Introduction to the latest signal isolator and saf

Introduction of new signal isolator and safety barrier

as the signal isolation transmitter equipment between industrial field and control room instruments, signal isolator and safety barrier have always played an important role and are an important part of industrial control system. With the progress of technology, both the primary instrument and the control system have changed, and the signal isolator and safety barrier also need to be further developed to meet higher requirements. Beijing Guodian zhongzi Electric Co., Ltd. has summarized the practical experience over the years, improved the products, and improved the performance of isolators and safety barriers to meet the needs of the market. New isolators and safety barriers have made greater progress in performance and technical indicators than in the past

first, the modular design ensures the rapid response to the market

the isolator and safety barrier are generally composed of four parts: input signal processing unit, isolation unit, output signal processing unit, power supply, etc. According to the flow direction of the signal, an intrinsically safe design is added to the input or output unit to form an isolator and a safety barrier

although the isolators and safety barriers in practical applications are basically composed of the above four units, the types and quantities of input and output are different, forming a wide variety of models. In order to meet the market demand, more and more models make the production burden of enterprises heavier, less quantity and more varieties make the delivery cycle longer and longer, and also increase the cost of commissioning and inspection. These conditions have seriously hindered the market promotion of products. In view of this situation, Yutong Company has divided the isolator and safety barrier into seven functional modules through careful analysis and modular design method, so as to better solve the above problems. The modular design method greatly solves the pressure of product processing, debugging, aging and inventory. The consistency of products is good, and the quality is improved. It fundamentally solves the pressure on the production link caused by the majority of varieties and small quantity, and greatly shortens the delivery cycle

second, low power consumption design

low power consumption is the endless pursuit of electronic product design. With the development of technology, the power consumption of isolators and safety barriers has been greatly reduced compared with the past, and the performance and technical indicators have also been improved

the power consumption of the product is the sum of the power consumption of each functional unit. Only by reducing the power consumption of each functional unit can the total power consumption be reduced, and then the thermal stability and life of the product can be increased. The isolator and safety barrier are composed of input, output, isolation, power supply, safety and other units. The safety unit is a passive voltage and current limiting network, and the possibility of low power consumption improvement in technology is very small. The technical improvement is mainly carried out in four units: input, output, power supply and isolation

1. Adaptive load technology of output unit module

the output module can dynamically adjust the output power of the output module according to the size of the load, so as to reduce its own heating. The traditional load design is to design the output power according to the size of the rated load. When the output load is very small, the excess load power is dissipated inside the instrument, so that the instrument itself heats up. Assuming that the output load of an isolator is designed to be 750 ohms, the output drive power is generally designed to be 0.5W. If the load of this isolator is used in a 50 ohm environment in practical application, the power of 0.5W – 0.02w = 0.48w will be converted into the heating of the instrument itself. If the multi-channel output will produce more heat, and reducing the rated power of the output module is difficult to cope with the complex situation of the market in practical application

adaptive load technology solves this contradiction well. The principle diagram of this technology is as follows:

the following table is the comparative test data:

test condition: power supply 24dc; Load change 50 ohms ~ 750 ohms

output module type standard output module adaptive load output module

dissipation power of module (50 Ω) 320MW 10mw

dissipation power of module (250 Ω) 220MW 10mw

dissipation power of module (500 Ω) 120mW 10mw

dissipation power of module (750 Ω) 20MW 10MW

from the above table, it can be seen that the adaptive load technology makes the dissipation power of the module constant at a very low level and will not be affected by load changes

load detection can adjust the output power according to the size of the load, which greatly reduces the heating of the output module. Users do not need to specify the size of the load when ordering, which greatly facilitates users' use and relieves the inventory pressure

2. Low power improvement of isolation unit module

isolation unit is an important unit that determines the technical indicators of products

at present, the isolation technology mainly includes magnetic isolation and optical isolation. The form of isolation circuit includes direct modulation coupling, feedback modulation coupling and other forms. The specific form to be adopted depends on the technical indicators of the product. Generally speaking, it can be roughly divided into switching signal adopting optical isolation, analog signal adopting magnetic isolation, and load reading pointer separation. In terms of technical complexity, magnetic isolation is more complex than optical isolation processing technology. With magnetic isolation technology, designers can adopt appropriate design schemes according to technical indicators, and the linearity and accuracy of isolation can be flexibly controlled according to product requirements. The linearity and accuracy of optical isolation can only depend on the technical indicators provided by the device manufacturer. Designers can adjust in few ways, and it is impossible to exceed the technical indicators provided by the manufacturer. Due to high power consumption, photoelectric isolation can not achieve passive isolation. Beijing Guodian zhongzi Electric Co., Ltd. adopts various magnetic isolation modes, such as current mutual inductance mode, current mutual inductance feedback mode, voltage mutual inductance feedback mode, current mutual inductance power compensation mode, etc. Choose different magnetic isolation modes according to the characteristics of the product

among the above isolation modes, current mutual inductance power compensation mode is the mode with the lowest power consumption. It is currently used in the new generation of passive isolation safety barriers, which reduces the power consumption of isolation units while ensuring technical indicators

3. The technical indicators of power supply module

power supply are the basis and determine the performance of products. Although there are many popular power topology forms at present, they are also very mature. However, we have made technological innovation in the power supply design of isolators and safety barriers. The current parametric switching regulated power supply design has won the national invention patent. According to the characteristics of isolators and safety barriers, the parametric switching regulated power supply improves the efficiency and reduces the complexity of the power supply. The process and cost are improved, and the failure rate of products is reduced

III. passive isolators and safety barriers

traditional isolators and safety barriers are active and require external 24V DC power supply. Passive isolators and safety barriers do not need external 24V DC power supply, and the number of wiring is reduced by one third, reducing the difficulty of installation and maintenance. Therefore, passive isolators and safety barriers are more and more widely used, especially in the interface application of DCS and PLC systems. The design mode of passive isolators and safety barriers is generally adopted.

schematic diagram of passive isolators and safety barriers:

passive can stretch, compress, zigzag, peel, shear and other functions for all kinds of data. Experimental isolators and safety barriers mean that there is no need to connect 24V DC power supply externally, The energy required for its operation comes from the 4 ~ 20mA current representing the signal. Therefore, the power consumption of passive isolators and safety barriers must be very small, which is a micro power design application. Lower power consumption and higher input and output linearity are the key indicators to measure passive isolators and safety barriers

schematic diagram of input and output transfer characteristics of passive isolation mode:

it can be seen from the above figure; The main factors causing input and output nonlinearity are the change of signal current and the size of load. The influence of this binary change can be well solved in the design of active isolators and safety barriers, because there is no limitation of power consumption. In the design and application of passive isolators and safety barriers, many mature technologies are limited by power consumption and cannot be adopted. Through the improvement of current mutual inductance magnetic isolation, the innovative current mutual inductance power compensation magnetic isolation solves this problem well

the following table shows the comparison of input and output linear indicators before and after the improvement of passive magnetic isolation mode

magnetic isolation mode nonlinear (50 Ω) nonlinear (250 Ω) nonlinear (500 Ω)

current transformer power compensation 0.1 0.1 0.1

current transformer 0.1 0.25 0.5

at present, the magnetic isolation mode of current transformer is used in the application of passive isolators and safety barriers at home and abroad, and its linear index is similar to the first generation products of Guodian zhongzi, and its linear index is limited by the isolation principle used

the company adopts current mutual inductance power compensation magnetic isolation in the design of passive isolators and safety barriers, and the designed passive isolators and safety barriers have reached the level of active isolators and safety barriers in terms of input and output linearity. Such linear indicators are leading at home and abroad. The impact should be applied in each of the three mutually perpendicular directions

IV. miniaturization and less wiring. In order to meet the installation requirements of high density, the isolator and safety barrier are installed in the control room as secondary instruments. The environment of the control room requires that the products should be as small as possible to achieve high-density installation, and the number of wiring should be as small as possible, so as to reduce the difficulty of installation and maintenance. Miniaturization of products is the development trend of isolators and safety barriers. At present, the thickness of MS series products of the company is only 6.2mm. The design and implementation of low power consumption is reflected in the appearance of the product, which is the miniaturization of the product. Only low-power products can realize intensive installation. With the progress of technology, we will design products with lower power consumption, better performance and smaller size

at present, the thickness of domestic mainstream products is generally between 20mm and 30mm, and the thickness of foreign latest products is 6.2mm. The gd-cb series of Beijing Guodian zhongzi Electric Co., Ltd. has reached the level of the latest foreign products

this article is from Beijing Guodian zhongzi Electric Co., Ltd. for detailed source reference: