Category Archives: Articles

Review: The Smart Tweezers Get Smarter

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…

All about current probes

Earlier this year, I published a tutorial on current probes and their application in Interference Technology (3/20/2012). The discussion included how to make your own probes from common ferrite cores, as well as commercial probes and how the DIY probes compared to the commercial ones. I finally wrapped up with how to use current probes to assess common-mode currents in I/O cables and how to predict pass/fail for radiated emissions by knowing the CM current on the cable.

Simple current probes made from clamp-on ferrite chokes.

First Impressions – Rigol DSA815TG Spectrum Analyzer

If there’s been one spectrum analyzer that’s created buzz lately, it’s the Rigol DSA815 budget ($1,295) spectrum analyzer, which tunes from 9 kHz to 1.5 GHz. A tracking generator option will run an extra $200 and the EMI option, which provides quasi-peak detection and the three EMI bandwidths (and especially excites us EMC engineers), is an extra $600. There are a number of other options available.

I was able to get my hands on a review unit and am putting it through it’s paces in the next couple weeks. However, with all the discussion of this product lately, I thought I’d give a few first impressions. The first thing that struck me was the compact size. It’s no larger than some of the smaller-size budget oscilloscopes with dimensions of 14″ wide by 7″ tall by just 5″ deep. The second thing that hit me was the weight of the unit for it’s size at 9.4 pounds. Obviously, there’s some shielding inside. The user guide is supplied on CD or available as a download from their web site. I added the guide to my iPad for easy reference.

I loved the large color screen (800×480 WVGA). The controls are arranged in logical groupings, duplicating to a large degree that found on Agilent spectrum analyzers. Besides the usual Frequency, Span and Amplitude buttons, major groupings include Control, Marker, Measure, Utility and Edit (numeric and text input). A vertical column of soft keys on the right side select secondary functions. Down along the left side you’ll find a column of analyzer status icons. There’s also a “Help” key that will describe each control for you.

Major “banner” specs include:

  • All digital IF technology
  • 9 kHz to 1.5 GHz frequency range
  • Up to -135 dBm displayed average noise level (DANL)
  • Resolution bandwidth (100 Hz to 1 MHz)
  • 1.5 GHz tracking generator option (-20 to 0 dBm)
  • EMI filter and quasi-peak detector option (200 Hz, 9 kHz and 120 kHz BWs) [updated 7/7/12]
  • Connectivity: LAN (LXI standard), USB host, USB device, GPIB (option)
  • Ultra Spectrum (PC) software option (provides additional analysis, including a waterfall display)

After getting some hands-on time in a local EMC test house where we performed some real conducted and radiated emissions measurements, I published a more detailed “first look” in Test & Measurement World’s EMC Blog. A full review will be upcoming on their web site soon. All in all, this appears to be very useful for EMC troubleshooting and pre-compliance testing – and at an affordable price, to boot!

Article on Harmonic Comb Generators

I recently published a tutorial article on Harmonic Comb Generators in RF Technology International Magazine, April 2012 issue. You can download the whole issue here or wait a few days, and I’ll post a link (in the comments) to the article itself.

EMC Troubleshooting Techniques Posted

I recently posted a list of EMC troubleshooting tips I’ve gathered over the years. Feel free to write me with your favorites and I’ll add them to the list!

Troubleshooting Radiated Emissions article published

I recently published an article, “Troubleshooting Radiated Emissions Using Low-Cost Bench-Top Methods”, in Interference Technology (ITEM) – EMC Directory & Design Guide (May 2011). It covers ways to identify sources of radiated emissions using DIY or low-cost probes and equipment.