Why you can trust Tom's Hardware Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.
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 operation of other close-by devices.
Electromagnetic Interference (EMI): This represents the electromagnetic energy a device emits, which can cause problems in other close-by devices if it is too high.
Electromagnetic Immunity (EMS): 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.
In order to minimize EMI noise, some standards have been established. The corresponding standards for Information Technology products are CISPR 32 and its derivative EN 55032. In the EU, every product featuring the "CE" marking has to comply with EN 55032. Both CISPR 32 and EN 55032 divide devices into two classes, A and B. B-class equipment is for domestic environments, so its allowed EMI emissions are significantly lower than for A-class devices.
| CISPR / EN55032 Limits | ||
|---|---|---|
| CISRP 32/ EN 55032 Class A Conducted EMI Limit | ||
| Frequency of Emission (MHz) | Conducted Limit (dBuV) | |
| Quasi-peak | Average | |
| 0.15 - 0.50 | 79 | 66 |
| 0.50 - 30.0 | 73 | 60 |
| CISPR 32/ EN 55032 Class B Conducted EMI Limit | ||
| Frequency of Emission (MHz) | Conducted Limit (dBuV) | |
| Quasi-peak | Average | |
| 0.15 - 0.50 | 66 - 56 | 56 - 46 |
| 0.50 - 5.00 | 56 | 46 |
| 5.00 - 30.00 | 60 | 50 |
EMI Results - Average Detector
Our equipment picks up a number of spikes in this test, three of which exceed the established limits.
EMI Results - Peak Detector
Again, we pick up a number of notable spurs. This time, however, they all duck in under the test's ceiling.
MORE: Best Power Supplies
MORE: How We Test Power Supplies
MORE: All Power Supply Content
