Working Principle, Function and Selection of Signal Isolator


Release time:

2021-02-14

Nanjing Paroken Technology Co., Ltd. Working principle: First, the signal of the transmitter or instrument is modulated and converted by semiconductor devices, then isolated and converted by light or magnetic sensing devices, and then demodulated and converted back to the original signal before isolation. At the same time, the power supply of the isolated signal is isolated. Ensure that the transformed signal, power supply and ground are absolutely independent. Function: One: Protect the control loop of the lower level. Two: weaken the influence of environmental noise on the test circuit. Third, inhibit the interference of public grounding, frequency converter, solenoid valve and unknown pulse to equipment; At the same time, it has the function of limiting pressure and limiting current for lower-level equipment, which is the faithful protection of transmitter, instrument, frequency converter, solenoid valve PLC/DCS input and output and communication interface. Standard series guide rail structure, easy to install, can effectively isolate: input, output and power supply and the potential between the earth. Can overcome the inverter noise and a variety of high and low frequency pulsation interference. The main types of signal isolators are 1) Isolator:(PA-1187) In industrial production, in order to increase the load capacity of the instrument and ensure that the instruments connected to the same signal do not interfere with each other, improve the electrical safety performance. it is necessary to collect, amplify, calculate and carry out anti-interference processing on the input signals such as voltage, current or frequency and resistance, and then output the isolated current and voltage signals, which can be safely sent to the secondary instrument or plc\\dcs for use. 2) Distributor:(PA-1317) Industrial sites generally need to adopt a two-wire transmission mode, which not only provides 24V power distribution for primary instruments such as transmitters, but also outputs isolated current and voltage signals after collecting, amplifying, calculating and anti-interference processing the input current signals for use by subsequent secondary instruments or other instruments. 3) Safety barrier:(PRG-1100) Some special industrial sites (such as gas companies and chemical plants) not only need two-wire transmission, but also need to provide power distribution and signal isolation functions. At the same time, they also need to have safe spark explosion-proof performance, reliably contain power supply, prevent ignition between power supply, signal and ground, limit current and step-down double limit signals and power circuits, and limit the energy entering dangerous places within the safe quota range. Signal isolator installation and maintenance should pay attention to what matters Due to different manufacturers, the production process and wiring definition of the isolator are not all the same, but the use occasions are basically the same, so the protection requirements and maintenance of the product are basically the same. 1. Read the instructions carefully before use. 2. When used as signal isolation, the input terminal should be connected to the loop circuit, and the output terminal should be connected to the sampling circuit. 3. When used as an isolated power distribution, the input terminal should be incorporated into the power supply circuit, and the output terminal should be connected to the transmitter. 4. If it does not work normally, first check whether the wiring is correct, and pay attention to whether the power supply is correct and the polarity is anyway. Sometimes the field signal received by the PLC has a large error and poor stability. There are many reasons for this phenomenon, and the potential difference between different instrument signal reference points is an important factor. Because of this "difference", the interference current is generated between the instrument signals, resulting in large PLC errors and poor stability. Therefore, it is the best condition that the signals of different equipment and instruments have a common reference point. The isolator completely isolates the input/output electrically and forms a common reference point in the PLC analog interface board to solve the problem of achieving the ideal situation. The 4-20mA channel is isolated, and there is no space for power supply in the cabinet. What should I do? A passive signal isolator that provides 4-20mA signal isolation without the need for an external power supply. Now the market has so many brands of isolators, the price is uneven, how to choose? The isolator is located between the two system channels, so the selection of the isolator must first determine the input and output functions, and at the same time, the input and output modes of the isolator (voltage type, current type, loop power supply type, etc.) should be adapted to the front and rear channel interface modes. In addition, there are many important parameters related to product performance, such as precision, power consumption, noise, insulation strength, bus communication function, etc., for example, noise is related to precision, power consumption and heat is related to reliability, which need to be carefully selected by users. In short, applicable, reliable and cost-effective products are the main principles for selecting isolators. The on-site two-wire pressure transmitter signal received by DCS is unstable, how to solve it? The two-wire transmitter is used frequently in the field of industrial automation. Like other industrial field equipment, the two-wire transmitter also has the problem of interference and anti-interference. According to the interface mode of DCS analog board (current type or loop power supply type), the isolation distributor with different functions is selected. In principle, it is required to provide isolated power supply to the transmitter, ensure that each transmitter has an independent power supply, and isolate the transmitter signal to DCS. The PLC analog board interface is a two-wire loop power supply mode, and the signal needs to be isolated. How should the product be selected? Two-wire loop power supply is a common analog interface. Products suitable for this interface are called two-wire circuit isolation series products. The isolation device inside the isolation transmitter adopts the transformer mode, on the one hand, it transmits the signal, on the other hand, it also transmits the electric energy of the power supply end to the input part, so that the various circuits of the input part can work normally.

NANJING PARROKEN TECHNOLOGY CO., LTDWorking principle:
First, the signal of the transmitter or instrument is modulated and converted by semiconductor devices, then isolated and converted by light or magnetic sensing devices, and then demodulated and converted back to the original signal before isolation. At the same time, the power supply of the isolated signal is isolated. Ensure that the transformed signal, power supply and ground are absolutely independent.
Function:
One: Protect the control loop of the lower level.
Two: weaken the influence of environmental noise on the test circuit.
Third, inhibit the interference of public grounding, frequency converter, solenoid valve and unknown pulse to equipment; At the same time, it has the function of limiting pressure and limiting current for lower-level equipment, which is the faithful protection of transmitter, instrument, frequency converter, solenoid valve PLC/DCS input and output and communication interface.
Standard series guide rail structure, easy to install, can effectively isolate: input, output and power supply and the potential between the earth. Can overcome the inverter noise and a variety of high and low frequency pulsation interference. The main types of signal isolators are
1) Isolator: (PA-1187)
In industrial production, in order to increase the load capacity of the instrument and ensure that the instruments connected to the same signal do not interfere with each other, improve the electrical safety performance. it is necessary to collect, amplify, calculate and carry out anti-interference processing on the input signals such as voltage, current or frequency and resistance, and then output the isolated current and voltage signals, which can be safely sent to the secondary instrument or plc\\dcs for use.
2) Distributor: (PA-1317)
Industrial sites generally need to adopt a two-wire transmission mode, which not only provides 24V power distribution for primary instruments such as transmitters, but also outputs isolated current and voltage signals after collecting, amplifying, calculating and anti-interference processing the input current signals for use by subsequent secondary instruments or other instruments.
3) Safety barrier: (PRG-1100)
Some special industrial sites (such as gas companies and chemical plants) not only need two-wire transmission, but also need to provide power distribution and signal isolation functions. At the same time, they also need to have safe spark explosion-proof performance, reliably contain power supply, prevent ignition between power supply, signal and ground, limit current and step-down double limit signals and power circuits, and limit the energy entering dangerous places within the safe quota range. Signal isolator installation and maintenance should pay attention to what matters
Due to different manufacturers, the production process and wiring definition of the isolator are not all the same, but the use occasions are basically the same, so the protection requirements and maintenance of the product are basically the same.
1. Read the instructions carefully before use.
2. When used as signal isolation, the input terminal should be connected to the loop circuit, and the output terminal should be connected to the sampling circuit.
3. When used as an isolated power distribution, the input terminal should be incorporated into the power supply circuit, and the output terminal should be connected to the transmitter.
4. If it does not work normally, first check whether the wiring is correct, and pay attention to whether the power supply is correct and the polarity is anyway. Sometimes the field signal received by the PLC has a large error and poor stability.
There are many reasons for this phenomenon, and the potential difference between different instrument signal reference points is an important factor. Because of this "difference", the interference current is generated between the instrument signals, resulting in large PLC errors and poor stability. Therefore, it is the best condition that the signals of different equipment and instruments have a common reference point. The isolator completely isolates the input/output electrically and forms a common reference point in the PLC analog interface board to solve the problem of achieving the ideal situation. The 4-20mA channel is isolated, and there is no space for power supply in the cabinet. What should I do?
a kindPassive Signal IsolatorIt can achieve 4-20mA signal isolation and no external power supply. Now the market has so many brands of isolators, the price is uneven, how to choose?
The isolator is located between the two system channels, so the selection of the isolator must first determine the input and output functions, and at the same time, the input and output modes of the isolator (voltage type, current type, loop power supply type, etc.) should be adapted to the front and rear channel interface modes. In addition, there are many important parameters related to product performance, such as precision, power consumption, noise, insulation strength, bus communication function, etc., for example, noise is related to precision, power consumption and heat is related to reliability, which need to be carefully selected by users. In short, applicable, reliable and cost-effective products are the main principles for selecting isolators.
The on-site two-wire pressure transmitter signal received by DCS is unstable, how to solve it?
The two-wire transmitter is used frequently in the field of industrial automation. Like other industrial field equipment, the two-wire transmitter also has the problem of interference and anti-interference. According to the interface mode of DCS analog board (current type or loop power supply type), the isolation distributor with different functions is selected. In principle, it is required to provide isolated power supply to the transmitter, ensure that each transmitter has an independent power supply, and isolate the transmitter signal to DCS. The PLC analog board interface is a two-wire loop power supply mode, and the signal needs to be isolated. How should the product be selected?
Two-wire loop power supply is a common analog interface. Products suitable for this interface are called two-wire circuit isolation series products. The isolation device inside the isolation transmitter adopts the transformer mode, on the one hand, it transmits the signal, on the other hand, it also transmits the electric energy of the power supply end to the input part, so that the various circuits of the input part can work normally.