In the power supply system of industrial automation equipment, good grounding design is the key to ensure stable operation of equipment and personnel safety. M12 L-code connectors are widely used for power transmission, and some of their models have "PE" or "FE" grounding terminals. However, many users are not clear about the difference between the two, and this article will briefly analyze it.
What are PE and FE?
- PE (Protective Earth): Usually connected to the device housing, used to prevent personal electric shock accidents caused by leakage, and is a necessary means to ensure electrical safety. It is marked with a yellow-green two-color line.
- FE (Functional Earth): Used to improve electromagnetic compatibility (EMC), reduce electromagnetic interference, and ensure data transmission quality. Generally, it does not assume the responsibility of protecting personal safety.
The two have different functions in the circuit and cannot be interchanged at will. Some M12 L-code connector models will clearly distinguish whether they have PE or FE to match the needs of different devices.
Comparison between PE and FE
| Ground Type | PE | FE |
| Full Name | Protective Earth | Functional Earth |
| Purpose | Safety – protect against electric shock | EMC – reduce electrical noise |
| Common Use Cases | Power supply systems, metal housing equipment | Signal-sensitive systems, EMC compliance |
| Wire Color | Yellow/Green | Usually Blue or Black |
| Connection point | Usually connected to the chassis, ground wire, and ground | Separate connection, often used for shielding and EMC requirements |
| Electrical function | Current should not flow through PE unless a fault occurs | Current may continue to flow to control interference paths |
| Use standards | Mandatory requirements, especially in hazardous voltage situations | Only considered for use in sensitive signals or high-speed devices |
Summary and suggestions
- If used in standard DC power supply, it is safer and more reliable to choose the version with PE (such as 2+PE, 4+PE);
- If the device has high-frequency signal/EMC requirements, it is recommended to choose the version with FE;
- If you pursue lightness and space saving, you can choose 2 Pin or 4 Pin without grounding.
- If you plan to use it for PROFINET, EtherCAT, and industrial automation field equipment power supply, it is recommended to use the standard model with 4+PE to ensure stability and safety.
If you need the corresponding model drawings or product configuration, you can also tell me at sales02@premier-cable.net
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