The Principle Of Action Of The Isolator

The cause of interference in the system
Monitoring and control in the industrial production process requires the use of various automated instruments, control systems and actuators, and the signal transmission between them has both weak to millivolt and microampere small signals, and large signals of tens of volts, even thousands of volts, hundreds of amperes; There are both low-frequency DC signals and high-frequency pulse signals, etc., and after forming the system, it is often found that the signal transmission between the instrument and the equipment interferes with each other, resulting in system instability or even misoperation. In addition to the performance reasons of each instrument and equipment itself, such as anti-electromagnetic interference, another very important factor is that there is a potential difference between the signal reference point between the instrument and the equipment, thus forming a "ground loop" that causes distortion during signal transmission. Therefore, to ensure stable and reliable operation of the system, the "ground loop" problem must be solved during the system signal processing.

Ways to solve the "ground loop"
Based on theoretical and practical analysis, there are three solutions:
The first scheme: all field devices are not grounded, so that all process loops have only one grounding point, can not form a loop, this method seems simple, but in practical applications is often difficult to achieve, because some equipment requirements must be grounded to ensure measurement accuracy or ensure personal safety, some equipment may form new grounding points due to long-term corrosion and wear or climate influences.
The second solution: make the potential of the two grounding points the same, but because the resistance of the grounding point is affected by many factors such as geological conditions and climate change, this scheme cannot be completely achieved in practice.
The third scheme: use the signal isolation method in each process loop to disconnect the process loop without affecting the normal transmission of the process signal, so as to completely solve the ground loop problem.