I recently posted a new technical paper to my EMC web site: “Making Your Own EMC Troubleshooting Kit”. This downloadable pdf file includes a summary of the six-part series of articles on the Test & Measurement World web site in The EMC Blog. I describe the complete list of contents, plus some advice on selecting a low-cost spectrum analyzer.
In my never-ending quest to search out useful reference books on EMC, I recently ran into the 3rd edition of “The ARRL EMC Book” (ISBN 9780872590915). First published in 1999, the new 3rd edition was released in 2010. For those unfamiliar with the ARRL (Amateur Radio Relay League), this is the national organization representing amateur radio operators (“hams”) in the U.S. Most hams are members of the league, which also publishes a range of useful operating, design and general radio reference books. Because hams are allowed to operate their two-way radios at up to 1.5kW, on occasion, this may be the cause of local interference to poorly-designed or poorly-shielded consumer products. Thus, several years ago it was decided to publish a reference book on RFI (radio frequency interference). In this article, I’ll describe the most important content and why you might want to buy it. More…
Posted in EMC Design, EMC Measurements, Reviews, Troubleshooting
Tagged EMC, RFI, troubleshooting
There are a number of engineering tools that work well for simulating EMC scenarios. One of these is MathCad, a tool that’s been around for a number of years. The neat thing about MathCad is that you can define a set of equations in free-form layout and plot out the analysis in several engineering-type graphs, including logarithmic and polar. These plots are easily copied and may be pasted into documents or technical papers.
As an example, I’ve calculated the harmonic content of a square wave given user-defined fundamental frequency, rise times, pulse widths and duty cycles. It’s very instructive to run through several scenarios prior to building hardware. By changing any of the user-defined parameters, you can quickly judge the outcome. More…
Many spectrum analyzers include tracking generators, but some new engineers my not completely understand what the purpose is and how they can help with certain measurements. In a nutshell, tracking generators are variable, or swept, RF generators that “track” with the spectrum analyzer sweep frequency. Some tracking generators have a limited frequency sweep as compared with their mating spectrum analyzer, so you need to know any frequency limitations in advance. In this article, I’ll use the new Rigol DSA815TG and the built-in tracking generator to measure a 150 MHz bandpass filter and a 10 dB attenuator. More…
Martin Rowe, Sr. Editor of Test & Measurement World, recently collected over 80 EMC-related blog posts and articles published in the last several years and has placed them all into a single location in the T&M World “Vault”. Look for “EMC EMI RFI ESD“.
Check them out!
RF Explorer is a handheld digital spectrum analyzer covering 15 MHz to 2.7 GHz. It is based on a highly integrated frequency synthesizer and double balanced mixer which offers high performance, compact size, low consumption and low cost. I’ve been beta-testing the unit for some time now and can confirm it works well as an affordable general-purpose analyzer.
Being battery-operated (chargeable via USB), it makes a great EMC troubleshooting tool. Probably, the major disadvantage is the limited user interface, being just seven push buttons, but there is available freeware PC and Mac remote client software to run and display waveforms. The display is also limited in resolution, but for the price, it’s tough to complain too much!
To read a review of the older model, which is very similar, click here…
The new RF Explorer is available now through SeeedStudio for $269.
While most larger companies may be able to afford just one EMC engineer (or a small handful) to cover all products under development, many smaller companies can’t afford one at all and must rely on their existing designers to deal with compliance issues (many times at the end of the product development process!). So where does the lone EMC engineer or inexperienced product designer turn to for help in answering EMC questions?
Having used Advance Devices Smart Tweezers for several years, I was surprised to find what appeared to be a clone in a local electronics store for about $30. They were designed by Chinese company, Artech, as their Model VC6015. I decided to purchase them and compare with the newest Smart Tweezer Model ST5.
The Artech VC6015 RC (doesn’t measure L) meter clone.
The first thing I noticed was the clever slide-on protective cover around the tweezers. My impression went downhill from there. The nickel-plated tweezer tips were not aligned well and I had to bend them straight. They had trouble grasping the smaller surface-mount parts, but worked OK on 0602 size and larger. The unit is powered by a CR2032 Lithium battery.
Whoa, I next noticed it doesn’t measure inductance; just resistance, capacitance and diodes – a major drawback. Also, the display can’t be oriented 180 degrees for us left-handed users.
Otherwise, the resistance and capacitance measurements were pretty accurate (see charts in the main article). The auto range worked well, but was slower than the Smart Tweezers. Also, the ranges were more limited, which reduced the accuracy of the smaller component values. The Hold button was useful to freeze the measurement.
Basic Specifications
Maximum Measurement Ranges
|
Parameter |
Range |
|
Resistance |
0.1 Ohms to 3.0MOhms |
|
Capacitance |
0.1nF to 30mF |
Basic Accuracy
|
Parameter |
Measurement Range |
Basic Accuracy |
|
Resistance |
300 Ohms to 300kOhms |
<1% |
|
3MOhms to 30MOhms |
<2% |
|
|
Capacitance |
3nF to 300uF |
<3% |
|
3mF to 30mF |
<5% |
Using the Artech VC6015
The meter fits OK in your hand, but I had to learn to read the display upside down. The Auto ranging worked well, but was slow. The Hold button would allow me to flip the unit around to read the measurement. Pressing the Func button would switch from the Auto measurement to only C or R, but with slightly wider measurement scales.
Conclusion
While the resistance and capacitance measurements seemed pretty accurate, the tweezer tips were a little fiddly when measuring very small surface-mount devices. The lack of an inductance measurement was a show-stopper for me.
The Artech Model VC6015 is available for about $30 and may be ordered through local dealers. Their Web site is: http://www.artech-instruments.com.
Not recommended.
For years, I’ve looked for an affordable LCR meter to measure unknown components–especially surface-mount. I ran into the Smart Tweezers (Model ST3) a couple years ago and wrote up a short review. Since then, Canadian company Advance Devices, has updated the design (Model ST5). This model is very similar, but there are a number of improvements worth mentioning.
The Smart Tweezers in use. When measuring components mounted to PC boards, you need to realize the measurement includes all components connected to the two measurement nodes. In some cases, the component must be measured “out of circuit”. However, by adjusting the new source voltage control lower, it will avoid turning on most semiconductor junctions, enabling more accurate measurements “in-circuit”. (Photo courtesy Advance Devices.)
Most LCR meters make basic measurements, but with limited ranges or inadequate accuracy. The ST5 is calibrated to NIST standards and includes a Certificate of Calibration. In addition, most conventional LCR meters aren’t really optimized to measure today’s SM (surface-mount) components. It’s tough enough working with SM parts…let alone trying to identify them once a few parts on your workbench get mixed together. Read more…
Many may not be aware, but Würth Electronics Midcom (WE Midcom) sells a monster 4-pound, 700-page book, the Trilogy of Magnetics, now in its 4th edition. The cost is 49 Euros or $49.99 USD, orderable through the WE Midcom web site or your local sales rep. This comprehensive design guide includes theory and applications for EMI filter, switch-mode power supply and RF circuit design. Now, many vendors supply application notes and white papers on their web sites or included with their catalogs, but usually, you need to wade through countless lists of products to find the meager theory and application information. While WE Midcom includes a few lists of ferrites in the book, the bulk of the content (99%) is packed with theory and applications. If you want the part information, that’s included on a CDROM in the back of the book. The CD also includes a copy of LTspice (from Linear Technology), plus a couple of WE selection/design programs.
The book, Trilogy of Magnetics, by Würth Electronics, is well worth adding to your reference library.
For a more detailed review, please check out the full article on the EMC Blog at Test & Measurement World (www.tmworld.com).
Electromagnetic Compatibility (EMC) design, troubleshooting and training.
design-4-emc.com 