Zener type safety barrier Structure principle: Fast fuse, current-limiting resistor or voltage-limiting diode are used in the circuit to limit the input electric energy, so as to ensure the energy output to the dangerous area. Its principle is simple, the circuit is easy to implement, and the price is low. However, due to its own principle defects, its reliability in its application is greatly affected, and its application range is limited. The reason for the Zener safety barrier structure principle: circuit Fast fuses, current-limiting resistors or voltage-limiting diodes are used to limit the input electrical energy so as to ensure the energy output to the hazardous area. Its principle is simple, the circuit is easy to implement, and the price is low. However, due to its own principle defects, its reliability in its application is greatly affected, and its application range is limited. The reasons are as follows: 1. The installation location must be very Reliable grounding system, and the grounding resistance of the Zener safety barrier must be less than 1Ω, otherwise the explosion-proof safety protection performance will be lost. Obviously, such requirements are very demanding and difficult to guarantee in actual engineering applications. 2. It is required that the field instruments from the dangerous area must be isolated, otherwise the signal cannot be transmitted correctly after the ground terminal of the Zener safety barrier is connected to the earth, and the signal grounding directly reduces the signal anti-interference ability and affects the stability of the system . 3. The Zener safety barrier has a greater impact on the power supply, and it is also easy to cause damage to the Zener safety barrier due to the fluctuation of the power supply. Isolated safety barrier uses a circuit structure that electrically isolates the input, output, and power from each other, and meets the requirements of intrinsically safe energy limitation. Compared with Zener-style safety, although the price is slightly higher, its other outstanding advantages have brought greater benefits to user applications: 1. Because of the use of three-way isolation, there is no need for system grounding lines, which makes design and On-site construction brings great convenience. 2. The requirements for instruments in hazardous areas are greatly reduced, and there is no need to use isolated instruments on site. 3. Since the signal lines do not need to share the ground, the stability and anti-interference ability of the detection and control loop signals are greatly enhanced, thereby improving the reliability of the entire system. 4. The isolated safety barrier has stronger input signal processing capability, and can receive and process signals such as thermocouple, thermal resistance, frequency, etc. This is something that Zener-type safety barriers cannot do. 5. The isolated safety barrier can output two mutually isolated signals to provide to two devices using the same signal source, and ensure that the signals of the two devices do not interfere with each other, and at the same time improve the electrical safety insulation performance of the connected devices . Therefore, comparing the characteristics and performance of Zener and isolated safety barriers, it can be seen that isolated safety barriers have outstanding advantages and a wider range of uses. Although its price is slightly higher than that of Zener safety barriers, from the design, Considering the cost of construction, installation, commissioning and maintenance, the overall cost may be lower than the Zener safety barrier. Almost without exception, isolation safety barriers are used as the main intrinsically safe explosion-proof instruments in high-demand engineering sites. Isolated safety barriers have gradually replaced Zener safety barriers and have been increasingly widely used in the field of safety and explosion protection. The definition of intrinsically safe equipment mark: Ex — Explosion-proof mark (ia) — Explosion-proof level IIC— Gas group Explosion-proof level of our company’s products: Ex (ia) IIC Explosion-proof level ia: Under normal working conditions, 1 failure or 2 failures The dangerous gas will not be ignited in the state, and the circuit must ensure that the safety features are still guaranteed when two faults occur at the same time. 'Ia' electrical equipment must adopt a 'triple' design for components that are susceptible to interference. 'Ib' electrical equipment can only guarantee that hazardous gases will not be ignited in one fault state. Gas group Ⅰ group electrical equipment: used in coal mine environment susceptible to methane. Group II electrical equipment: It can be used in explosive environments other than coal mines. Group II electrical equipment is further subdivided according to the ignition energy of different flammable substances. Each subgroup is distinguished by uppercase English subgroups. From the table below, it can be seen that subgroup C requires the least ignition energy, that is, in this group of electrical equipment, the equipment of group C is universal.
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