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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 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 22 and its derivative EN 55022. In the EU, every product featuring the "CE" marking has to comply with EN 55022. Both CISPR 22 and EN 55022 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 / EN55022 Limits | ||
|---|---|---|
| CISRP 22/ EN 55022 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 22/ EN 55022 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
The PSU clearly fails in this test.
EMI Results - Peak Detector
With the peak detector engaged, there are some notable spurs. However, they remain below the corresponding limits.
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