At some point in an electrical or electronic engineering career, you might come across MIL-SPEC Connectors, also known as Military Standard Connectors, also known as MS.
Originally known as AN or Army/Navy connectors, these electrical or fiber optic circular shell connectors were created by the military in the 1930s for tactical service and aeronautical applications.
You can learn everything there is to know about MIL-SPEC connectors by continuing to read.
Table of Contents
What Are MIL-SPEC Connectors?
MIL-SPEC connectors are usually composed of a mating pair, one half of which is a plug and the other a receptacle. Each pair must have a male (pin) contact and a female (socket) contact.
Commonly, phosphor-bronze or beryllium-copper alloys are used to create the connectors’ electrical connections. Then, a highly conductive and non-corrosive metal, such as gold, is applied to the surface.
Typically, male plug connectors with a protruding ferrule are used for fiber optic connections. By aligning the two fibers and holding the fibers in place, the connection can be made.
The insertion loss specification is a crucial one to consider when choosing fiber optic connectors. The amount of signal power or light that will be lost during the connection is measured in decibels (dB).
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How to Choose Your MIL-SPEC Connector?
You need to have a few basic things in mind when you’re choosing your MIL-SPEC connectors.
The number, type, size, and coupling method of the contacts, the shell specifications, and the terminals are among the product parameters that need to be considered.
Contacts
The quantity of conductive elements in a MIL-SPEC connector is determined by the number of contacts. When a connection is made between two different types of contact, such as pins and sockets, these components offer the electrical path.
American Wire Gauge (AWG) measurements are typically used to identify contact sizes and set them apart from one another. There are various different types of coupling available:
- When two connectors are paired, a threaded coupling locks into the screw threads.
- With only a small amount of rotational movement, bayonet coupling offers quick locking and jacking capabilities. It offers constant impedance and is frequently used for coaxial cable-based network or video transmission.
- Breech lock couplings have a detachable locking ring that securely fastens the parts together and makes it simple to disassemble them for cleaning and maintenance.
- Many different industries use quick connect/spring rack coupling for corrosive liquid flow applications.
- A quick push-pull, self-locking coupling called a “ball detent coupling” can guard against overload damage to rotating elements.
Connector Shells
The shell, which is the common name for the connector’s main housing, is frequently made of aluminum that has been anodized or plate to prevent corrosion. Shell housings are available in various styles, including:
- Straight or angled plug
- In-line or cable receptacle
- Wall or box-mount receptacle
- Dummy receptacle
- Jam nut receptacle
- Solder or weld-mount receptacle
- Through-bulkhead receptacle
Standard connector shells come in a range of sizes, starting at size 8 (0.50″) and increasing in 0.0625″ increments up to size 36 (2.25″). Circular MIL-SPEC connectors have a cylindrical shell that comes in incremental diameter sizes starting at about 0.375″.
MIL-SPEC connectors attach back-shells to the shell housing using threads, and are usually equal to the connector shell size or within 0.062″ of it.
There are male and female connector shells. The male plug, also known as a header or free connector, is typically movable and connected to a cable that can be removed from the sub-assembly. A female connector, such as a jack, receptacle, or other outlet, must be inserted into it in order to complete a circuit.
Terminals
To make an electrical connection, terminals can be screwed onto studs, posts, or other kinds of conductors. The simple terminal device comes in a variety of forms, such as crimping, quick-connect tabs, cage clamps, lugs, screws, and wires soldered onto a PCB.
Using an IDC, or insulation displacement connector, to make a connection by slicing through cable insulation is one of the more complex terminals. Another is inserting connectors into a solder cup or terminal and then soldering it to another metal surface.
This type of mass termination connector requires no stripping of insulation and is often used in flat cables. Other connections use quick-disconnect lanyard release terminals or THT (through-hole technology), which mounts components by forcing them through holes in a PCB.
Use a specialized wrapping tool to wrap wire around a terminal post to create solderless electrical connections.
SPECIAL FEATURES of MIL-SPEC Connectors
MIL-SPEC connectors are also available with special additional features for specific environmental applications:
- Connectors designed for underwater use have the proper sealing for those uses.
- Connectors with hermetically sealed joints stop any internal moisture from escaping.
- Connectors with integrated filters include a filter to guard against magnetic interference and unwanted signals.
- Connectors with an ESD/EMI shield or an RFI/EMI filter are protected from electrostatic discharge (ESD) and/or electromagnetic interference (EMI), or they have a filter to block both.
- Connectors made to withstand the effects of the environment include dirt, sunlight, chemicals, etc.
Final Words on MIL-SPEC Connectors
MIL-SPEC connectors are now a standard feature in military equipment and other severe or demanding environments, including marine, aerospace, oil and gas applications, and various industrial and automotive contexts.
This kind of electrical connector was created specifically to safeguard the connection from the harshest environments and is built to last.
