Passive isolator

The passive isolator can deal with the impact of the common "ground" in the middle of the machine and equipment, and the more prominent feature of the passive isolator is that it does not have to be independent of the external power supply source, but also can work normally to deal with the impact of the industrial production problem on the spot. Widely used in power engineering, railway lines, petrochemical industry, metallurgical industry, chemical plants, food, warehousing logistics and other fields of automation technology, is a cost-effective commodity. So how to wire the passive isolator? Below we will follow the Thai Hua Xiaobian together to understand.

Passive isolator (isolator itself is not powered by switching power supply) is to use the data signal current in the input control loop to power the instrument panel (refers to taking a part of the kinetic energy of the input data signal inside the signal isolator to drive the isolator work), without any external switching power supply.

1. Input loop power supply isolation type

For this kind of isolation technology, the electromagnetic energy required for the input output component route comes from the input end, the input end provides electrical energy by the control loop power supply method, the control loop current is generally 4 ~ 20mAh specification data signal, here as the input data signal (for example, PLC output card), The input data signal is protected and presented to the electric actuator or controller according to the output end. The control loop powered isolator is easy to use without additional auxiliary switching power supply.

2. Output loop power supply isolation type

For this kind of isolation technology, the electromagnetic energy required for the input output component route comes from the output end, the output end is the method of control loop power supply to obtain electromagnetic energy (such as PLC input card), the control loop current is generally 4 ~ 20mAh standard data signal, here as the output data signal. The input end can be the data signal of a variety of sensors, and it can also be the 4 ~ 20mAh standard data signal. A key feature of this technique is that the data signal current flowing into the output not only supplies power to the guard module, but it also supplies the isolator load. (such as the input resistance of the PLC key card).

3, output loop power supply isolation

For this type of isolation technology, the electromagnetic energy required for the input output component route is from the output end, and the output end is obtained by the control loop power supply method of the electromagnetic energy control loop current is generally 4~20mAh specification data signal, here as the output data signal.

In addition, the input side must also get electromagnetic energy from the output side as an auxiliary switching power supply, that is, the working voltage of the distribution equipment, the working voltage for a variety of intelligent transmitter applications, intelligent transmitter output current is the input current of the isolator. Isolators of this type are convenient for protection between smart transmitters and PLC or DCS. Select a control loop powered PLC or DCS keycard without additional auxiliary switching power supply.

Attention:

When applying the passive isolator, it must be noted that the accurate measurement of the working voltage UB of the smart transmitter driver should be enough to maintain the large current flow through the passive isolator and the load RB, the value of 50mA. The loss operating voltage on the passive isolator is UV=2V. Enter the relationship between the working voltage UE and the load characteristic impedance RB when considering the loss of the working voltage UV. If your load is known, you can calculate the minimum operating voltage that the sensor must show according to the formula to maintain a larger current of 50mA in the passive isolator and load.