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2011

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06

Forms of passive signal isolators


In order to solve the mutual interference caused by grounding between various instruments and equipment, it is usually used.IsolatorTo solve. The role of the isolator is to make the connection between the instrument equipment completely electrically isolated, in other words, so that there is no common "ground" between the input and output, so it will not affect the normal transmission of the signal.
The isolator can be dividedactive isolatorandpassive isolator. The following describes the form of passive isolator:
1. Input terminal loop power supply isolation type (PA-0133)
For this isolation technology, the electrical energy required by the input and output component lines comes from the input end. The input end provides electrical energy in the form of loop power supply. The loop current is usually 4 ~ 20mA standard signal, which is used as an input signal (for example, PLC output card). The input signal is isolated and provided to the actuator or regulator through the output end. Loop-powered isolator without additional auxiliary power supply, easy to use.
2. Output terminal loop power supply isolation type (PA-0371
For this isolation technology, the electrical energy required by the input and output component lines comes from the output end, and the output end obtains electrical energy by means of loop power supply (for example, PLC input card). The loop current is usually 4 ~ 20mA standard signal, which is used as the output signal here.
The input terminal can be the signal of various sensors or the standard signal of 4 ~ 20mA. An important feature of this technique is that the signal current flowing to the output not only supplies the isolation unit, but it also supplies the load of the isolator. (e. g. input resistance of PLC input card).
3. Output loop power supply isolation, and input power distribution type For this isolation technology, the electrical energy required by the input and output component lines comes from the output end, and the output end obtains electrical energy by loop power supply (for example, PLC input card). The loop current is usually 4 ~ 20mA standard signal, which is used as the output signal here.
In addition, the input terminal also needs to obtain electrical energy from the output terminal as an auxiliary power supply, that is, the distribution voltage, which is used for variousTransmitterUsing, the transmitter output current is the isolator input current.
Passive signal isolators are convenient for isolating the transmitter from the PLC or DCS. Loop-powered PLC or DCS input cards do not require additional auxiliary power.