Abstract：During production, control systems and monitoring systems frequently encounter challenges posed by complex environments, such as short circuits, overvoltage, and unknown pulses.To ensure system stability and data accuracy, signal isolators are particularly important.It effectively protects downstream control circuits, reduces environmental noise interference, and suppresses the effects of grounding. Additionally, the isolator incorporates overvoltage protection and choke functions, providing comprehensive safeguarding for the control system's input/output and communication interfaces. Therefore, signal isolators have become an indispensable component in modern production processes.

Introduction：The principle of a signal isolator lies in its ability to modulate and convert signals from transmitters or instruments using semiconductor devices.This process involves the application of optical or magnetic sensing devices to achieve isolated signal conversion. Subsequently, these signals undergo demodulation to restore them to their original form prior to isolation.Simultaneously, the isolator also isolates the power supply for the isolated signal, ensuring absolute independence between the converted signal, power supply, and ground.Additionally, it can filter out interference signals superimposed on the measured values and match the signals according to the requirements of the control system's inputs and outputs.

一、Classification of Signal Isolators

Signal isolators are primarily divided into two major categories: active signal isolators and passive signal isolators.

1. Active Signal Isolator

Sunyuansz series active signal isolators rely on an independent power supply to ensure stable operation. .On the input side, these modules must receive active signals and provide filtered and amplified signals on the output side.Additionally, depending on application requirements, input/output and power supply can be mutually isolated.The three-terminal isolation technology for signal input/output/operating power requires only a single power supply, which is isolated from the measurement circuit. Modules employing this technology ensure that components on the input, output, and power supply terminals do not interfere with each other, achieving electrical isolation between the three terminals.

2. Passive Signal Isolator

Sunyuansz series passive signal isolators require no external power supply. Their operating power is derived from either the input or output circuits, and the internal circuitry consumes minimal current, ensuring no interference with normal signal transmission.This type of isolator is further classified based on its power supply method into input-side powered, output-side powered, and passive feed types.

Input-side powered modules draw energy from active input circuits (such as electromagnetic flowmeters or control system output cards) to enable signal transmission and electrical isolation, while simultaneously providing processed current signals at the output side for control or regulation purposes.

Output-side powered modules draw energy from the active output circuit (ideally supplied by the auxiliary power from the control system input card), which also serves for signal transmission and electrical isolation.

The passive feed isolator draws energy from the active output circuit while simultaneously supplying this energy to a passive sensing probe (such as a pressure transmitter) connected to the input side. The detection probe generates an active signal using the supplied power, which is electrically isolated via the passive isolation feeder and then output from the output side.

二、Key Considerations for Selecting Signal Isolators

As a critical component between two system channels, the selection process for isolators requires comprehensive consideration of multiple factors. First, the input/output functions of the isolator must be clearly defined to ensure that its input/output mode matches the interface mode of the front-end and back-end channels. Additionally, numerous critical parameters influence product performance, such as precision, power consumption, noise levels, insulation strength, and bus communication capabilities.For example, noise levels are closely related to precision, while power consumption and heat generation directly impact product reliability.Therefore, when selecting signal isolators, it is necessary to comprehensively consider these factors to choose isolators that are both suitable and reliable, thereby enhancing the cost-effectiveness of the product.