1. Signal isolator the role of
(1) Geocirculation Interference
The implementation of monitoring and control in industrial production processes relies on a wide range of automated instruments, control systems, and actuators. Signal transmission among these components encompasses both very weak signals—on the order of millivolts or milliamperes—and much stronger signals—ranging from tens to thousands of volts and hundreds of amperes; it also includes low-frequency DC signals as well as high-frequency pulse signals. Once such systems are assembled, it is often observed that mutual interference occurs during signal transmission between instruments and equipment, leading to system instability or even erroneous operation. In addition to inherent performance limitations of individual instruments and devices—such as their susceptibility to electromagnetic interference—another critical factor is that virtually all instruments and equipment must be grounded according to their specific requirements and purposes. For example, chassis grounding is essential for safety; a common reference point is necessary for proper circuit operation; and shielding enclosures are typically employed to suppress interference, which likewise require grounding. However, because potential differences exist between the reference points of different instruments and equipment—that is, because each device has a different ground connection—a phenomenon known as “ground loop current” or “grounding loop current” arises. This issue must be addressed when processing signals within the system.

(2) Natural Disturbance
Lightning is a major natural source of interference, with its associated disturbances capable of propagating over distances of several thousand kilometers. The time-domain waveform of lightning-induced interference consists of a large, sharp spike superimposed on a background of random pulses. Cosmic noise arises from ionizing radiation and varies continuously throughout the day, while solar noise fluctuates dramatically in response to changes in solar activity. Natural noise primarily interferes with communication systems, whereas the high-energy spike pulses generated by lightning can damage numerous pieces of equipment; therefore, such interference should be avoided or mitigated to reduce potential damage and losses.

(3) Human Interference
The fundamental cause of electromagnetic interference is the variation of voltage or current in conductors, i.e., a large dv/dt or di/dt. Such rates of change can induce electromagnetic wave radiation from the conductors. On the one hand, this phenomenon can be harnessed to achieve specific functions, such as wireless communication, radar, or other applications; on the other hand, during operation, electronic equipment generates accompanying electromagnetic radiation due to the dv/dt and di/dt present in its conductors. Regardless of the intended purpose, this objectively leads to pollution of the electromagnetic environment. Furthermore, industrial facilities often operate large-scale equipment—such as motors and variable-frequency drives—that are frequently switched on and off, which in turn produces capacitive and inductive interference that can adversely affect the normal display and data acquisition of instruments and meters. In any situation where there is a sudden change in voltage or current, electromagnetic interference will inevitably be present. Digital pulse circuits are a typical source of such interference, and with the widespread adoption of electronic technologies, electromagnetic pollution is becoming increasingly severe.

2. Methods for Addressing Various Interferences
The three essential elements of interference are the interference source, the sensitive device, and the coupling path; if any one of these is missing, electromagnetic compatibility issues will not arise. Therefore, it is crucial to address the problem by focusing on these three elements and identifying the most practical solution. In most cases, the interference source and the sensitive device cannot be directly eliminated, so the primary approach is to target the coupling path—this is also the most commonly used method. Examples include adding shielding or incorporating filters. Among these, dealing with circulating currents is both the most common and the most challenging issue, and this is precisely the topic we will explore here.
(1) The first method: all field equipment is left ungrounded, ensuring that each process loop has only a single grounding point and no ground loops can form. While this approach appears straightforward, it is often difficult to implement in practice. This is because some instruments must be grounded to maintain measurement accuracy or ensure personal safety, and others may develop new ground connections over time due to corrosion, wear, or environmental factors.

(2) The second method: equalizing the potentials of the two grounding points. However, since the grounding resistance is influenced by numerous factors such as geological conditions and climate change, this approach is, in practice, impossible to implement perfectly.

(3) The third method: using signals in each process step Isolator , it breaks the ground loop while ensuring the normal transmission of process signals, thereby completely resolving the ground-loop issue.

3. Use signals Isolator the superiority
Use signals in each process loop. Isolator The solution can be implemented using isolation cards for DCS or PLC systems, or field-mounted isolated transmitters (which is feasible for some equipment), or alternatively by using signals. Isolator to achieve this. In comparison, using signals Isolator It has the following advantages:
• In most cases, signals are used. Isolator +Non-isolated cards are cheaper than isolated cards.
•Signal Isolator The isolation card offers superior performance in isolation capability and electromagnetic interference resistance, among other aspects.
•Signal Isolator It is highly flexible in application and also offers functions such as signal conversion, signal distribution, and interface adaptation, making it even more convenient to use.
•Signal Isolator Typically, configurations include single-channel and dual-channel options, with fully independent channels that can be integrated into a system, making routine maintenance more convenient.