safety barrier

I would like to understand the fundamental differences between isolated safety barriers and Zener safety barriers, as well as their power distribution methods; it would be great if there were wiring diagrams that could illustrate this clearly. Waiting for the expert

Safety barriers are generally installed in the control room (safe area), while measurement instruments and equipment that require explosion protection are located in the hazardous area. The signals from hazardous areas are fed into safety barriers and then sent to DCS systems located in safe areas; in this case, isolation safety barriers at the detection end are used ； The DCS system located in the safe area sends signals to the field instrumentation devices in the hazardous area through safety barriers; in this case, an operational isolation safety barrier is used. The isolation safety gates at the operating end and those at the detection end serve different purposes; for specific parameters, please refer to the technical documentation provided by each manufacturer. What are the similarities and differences in performance and features between Zener safety barriers and isolated safety barriers? Safety barriers are auxiliary units of electric combined instrument panels, and their main purpose is to serve as isolation devices in explosion-proof systems. The safety barrier transmits the signals from the hazardous area through isolation, outputting isolated current signals to the safe area. It is used in intrinsically safe explosion-proof systems, where current-limiting and voltage-limiting circuits are employed to restrict the energy sent to the field circuit, thereby preventing dangerous energy from non-intrinsically safe circuits from entering the intrinsically safe circuits. Common safety barriers can be classified into Zener type and isolation type based on their structural design. 1. Zener safety barrier: A Zener safety barrier uses fast fuses, current-limiting resistors, or voltage-limiting diodes to limit the electrical energy entering the system, thereby ensuring control over the amount of energy that is sent to the hazardous area. However, due to flaws in the principle, its reliability in application is affected, which limits its scope of use. Zener safety barriers require a highly reliable grounding system, with a grounding resistance of less than 1Ω; otherwise, they lose their explosion-proof protection capabilities. Clearly, such requirements are difficult to meet in factory environments. It is required that the field instruments in hazardous areas must be isolated-type; otherwise, when connected to ground through the grounding terminal of the Zener safety barrier, the signals cannot be transmitted properly. Moreover, grounding the signals reduces their resistance to interference, thereby affecting the stability of the system. Zener safety barriers have a significant impact on the power supply, and they can also be damaged due to fluctuations in the power supply. http://yunrun.com.cn/upload/201604/08/201604081910354247.jpg 2. Isolated safety barriers: Isolated safety barriers employ a circuit structure that provides electrical isolation between the input, output, and power supply, in order to meet the energy limitation requirements of intrinsically safe instruments. Thanks to the input-input-power supply-output and output isolation design, a system ground wire is not required, which facilitates both design and on-site installation. Isolated instruments are not required for the field instruments in hazardous areas. Furthermore, the signal lines do not need to be shared over a common ground, which **improves** the stability and interference resistance of the signals in the detection and control circuits, thereby enhancing the reliability of the entire system. When an isolated safety barrier possesses stronger input signal processing capabilities, it is able to accept and process signals from thermocouples, thermal resistors, frequencies, etc., something that zener safety barriers cannot do. An isolated safety barrier can output two mutually isolated signals, which are provided to two devices that use the same signal source; this ensures that the signals from the two devices do not interfere with each other, while also improving the electrical insulation between the connected devices. By comparing the performance and characteristics of Zener-type and isolated safety barriers, it can be seen that isolated safety barriers have significant advantages and a wider range of applications; in production environments with high requirements, isolated safety barriers are almost always used.