EMC/EMI Testing

Reverb & Resonance: Beyond the Hype

Posted on October 10, 2013 by - EMC/EMI Testing

Reverberation chambers, Mode-Stirred and Mode-Tuned Testing, and Resonant Cavities are common terms we hear in the EMC community.  But what’s behind this technology–Is it really that new? And why is it important for EMC testing?

The physics of resonance has been studied and applied for years. We recognize its importance in acoustics for musical instruments and concert halls, and also with mechanical vibrations in buildings, bridges, and machinery.  More recently, nuclear magnetic resonance and optical resonance in lasers have brought new understanding and great benefits to our everyday lives. 

Here at Elite, resonance and reverberation chamber technology are used for testing digital electronics for RF susceptibility. Mode-Tuned testing in our reverberation chambers provides a very robust evaluation of RF susceptibility because of the characteristic “isotropy, random polarization, and uniformity” of this method. 

To help explain this very interesting convergence of electromagnetics and statistics, Elite will host an IEEE technical presentation on reverberation chamber testing for EMC.  Don’t miss this great opportunity to learn about this topic and why concepts like isotropy and random polarization make a difference in your EMC tests…And it’s Oktoberfest-themed!

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CISPR 12 vs. CISPR 25 – Deciphering Standard Applications

Posted on August 21, 2013 by - Automotive, EMC/EMI Testing

Knowing which standard to use is very important when selecting a test method for evaluating a product. When selecting a specification, the user needs to take into consideration the purpose of the standard. A good example is CISPR 12 and CISPR 25. Both CISPR 12 and CISPR 25 include radiated emissions measurements for vehicles. However, there are a few fundamental differences that the user should take into consideration when determining which standard to use for vehicle emissions measurements.

The radiated emissions measurements of CISPR 12 are performed for the protection of off-board receivers. As an example, this test is done to assure that receivers are not affected when the vehicle drives them. This is very important when the vehicle drives past houses in a city (which are typically closer to the roadway). The radiated emissions measurements of CISPR 25 Clause 5 are performed for the protection of on-board receivers. This test measures the RF interference that is generated by the vehicle and then picked up by vehicle mounted antennas (such as the AM/FM radio or GPS antenna). This is a “RF Terminal” noise voltage measurement that is made at the point where the antenna would connect to the vehicle mounted receiver (such as the AM/FM Radio or Navigation System).

Another thing to consider is regulatory vs. engineering testing. CISPR 12 is used as a regulatory standard by many countries. CISPR 25 is an engineering standard that is used mainly by vehicle manufacturers and not for regulatory purposes. As a quick recap, the next time you are trying to figure out which test to perform when radiated emissions from a vehicle is the concern, ask yourself a couple of questions:

  • Question #1 – What are we trying to protect (off-board or on-board receivers)? 
  • Question #2 – Are we doing this for regulatory or engineering purposes?

Once those questions are answered, you will know if CISPR 12 or CISPR 25 (or both) are applicable.

Do you have any questions about CISPR Test Applications, EMC Standards, or other related topics? Please share your comments or questions below and our expert, Craig Fanning, will get back to you ASAP. 

Craig recently guest-presented a webinar, “EMC for Vehicles: Truly Mobile Electronics”, with Washington Labs on Thursday, August 15, 2013.  Please follow the link if you would be interested in learning more about other learning opportunities. 

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