Ask an Expert:

Q: Doesn't the Automotive Directive require conformity to EN55025? What are the corresponding requirements in the US, if any?
-Keith, Sunnyvale, CA

A: In US, SAE is primarily responsible for automotive standards, not the FCC. The closest to EN55025 for EMC is SAE J1445: 2006.
In addition, the 3 major U.S. automotive manufacturers have their own standards for EMC, which are based on EN55025 for most part. But these standards are not mandatory. EMC automotive standards are still voluntary, despite issues with Toyota and other vehicles electrical systems.

Q: Is ANSI C37.90.1 (Surge Withstand Capability Tests for Relays and Relay Systems Associated with Electric Power Apparatus ) equivalent to the IEEE standard? My customer is looking to the 2002 version, so that’s a plus. His only question is, is there a way he could be exempt if he is low voltage?
-Anthony, Allentown, PA

A: IEEE and ANSI sometimes each take various responsibilities in the same standard.  Within IEEE C37.90.1-2002, previous versions of the standard are referred to as ANSI/IEEE C37.90.1.  The prefix ANSI and IEEE are used interchangeably in referring to C37.90.1.  MET tests to the current version of this standard, which is the 2002 version.

IEEE C37.90.1 is applicable to relays and relay systems. The tests described in IEEE C37.90.1 are to be applied to any part of the relay system that can be exposed to conducted or coupled transients under normal installed operating conditions.

Testing to IEEE C37.90.1 is not a regulatory requirement. It is sometimes a requirement of power utilities and similar companies. The acceptability of any exemptions claimed by the manufacturer of the equipment under test would be the responsibility of the purchasing company.

Q: Why aren't European and US wireless standards harmonized?
-Richard, Baltimore, MD

A: The short answer is power, frequency and test methodology. There are significant differences in radiated power requirements and operating voltages - 120V / 60Hz for US and 240V/ 50 Hz for Europe. Europe addresses immunity, whereas in the US it is not as much a concern.

Even basic test criteria of positioning the EUT differ. US standards require 0.8 meter above the ground plane devices for unlicensed devices, 1 meter for licensed devices. European standards require 1.5 meters for all devices.