What is an M12 Connector?

By Amy Goetzman | February 08, 2022

Meet the Connector: M12 Circular Connectors

M12 connectors are a metric circular connector with 12 mm locking threads used in industrial automation and other harsh environment applications where compact, rugged, and reliable power, signal, and data connections are needed. One of the most commonly specified connectors in the industrial market, the M12 is considered the backbone of Industry 4.0 connectivity. In factory automation settings, they are used for actuators, sensors, industrial Ethernet, and Fieldbus applications.

The M12 connector is part of the M-type family of circular connectors (M5 through M12) identified by the diameter of its outer threads. Standardized to IEC-61076-2-101, they are a highly versatile product type, and manufacturers offer a wide range of locking mechanisms and other options. Per the standard, this connector is interchangeable and backwards compatible with other M12 interfaces with the same coding, including interoperability among manufacturers. They handle bandwidth needs up to 10 Gb/s, power to 16 V, and may be configured to support Profinet, SPE, and fieldbus protocols.

German connector company Lumberg introduced the M8/M12 connector interface at Hannover Fair in 1985. It was initially devised as a waterproof alternative for the older RK30 sensor connector, a common choice for automotive manufacturing facilities at the time. The M12 is now available from many manufacturers.

M12 connectors from Lumberg

Lumberg’s Lutronic M12 color-coded female and male M12 color-coded connectors

Design Notes

  • Standards: M12 connectors are compliant with the IEC 61076-2-101:2012 standard. The original IEC standard was published in 2003 and is currently in its third revision. In 2021, a new push-pull M12 standard, known as IEC 61076-2-010;2021, was released.
  • Coding: In order to prevent mis-mating, M-family circular connectors are available in specific coding options that define pin counts and arrangements. M12s are available in A (3-17 poles), B (2, 4, or 5 poles; mainly used on Profibus and Interbus applications), C (3 to 6 poles; includes a dual keyway to prevent mismating), D (4-poles; standard on Ethernet, ProfiNet, and EtherCat field devices and industrial CAT5e cables), K (5 poles [4+PE]; rated up to 630VAC/DC), L (4 poles or 5 poles [4+PE] with a current rating of up to 16A per pole and a maximum voltage rating of 63VAC/DC), S (3-pole [2+PE] or 4-pole [3+PE]), T (designed for DC power connections; rated up to 63VDC/AC, 4 poles with each pole rated to 12A), X (8 poles, up to 10 Gb/s), and Y (power and data in a single cable; 8 poles split into two groups of 4 that are galvanically separated with a metal coding that looks like a Y).
  • Pins: M12s are available with 3, 4, 5, 8, and 12 pins. Users must select the correct pin count for specific applications. Sensors and power applications require 3 and 4 pins; PROFINET and Ethernet require 4 and 8 pin counts; Fieldbus, CAN bus, and DeviceNet typically use 4 and 5 pin counts; and 12 pins are used for signal requirements.
  • Cable Considerations: M12 connectors are commonly used with Cat5e and Cat6A cable types.
  • Current Rating: Up to 16V
  • Mounting Options: M12s are available in mounting options including through-hole, surface mount, and wave soldering.


M12s with various connection types from binder

M12s with various connection types from binder, including crimp connection and moulded, ready-to-connect cable, and easy-to-mount flange versions with solder, dip solder, and stranded wire connection methods.

  • Materials: Metals used for M12 shells include stainless steel, brass, copper, gold, and alloys.
  • Ruggedization: M12 connectors and their cable assemblies are designed to ensure rugged performance in high-reliability and harsh environment applications, including washdown and corrosive environments and those that feature temperature extremes, radiation, rough handling, chemicals, and other environmental factors.
  • Sealing: M12 connectors are available in IP67, IP68, and IP69 versions. Environmental protection against fluid and particulate ingress is part of what makes this connector a mainstay in rugged operational environments. Waterproofing and sealing are especially important in fluidic and pneumatic configurations.

Amphenol LTW’s robust M12 high-temperature connector, the HDM12, is engineered for applications with elevated vibration and challenging environmental conditions. The HDM12 excels in heavy-duty and harsh surroundings. Compliant with IEC 61076-2-101 and SAE J2839 standards, the HDM12 connectors emerge as the ideal solution for ultra-rugged applications such as heavy equipment,  automotive, rail, factory automation, and more.

  • Interference: Electromagnetic interference (EMI) or radio-frequency interference (RFI) is a significant concern for devices used in environments filled with electronic equipment. Shielded and unshielded connector and cable assembly options are available.
  • Handling Advantages: M12 connectors are designed to provide fast and easy connections even in challenging conditions. They are available in screw-type, bayonet, and ergonomic push-pull locking mechanism for blind mating situations. Keying, color coding, and LED options are available to increase mating reassurance. This is considered a field serviceable connector and it is backwards compatible.

Markets and Applications

Industrial (factory automation and control systems, I/O modules, sensors, actuators, motors, Industry 4.0 and IIoT applications, renewable energy), Automotive (manufacturing), Transportation (heavy equipment, agricultural equipment); machine tools, communications, measurement and control, robotics, and other applications.


Weidmuller’s M12 connectors

Weidmuller’s M12 connectors are available in shielded and non-shielded versions, straight or angled, and in different codings, with tension clamp, screw termination, and crimp and IDC technology. A new series of M12 offer push-in technology.


M12 connectors are available in many variations from many manufacturers, including Amphenol Industrial, Amphenol LTW, binder, Bulgin, ERNI, HARTING, ITT Cannon, JAE, LEMO Connectors (available from PEI-Genesis), Lumberg, METZ Connect, Molex, Norcomp (available from Heilind Electronics), Phoenix Contact, TE Connectivity, WAGO, Weidmüller

Metz Connect M12 circular connectors

Metz Connect’s M12 circular connectors for data communications in harsh environments include M12 D-code circular connectors for two-pair twisted-pair connections, and M12 X-code circular connectors for four-pair twisted-pair connections.

Related Products

Amy Goetzman
Get the Latest News