Posted in:

What are the Differences Between M8 and M12 Circular Connectors?

© by

Circular connectors are an essential part of the industrial world, providing a cylindrical, multi-pin electronic connection between various devices. These connectors are designed to facilitate the exchange of data and power between components. The circular connector family encompasses a wide range of connectors, including low-frequency circular connectors, RF coaxial connectors, and audio connectors. 

In this blog post, we will explore M8 and M12 circular connectors details.

What Are Circular Connectors?

Circular connectors are robust, cylindrical connectors with a natural strength that sets them apart from connectors of other shapes. They are typically made from materials like zinc alloy or PBT engineering plastic and offer various connection mechanisms, including quarter-turn quick-release, push-pull, bayonet locking, and threaded connections.

The Versatility of Circular Connectors

Circular connectors find applications in various scenarios where components need to be interconnected, as well as in cable-to-cable connections. These connectors are widely used in sensor technology, actuators, encoders, electric motors, industrial grid curtains, factory automation and process control, battery-powered devices, semiconductors, packaging label printers, fieldbuses, industrial instruments, shipboard electronics (NMEA 2000), rail transportation, EMS printed circuit board components, outdoor LED displays, and outdoor LED lighting.

Why Are Circular Connectors Circular?

The circular design of these connectors is defined by a series of specifications set by the International Electrotechnical Commission (IEC). IEC 61076, for instance, defines various circular connectors, with the most common ones being M5, M8, M12, and M16. These specifications outline their physical dimensions, pin configurations, mechanical and electrical characteristics, among other parameters.

For instance, the M12 connector has different coding types for specific applications. The A-coding is used for direct current (DC) transmission, standard 24VDC, and sensor signal interfaces. The B-coding is suitable for DC signal transmission, such as early Profibus and Interbus fieldbuses. The C-coding is used for alternating current (AC), with standards of 24/110/230VAC and is commonly used in the United States. The D-coding is often employed for Profinet, Ethernet, CC-LinkIE, and other Ethernet communications. The X-coding is utilized for Gigabit Ethernet and similar applications.

Common Circular Connectors

M5 Circular Connectors

M5 circular connectors are small in size and are ideal for electrical and signal connections between control systems and various sensors, including pressure sensors, position sensors, acceleration sensors, and temperature and humidity sensors.

M8 Circular Connectors

Common M8 connectors have an M8x1.0 thread specification. Unlike the M12 series, which has a wide range of specifications, the M8 series generally features only three to four coding types and five pin counts. Due to the small pin spacing of the M8 connectors, they are not suitable for high-voltage applications and are best used in scenarios with 50V AC or 60V DC or lower.

M12 Circular Connectors

The M12 connector is one of the most common connectors in the industrial market and is considered a backbone connector for Internet of Things (IoT) systems. It is part of the electrical connector series (ranging from M5 to M12) and is determined by the outer thread diameter. It complies with the IEC 61076-2-101 standard.

The M12 is a highly versatile connector type, offering multiple locking mechanisms and other options. According to the IEC standard, this connector is interchangeable and backward-compatible with other M12 interfaces of the same coding.

IEC 61076-2-101 defines five coding options for M12 circular connectors, with the A and C coded having various types. The more pins a connector has, the lower the rated voltage and current. This diversity allows M12 connectors to cater to a wide range of applications.

M12 A-coded Circular Connector with 5 Pins – Dimensions:

M12 Circular Connector A-coding with 5 Pins – Pin Configuration:

(From 2 pins to 5 pins, the dimensions of M5 circular connectors are compatible, meaning a 2-pin male connector can be inserted into any female connector of the same type.)

The red-circled area shown in the diagram indicates a small gap between pins 1 and 2 on the female connector, while the corresponding area on the male connector features a protrusion. This design prevents mismatched connections, ensuring that only connectors with the same coding and pin count can be correctly inserted.

M12 A-coded Circular Connector with 8 Pins:

Several pin types are also compatible, with a pin diameter of 0.8mm, a rated voltage of 30V, and a rated current of 2A.

M12 Circular Connector A-coding with 12 Pins and 17 Pins:

These are also compatible, featuring a pin diameter of 0.6mm, a rated voltage of 30V, and a rated current of 1.5A.

M12 B-coded Circular Connector:

The pin configuration is similar to that of M12 A-coded but the anti-mismatch (polarization) structure is different to prevent incorrect connections.

M12 C-coded Circular Connector: Not compatible.

3-4 pin diameters of 1mm, rated voltage of 250V, and rated current of 4A; 5-pin diameter of 0.76mm, rated voltage of 60V, and rated current of 2A; 6-pin diameter of 0.76mm, rated voltage of 30V, and rated current of 2A.

M12 D-coded Circular Connector :

A pin diameter of 1mm, a rated voltage of 250V, and a rated current of 4A. It’s essential to note that the D-coding and A-coding 4-pin connectors have the same dimensions but different anti-mismatch mechanisms, so they cannot be interchanged, ensuring reliability.

M12 P-coded Circular Connector:

A pin diameter of 1mm, a rated voltage of 60V, and a rated current of 4A. Similarly, the P-coding and A-coding 5-pin connectors have the same dimensions but different anti-mismatch mechanisms, ensuring reliability.

M16 Circular Connectors

M16 connectors were originally developed to meet the requirements of the German Institute for Standardization (DIN). DIN standards define circular connectors for analog audio signals. These connectors have been widely used for many years and are well-known in the audio industry, often referred to as DIN-standard connectors.


In this blog, we’ve explored several common M-series circular connectors. Well-known brands in the circular connector market include TE Connectivity, Amphenol, Molex, Shine Industry, Phoenix Contact, Binder, JST, JAE, and more. When choosing a connector, you can consider these factors such as the manufacturer’s brand, price, and after-sales service to find the most cost-effective product.