Why do control systems need signal isolators?
Release time:
2024-02-01 21:55
Principle of signal isolator
The principle of the signal isolator is to convert the signal of the transmitter or instrument through semiconductor device modulation, then realize isolation conversion through light sensing or magnetic sensing device, then implement demodulation conversion back to the original signal before isolation, and at the same time implement isolation processing on the power supply of the isolated signal, and the converted signal, power supply and ground are independent. At the same time, the interference signal superimposed on the measured value is filtered, and the signal is matched according to the input and output requirements of the control system. Therefore, isolation, amplification, filtering and matching are the functions of the signal isolator.
Some DCS modules have their own photoelectric isolation function, which can fully meet the normal working requirements in some systems. However, the system cannot always be in normal working condition. Once the device is damaged due to an accident, replacing the isolator is more time-saving and cost-saving than replacing the DCS module. Therefore, it is suggested that it is still necessary to determine whether to install isolators according to the actual situation.
The isolator is located between the two system channels, so the selection of the isolator must first determine the input and output functions, and at the same time, the input and output modes of the isolator (voltage type, current type, loop power supply type, etc.) should be adapted to the 1:3 mode of the front and rear channels. In addition, there are precision, power consumption, noise, insulation strength, bus communication function and many other important parameters related to product performance, such as: noise and precision, power consumption heat and reliability, these need to be carefully selected by users. In short, applicable, reliable and cost-effective products are the main principles for selecting isolators.
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