Service Support

27

2011

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10

Key Points for Selection of Signal Isolator


IsolatorKey points of selection
One. Common mode interference rejection capability, isolator advantage prerequisite.
IsolatorWithin the scope of the unique industry, whether it isTemperature isolation transmitter,signal distributor,Isolated distributorandCurrent and voltage transmitterIn such products, they have the common feature of absolute electrical isolation between ports, that is, there is no electrical connection between primary instruments, power supplies and acquisition equipment, and there must be a certain isolation withstand voltage range. This is the ability to solve the so-called "ground" potential difference between equipment (common mode interference suppression capability). A most common isolator must also have a leakage current of less than 1mA when the 1500V-2000V port withstand voltage, so as to meet many domestic industrial occasions. Some strong electric field environment or aviation, aerospace measurement and control field requirements will be higher.Paragon(NanjingPARROKEN TECHNOLOGY LIMITED) PA and PR series products have unique advantages in this respect. The products abandon the traditional isolation method and adopt EMI method. Some products have a withstand voltage of more than 5000V and have been successfully used by some foreign manufacturers.

II. The current consumption of the product and the power loss during the operation of the product.
In today's society, energy conservation and environmental protection is the mainstream advocated by various industries in society, household appliances are particularly prominent in this regard, and it is also an important indicator to measure the quality of products. However, the performance of the instrumentation industry may not be very prominent. General instrumentation is a few watts to tens of watts. Energy saving is not the mainstream. But the useless loss will bring many disadvantages to the service life and working stability of the instrument. Isolator due to the special role, it is to improve the industrial field I/O plug-in a class of products, in the cement, environmental protection, metallurgy and other harsh industrial environment, in order to better the field instrument signal acquisition, control often in the system integration is equipped with a special isolation cabinet. At this time, dozens or hundreds of isolation products will be intensively installed in an isolation cabinet. When one product is used independently, the temperature difference may not be obvious, but when ten or one hundred are installed at the same time, the temperature will be obviously different. There is experimental proof:
● 1 power consumption 40mAIsolatorThe temperature measured in the cabinet with a temperature of 25 ℃ and a space of 1 ㎡ is 28.7 ℃;
The temperature of 10 intensive installation is 35.4 ℃;
● The temperature is 52.6 ℃ when the 100 is installed intensively;
Visible product temperature and quantity is a multiple relationship.
At this time, the problem is not only the problem of more current consumption, but also directly affects the service life of the product and the stability of the parameters, which is one of the reasons why many manufacturers have requirements for product installation. So how to solve the problem? There are many ways (expanding the installation space, increasing the heat dissipation device, etc.) but it can only cure the symptoms, not the root cause. A good product also starts with the low-loss design of the product itself. Because of any electronic products, the life of internal devices has a great relationship with temperature, (such as capacitors in each increase of 15 ℃-20 ℃, the service life will be reduced by about 1/3).
What we need to do is to minimize the excess loss of the product. The current consumption of the single-channel product is within 25mA, and due to the special isolation method, our product can ensure extremely high stability at -25 ℃-85 ℃. (The full value of the product measured by the experiment at -25 ℃-85 ℃ only changes ≤ 1 ‰ full value)

Three. Product transmission accuracy
An isolator product must ensure the accuracy of on-site signal transmission, which puts forward a series of requirements for isolation products, first of all, the ability to suppress differential mode interference. The so-called differential mode interference is that the signal is affected by external interference sources in the transmission process and superimposed on the signal some useless signals. When these interference signals are serious, they can cause misoperation and inaccurate acquisition and control of the equipment. Due to the special area of the industrial environment, it is difficult to effectively shield and remove the interference source, so the isolation products and put forward such problems. For thermocouple and small signal processing, it is not only necessary to add some noise reduction and noise filtering means, but also to select a differential circuit with high precision and high stability.
In addition, to ensure that the entire signal transmission accuracy of the isolation products of their own conversion, transmission accuracy also has high requirements, including the stability of the product itself, the impact of external interference, the impact of environmental temperature changes, and signal resolution and many other factors.
In short, when using such products, we should consider comprehensively from many aspects, and do not let inferior isolation products become the weakest link in your huge system.