1: Insulation resistance

Insulation resistance refers to the resistance value exhibited by applying a voltage to the insulating part of the aviation plug, so that leakage current is generated in or on the surface of the insulating part. It is mainly affected by factors such as insulation material, temperature, humidity, and contamination. The insulation resistance value provided on the aviation plug sample is generally an index value under standard atmospheric conditions. Under certain environmental conditions, the insulation resistance value may drop to an unused degree. Also pay attention to the test voltage value of the insulation resistance. Depending on the insulation resistance (MΩ) = voltage (V) applied to the insulator (V) / leakage current (μA), different voltages will have different results. In the test of aviation plug, the applied voltage is generally 10V, 100V, and 500V.

2: Withstand voltage

Withstand voltage is the critical voltage that can withstand higher than the rated voltage within a specified time between the mutually insulated parts of the contact pair or between the insulated part and the ground without causing breakdown. It is mainly affected by contact spacing and creepage distance and geometry, insulator material, ambient temperature and humidity, and atmospheric pressure.

3: Flammability

Any aviation plug is inseparable from current when it is working, so there is a risk of fire. Therefore, the aviation plug is required not only to prevent ignition, but also to self-extinguish in a short time once it ignites and catches fire. When selecting, pay attention to choosing the aviation plug with flame-retardant, self-extinguishing insulating material.

4: Mechanical parameters

The contact pressure in the aviation plug is an important indicator, which directly affects the size of the contact resistance and the amount of wear of the contact pair. In most structures, it is quite difficult to directly measure the contact pressure. Therefore, the contact pressure is often measured indirectly through the separation force of one foot. For circular pinhole contact pairs, a standard pin with a specified weight is usually used to test the ability of the female contact to hold the weight. Generally, the diameter of the standard pin is the lower limit of the diameter of the male contact, which is -5μm. The total separation force is generally twice the sum of the separation force on a single foot. When the total separation force exceeds 50N, it is quite difficult to insert and remove manually. Of course, for some test equipment or occasions with special requirements, you can choose zero-plug force aviation plugs, automatic fall-off aviation plugs, and so on.

5: Mechanical life

The mechanical life of aviation plugs refers to the plug life, which is usually specified as 500 to 1000 times. When the specified mechanical life is reached, the contact resistance, insulation resistance and withstand voltage of the aviation plug should not exceed the specified value. Strictly speaking, mechanical life is a fuzzy concept. The mechanical life should have a certain relationship with time. After 500 times in 10 years and 500 times in 1 year, the situation is obviously different. But there is still no more economical and more scientific method to measure it.

6: Number of contact pairs and pinhole

First, the number of contact pairs can be selected according to the needs of the circuit, while the volume of the electrical connector and the total separation force should be considered. The number of contact pairs is large, of course, the volume is large, and the total separation force is relatively large. In some cases where the reliability is high and the volume is allowed, two pairs of contact pairs can be used in parallel to improve the reliability of the connection.

In the plugs and sockets of aviation plugs, the pins (male contacts) and jacks (female contacts) are generally interchangeable. In actual use, it can be selected according to the live conditions at both ends of the plug and socket. If the socket needs to be charged frequently, you can choose a socket with a socket, because the socket with a socket has its live contacts buried in the insulator, and the human body is not easy to touch the live contacts, which is relatively safe.

7: Vibration, shock, collision

The main consideration is the electrical continuity of the contact pair when the aviation plug is subjected to vibration, impact, and collision under specified frequency and acceleration conditions. The contact pair will instantaneously disconnect under this dynamic stress. The specified instantaneous time is generally 1μs, 10μs, 100μs, 1ms and 10ms. What should be noted is how to judge that a contact pair has a transient fault. It is generally believed that when the voltage drop across the closed contact pair (contact) exceeds 50% of the electromotive force of the power supply, it can be judged that the closed contact pair (contact) has a fault. That is to say, there are two conditions for judging whether a transient interruption occurs: duration and voltage drop, both of which are indispensable.

8: Connection method

Aviation plugs are generally composed of a plug and a socket. The plug is also called a free-end aviation plug, and the socket is also called a fixed aviation plug. The connection and disconnection of the circuit is realized through the plug, the socket, and the insertion and separation, so various connection modes of the plug and the socket are produced. For circular aviation plugs, there are mainly three ways: threaded connection, bayonet connection and marble connection. Among them, the threaded connection is the most common. It has the advantages of simple processing technology, low manufacturing cost, and wide application range, but the slow connection speed is not suitable for occasions that require frequent plugging and quick connection. The bayonet type connection has a longer lead of the three bayonet slots, so the connection speed is faster, but it is more complicated to manufacture and the cost is higher. The marble connection is the fastest of the three connection methods. It does not need to be rotated, but only needs to be linearly moved to achieve the functions of connection, separation and locking. Because it belongs to the direct push-pull connection, it is only suitable for aviation plugs with a small total separation force. Generally it is more common in small aviation plugs.

9: Installation method and appearance

The installation of aviation plug includes front installation and rear installation, and the installation and fixing methods include rivets, screws, clamp rings or quick locking of the aviation plug itself. There is also a kind of plug and socket that are both free-end aviation plugs, the so-called relay aviation plugs.

10: Environmental parameters

Environmental parameters mainly include ambient temperature, humidity, sudden temperature changes, atmospheric pressure and corrosive environment. The environment in which the electrical connector is used, stored, and transported has a significant impact on its performance, so the corresponding aviation plug must be selected according to the actual environmental conditions.

11: ambient temperature

The metal material and insulating material of the aviation plug determine the working environment temperature of the electrical connector. High temperature will destroy the edge material, causing the insulation resistance and pressure resistance to decrease; for metals, high temperature can make the contact pair lose elasticity, accelerate oxidation and cause coating deterioration. The usual ambient temperature is -55~100 ℃, which may be higher in special occasions.

12: wet

Relative humidity greater than 80% is the main cause of electrical breakdown. Humid environment causes the absorption and diffusion of water vapor on the surface of the insulator, which can easily reduce the insulation resistance to below MΩ. Long-term exposure to high humidity will cause physical deformation, decomposition, and escape of products, resulting in respiratory effects, electrolysis, and corrosion. And cracks. Especially for electrical connectors outside the equipment, environmental conditions such as humidity, water seepage and pollution are often considered. In this case, sealed aviation plugs should be used. For water-tight and dust-tight electrical connectors, GB4208 shell protection level is generally used to indicate.

13: sudden temperature change

The humidity sudden change test is to simulate the actual use of aviation plug equipment in a cold environment into a warm environment, or to simulate the situation of a sudden change in the ambient temperature of a space vehicle or probe. Rapid changes in temperature may crack or delamination of the insulating material.

14: Atmospheric pressure

At high altitudes where the air is thin, the plastic emits gas to contaminate the contact pair, and the corona tends to increase, the pressure resistance decreases, and the circuit produces a short circuit failure. When the altitude reaches a certain value, the performance of the plastic deteriorates. Therefore, when using non-sealed aviation plugs at high altitudes, they must be derated. The recommended voltage derating factor under low air pressure is shown in the table.

15: Corrosive environment

According to different corrosive environments of aviation plugs, choose aviation plugs with corresponding metal, plastic, and plating structures. Like aviation plugs used in salt spray environments, if there is no anti-corrosion metal surface, the performance will deteriorate rapidly. In an environment with a considerable concentration of SO2, it is not suitable to use silver-plated aviation plugs. In hot flash areas, mold is also an important issue.

16: Termination method

Termination mode refers to the connection mode between the contact pair of the aviation plug and the wire or cable. Reasonable choice of termination methods and correct use of termination technology are also an important aspect of the use and selection of aviation plugs.

17: Welding

The most common soldering is soldering. The most important thing in soldering connection is the continuity of metal between the solder and the surface to be soldered. Therefore, for aviation plugs, solderability is important. The most common coatings on the welding end of aviation plugs are tin alloy, silver and gold. The reed type contact has the welding piece type, the punching welding piece type and the notched welding piece type for the common welding end: the pinhole contact has the drilling arc notch type for the common welding end.

18: crimping

Crimping is a technique for compressing and displacing metal within specified limits and connecting wires to contact pairs. A good crimp connection can produce metal mutual fusion flow, so that the wire and the contact pair material symmetrically deform. This kind of connection is similar to cold-welded connection, it can get better mechanical strength and electrical continuity, it can withstand harsher environmental conditions, it is generally believed that the correct crimp connection is better than soldering, especially in high current occasions. Crimping. Special crimping pliers or automatic or semi-automatic crimping machine must be used for crimping. According to the cross section of the wire, the correct wire barrel should be selected correctly. It should be noted that the crimp connection is a permanent connection and can only be used once.

19: Winding

Winding is to wind the wire directly on the angular contact winding post. During winding, the wire is wound under controlled tension, pressed in and fixed at the corners of the contact piece winding post to form an airtight contact. There are several requirements for winding wires: the nominal value of the wire diameter should be within the range of 0.25mm~1.0mm; when the wire diameter is not greater than 0.5mm, the elongation of the conductor material is not less than 15%; when the wire diameter is greater than 0.5mm, the conductor The elongation of the material is not less than 20%. Winding tools include winding guns and fixed winding machines.

20: Pierce one after another

Piercing connection, also known as insulation displacement connection, is a novel terminal technology invented by the United States in the 1960s. It has the characteristics of high reliability, low cost, and convenient use. It has been widely used in various electrical connectors for printed boards. It is suitable for the connection of ribbon cables. When connecting, there is no need to strip the insulation layer of the cable. The tip of the "U"-shaped contact reed of the aviation plug is pierced into the insulation layer, so that the conductor of the cable slides into the groove of the contact reed and is clamped. A tight electrical connection is formed between the cable conductor and the aviation plug reed. It only requires simple tools, but cables with specified wire gauges must be selected.

21: Screw connection

Screw connection is a connection method using screw-type terminals. Pay attention to the maximum and minimum cross-sections of the connecting wires and the maximum tightening torque allowed by screws of different specifications.