spares were hard to find, then it would be a good reason for choosing more modern equipment (i.e., 10 years old rather than 25).
h) Disposal and small print issues Are there any toxic materials used in the instrument’s manufacturing that will cause future disposal issues? Is it going to cost you more to dispose of it than it did to buy it?EBay dealers only cover equipment faults detected within the initial weeks of a purchase. The buyer will be responsible for any repairs costs that fall outside of this guarantee period.
i) Overall value for money Does the equipment have a reputation for being reliable and consistently doing what is written on the packaging, year after year? What’s included with your purchase? Probes? Extended warranty? On-site maintenance? Service contracts?Often, eBay purchases come without peripherals (e.g., probes) and these need to be found elsewhere. Sometimes, there are lucky buys to be had. Generally, most traders only want to maximize their profits, so beware of this.
j) Deal or no deal 1) Does the equipment fit your test requirements?2) Is it within your budget?3) And finally, do you really need it?

 

Rules for reviewing equipment are often best understood by offering an example. To foster understanding, I have made a comparison between two spectrum analyzers—a used Agilent 8591a and a new Rigol DSA815-TG. Both have very similar specifications in terms of maximum frequency, dynamic range, and resolution. While the Rigol offers the latest color LCD, portability, and connectivity, the HP provides the reassurance that it still works after all these years. When new, the HP was a very high-end instrument (costing $18,000 in the 1980s). But evolving technology has enabled us to purchase entry-level spectrum analyzers, such as the Rigol DSA815-TG, with virtually the same specifications. This is really mind-blowing.

When considering instrument performance by comparing marketing data, you should keep in mind manufacturers will try to legitimately report best values for important parameters. Although the two analyzers appear identical, the phase noise performance of the HP is better than the Rigol. The phase noise represents the short-term stability of the frequency reference and the analyzer’s ability to distinguish weak signals next to a strong carrier. With my preference for high performance, value for money, and a hint of nostalgia, I would buy the HP 8591a rather than the Rigol DSA815-TG.

For a “feel good factor” comparison of the HP 8591a and Rigol’s DSA815-TG, see Table 2.

Table 2

Feel good factor Instrument 1: HP 8591a Instrument 2: Rigol DSA815-TG
a) Space utilization 163 mm x 325 mm x 427 mm 399 mm × 223 mm × 159 mmThe Rigol is approximately half the volume of the HP.
b) Connectivity GPIB, serial port, and analogue monitor output USB interface allows connection to PC and memory stick; LAN
c) Portability Not very portable at 15 kg and has no battery feature. It will accept 86-127/195-250 VAC; 47-66 Hz. Very portable at 7.5 kg including battery and also accepts 100-240 VAC, 45-440 Hz.
d) Ease of use Although the instrument is old, the menu system is easy to use. ROM updates for the software are available but no longer updated. The Rigol also has an excellent indexed menu system with hot keys on the side of the screen. The operating system can be switched instantly to a range of different languages
e) Special features and add-ons/expansions 004 precision frequency reference, 010 tracking generator, 101 fast time domain sweeps, 102 AM/FM demodulation Optional USB to GPIB; tracking generator and preamp are not standard features.
f) Resolution/accuracy Frequency resolution bandwidth 3 kHz to 3 MHz in a 1, 3, 10 sequence; 10 MHz frequency reference with option 4 has 0.2 ppm drift/year. The phase noise sidebands at 10 kHz offset from the carrier is <-90 dBc/Hz. Signal amplitude dynamic range of −115 dBm to 30 dBm from 1 MHz to 1.8 GHz and 0.01 dB resolution 100 Hz to 1 MHz in 1-3-10 sequence. Frequency reference has 2 ppm drift/year10 kHz offset from the carrier is <-80 dBc/Hz.−115 dBm to 20 dBm across 1 MHz to 1.5 GHz without preamplifier and 0.01 dB resolution
g) Price vs. functionality 9 kHz–1.8 GHz spectrum analyzer with tracking generator. This unit was originally sold from 1978 to 1990 for $18,000 including options. Today a good uncalibrated unit on eBay will fetch $1,750. 9kHz–1.5GHz spectrum analyzer with tracking generator currently sells for $2,000, including tax, from both eBay and directly from a Rigol supplier. With this, you are buying the latest instrument 2012 production date.
h) Disposal and small print issues Has beryllium oxide RF components inside, which could be a problem for disposal Repairs are only carried out by the manufacturer in Beijing. In 2010, I remember this was the situation.
i) Overall value for money Reliable and time-honored equipment made of excellent quality components and built to be repairable. Boasts 8″ WVGA 800 × 480 pixel screen. Has all the bells and whistles that your portable lab needs. Not really built to be repaired by the broker or individual, with all the FPGA and surface-mounted components.
j) Deal or no deal Personally, I would buy the used equipment, as there is more margin to negotiate the price and it is built to last. The product will not substantially depreciate, as with a new model such as the Rigol. This excellent equipment built from Analog Devices components is a budget spectrum analyzer and offered at the lowest price in the Rigol range.

The Key Questions

Always remember, making the right choice doesn’t have to be painful and costly. Just ask yourself the key questions:

1) Is the equipment a fit for your test requirements?

2) Is it within your budget?

3) Do you really need it?

If you manage to convince your line manager (or your spouse) that the answer to all three is “yes,” then you’re likely to get the thumbs up to make that important purchase.