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be quiet! SFX L Power 600W PSU Review

EMC Pre-Compliance Testing

EMC, EMI & EMS Acronyms

Electromagnetic Compatibility (EMC): The ability of a device to operate properly in its environment without disrupting the proper operation of other close-by devices.

Electromagnetic Interference (EMI): It stands for the electromagnetic energy a device emits, which can cause problems in other close-by devices if it is too high.

Electromagnetic Immunity (EMS): The tolerance to electromagnetic emissions.

Equipment & Standards

To properly measure the EMI that a device emits you need special equipment which is pre-defined by the CISPR 16-1-1 specification. To learn more about our EMI testing equipment, please check out How We Test Power Supply Units.

In order to minimize EMI noise, some standards have been established. The corresponding standards for IT (Information Technology) products are CISPR 22 and its derivative EN 55022, which is for products sold in the EU. In the EU, every product featuring the "CE" marking has to comply with the EN 55022 standard. Both CISPR 22 and EN 55022 standards divide devices into two classes, A and B. B-class equipment is for domestic environments, so their permitted EMI emissions are significantly lower than for A-class devices. 

CISPR / EN55022 Limits
CISRP 22/ EN 55022 Class A Conducted EMI Limit
Frequency of Emission (MHz)Conducted Limit (dBuV)
0.15 - 0.507966
0.50 - 30.07360
CISPR 22/ EN 55022 Class B Conducted EMI Limit
Frequency of Emission (MHz)Conducted Limit (dBuV)
0.15 - 0.5066 - 5656 - 46
0.50 - 5.005646
5.00 - 30.006050

Conducted EMI Results

To conduct our EMC pre-compliance testing, we use the EMCView software kindly provided by TekBox Digital Solutions.

There are two peaks on the EMI graph, one of which goes over the quasi-peak limit. Otherwise, conducted EMI transmissions are pretty low.

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Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.