Overview of M8, M12, M16 Connectors

M12 connectors are a class of circular connectors. The advantage of proximity switches with connectors is that they are easy to install and replace. For example, if a sensor is broken at the equipment site, if it is directly out of the line, then the maintenance personnel need to remove the sensor when replacing it and then follow the line to remove the ties that tie up the wires, take off the wire channel cover, and sometimes even remove certain parts of the equipment.

Then we choose this connector sensor. It would help if you considered the choice of matching cable. I do not know if you have been a variety of M connectors dizzy, rectangular, round, M8, M12, A code, B code, or D code. Many styles and complex.

IEC Standard

Most of the sensors use a connector type that is round. The more common is the M connectors. Here M12 and M8 refer to the combined connection threads with specifications of M12X1 and M8X1.

There is a reason for this, IEC has a series of specifications specifically defined circular connectors. This is IEC61076. IEC61076 defines a variety of connectors, the second part of which is the definition of circular connectors, and then subdivided into more than a dozen specifications specify a variety of specifications of circular connectors, such as M5, M8, M12, and M12 for high-speed data transmission, and so on.

For example, IEC61076-2-109 Connectors for electronic equipment – Product requirements – Part 2-109: Circular connectors – Detail specification for connectors with M 12 x 1 screw-locking, for data transmission frequencies up to 500 MHz, is the detailed specification for M12 x 1 screw-locking connector for data transmission frequencies of 500 MHz.

The IEC does not specify which connector is used on what occasion but only specifies the form factor of each connector, pin distribution, mechanical and electrical characteristics, etc. Following the characteristics of each connector, the manufacturers have slowly formed some rules of the agreement.

Examples are the M12 connector A code for direct current transmission, the standard 24VDC and sensor signal interface, and the B code for DC signals. C code for AC power, standard 24V/110V/230V AC, mostly used in the US D code is mostly used for Profinet, Ethernet, CC-Link IE, and other Ethernet communications. x code for Gigebit Ethernet, etc.

1.M12 Connector(IEC61076-2-101)

M12 A Code

Coding	Style	Contacts	Rated voltage a.c. or d.c. V	Rated current A
A-coding	5 way	2 to 4	250	4
		5	60
	8 way	6 to 8	30	2
	12 way	9 to 12	30	1.5
	17 way	13 to 17	30	1.5
B-coding	5 way	5	60	4
C-coding	3 way(2+PE)	3(2+PE)	250	4
	4 way(3+PE)	4(3+PE)	250	4
	5 way(4+PE)	5(4+PE)	60	2
	6 way(5+PE)	6(5+PE)	30	2
D-coding	4 way	4	250	4a
P-coding	5 way(4+PE)	5(4+PE)	60	4
a The M12 connectors with D-coding(4 way) are tested for use with frequencies up to 100 MHz.

As you can see above, the 101 detailed specification specifies five coding methods for M12 circular connectors. A, C code has a variety of types. The higher the number of pins, the smaller the rated voltage and rated current, according to its characteristics, can be suitable for different applications.

The above diagram is the dimensional drawing of the A-code 5-way type. This coding method is the most commonly used one; basically, most proximity switches are used this way. Only some 3-pin or 4-pin ones are in which individual pins are not in use.

The diagram above shows the pinout of the A-code 5-way type, from 2-way to 5-way, and they are compatible in size. That is, if there is a 2-pin male header, it can be inserted into any of the female headers of that type.

Most manufacturers make female headers of the 5-hole type for the convenience of mold opening. Only the number of lead wires is different.

As you can see from the red circle shown in the figure, there is a small gap between the 1,2 pins of the female head. The corresponding position of the male head is a bump, designed to prevent misplacement and ensure that only the same code and the same number of plugs can be inserted correctly.

A code 5-way type using the pin thickness of 1mm, rated current 4A. 2,3,4 way pin distance to ensure the rated voltage to 250V, 5-way pin due to the 5th pin is located in the middle resulting in pin distance shortened, electrical insulation distance reduced, so the rated voltage of 60V. If you use the 5-way pin structure, please note that the use of occasions does not exceed 60V.

Several M12 A-code 8-way type pin types are also compatible, with a pin diameter of 0.8mm, a rated voltage of 30V, and a rated current of 2A.

The M12 A-code 12-way and 17-way types are also compatible, using a pin diameter of 0.6mm, a rated voltage of 30V, and a rated current of 1.5A.

M12 B Code

M12 B code pin size 1mm, rated voltage 60V, rated current 4A. The pin distribution is no different from the A code, but their anti-mistake (anti-dull) structure is different and can not be inserted incorrectly.

M12 C Code

M12 C code several sizes are incompatible, 3,4-way pin diameter 1mm, rated voltage 250V, rated current 4A. 5-way pin diameter 0.76mm, rated voltage 60V, rated current 2A. 6-way pin diameter 0.76mm, rated voltage 30V, rated current 2A.

M12 D Code

M12 D-code pin diameter 1mm, rated voltage 250V, rated current 4A. It is worth mentioning here that D-code and A-code 4-way have the same size but do not interpolate due to the different anti-error insertion mechanisms, ensuring reliability. Care needs to be taken when selecting the type.

The D-code specification specifies that a data rate of 100MHz can be achieved, so this coding method was also used for Fieldbus in the early days.

M12 P Code

M12 P-code pin diameter 1mm, rated voltage 60V, rated current 4A. P-code and A-code 5-way have the same size but are not inter-inserted due to the different anti-mis-insertion mechanisms, ensuring reliability.

Rated M12 Connector Products

2.M8 Connector(IEC61076-2-104)

In addition to the M12 circular connector, there is a standard M8 connector with a thread specification of M8X1. This connector is different from M12 in many specifications. There are only two codes. Among them, the A code of 3,4 way two specifications are most common.

Because the M8 pin pitch is too small, it can not be used in high voltage applications. Only suitable for 50V AC or 60V DC or less.

Connector ratings related to coding and number of contacts
Coding	Contacts	Rated voltage	Rated current
A	3	50 V a.c./ 60 V d.c.	3 A
A	4	50 V a.c./ 60 V d.c.	3 A
A	6	30 V a.c./ 30 V d.c.	1.5A
A	8	30 V a.c./ 30 V d.c.	1.5A
B	5	30 V a.c./ 30 V d.c.	3 A

The above two diagrams show the pin arrangement of two M8 codes, A code 3,4 way, and B code pin diameter is 1mm, A code 6 way is 0.7mm, and A code 8 way is 0.6mm.

Rated M8 Connector Products

3.M5 Connector(IEC61076-2-105)

M5 connectors are less commonly used

Rated voltage – Rated Impulse voltage – Pollution degree
No. of ways according to 3.2.1	Rated voltage V	Rated impluse voltage kV	Pollution degree a
3	60	1.5	3
4	60	1.5	3
a Only in mated and locked condition.

4.M16 Connector(IEC61076-2-106)

M16 connector rating parameters

Rated voltage – Impulse voltage – Pollution degree
Contact arrangement according to 4.3.5	Rated voltage V	Rated impulse voltage kV	IP40 variants Pollution degree a	IP65/67 variants Pollution degree b
02-a	100	1.5	2	3
03-a	100	1.5	2	3
04-a	100	1.5	2	3
05-a	63	1.5	2	3
05-b	32	0.8	2	3
06-a	63	1.5	2	3
07-a	63	1.5	2	3
07-b	32	0.8	2	3
08-a	32	0.8	2	3
012-a	32	0.8	2	3
14-a	32	0.8	2	3
14-b	32	0.8	2	3
19-a	32	0.8	2	3
a    In mated condition    b   The rated voltage and impluse voltage are based on pollution degree 2. This results from application of the rules from IEC 60664-1.

Rated M16 Connector Products

5.M12 Circular Connector Type X and H(IEC61076-2-109)

There are also X-coded M12 circular connectors today, mainly for high-speed Ethernet transmission. One hundred nine specifications use type X and type H, type X, and H no longer use X coding and H coding, but most manufacturers still use X coding and X coding to describe to unify.

The rated voltage of the two connectors: 50V AC/60V DC, rated current: 0.5A, the number of pins is 8 pins 4 pairs.

Type X pinouts and dimensions.

Interface dimensions, connector type X with male contacts
Reference	Minimum  mm	Nominal  mm	Maximum  mm
A	5.6	5.6	5.6
B	2.8	2.8	2.8
C	0.9	1	1
D	1.4	1.5	1.5
E	0.3	0.4	0.4
F	1.06	1.06	1.11
G	8.3	8.3	8.45
H	1.1	1.2	1.2
I	0.57	0.6	0.63
K	0.07	0.1	0.13
L	10.2	10.5	10.5
M	M12*1
N	0.9	1	1
O	5.3	5.5	5.7
P	8.7	8.9	8.9
Q	1.1	1.1	1.2
R	94.5°	95°	95°
S	4.1	4.1	4.2
T	2.5	2.5	2.6
U	10
V			3
NOTE  All radii without dimensions are 0.1.

Type H pinouts and dimensions.

Interface dimensions for connectors type H with male contacts
Reference	Minimum  mm	Nominal  mm	Maximum  mm
A	2.9	2.9	2.9
B	1.6	1.6	1.6
C	3.25	3.25	3.25
D	3.55	3.55	3.55
E		0.74
F	1.1	1.2	1.2
G		1.35
H	22.5°	23°	23.5°
I	0.57	0.6	0.63
K		R 0.30 typ.
L	10.2	10.5	10.5
M	M12*1
N	∅ 8.15	∅ 8.30	∅ 8.45
O	6.7	6.9	7.1
P	8.7	8.9	8.9

Recommended TIA568B wiring method.

Example of contact and pair designation for balanced cabling (informative)
Pair	Contact	Colour
2	1	white-orange
	2	orange
3	3	white-green
	4	green
4	5	white-brown
	6	brown
1	7	white-blue
	8	blue

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