Classification of signal isolator

How to classify the signal isolator of the signal isolator? There are many types. If the power supply method is used, it is divided into three types: loop-powered, independent-powered, and output-loop powered.

First, the loop power supply input and output are two lines, the wiring is very convenient, it to DCS, PLC or display table power supply is isolated to the two-wire transmitter power distribution, while the two-wire transmitter generates 4 ~ 20mA signal isolation input To DCS, PLC or display meter. It is especially suitable for on-site two-wire transmitter, need to isolate input to DCS, PLC system or display meter, and the input device's input card has internal power supply function, but it has insufficient Department:

1, the isolator is equivalent to a load, there is a pressure drop of not more than 6V between the isolated ends through the isolator, so it will reduce the distribution work voltage for the two-wire transmitter, generally require the transmitter 12V power supply jobs.

Example: Power supply 24V, RL = 250Ω, when 20mA, supply two-wire transmitter distribution voltage UO ≈ 24V-0.02 × RL-6 ≥ 13V, this generally requires two-wire transmitter to work in 12V voltage.

2, the transmission accuracy is relatively independent of the power supply of the isolator to 0.4% FS, when you choose to pay special attention.

Second, the independent power supply This is the most commonly used distribution transmitter with two wire transmitter, it requires the independent power supply to the isolator, which is characterized by:

1, the transmission accuracy is high, reaching 0.1% FS.

2, flexible wiring, you can connect two-wire transmitter, three-wire transmitter or current source signal, the use of flexible and convenient.

3, power, input, output completely isolated to ensure high anti-jamming performance.

4, need to be equipped with an independent 20-35VDC DC power supply.

Third, the output loop power supply type In the actual industrial monitoring system, DCS, PLC or display instrument with the card internal power supply is more and more widely used, loop power supply isolator and often can not meet these clips for signal isolation transmission and high precision requirements Two-wire transmitter requires high distribution voltage, so there is output loop power supply product, which not only retains the superior performance of independent power supply isolator, but also meets the output loop power supply interface requirements.