How to choose the right signal isolator?

The signal isolator is a signal isolation device, which converts the input single or double current or voltage signal to the output isolated single or double current or voltage signal, and improves the electrical isolation performance between the input, output and power supply. Signal in the transmission process will encounter a variety of interference, in order to ensure the stability of the signal, the use of signal isolators is particularly important. Which brand of signal isolator is better? How to choose an isolator with strong anti-interference ability and good quality?

Isolator selection should be based on the field instrument, control system or secondary instrument interface, the current automation industry input/output signal standard is: 4 ~ 20mADC or 1 ~ 5VDC, of course, there are some special input/output signals.

According to the interface of the instrument is divided into: signal isolation class; One in multiple out isolation class; Power distribution; One input multiple output distribution class; Temperature isolation transducers; Passive isolation class; Two-wire isolation class; Two-wire distribution; Two wire temperature isolated transmission class, etc.

In addition to determining the function of the isolator and adapting to the front and back end interfaces, many parameters such as accuracy, output ripple, temperature drift, power consumption, and response time need to be carefully selected when selecting the isolator. Specific precautions are as follows:

1. Accuracy

The accuracy of the isolator is a very important parameter, and the accuracy is directly related to the normal use of the isolator. The precision of the isolator reflects the design and manufacturing level of the isolator. Users should choose products with high precision when choosing.

2. Output ripple

Other parameters that affect the accuracy of isolators are output ripple. The output ripple is generated because the isolator uses a DC/DC circuit to isolate the working power supply of the isolator to supply power to the internal circuit of the isolator. The input signal should also be first modulated into an AC signal by the DC/DC circuit and then isolated through the isolated part of the circuit for signal isolation. The isolated signal is demodulated and then converted into a DC signal output. The isolators with CPU as the core also have pulse signals. The presence of this high-frequency AC component inside the isolator is the cause of the output ripple. These high-frequency AC components generally have a frequency of several hundred KHZ, more harmonics, and the pollution of the signal is difficult to completely remove. If the output ripple is high, the error of the signal collected by the analog input template of the control system is large, especially for the analog input template of high-speed input. Therefore, when selecting the isolator, the peak-to-peak of the output ripple should be required to be as small as possible. The isolators of various series of Ci-link electronics adopt efficient filter circuit, which can suppress the output ripple better. Users should choose products with small ripple when choosing.

3. Temperature drift

The temperature drift is caused by the heat generated during the operation of the isolator, which leads to the decline of the performance indicators of the electronic components used in the isolator, resulting in the change of the output value of the isolator. When selecting isolators, the temperature drift should be as small as possible. In order to prevent temperature drift, Parocon isolator products are designed with low power consumption and micro power consumption, so that the heat of the isolator itself is very small or even no heat, so that the performance indicators of the components used can be prevented from decreasing due to the heat of the product during work, and the temperature drift can be prevented. Users should choose products with small temperature drift when choosing.

4, low power consumption

Power consumption refers to the electrical energy consumed by the isolator during operation. It relates to the heat output of the product at work, and this parameter is closely related to the service life, reliability and appearance and installation of the isolator. When selecting isolators, choose products with low power consumption. The new technology is adopted in the circuit design of isolator: the output part can dynamically adjust the output power according to the size of the load adaptive load technology; Current mutual inductance power compensation technology of isolated part; Power supply part of the parametric switching voltage regulation power supply technology. The power consumption of our isolators is less than half of the power consumption of world-class brands.

    If the power consumption of the product is large, the heat generated when the product is working is large, resulting in a high temperature in the product housing. The electronic components of the product are in a high temperature environment for a long time, which will lead to the parameter disintegration of the operational amplifier, the change of resistance value, and the increase of capacitor leakage. These problems will make the product performance decline, and even lead to product failure, failure.

    Without the guarantee of low-power design, it is impossible to achieve ultra-thin, miniaturized and terminal isolators. Our company has launched the thinnest low-power MZ series products, micro-power MZ two-wire series products and passive series products. The thickness of the mainstream products in China is generally between 20mm and 30mm, and the thickness of the latest foreign products is 6.0mm. In order to save engineering costs such as control cabinet, power supply, wiring terminals, connecting cables and labor costs of the control system, users should choose low-power products when selecting.

5. Response time

Response time refers to the time between the change in the input quantity of the product and the correct output reflecting the change in the output quantity of the product. The shorter the response time, the more truly and correctly reflect the changes in the input volume, and effectively monitor and control the production process. The shorter the response time required when selecting isolators, the better. Users should choose products with low response time when choosing.