CISPR 12 vs. CISPR 25 - Deciphering Standard Applications

Today's Elite Expert is Craig Fanning, our EMC Lab Manager and US National Committee Technical Advisor for CISPR-D. Read below to see what he has for us this week. 

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.