Multi-pin circular connectors are primarily used for interfacing with external sources. These connectors can be used for data transmission, electrical signal transmissions, and for powering electric devices. Some circular connectors can carry a mixed signal, which may be called a power or control connector. These multi-pin connectors can be used for signal and power transmissions.
The term “circle connector” was first used to describe a circular plastic connector (CPC). These connectors are also known as circular metal-shell connectors (CMC) and are used for industrial applications that require a strong, secure wire connection. These connectors are resistant to extreme environments and provide a reliable connection for industrial applications. Other types of connectors such as military connectors, DIN connectors, and micro- or nano connectors can also be described by circular connectors.

Circular plastic connectors and circular metal-shell connectors are both manufactured by OEMs. The plug and receptacle can be configured to only mate with their connectors. Connectors manufactured by other OEMs or for other purposes are not allowed to be inserted due to the contact arrangement, thread size and coupling.

MIL-SPEC connectors for military use are made in accordance to military specifications. They are designed to be protected from environmental factors and can be used in military or aerospace applications.

DIN connectors are multi-pin, high frequency electrical connectors. They meet the standards of Deutsches Institut fur Normung, a German national standardization organization. DIN connectors have rounded ends that are notched and covered by a metal skirt. This protects pins from rubbing against each other.

Contact pitches for micro and nano connectors are 0.05″ (micro), and 0.025″, (nano). They can be straight-angled or right-angled and have one or more rows plated contacts.
Shell Sizing, Insert, and Contacts

The number of contacts, shell size, and contact diameter define circular connectors. Each connector is sized to suit its purpose. Standard connectors can be made according to military or DIN standards. You can choose from a variety of insert options and the connector will accept different contact sizes. Some connectors come without contacts or inserts. These connectors can be used as protective housings that can be tailored for specific applications.

Insert

The shell contains an insert, which is an insulating material. It is used for orientating the electrical connections. Each insert can support different types and sizes of contacts. They can accommodate as many conductors and as many contact slots as possible. It is not necessary that every contact slot be used when wiring the contacts. An insert that can hold more than six terminations may be used for a six-conductor cable that is within the required cable diameter. It is possible to only use a small portion of the contact slots in some cases. This allows the plug and receptacle to be aligned by aligning the missing or blind contacts.
Electrical Contacts

The electrical contacts are soft, high conductivity, and oxidation-resistant materials that are used to make electrical connections. This material allows for the flow of electrical current.
Shell Sizing

A shell is used to indicate the size of the connector. A shell size is a nominal number that is usually followed by a two-digit number. This two-digit number specifies the number of 1/16 inch increments in diameter of the shell.

For larger power contacts, larger shells are used. Inversely smaller shells can be used to house sensors-relevant contacts. To allow for flexibility in the size and arrangement of contacts, intermediate shell sizes are used. You can use each shell with different cable diameters.
Selection Criteria

When specifying circular connectors, it is important to consider the type, gender, options for terminals, mounting options, and performance criteria.
Gender

The connector can be either male (with pins), or female (with sockets). Pins that plug into sockets or similar receptacles make up a male connector. A female connector is made up of sockets that mesh with a pin-type connector.

Terminals

Connector termination is the way that the conductive elements are paired with the electrical contacts of the connector. There are many types of terminal options. There are many options for termination: solder cup or soldering, insulation displacement, PCB solder and wire wrap.
Mounting

A circular connector can be used to attach to a panel, cable end, circuit board, or any other entry point. There are many ways to attach the connector, including bulkheads, jam nuts and flanges.
Current and Voltage Ratings

The maximum rated voltage and current is the carrier signal that the connector can accommodate. The type and size of the contacts are what determines the voltage and current ratings. Products used to transmit electrical signals and sensors have low amperage ratings. A device requires a greater load to run. Products that use power connectors or transmissions with higher current and voltage ratings are more expensive.

Current is the amount of current (rate at which electricity flows) that a connector is intended to carry. It’s measured in amps (A). Connectors have a range of current ratings, usually ranging from 1A up to 50A.
The voltage rating for the connector is measured in volts (V). The most common ratings are 50V to 125V, 250V to 600V and 250V respectively.

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The term “termination size” is used to refer to the range of wire gauges that are compatible with each contact. You could also refer to the contact’s diameter.

North America uses the American Wire Gauge (AWG), standard to measure wire size. The thinner the wire, the higher the AWG number. AWG is a measurement that indicates how many times the wire has been run through a machine to reduce its diameter. The machine ran 24-gauge wire 6 times more than 18-gauge.
Number of contacts

The number of contacts refers to the number of conductive elements within a connector that mate with one another to create an electrical path.