The production and use of combustible materials such as alcohol and gasoline in industry all involve explosion-proof technology.

Commonly used explosion-proof technologies include: flameproof, intrinsic safety, oil immersion, sand filling, casting and sealing. In electrical explosion-proof, intrinsic safety is the most used technology, it needs to use a key component - safety gate.

Today, in this article, we will talk about the safety gate related topics.

In electrical intrinsic safety explosion-proof (referred to as: intrinsic safety explosion-proof), we generally divide the workplace into explosion-proof areas and non-explosion-proof areas.

There is power transmission between the explosion-proof area and the non-explosion-proof area, for example, the switch, button, sensor, etc. in the explosion-proof area is connected with the PLC placed in the electric cabinet in the non-explosion-proof area by wire.

The role of the safety gate is to play an energy current limiting role between the explosion-proof area and the non-explosion-proof area, which reduces the electrical energy of the signal in the explosion-proof area, thereby reducing the risk of generating electrical sparks.

According to the different structure, the Safety fence is divided into two categories: Zener Safety barrier and Isolated Safety barrier.

1, the Zener safety gate in its internal circuit series fast fuse wire, current limiting resistance and parallel voltage limiting Zener diode, so as to achieve the role of limiting energy, it has the following characteristics:

① There must be a separate, very reliable grounding system (intrinsic safety system grounding), grounding resistance should be less than 1Ω;

(2) can not be electrical signal conversion, for the thermocouple/thermal resistance (RTD) signals may be due to electromagnetic interference errors, so it is not suitable to connect this type of sensor;

(3) The influence on the power supply voltage is very large, and the fluctuation of the power supply voltage may cause the current leakage of the Zener diode, which causes the error of the signal or the wrong level, and will cause the rapid fuse to be burned and permanently damaged. According to the provisions of Zener safety gate internal Zener tube, current limiting resistance, fuse integral pouring seal, once damaged can not be repaired;

④ Small size, cheap price, no need for additional power supply;

2. The input, output and power supply of the isolated safety gate are isolated from each other, which has the following characteristics:

① No need for ground line, site construction is very convenient;

Because the signal line does not need to be common ground, the stability and anti-interference ability of the entire system are greatly enhanced;

③ With signal conversion ability, you can process signals such as thermocouple/thermal resistance/frequency, such as converting it into 4~20mA current signal output, anti-interference ability is relatively strong;

General isolated safety grid has two output channels, electrical isolation between each other, do not affect each other;

⑤ The price is relatively expensive, and external power supply is required;

Although the price of the isolated safety fence is relatively expensive, its excellent performance and easy construction characteristics make it widely used in industrial sites.