【 Weak current College 】 how to correctly select signal isolator 】

Working principle:

First transmitter or instrument signal modulation by semiconductor devices, and then transform light perception or isolated magnetic sensing device, and then transform back to quarantine before demodulating the original signal, the signal after the isolation of the power to carry on the isolation process. Ensure that the transformed signal, power supply, between absolute independence.

Function:

A: to protect the child's control loop.

Second: weakening environmental noise on a test circuit.

Three: public grounding, inverter, solenoid valve and unknown pulse interference on the device; at the same time on a subordinate devices have limited pressure, the amount of flow feature is the transmitter, instruments, transducers, solenoid valve PLC/DCS input output and faithful communication interface. Standard series guide structure, easy to install, can be effective in isolation: input, output, and power and potential of the Earth. To overcome the noise frequency converters and various high and low frequency pulse interference.

The main types of signal isolators?

1) isolator: industrial production to increase the load capacity and to ensure that the instrument is connected to the same signal interference between the instruments to improve electrical safety performance. You need to input voltage, current or frequency, resistance, signal acquisition, magnification, operations, and a antijamming processing, and output isolation of current and voltage signals, safety for secondary instrument or plc\dcs use.

2) appliances: industry field generally need two wire transmission mode, both for the transmitter, an instrument with 24V power supply, and also to the input current signal acquisition, magnification, operations, and a antijamming processing, and output isolation of current and voltage signals for subsequent secondary instrument or other instrument.

3) safety barrier: some special industrial field (such as the gas company and chemical plant) not only need two wire transmission, both distribution power and signal isolation capabilities while also need to have security spark and explosion-proof performance, reliably contain power, preventing power, signal and between the ignition, current limiting, Buck dual limit signal and power supply circuit, make into dangerous places of energy limited to secure fixed range.

Signal isolator installation maintenance what considerations exist?

As the manufacturer, the production process of the isolator, wiring definition nor are the same, but essentially the same as using the occasion, so for product protection and maintenance of basically the same.

1. should read carefully before use.

2. when used as a signal isolation, the input string into the loop circuit, output termination sampling circuit.

3. when used as a quarantine distribution should be input into the power supply circuit, output termination transmitter.

4. If not properly you should check the wiring is correct, note that there is no power supply and polarity anyway.

Why sometimes PLC received field signal errors and poor stability?

This might be caused by many different instrument signal reference potential difference between the points is an important factor. Because of this "gap" between the resulting instrument signal interference current, causing the error and the stability of the PLC. So different equipment, meter's signals have a common reference point is the best condition. Isolator allows input/output electrical complete isolation on the PLC analog interface board form a common reference point, to achieve the ideal situation you have resolved the problem.

On the 4-20mA-channel isolated, and there is no place in the Cabinet room, the power supply?

A passive signal isolators, it can achieve 4-20mA signal isolation and eliminates the need for external power supply. PH1033 is this type of product. Now market with so many brands of isolators, price, what to choose? isolator is located between the two systems channel, so select isolator first to determine the input and output capabilities as well as the isolator input output mode (voltage, current-loop supply type, etc.) fit rear channel interface mode. In addition there are precision, low power consumption, noise, dielectric strength, bus communication function and many other important parameters involved in product performance, such as noise and precision for thermal and reliability, low power consumption, which requires users to be careful. In short, applicable, reliable, and product price are the main principles of choice of isolator.

DCS received live two-wire pressure transmitter signal instability, how to solve?

Two-wire transmitter in the industrial automation field using the frequency is high, and other industrial equipment, two-wire transmitter there are disturbed and interference problems. According to the DCS simulation Board interface mode (current or loop powered) selection feature different isolation with electrical equipment requires, in principle, it is able to provide isolation transmitter power supply, ensure each transmitter has an independent power supply, and the transmitter signal isolation to the DCS. PLC analog panels interface is the second-line loop power supply, and need to be isolated to the signal, how to choose products? second-line loop power supply is a common analog interface. And the interface that's appropriate for offerings are called two-wire circuit isolation products. This isolation transmitter internal isolation devices uses the transformer manner, on the one hand, passed signal on the one hand, and the supply side of energy transfer to the input part to enter part of the various circuit can work properly. Cases with electrical products such as PH2217. There are several commonly used second-line wiring electrical? common two-wire isolation with electric has two varieties can be chosen. Two series of products have in common is to pass an external power supply after the isolation to two-wire transmitter provides an independent, isolated power supply; transmitter power distribution depends on the scene with PLC, DCS analog transmission.