FSP Hydro PTM 750W PSU Review

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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 nearby devices.

Electromagnetic Interference (EMI): This represents the electromagnetic energy a device emits, which can cause problems in other nearby 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 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.

The corresponding standards for minimizing EMI in IT products are CISPR 22 and its derivative EN 55022, which is for devices sold in the EU. There, every component 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 permitted EMI emissions are significantly lower than for A-class devices.

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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 which was kindly provided by TekBox Digital Solutions.

Our results in this test don't look particularly good; the quasi-peak emissions at frequencies up to 959 kHz are higher than they're allowed to be. Apparently, FSP's EMI filter needs fine-tuning, since it at least includes the proper list of components.

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Contributing Editor

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