What is Conducted Emissions Testing?
Your device creates electromagnetic energy and a certain portion of it will be conducted onto the power supply cord.
In order to restrict the amount of interference your device can couple back onto a power supply, test labs measure these emissions (usually from 150 kHz – 30 MHz, and verify that they comply with specified limits.
This helps to ensure that the local power supply remains relatively ‘clean’ and nearby devices won’t be affected by your device.
You can see the FCC’s conducted emission limits for class A and class B devices. You’ll notice that class B limits (for domestic environments) are more strict, probably because the number of devices expected in a household is large, and users want to be sure that devices won’t interfere with each other through conducted noise on the AC power supply.
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