Basic performance and working principle of connectors

2021-09-27 10:45

Working principle of connectors

　　People may not have much understanding of connectors. A connector is two or more containers that are interconnected below the liquid surface. In interconnected containers filled with the same liquid and with equal pressure on the liquid surface, the liquid levels are equal.

　　(1) If the connector contains the same liquid, but the pressure on the liquid surface is unequal, then the pressure difference on the liquid surface is equal to the pressure difference generated by the height difference of the liquid surface in the two containers of the connector.

　　(2) If the pressure on the liquid surface of the connector is equal, but there are different liquids on both sides that do not mix with each other, then from the interface, the height of the two liquid surfaces is inversely proportional to the density of the liquid.

　　The principle of connectors has wide applications in engineering. For example, various liquid level gauges (water level gauges, oil level gauges, etc.), mercury vacuum gauges, liquid column pressure gauges, differential pressure gauges, etc., are all made using the principle of interconnected containers.

　　Understanding the definition and working principle of connectors helps us better understand and develop the connector market.

Basic performance of connectors

　　Connector knowledge The basic performance of connectors can be divided into three categories: mechanical performance, electrical performance, and environmental performance. Another important mechanical property is the mechanical life of the connector. Mechanical life is actually a durability indicator; in national standard GB5095, it is called mechanical operation. It is defined as one insertion and one extraction as one cycle, and the judgment is based on whether the connector can normally complete its connection function (such as contact resistance) after a specified number of insertion and extraction cycles.

Connectors

1. Mechanical Performance In terms of connection function, insertion force is an important mechanical property. Insertion force is divided into insertion force and extraction force (extraction force is also called separation force), and the requirements for the two are different. Relevant standards specify the maximum insertion force and minimum separation force, indicating that from a usage perspective, the insertion force should be small (thus, there are low insertion force (LIF) and zero insertion force (ZIF) structures), while if the separation force is too small, it will affect the reliability of the contact. The insertion force and mechanical life of the connector are related to the contact structure (magnitude of normal pressure), the quality of the plating on the contact surface (coefficient of sliding friction), and the dimensional accuracy (alignment) of the contact arrangement.

　　2. Electrical Performance The main electrical performance of connectors includes contact resistance, insulation resistance, and dielectric strength.

　　① Contact Resistance A high-quality electrical connector should have low and stable contact resistance. The contact resistance of a connector ranges from a few milliohms to tens of milliohms.

　　② Insulation Resistance This indicator measures the insulation performance between the contacts of an electrical connector and between the contacts and the shell; its order of magnitude ranges from hundreds of megohms to thousands of megohms.

　　③ Dielectric Strength Also known as voltage withstand or dielectric withstand voltage, this characterizes the ability of a connector to withstand the rated test voltage between contacts or between contacts and the shell.

　　④ Other Electrical Performance

　　Electromagnetic interference leakage attenuation is used to evaluate the electromagnetic interference shielding effect of connectors. Electromagnetic interference leakage attenuation is used to evaluate the electromagnetic interference shielding effect of connectors, generally tested in the 100MHz~10GHz frequency range.

　　For radio frequency coaxial connectors, there are also electrical indicators such as characteristic impedance, insertion loss, reflection coefficient, and voltage standing wave ratio (VSWR). Due to the development of digital technology, in order to connect and transmit high-speed digital pulse signals, a new type of connector, the high-speed signal connector, has emerged. Correspondingly, in terms of electrical performance, in addition to characteristic impedance, some new electrical indicators have also appeared, such as crosstalk, transmission delay, and skew.

　　3. Environmental Performance Common environmental performance includes temperature resistance, humidity resistance, salt spray resistance, vibration resistance, and impact resistance.

　　① Temperature Resistance Currently, the highest operating temperature of connectors is 200℃ (except for a few high-temperature special connectors), and the lowest temperature is -65℃. Since the connector generates heat at the contact point when working, resulting in a temperature rise, it is generally believed that the operating temperature should be equal to the sum of the ambient temperature and the contact temperature rise. In some specifications, the maximum allowable temperature rise of the connector at the rated operating current is clearly specified. ② Humidity Resistance The intrusion of moisture will affect the insulation performance of the connection and corrode metal parts. The constant humidity and heat test conditions are relative humidity 90%~95% (according to product specifications, it can reach 98%), temperature +40±20℃, and the test time is as specified by the product, at least 96 hours. The alternating humidity and heat test is more stringent. ③ Salt Spray Resistance When the connector works in an environment containing moisture and salt, the metal structural parts and the surface treatment layer of the contact parts may undergo electrochemical corrosion, affecting the physical and electrical performance of the connector. In order to evaluate the ability of the electrical connector to withstand this environment, a salt spray test is specified. It involves suspending the connector in a temperature-controlled test chamber and spraying a solution of specified concentration of sodium chloride with compressed air to form a salt spray atmosphere. The exposure time is specified by the product specification, at least 48 hours. ④ Vibration and Impact Resistance Vibration and impact resistance are important properties of electrical connectors, especially important in special application environments such as aerospace, rail and road transportation. It is an important indicator for testing the robustness of the mechanical structure and the reliability of electrical contact of electrical connectors. Relevant test methods have clear regulations. In the impact test, the peak acceleration, duration, and impact pulse waveform, as well as the time of electrical continuity interruption, should be specified.

　　⑤ Other Environmental Performance According to the requirements of use, other environmental performance of electrical connectors includes sealing (air leakage, liquid pressure), liquid immersion (resistance to specific liquid deterioration), low air pressure, etc.

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