How to judge the quality of wiring terminals?
To determine the quality of wiring terminals, the following key aspects can be taken into account:
Appearance details
Surface technology: The surface of high-quality wiring terminals is usually well treated, such as electroplating, spraying, etc. Taking electroplating as an example, the coating should be uniform, smooth, and free from obvious defects such as bubbles, peeling, and flaking. If the coating is uneven, the wiring terminals are prone to damage due to local corrosion in harsh environments such as humidity.
Dimensional accuracy: The size of the terminal block should comply with relevant standards and design requirements, and the dimensional accuracy should be high. For example, the aperture size used to connect wires should be compatible with the wire specifications, with an error within the allowable range. If the aperture is too large, the wires may become loose after connection, leading to poor contact; If the aperture is too small, the wire will be difficult to insert and may even damage the terminal block or wire.
Plastic shell quality: Many wiring terminals use plastic shells to provide insulation protection. A high-quality plastic casing should have a uniform texture and no obvious impurities or cracks. Pressing the plastic shell with your hands should feel solid, have a certain degree of toughness, and not easily deform or break. If the plastic shell has loose texture and cracks, it will not only reduce the insulation performance, but may also cause the shell to break during use, thereby exposing the internal metal components and causing safety accidents.
Electrical performance
Contact resistance test: Contact resistance is an important indicator for measuring the electrical performance of terminal blocks. Use a professional contact resistance tester to test the wiring terminals. The contact resistance of high-quality wiring terminals should be low and stable, generally in the milliohm range. For example, the contact resistance of wiring terminals used in some small electronic devices may be below 10 milliohms. If the contact resistance is too high, it will cause an increase in electrical energy loss at the connection point, generate excessive heat, and thus affect the normal operation of the circuit, and may even cause safety issues such as fires.
Voltage withstand test: Voltage withstand test is used to evaluate the insulation performance of wiring terminals, ensuring that insulation breakdown and other faults will not occur at the specified voltage. Use a voltage tester to apply a certain voltage to the terminal block, such as AC 1000V or higher, for a certain period of time, usually 1 minute or longer. During the testing process, high-quality wiring terminals should be able to withstand the specified voltage without experiencing phenomena such as flicker, discharge, breakdown, etc. If insulation breakdown occurs in the voltage withstand test of the terminal block, it indicates that its insulation performance does not meet the requirements. In practical use, when the circuit voltage fluctuates or rises instantly, it is easy to cause electrical accidents such as short circuits, seriously threatening the safety of equipment and personnel.
Temperature rise test: The temperature rise test is to check the heating condition of the wiring terminal under normal working current. Install the terminal block on the designated testing device and apply the rated current for a certain period of time until the temperature of the terminal block reaches a stable state. The temperature rise of high-quality wiring terminals in temperature rise tests should be within the specified range. Generally, the surface temperature rise should not exceed 50 ℃ to 60 ℃ (depending on different standards and product types). If the temperature of the terminal block rises too much during the temperature rise test, it indicates that it will generate excessive heat during normal operation. This not only accelerates the aging of the internal materials of the terminal block, reduces its service life and reliability, but also may cause thermal damage to surrounding electronic components and equipment, affecting the normal operation of the entire system.
Mechanical properties
Connection firmness test: Connection firmness is one of the key indicators of the mechanical performance of terminal blocks. For screw connected terminal blocks, use a suitable screwdriver to tighten the screws to the specified torque value, and then try to pull the connected wires with appropriate force. High quality terminal blocks should be able to firmly clamp wires, and under normal use and certain external forces, wires will not come out of the terminal blocks. For spring connected terminal blocks, insert the wire into the spring clip of the terminal block and perform a similar tensile test. Similarly, high-quality spring connected terminal blocks should be able to firmly clamp wires with the elastic force of the spring, ensuring the reliability of the connection. If the wire is easily detached from the terminal block during the connection firmness test, it indicates that there is a defect in its connection design or manufacturing process. In actual use, this type of terminal block may cause poor contact due to loose wires, leading to circuit faults and seriously affecting the normal operation and safety of the equipment.
Mechanical strength testing: Mechanical strength testing is used to evaluate the ability of terminal blocks to resist external damage. Use specialized mechanical strength testing equipment, such as universal material testing machines, to apply certain pressure or tension to the wiring terminals, simulating the external forces they may experience during actual use. High quality wiring terminals should have sufficient mechanical strength and should not experience cracking, deformation, damage, or other phenomena when subjected to specified external forces. For example, for wiring terminals installed in industrial equipment or outdoor facilities, they may be subjected to significant external forces such as vibration, collision, and compression, thus requiring higher mechanical strength. In mechanical strength testing, if the terminal block ruptures or deforms severely when subjected to small external forces, it indicates that its mechanical strength is insufficient and cannot meet the requirements of the actual usage environment. In practical use, this type of terminal block may be damaged by external forces, causing circuit interruption, affecting the normal operation of equipment, and even causing safety accidents, resulting in losses to personnel and property.
Durability testing: Durability testing aims to verify whether the terminal block can maintain its stability and reliability in long-term use. Durability testing typically involves multiple connection and disconnection operations, as well as long-term operational testing under different environmental conditions. For wiring terminals that require frequent plugging and unplugging of wires, such as those used at interfaces of some electronic devices, multiple plugging and unplugging tests should be conducted. After the specified number of insertion and extraction operations, the connection performance, electrical performance, and mechanical performance of high-quality terminal blocks should remain basically unchanged, and there should be no problems such as poor contact, looseness, deformation, etc. At the same time, place the wiring terminals in different environmental conditions, such as high temperature, low temperature, humidity, dust, etc., for long-term operation testing. Within the specified test period, high-quality wiring terminals should be able to operate normally under various environmental conditions, and their performance indicators should always be maintained within the specified range, without any performance degradation, malfunction or other problems caused by environmental factors. If the terminal block experiences poor contact or looseness after a few insertion and extraction operations during durability testing, or if its performance indicators significantly decrease or malfunction after long-term operation under different environmental conditions, it indicates that its durability is insufficient and cannot meet the requirements for long-term stable use. In practical use, this type of terminal block may gradually lose its stability and reliability due to frequent use or environmental factors, leading to frequent circuit failures, seriously affecting the normal operation and service life of the equipment, increasing maintenance costs and usage risks.
Brand and Certification
Brand reputation: Well known brands usually have strict quality control systems and advanced production processes, and their produced wiring terminals are more guaranteed in terms of quality and reliability. For example, some internationally renowned brands have years of research and production experience in the field of electrical connections. Their products are widely used in various high-end electronic devices, industrial automation systems, and power engineering, and have gained high recognition in the market and a good reputation from users. In contrast, some small or unknown brands may have significant differences and unstable factors in the quality and performance of their produced wiring terminals due to limited technical strength, rudimentary production equipment, and lax quality control, which cannot meet users' requirements for product quality and reliability. Therefore, when choosing wiring terminals, prioritizing products with good brand reputation is one of the important ways to ensure product quality and reliability.
Certification standards: Wiring terminals should have relevant international, national, or industry certifications, which are authoritative recognition of their quality and performance. Common certifications include International Electrotechnical Commission (IEC) certification, Underwriters Laboratories (UL) certification, T Ü V Rheinland certification, and China's CCC certification. Taking IEC certification as an example, IEC is one of the most authoritative electrical standard setting organizations in the world, and its standards cover various aspects of electrical equipment, including safety, performance, electromagnetic compatibility, etc. Obtaining IEC certification for wiring terminals means that the product strictly follows the requirements of IEC related standards in the design, production, and testing processes, and its quality and performance have reached internationally recognized levels. Similarly, UL certification is an important certification for the safety performance of electrical products in the US market. Terminal blocks that have obtained UL certification indicate that they meet the requirements of relevant US standards and regulations in terms of electrical safety and can be used safely and reliably in the US market. Therefore, when judging the quality of wiring terminals, checking whether they have relevant authoritative certifications is an important reference. Wiring terminals with multiple authoritative certifications are usually more guaranteed in terms of quality and performance, and can meet the requirements of different users and application scenarios for product quality and reliability.
Through comprehensive consideration and testing of multiple dimensions mentioned above, it is possible to comprehensively and accurately determine the quality of wiring terminals, thereby selecting reliable products for practical applications.