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Industry Information
Safety barrier
2011-6-9 8:07:24

Jinhu Dongxiang Instrument's safety barriers are mainly sold in the mainland China market and are unanimously approved by new and old customers! The safety barrier is introduced in detail below!

接在本质全电路和非本质安全电路之间。 Definition of safety barrier : connected between intrinsically full circuit and non-intrinsically safe circuit. A device that limits the voltage or current supplied to an intrinsically safe circuit within a certain safe range

structure type:

Zener barrier

Fast fuses, current-limiting resistors, or voltage-limiting diodes are used in the circuit to limit the input electrical energy, thereby ensuring 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 the defects of its own principle, the reliability in its application is greatly affected, and its application range is limited. The reasons are as follows:

1. The installation location must have a 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 harsh and difficult to guarantee in practical 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 connecting to the ground through the ground terminal of the Zener safety barrier, and because the signal is grounded, the anti-interference ability of the signal is directly reduced and the system stability is affected .

3. The Zener safety barrier has a large impact on the power supply , and it is also easy to cause damage to the Zener safety barrier due to power supply fluctuations.

4. Because the circuit principle of the Zener safety barrier needs to absorb the energy of the input circuit, it is easy to cause the output to be unstable.

Isolated safety barrier

It adopts a circuit structure that electrically isolates the three parties of input, output and power, while meeting the requirements of intrinsically safe energy limitation. Compared with Zener-type security, although the price is more expensive, its outstanding advantages in performance have brought greater benefits to user applications:

1. Because the three-way isolation method is used, no system grounding line is needed, which brings great convenience to the design and field construction.

2. The requirements for instruments in dangerous areas are greatly reduced, and isolated instruments are not required 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.Isolated safety barrier has stronger input signal processing ability, can accept and process signals such as thermocouple , thermal resistance, frequency, which cannot be achieved by Zener safety barrier.

5.Isolated safety barrier can output two isolated signals to provide two devices using the same signal source, to ensure that the signals of the two devices do not interfere with each other, and to improve the electrical safety insulation performance of the connected devices. .

Therefore, after comparing the characteristics and performance of Zener barriers and isolated barriers, it can be seen that isolated barriers have outstanding advantages and a wider range of uses. Although their price is slightly higher than that of Zener barriers, from the design, Considering the cost of construction, installation, commissioning and maintenance, the overall cost may be lower than the Zener barrier. Isolation safety barriers have been used as the main intrinsically safe explosion-proof instruments in engineering sites with higher requirements. Isolation safety barriers have gradually replaced Zener safety barriers and have been increasingly used in the field of safety and explosion protection.

Definition of intrinsically safe equipment mark

Of which: EX — Explosion-proof mark

(Ia) —Explosion- proof grade

ⅡC — Gas group

Our company's explosion-proof grade: EX (ia) IIC

Isolated application advantages

①Compared with Zener barrier, although the barrier is more expensive, its many advantages and characteristics still bring a lot of convenience to users, and more and more users prefer to choose the barrier.

② The use of an isolated safety barrier can effectively isolate the on-site circuit signals in the danger zone from the safety zone circuit signals. In this way, the intrinsically safe automatic control system does not require an intrinsically safe grounding system, which simplifies the construction when the intrinsically safe explosion-proof system is applied.

③ The use of an isolated safety barrier greatly enhances the anti-interference ability of the detection and control circuits and improves the system reliability .

④ Use an isolated safety barrier to allow field instruments to be grounded and allow field instruments to be non-isolated.

⑤Isolated safety barrier has many protection function circuits, and the possibility of accidental damage is small, allowing field instruments to be repaired with power on, which can shorten the engineering startup preparation time and reduce the downtime.

⑥Isolated safety barrier has strong signal processing ability. Such as switching value input state control, mV, Pt100 becomes 4 ~ 20mA and so on. This provides greater convenience, rationality and effectiveness for the application of field instruments and control systems.

用户 When the user applies DCS and ESD at the same time, the one-in two-out safety barrier can be used to effectively isolate the two systems and avoid mutual influence between the systems.

供电 The loop-powered isolated safety barrier not only maintains the advantages of an active isolated safety barrier , but also has the same wiring as a Zener safety barrier, and does not require another 24V power supply. It is especially suitable for DCS systems that are directly powered by I / O cards.