Understanding functions and performance criteria for EMC testing

Knowledge of the EMC testing process and the performance criteria against which a product is assessed is essential to success when preparing for EMC testing.

EMC compliance is determined by how a product operates and performs during testing. When testing for emissions, which is the measurement of the generation of electromagnetic energy by a source and its release into the environment, your device must be exercising all parts of the circuit fully.  

The limits for emissions vary by product type and geographical region. In addition, specific industries such as military, automotive or aerospace will usually have more rigorous and demanding requirements.

When testing for immunity, which is the ability of equipment to function correctly in the presence of ElectroMagnetic Interference (EMI), some tests will use continuous (usually modulated) waves and others will involve very short bursts (transient) phenomena.  

A wide range of tests are available dependent on the type of immunity to which you are testing. These include radiated radio frequency, magnetic field, ElectroStatic Discharge (ESD) conducted radio frequency, electrical fast transients (EFT), surges, and voltage dips/interruptions.

If testing to commercial standards for the European Union (EU), your device must comply with one of the following general summarized performance criteria:

Performance Criterion A

No degradation of performance or loss of function is allowed below a minimum performance level specified by the manufacturer (or what the user may reasonably expect) when the equipment is used as intended.

(Criterion A means that your product has performed normally and within specifications that have usually been outlined in the product manual, both during and after the test)

Performance Criterion B

No degradation of performance or loss of function is allowed, after the application of the phenomena below a performance level specified by the manufacturer (or what the user may reasonably expect) when the equipment is used as intended.

(Criterion B means that the product may have had a temporary loss of function or degradation of performance but after the test has finished, recovers to its normal performance without operator intervention)

Performance Criterion C

During and after testing, a temporary loss of function is allowed, provided the function is self-recoverable, or can be restored by the operation of the controls or cycling of the power to the EUT by the user in accordance with the manufacturer’s instructions. 

(Criterion C is similar to B, but the test includes allowance for operator intervention. For example, this might mean that you need to turn the device back on to resume normal performance)

Which of these three performance criteria you will need to test to will depend upon the test standard that applies to your particular product.  

Learn more about preparing for EMC testing here.

If you would like to find out more about EMC testing requirements or speak to one of Element’s Engaged Experts about your EMC testing requirements, contact us.

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