1. Input loop power supply isolation type
With this isolation technique, the power required for the input and output component lines comes from the input. The input terminal provides power in the form of loop power supply, and the loop current of the signal isolator is usually a standard signal of 4-20mA, which is used as an input signal here (for example, a PLC output card). The input signal is isolated and provided to the actuator or regulator through the output terminal. Loop-powered isolators require no additional auxiliary power and are easy to use.
2. Output loop power supply isolation type
With this isolation technique, the power required for the input and output component lines comes from the output. The output end of the signal isolators obtain electric energy by means of loop power supply (for example, PLC input card), and the loop current is usually a 4-20mA standard signal, which is used as the output signal here.
The input terminal can be the signal of various sensors, or it can be the standard signal of 4-20mA. An important feature of this technique is that the signal current flowing to the output not only supplies power to the isolation unit, but it also supplies the load of the signal isolator. (eg input resistance of PLC input card).
3. Output loop power supply isolation
Signal isolator suppliers typically enter the distribution type of this isolation technology. The power required by the signal isolator input and output component lines all come from the output end. The output terminal obtains electrical energy in the form of loop power supply (for example, PLC input card), and the loop current is usually a 4~20mA standard signal, which is used as the output signal here.
The isolation methods of the signal isolator are mainly divided into: transformer isolation and photoelectric isolation, all of which have the functions of isolation, power distribution, conversion, distribution and alarm identification. The isolator has a withstand voltage level of 2000VAC between the input to output to the power supply to the ground and the four-terminal triple fully isolated channel.
The characteristics of the transformer signal isolator: stable performance, long life, strong load capacity, high isolation strength, but the circuit is complex, and the production process requirements are higher.
The photoelectric isolation has stable performance, strong anti-interference ability, simple circuit, low cost, and its lifespan and isolation strength are slightly lower than transformer isolation;
Signal isolators with these two isolation methods have been widely used in many hydropower station projects in recent years. Signal isolator can effectively solve the problem of automatic control and monitoring system sensor working power supply and analog signal input isolation in the environment of hydropower station, resist the harm of power frequency electromagnetic interference and lightning strike overvoltage, and ensure the measurement accuracy of the sensor and the safe, stable and reliable operation of the system.